Third International Conference on Experimental Mechanics and Third Conference of the Asian Committee on Experimental Mechanics

Biologically inspired robotic inspectors: the engineering reality and future outlook

Yoseph Bar-Cohen

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Human errors have long been recognized as a major factor in the reliability of nondestructive evaluation results. To minimize such errors, there is an increasing reliance on automatic inspection tools that allow faster and consistent tests. Crawlers and various manipulation devices are commonly used to perform variety of inspection procedures that include C-scan with contour following capability to rapidly inspect complex structures. The emergence of robots has been the result of the need to deal with parts that are too complex to handle by a simple automatic system. Economical factors are continuing to hamper the wide use of robotics for inspection applications however technology advances are increasingly changing this paradigm. Autonomous robots, which may look like human, can potentially address the need to inspect structures with configuration that are not predetermined. The operation of such robots that mimic biology may take place at harsh or hazardous environments that are too dangerous for human presence. Biomimetic technologies such as artificial intelligence, artificial muscles, artificial vision and numerous others are increasingly becoming common engineering tools. Inspired by science fiction, making biomimetic robots is increasingly becoming an engineering reality and in this paper the state-of-the-art will be reviewed and the outlook for the future will be discussed.

Optics-based sensor for DNA screening applications

Wei Ming Chiang, Chu Sing Lim, Tet Fatt Chia, et al.

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Short Tandem Repeats (STRs) are non-coding regions in genomic DNA that consist of short segments of core tandem repeat sequences. As these sequences are highly polymorphic in nature, they are extremely specific and unique to the individual. The STR fragments are amplified through the Polymerase Chain Reaction (PCR) before they are separated and analyzed. In this study, an optic-based system was developed to detect two STR loci in a gel matrix. Results show that the system is able to detect the STR fragments with a precision of +/- 1.0 bp, which is considered acceptable, given that the chosen STR loci have 4 bp repeat sequences. This system offers an inexpensive yet efficient method of STR DNA typing.

Using a new liquid-crystal polarization modulator for a polarimetric glucose sensor

Tsung-Chih Yu, Yu-Lung Lo

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This paper presents a new liquid-crystal polarization modulator comprising a nematic liquid-crystal variable retarder (LCVR) and two quarter-wave plates for the measurement of glucose concentrations. Rather than using a conventional Faraday modulator, this study firstly adopts a LCVR driven by sinusoidal signals to modulate the polarization angle of the light as a sinusoidal function. It is found that the variation frequency of the polarization angle doubles that of the driving signal, and the modulation depth is not proportional to the driving amplitude. These features are quite different from a Faraday modulator. Therefore, a signal demodulation algorithm which developed to adapt the particular features of the LC modulator enables the polarization rotation angle corresponding to the glucose concentration to be derived. The proposed measurement method has a minimum resolution of 0.05 degrees corresponding to a glucose concentration of 0.2 g/dl. Compared to its conventional counterparts, the developed polarimeter has a simpler structure, fewer optical elements, and a cheaper modulator component.

Converting signals to knowledge in structural health monitoring systems

James M. W. Brownjohn, Pilate Moyo, Piotr Omenzetter, et al.

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Academic approaches in structural health monitoring (SHM) usually focus on fine detail or on aspects of the technology such as sensors and data collection, and areas that may be less useful to operators than information about the level of performance of their structures. The steps in the process of SHM such as data management, data mining, conversion to knowledge of structural behaviour and integrity are frequently absent, and even the most operationally successful SHM systems may lack the component where deep understanding on the nature of the structure performance is obtained. This paper presents experience gained in a number of SHM exercises where static and dynamic response data have been interpreted, with or without the aid of calibrated structural models, in order to characterise the mechanisms at work and the experiences of the structure.

Comparative study of all optical fibers in different smart structures and non-destructive evaluation

Gopalkrishna Hegde, Anand Asundi

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This paper deals with comparative study of various types of optical fibers in non-destructive evaluation of different smart structures. Performance of single mode, high-birefringent, low-birefringent fibers, multifibers and plastic fibers embedded into concrete and composite structures are experimentally evaluated under different conditions. The results are discussed with respect to overall sensor performance and structural environment, which facilitates the selection of appropriate fiber sensor for a particular structure.

Structural health monitoring of smart civil structures using fibre optic sensors

Jin Shong Leng, Darren Winter, R. A. Barnes, et al.

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A number of embedded sensor protection system (ESPS) and surface-mountable sensor protection system (SSPS) for fibre optic sensor (FOS) have been developed in this paper. Fibre Bragg Grating (FBG) and Extrinsic Fabry-Perot interferometric (EFPI) sensors protected by the designed protections system have been used to monitor the cure progress and structural health status of concrete cylinders. Results indicate that the sensor protection systems for the FOS perform adequately and effectively in concrete environment. The protected fibre optic sensors are suitable achieve the structural health monitoring in practical. It is also revealed that there is excellent correlation between the results obtained from the protected FOS and reference electrical resistance strain gauges.

Vision-based automatic measurement of endface geometry of single-fiber optical connectors

Xiaoming Yin, Shihua Wang, Ivan Reading

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Fiber optic connectors are an important factor in the performance of fiber optical systems. In order to ensure good fiber to fiber contact, the endface geometry of fiber connectors needs to be measured quantitatively. In this paper, we present a vision-based automated measurement system for measurement of the endface geometry of a single fiber connector. The optical setup of the system developed is based on a Mirau interferometer and the 3D profile of the connector endface is obtained by using phase shifting techniques. Image processing techniques are applied to automatically find the fiber center and retrieve the geometric parameters of the connector endface, such as radius of curvature, apex offset and protrusion or undercut. Experimental results have demonstrated the feasibility of the proposed system.

The dynamic properties behavior of high strength concrete under different strain rate

Hasballah Abdullah, Saiful Husin, Hamdani Umar, et al.

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This paper present a number experimental data and numerical technique used in the dynamic behavior of high strength concrete. A testing device is presented for the experimental study of dynamic behavior material under high strain rates. The specimen is loaded by means of a high carbon steel Hopkinson pressure bar (40 mm diameter, 3000 mm long input bar and 1500 mm long out put bar) allowing for the testing of specimen diameter is large enough in relation to the size of aggregates. The other method also proposed for measuring tensile strength, the measurement method based on the superposition and concentration of tensile stress wave reflected both from the free-free ends of striking bar and the specimen bar. The compression Hopkinson bar test, the impact tensile test of high strength concrete bars are performed, together with compression static strength test. In addition, the relation between break position under finite element simulation and impact tensile strength are examined. The three-dimensional simulation of the specimen under transient loading are presented and comparisons between the experimental and numerical simulation on strain rate effects of constitutive law use in experimental are study.

Optical large mirror design

Jeong-ick Lee, Seong-sik Choi

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The development of a mechanical structure is required to be started from the conceptual design with low cost, high performance and quality. In this point, a structural-topological shape of system concerned with conceptual design of mechanical structure has a great effect on performance of the system such as the structural rigidities and weight reduction. In this paper, the optimization design methodologies are presented in the design stages of large optical mirror. First, using topology optimization, we obtain the optimal layout and the reinforcement structure, and then carry out the detail designs using size optimization for the structural rigidity.

Quantitative image quality evaluations of enhanced images in turbid water medium

Gerald G. L. Seet, Andrzej Sluzek, ChingSeong Tan

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In order to improve underwater visibility, general considerations are planned in two stages. There is hardware upgrading followed by system optimization stage. For the former, we choose to improve the underwater visibility with advanced techniques: range gated imaging system, and the optimization in terms of image processing techniques. Four selected image enhancement technique has been tested, namely Contrast Stretching, CLAHE, Illumination-reflectance Model and Homomorphic Filtering. Quantitative image quality measures are used to evaluate the enhanced imaging techniques. Three image assessment techniques are used to quantify image quality of the imaging system in increased turbidity condition, namely Modified Fidelity (MF), Modified Strehl Ratio (MSR2), and Contrast-to-Noise Ratio (CNR). In the first stage, the quantitative measures have shown at least 40% improvement from non-gated to gated images in increased turbidity. Finally, the enhancement techniques further improve the gated images with limited noise amplification issues.

Optical image sensing through turbid water

Duo-Min He, Gerald G. L. Seet

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Optical image sensing through turbid seawater is one of the most challenging problems in underwater vision for underwater robotic vehicles (URVs). In this article, we intend to briefly review the basic of underwater optical imaging for a start. For more advanced systems, there are two major techniques: time discrimination (lidar imaging, or range-gated) and spatial discrimination (scanning method). Here, we present our underwater lidar imaging (UWLI) experimental system which give very clear revelation of "sliced-view" phenomenon in a 3m tank with very turbid water (1.0/m). And then, we suggest an underwater Lidar PanCam system, which is the combination of the two major techniques above and based on photo-mosaicing approach.

Designing, manufacturing, and testing of embedded EFPI strain sensor for damage detection of smart composite beams

Lay May Sim, Gang Zhou

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Designing a fiber optic sensor in the development of a real-time damage detection and evaluation system is important for providing reliable results. This paper describes the manufacturing and implementation of an Extrinsic Fabry-Perot Interferometer (EFPI) strain sensor for the non-destructive quantitative evaluation of carbon fiber reinforced composites. The EPFI strain sensors were examined for their integrity and performance. The integrity of the sensors was assessed experimentally by determining the bending strength of the glass tube, which was used in the fabrication of the sensor. Further validations on the survival of the sensors when embedded were also carried out with the application of the modified classical lamination theory (CLT). The sensor performance was examined extensively by either bonded on the surface or embedded in the tensile region of simple quasi-isotropic (QI) composite beams. These smart beams were loaded quasi-statically in three-point bend and cantilever loading The EFPI strain sensors have shown to surface a maximum tensile strain of up to 0.8%, which was adequate and reliable for strain measurements in the current system. The understanding of the EFPI strain sensors behaviour have paved way for the success in achieving a fiber optic strain sensor based damage detection and evaluation system (FODDAS).

Plastic optical fibre sensor for structural health monitoring

Kevin S. C. Kuang, Ser Tong Quek, Mohamed Maalej

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Plastic optical fibre sensors offer remarkable ease of handling and recent research has shown their potential as a low-cost sensor for damage detection and structural health monitoring applications. This paper presents details of a novel plastic optical fibre sensor and the results of a series of mechanical tests conducted to assess its potential for structural health monitoring. The intensity-based optical fibre sensor proposed in this study relies on the modulation of light intensity as a function of a physical parameter (typically strain) as a means to monitor the response of the host structure to an applied load. Initially, the paper will reveal the design of the sensor and provide an summary of the sensor fabrication procedure followed by an outline of the experimental programme conducted in this study. Two types of sensor design will be evaluated in terms of their strain sensitivity, linearity and signal repeatability. Results from a series of quasi-static tensile tests conducted on aluminium specimen with four surface-attached optical fibre sensors showed that these sensors offer excellent linear strain response over the range of the applied load. Free vibration tests based-on a cantilever beam configuration were also conducted to assess the dynamic response of the sensor. The results demonstrate excellent agreement with conventional sensor readings.

Drop-test study of parachute textile with embedded fiber optic sensors

Min Li, Yulin Li

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We developed here a novel embedded strain measurement system that fulfilled a dynamic analysis of the characteristics of parachute canopy based on fiber optics technology. As a continue study of the dynamic characteristics of the parachute canopy, a series of drop tests were developed in the laboratory, and followed by the field test. Sample results obtained by both mode power distribution (MPD) system and fiber Bragg grating (FBG) sensors are taken into the comparison between the optical and mechanical testing results. Drop test results from both MPD and FBG sensors were analysis and correlated to the mechanical characteristics of the parachute canopy textile based on the previous relatins derived from quasi-static test. The curves show clearly that the results of the two types of sensors are consistent. The achieved results provided a nice correlation between the optical and mechanical signals, which dues primarily to the model built up in previous quasi-static test, and will be discussed in this paper.

Tool breakage detection in millin operations using a fiber optic sensor

Guillermo de Anda-Rodriguez, Eduardo Castillo-Castaneda, Salvador Guel-Sandoval

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In this work a method is presented for determining the wear and fracture of a cutting tool, by means of a fiber optic sensor with high resolution and large bandwidth, used during the manufacturing process. The sensor has been configured with two groups of fibers, distributed in a ramdom fashion. One of the groups works as a light emitter that illuminates the tool, while the other captures the light reflected by the tool surface itself. The light is generated by a photodiode, which does not represent any risk to the health. This technique will allow observing the wear and breakage of the tool in real time while the tool is rotating, with a high degree of accuracy.

Air-coupled ultrasonic measurements in composites

Vamshi Kommareddy, John J. Peters, David K. Hsu

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Air-coupled ultrasound is a non-contact technique and has clear advantages over water-coupled testing. This work aims at gaining quantitative understanding of the principles underlining air-coupled ultrasonic measurement. The transmission of air-coupled ultrasonic energy through a plate is measured experimentally; model calculation of the transmission coefficient, taking into account the real transducer characteristics, is compared with the experimental results. The occurrence of "Poisson bright spot" in the flaw images of thin laminates and honeycomb composites were investigated; A qualitative comparison with a model based on the Fresnel's wave theory of light is discussed. Through transmission C-scans at 120 and 400 kHz using focused transmitter and receiver were studied.

Modified single lap joint (MSLJ) test configuration for the determination of adhesive fracture energy

S. B. Kumar, I. Sridhar, S. Sivashanker, et al.

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In this work, a modification has been proposed to the traditional single lap joint (SLJ) configuration, to overcome the wide scatter in the fracture toughness measurement due to adhesive fillets. This modification, referred to as the Modified Single Lap Joint (MSLJ), is made by implanting end pre-cracks in the adhesive layer at the center of the bond line in a conventional SLJ. This ensured that during testing, the crack propagated from both ends of the overlap and reduced the effect of spew fillets. MSLJ joints made from unidirectional fibre composite substrates (913C - HTA 12K 5-34%) and either of two types of (Redux 322 and Redux 335K) film adhesive were tested to measure the adhesive fracture energy, G_ac. The values of G_ac measured were compared with those from similar tests conducted on SLJ and double cantilever beam (DCB) configurations. It was observed that the scatter in the fracture energy measurements obtained from the MSLJ specimens were reduced by more than 30% in comparison with those from the SLJ specimens. The values of adhesive fracture energy from the MSLJ and DCB test geometries were in good agreement. These results are especially useful in the critical design of structural components for aerospace and defense applications as a typical design engineer can use the value of Gac to design for how long an adhesively bonded joint will last when subjected to stresses in friendly or hostile environments.

Composite materials based on carbon nanotubes for aerospace applications

S. Bellucci, C. Balasubramanian, F. Mancia, et al.

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Electrical and mechanical properties of composite materials based on Carbon Nanotubes are considered for aerospace applications. Nanostructured materials gained great importance in the past decade, owing to their wide ranging potential applications in many areas, e.g. mechanical, structural, sensor, biomedical, electronics. Of particular interest are carbon nanotubes, which can be used as a main constituent of composite materials with exceptional mechanical and electrical properties, very suitable for aerospace applications, also due to their light weight, mechanical strength and flexibility. We present results obtained recently in our laboratories concerning the electrical and mechanical properties (including resilience measurement, stress analysis, conductivity) of carbon nanotubes we synthesized by arc discharge and other techniques, embedded in a polymer matrix.

Influence of high pressure water-jet-assisted machining on surface residual stresses on the work-piece of Ti-6AL-4V alloy

Manouchehr Vosough, Inge Svenningsson

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Titanium alloys are used in aerospace industry owing to their high strength to weight ratio. These alloys are considered to be difficult to machine due to their rigidity and poor thermal conductivity. High-pressure jet-assisted machining of titanium alloys is beneficial. It not only increases production efficiency, by increasing the cutting speed and lowering temperature both in cutting zone and the cutting tool, but also improves chip control and increases tool life. It also produces better surface integrity and compress residual stress, which improves the properties of work-piece. Ti-6Al-4V (Ti-64) rod was machined by turning in two different manners, finishing and roughing. Tests were conducted on a lathe using the same cutting data and different cooling systems, high pressure and conventional. In order to illustrate the effect of high-pressure jet-assisted machining on the properties of the work-piece of Ti-6Al-4V and its residual stress, x-ray defractometery was used. The present study revealed that there were compressive residual stresses in the transversal and longitudinal directions of the cut and the residual stresses in both directions were nearly of the same magnitude. The depth profile of residual stress was measured as well after removing the material by etching. The shear stress was very low, almost negligible. High pressure cooling affected residual stresses in finishing more than in roughing.

In situ inspection of inclusions in toughened glass panels of high-rise buildings

Xiang Li, Zhong Ping Fang, Ivan Reading, et al.

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Transparent toughened glass panels are widely installed in high-rise buildings. There is a growing need for inspection to detect the presence of detrimental inclusions of Nickel Sulfide. These inclusions can cause toughened glass to shatter, possibly causing property damage or injury. Optical equipment has been developed which can detect the inclusions in-situ. Light is coupled into a glass panel and propagates along the glass by total internal reflection. An inclusion in the glass will cause the light to scatter. Once an inclusion is found, it will be observed at higher magnification and the detailed image will be processed. By the analysis of its key features, the inclusion type can be identified. The coupling medium is made of a transparent, soft and deformable material. The equipment can be attached to a glass panel by vacuum suction. The optical system can scan the whole glass panel with a constant force spring as anti-weight structure. The whole system is fast, convenient and highly effective. A patent has been filed for this apparatus.

Effect of distribution types of variables on reliability estimation of buried pipelines

Ouk Sub Lee, Dong Hyeok Kim

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This paper presents the effects of boundary conditions of failure pressure model for buried pipelines on failure prediction by using a failure probability model. The FORM (first order reliability method) is used in order to estimate the probability of failure in the buried pipelines with corrosion defects. This method estimates the failure probability of buried pipelines using the first order Taylor series expansion of the LSF(limit state function). The effects of varying distribution types of variables such as normal, lognormal and Weibull distributions on the failure probability of buried pipelines are systematically investigated using the FORM for the corrosion pipeline.

Shape measurement by unwrapping method using aliasing of Fourier spectrum

Yoshiharu Morimoto, Motoharu Fujigaki, Toshio Toyotake

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We previously proposed the integrated phase-shifting method for real-time shape measurement using grating projection method. However, the measurement range in this technique is not so wide, since phase-unwrapping has not been made. In this study, a grating synthesized two cosinusoidal waves of which the frequencies differ from each other, was used in order to perform unwrapping. If the frequencies are 3 and 4, in order to analyze frequencies and phases, the minimum sampling number of phase-shifted images is 8 according to the Whittaker-Shannon sampling theorem. We propose a new unwrapping method using only 5 phase-shifted images. The phase values are obtained from the aliased frequency components of the Fourier spectrum of the grating. The theory is shown and the effectiveness is confirmed by experiment.

A novel phase measurement profilometry based on linear CCD array

Hong Zhao, Zhihua Zhao, Kejian Jiang, et al.

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A new fast 3D profilometry is presented in this paper. Although the phase measuring method can reach more high precision , its real measurement speed is very low and can't be applied on production lines because of its phase-shift operations. Three lines CCD arrays, 1024 pixels each, are mounted together with the same distance intervals. Needless to perform phase shift operations, the CCD can consecutively scan and grab 3 phase distributed pictures which will be separately calculated by 3 DSP processors. Thus the whole measurement process is finished. The experimental results show that the phase measurement system by using three-line CCD has high application values for its high precision and speed.

Surface contour measurement by grating projection method based on Talbot effect

M. Thakur, Chenggen Quan, Cho Jui Tay

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Motivated by the Talbot-effect, a grating projection system was designed. Periodic patterns were produced from the projection of a grating illuminated by collimated laser beam. The self- image of the grating is projected on object surface and the deformed grating image is captured by a CCD Camera for subsequent analysis. The phase variation is achieved by using a linear translation stage incorporated to the grating. In this application, a coin with an uneven surface of less than 0.2 mm is tested to demonstrate the validity of the method. The experimental results are compared with test results using mechanical stylus method.

Numerical simulation effect of DMD spatio-temporal characteristic on phase measuring profilometry

Yiping Cao, Xianyu Su, Liqun Xiang, et al.

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Digital micro-mirror device(DMD) is a new type of component which integrates with micro-electronics, micro-machinery and micro-optics. It used as a new type of spatial-light modulator will have a wide prospect in optical information processing and structured illumination three-dimensional sensing. The basic principles of DMD and digital light processor(DLP) have been particularly introduced. The spatio-temporal characteristic of DMD has been extensively studied. The effect on the Phase Measuring Profilometry due to the Spatio-temporal characteristic of DMD is discussed by computer simulation. Experiments have approved the validity of the simulation results which can give the guidance for the application of DMD in structured illumination three-dimensional sensing.

Profilometry using optical edge projection

Hong Miao, Chenggen Quan, Cho Jui Tay, et al.

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A novel optical edge projection method to measure the profile of an object is proposed. It can be applied to some special field for example to measure a profile of a specimen with a black and soft surface. A structured black-and-white light edge is projected onto an object surface and the distorted optical edge shadow image is captured by a CCD camera. The border line of the optical edge shadow is extracted and compared with a reference line, the distortion modulated by the height of the object surface is then obtained. By calculating the height, and scanning the optical edge shadow along the object, the height information obtained from a series of images can be determined. Combining the border line in these images, the profile of the object can be measured.

Determination of phase-shift from two fringe patterns using windowed Fourier ridges

Kemao Qian, Hock Soon Seah, Anand Asundi

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In phase-shifting interferometry, it is important yet difficult to determine the phase-shift accurately. A windowed Fourier ridges approach is proposed which is able to obtain the phase-shift from two consecutive fringe patterns.

Electroholography unit for three-dimensional display using special-purpose chip and high minute LCD panel

Tomoyoshi Shimobaba, Atushi Shiraki, Nobuyuki Masuda, et al.

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We developed an electroholography unit for a three-dimensional display, which consists of a special-purpose c-omputational chip and a high minute reflective liquid-crystal display panel. We implemented them on one board whose size is approximately 28 cm x 13 cm. The chip can compute a computer-generated hologram whose size is 800 x 600 at nearly real time (0.15 s) for an object consisting of 400 points. After the calculation, the LCD panel displays the computer generated hologram made by the chip, and we can observe a three-dimensional (3D) motion image whose size is approximately 3 cm x 3 cm x 3 cm. The pixel pitch of the display panel is 12 μm, and the resolution is 800 x 600. To obtain a 3D motion image with large viewing zone and image size, we need to parallelize the unit. The unit can be readily scaled up, since the units consisting of the chip and the display are easily set in parallel

Temporal phase processing with compression in interferometry

Kar Tien Ang, Tuck Wah Ng

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Interferometry is increasingly used in transient phenomena studies. Temporal fringe pattern analysis is ideal for this form of study but necessitates large data storage. Current compression schemes do not facilitate efficient data retrieval and may even result in important data loss. Here, we describe an encoding scheme that results in low crucial data loss and performs temporal fringe analysis at the same time. From the encoded data, intensity fringe patterns and phase maps can be retrieved with ease. The scheme is demonstrated here with simulated wavefront interferometry temporal fringe patterns albeit it portends usage in other forms of fringe-based techniques as well.

New initiatives in phase unwrapping in digital photoelasticity

P. L. Prashant, K. R. Madhu, K. Ramesh

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Phasemaps obtained by phase-shifting techniques contain ambiguous zones. To obtain total fringe order by phase unwrapping, the phasemap should be corrected for ambiguity. Each available ambiguity removal method can resolve ambiguity for only a class of problems. Appropriate selection of these algorithms and their combination for a specific case can give a better result. A comprehensive ambiguity removal methodology is demonstrated in this paper. Disturbance in the intensity pattern of the phase shifted images due to lines and marks on the models lead to noise in phasemaps. This in turn affects the ambiguity removal and unwrapping procedures. A methodology has also been proposed to remove the lines and marks from the phase-shifted images.

Simplified Carre method for phase extraction

Lujie J. Chen, Chenggen Quan, Cho Jui Tay

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A phase-shifting algorithm for speckle patterns with a constant but unknown phase shift is proposed. The algorithm is based on the well known Carre's method. Prior to applying the phase-shifting algorithm a speckle pattern background is removed. In this process, manual intervention is minimal and high computational speed is achieved. In addition, high-frequency phase signal would not be filtered out in the noise reduction process as is the case in band-pass filtering technique. Its validity is tested on the deformation measurement using digital speckle shearing interferometry (DSSI).

Spatially sampling effect on fringe phase-shifting detection

Bing Zhao, Huimin Xie, Anand Asundi

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One effect of spatially sampling of an image is averaging the image intensity over each pixel. In this paper, this spatial average effect on phase-shifting detection of fringe pattern is investigated. The phase error due to pixel size and sampling rate is formulated. It is shown that lower sampling frequency, for example, 1/4 fringes per pixel for 1-D fringe signal, 1/6 fringes per pixel for 2-D signal, will cause larger measurement error.

Mobile shearography

Michael Kalms, Werner Jueptner

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By reason of their sensitivity, accuracy and non-contact as well as non-destructive characteristics, modern optical methods such as digital speckle shearography have found an increasing interest for NDT applications on the factory floor. With new carbon filter technologies and other lightweight constructions in aircraft and automotive manufacturing, adapted examination designs and especially developed testing methods are necessary. Shearography as a coherent optical method has been widely accepted as an useful NDT tool. It is a robust interferometric method to determine locations with maximum stress on various material structures. However, limitations of this technique can be found in the bulky equipment components, the interpretation of the complex sherographic result images and at the work with non-cooperative surfaces (dark absorber, bright shining reflectors). We report a mobile shearography system that was especially designed for investigations at aircraft and automotive constructions.

Non-contact damage monitoring by laser AE technique

M. Enoki, S. Nishinoiri

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AE method is a well-known technique for in-situ monitoring of fracture behavior by attaching piezoelectric transducer. However, conventional AE transducer cannot be used at elevated temperature or severe environment. Laser based ultrasonic (LBU) technique has been developed to characterize materials properties and detect flaws in materials. We developed the AE measurement system with laser interferometer to apply this technique to microfracture evaluation in various materials. AE during sintering of alumina ceramics and thermal spying of alumina powder on steel substrates were successfully measured by laser interferometers. The effect of processing parameters on AE behavior was clearly observed by analyzing AE waveforms. One of the most advantages of this laser AE technique is to estimate the temperature where microcracks are generated. These results could give a feed back to control processing conditions in order to avoid damage in materials. It was concluded that the laser AE method was very useful to detect microcracks in ceramics during fabrication.

Vibration analysis of gyro sensors by using ESPI technique

Seon-il Ham, Jae-huk Lee, Sang-duck Park

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Recently, micro gyroscope sensors are adopted in handy camcorders to compensate external shock or vibration such as hand shakes. In developing micro gyroscope sensors, vibration analysis is inevitable but not easy since the micro gyroscope sensors are too small. In this paper, non-contact full-field ESPI (Electronic speckle pattern interferometry) measurement technique is introduced in vibration analysis of micro gyroscope sensors. Resonant frequencies and ODS(Operational deflection shapes) are measured and compared to each other. It is found that structure and PCB molding mass is one of most sensitive factors in designing micro gyroscope sensors.

A novel fiber optic sensor for the measurement of pH of blood based on colorimetry

A. L. Chaudhari, D. D. Patil, Arvind D. Shaligram

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Fiber optic sensors designed to the date are largely based on monitoring the absorption change of several immobilized indicators or change in fluorescence of fluorometric indicators. The present paper reports a new type of fiber optic sensor for the measurement of blood pH based on Colorimetric principle. The sensor consists of two multimode step index fibers, mirror as reflector and blood serum with universal indicator as medium. LED is used as source and photodiode as detector. The intensity of color produced due to addition of indicator to blood serum depends upon hydrogen ion concentration. The output intensity from receiving fiber is measured as a function of pH of blood. The developed sensor is calibrated against the standard pH meter. The design, construction and calibration details are presented in paper.

Bar code identification of digital levels

Jinhui Li, Liqing Geng

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This paper introduced the algorithm of bar code identification of digital level. In the digital level system, the original gauge rod is substituted by bar code rod. The CCD-sensor is used to substitute the eyes of people. The automatic measuring is realized by identifying the bar code on the rod using image process, code principle and the geometry optics technology. The data processing algorithm is achieved purposively after analyzing the data and waveform of CCD output signal. At first, the noise is attenuated with the filter algorithm and signal noise ratio is increased. Then the bar code information from bar image of the gauge is gotten with the speedy edge detection algorithm based on exponent, and the load of calculation is decreased. According to the principle of photoelectric transform of CCD, identify the corresponding bar code and the altitude of the point was calculated. The experiment results indicate that the algorithm of bar code identification is feasible.

Improvement of elliptically polarized white light technique for photoviscoelasticity

Akihiro Yokota, Kenichi Sakaue, Masahisa Takashi

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Viscoelastic materials such as rubbers and plastics are widely used not only in industrial fields but in daily life. The mechanical properties of the materials are remarkably dependent on time and temperature. Photoviscoelastic technique has been used for stress field measurement in the kind of material. However, the conventional techniques are not suitable to measure fringe order and the principal direction of birefringence simultaneously. Yoneyama et al proposed an elliptically polarized white light technique which can measure fringe order and the principal direction of birefringence simultaneously with a single exposure. However, the technique involves still three severe problems. First, the accuracy in determination of the principal direction of birefringence is severely influenced not only by noise but by the accuracy of fringe order determination, because the principal direction of birefringence is determined by utilizing the attenuation of light intensity and the fringe order. Second, it is difficult to determine fringe order automatically and accurately. And the third, this technique needs long time to manipulate images. In this paper, the authors describe how to improve the technique and to solve the problems. In this situation, the polarization angle for the largest attenuation in light intensity is calculated and examined to obtain good results. Also, an algorithm for the determination of fringe order is developed. As the results, the angle for the highest attenuation is obtained as 45 degrees, and the fringe order is successfully determined by applying a window field reference technique.

Measurements of the principal axis and phase retardation using a new circular polariscope and the Senarmont setup

Jing-Fung Lin, Yu-Lung Lo, Sen-Yung Lee, et al.

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Measurements of the principal axis and phase retardation using a new circular polariscope and the Senarmont setup with electro-optic modulation is presented. In the first step of measurements, we use the electro-optic modulated circular heterodyne interferometer and the phase-lock technique to precisely measure the principal axis angle. After removing the first quarter-wave plate in the first setup, a Senarmont setup is designed to determine the phase retardation also using the phase-lock technique. The simple phase extraction algorithm for the principal axis angle and the phase retardation measurement is presented. The average absolute errors of the principal axis angle and the phase retardation of the λ/8-wave plate are determined to be only 0.468⁰ and 0.23%.

3-D stress analysis using the Jones matrix image Fourier polarimetry technique

Souichirou Katsumata, Kenichi Sakaue, Masahisa Takashi

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Although various kinds of optical techniques for the analysis of 3-D stress fields have been proposed up to date, they are still far from being satisfied. The integrated photoelastic technique is widely adopted in the analysis of 3-D stress field over the world including the Jones matrix image Fourier polarimetry Technique in this study. In the previous research, it has been confirmed that three optical parameters which has been related to stress components, can be measured in high accuracy, and the separation of stress components by the Simplex method was examined. Moreover, the authors successfully separated and determined the optical parameters in each laminated thin disk loaded in different directions each other standing on the equivalence theorem in polarimetry. In this paper, the authors evaluate laminated layer 2-D stress fields in a set of 3 sliced disks and compare them with an actual 3-D stress field under an equivalent loading condition. Namely, disks made of quartz 2mm and 3mm in thickness were loaded at several locations and directions to realize 3-D stress field. A 3-D stress field on laminated layers model was loaded in the similar condition. Since the phase difference and azimuth angle are measured in high accuracy, the technique is expected to be an effective technique for the analysis of actual 3-D stress field.

Calculation of Fourier holographic storage density

Zhongyu Chen, N. K. Bao, Po S. Chung

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This paper describes an optical system model of Fourier holographic recording. Its numerical calculation is based on the Fraunhofer diffraction theory. According to Fourier optics principle, the spatial fundamental frequency will have a minimum value. It will limit the increase of the storage density. This paper shows the results of the simulative storage and the digital storage. When the digital storage used on the film optical disk system (for example, photopolymer medium), the storage density of Fourier hologram can be evaluated by bit error rate (BER) and signal noise rate (SNR).

3D information acquired by the correlation of projected fringe patterns

Xiaoyuan He, Ming Jiang

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This paper presents a new method that acquires the height information automatically in projected fringe patterns for 3D profile. The principle is to project the gratings on reference plane and object surface to be measured respectively, and then record them by a CCD camera. Through comparing these two images with digital image correlation method, the offset of the fringe that modulated by the object surface can be obtained. Further the 3D profile or deformation will be inferred. In this new method, an important characteristic is that the principle and processing are only need one fringe pattern on object surface, so it can be well used in real time and dynamic measurement. Another advantage is no need of the complex unwrapping process. At last, this paper shows the experiment results and compared them with phase shifting method.

A new positioning and loading system for the study of the mechanical behavior of small and micro components

Xide Li, Ye Gu

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A new positioning and loading system has been designed and implemented to provide spatial positioning and loading in small and micro components test. The system consists of a micro-loading unit and a spatial positioning stage. The micro-loading unit includes two parts: loading cell and micro lo ad measuring part. The spatial positioning stage is a three-dimensional moving platform driven by the piezoelectric ceramics. Typical parameters of the system are 8mm long in shifting range of the positioning stage, sub-micrometer resolution in spatial positioning, and from several Newtons to several tens micro Newtons for loading. The elaboration on the system is presented in the paper and an experiment is performed to demonstrate its performance.f

Thermo-mechanical data bit formation of small-sized microcantilever probe tip array

Nyok Boon Chong, Jiaping Yang, Jianqiang Mou, et al.

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Unlike the large array of microcantilever design which covers entire recording media area adopted by majority researchers in probe storage, we have designed and fabricated two types of small-sized array of (20X1 and 30X1) microcantilevers, which is driven by an electromagnetic translational actuator to targeted media area, for carrying out recording functions on a relative larger recording media area. This paper presents the prototype of a small-sized microcantilever probe tip array for use in the promising high-density thermo-mechanical data storage technology. Characterization of the microcantilever probe tip such as current versus voltage measurement, thermal time constant measurement and heat emission phenomenon at heater platform were investigated. Preliminary hole indentation or data bit formation results by utilizing the fabricated small-sized microcantilever probe tip array were demonstrated on poly methyl methacrylate (PMMA) recording media.

New radiation sources from channeling in micro- and nano-structures

S. Bellucci

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We review recent developments in probing the capability of the channeling technique to produce micrometric or nanometric sized beams using micro-structured crystals or nanotubes. A particle bema of very small cross-section can be used in many accelerator applications including biological and medical ones. The channeled beam can be deflected and thus well separated in angle and space from the primary and scattered particles. Monte Carlo simulation is done to evaluate the characteristics of a channeled microbeam. Emittances down to 0.1-0.001 nanometer radian, and flux up to 1 million particles per square micron per second, can be achieved for protons and ions. We review also the possibility for experiments with high-energy particles channeled in crystalline undulator, a novel compact source of radiation. The first experiment on photon emission in crystal undulator has been started at LNF with 800 MeV positrons aiming to produce 50 keV undulator photons.

Fabrication and characterization of piezoelectric cantilever for micro transducers

Jin Xie, Min Hu, Shih-Fu Ling, et al.

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A modified sol-gel process for lead zirconate titanate (PZT) thin film deposition has been presented to overcome the problems of film cracking, short-circuiting and diffusion of PZT to substrate. In the modified sol-gel process, we pattern the pyrolyzed PZT thin film by wet etching before every treatment of post-annealing for crystallization. The modification brings two advantages: film cracking is eliminated due to the reduction of internal stress; PZT diffusion to substrate is avoided due to removing PZT film from the areas without Pt buffer layer before high-temperature post-annealing treatment. The modified sol-gel process is applied to fabrication of piezoelectric cantilever, which includes sputtering and patterning top and bottom electrodes, depositing PZT layer by the modified sol-gel process and releasing cantilever structure by a double side deep reaction ion etching process. After the fabrication, performances of PZT thin film such as hysteresis loop upon polarization and X-ray diffraction pattern are evaluated. Finally, resonant frequency is measured for the fabricated piezoelectric cantilever to verify its self-exited capability for future applications as micro sensors or actuators. These experimental results indicate that the modified sol-gel process for PZT deposition can greatly improve quality and yield rate of the fabrication of piezoelectric devices without causing any adverse effect.

Size effect on quasi-brittle fracture

Xiaozhi Hu, Kai Duan

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Size effect on fracture properties of MEMS and traditional materials is determined by the relative size of a testing specimen versus the material microstructure. In this study, size effect on quasi-brittle fracture is related to the length ratio determined by the fracture process zone (FPZ) and distance of a crack-tip to its nearest specimen boundary. It is shown that the tensile strength criterion applies if the specimen boundary is close to the crack-tip, and the fracture toughness criterion applies if the specimen boundary is away from the crack-tip. The specimen boundary influence reflects the dominant size effect mechanism, i.e. the interaction of the crack-tip FPZ with the specimen boundary. The boundary effect model proposed in the study is compared with the common size effect model emphasising exclusively the influence of specimen size, and the major difference is discussed.

Mechanical properties of lead-free solder alloys evaluated by miniature size specimen

Yoshiharu Kariya, Tsuyoshi Asai, Tadatomo Suga

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Tensile and fatigue testing using miniature specimen was proposed to compare the mechanical behaviors of Sn-3.0%Ag-0.5%Cu alloy in small and large volumes respectively. It was found that the tensile strength data of the miniature specimen was not similar with clear inferiority to that of the large volume under all test conditions. The differences in their mechanical properties are attributed to dendrite morphology and intermetallic compounds size. Thus, the mechanical behavior and the solidification microstructure strongly depend on specimen volume, which suggests that small size be used to measure mechanical behaviors of solder alloys.

Deformation field measurement on micro and nanotechnology components utilizing SFM and FIB equipment

Dietmar Vogel, Juergen Keller, Astrid Gollhardt, et al.

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The authors present a digital image correlation (DIC) tool, which allows to measure deformation fields on micro and nano system components under thermal and/or mechanical impact. Load state micrographs are used to extract displacement and strain fields. An earlier developed DIC concept for that purpose has been extended from SEM to AFM and FIB imaging. As a consequence ultimate measurement resolution can be achieved by AFM imaging. The advantages of the new focused ion beam (FIB) approach occur in the incorporation of specimen preparation (ion milling, ion beam surface polishing and DIC patterning), specimen loading by ion milling and DIC deformation measurement in a single equipment. The application of DIC techniques on AFM base is illustrated for the investigation of thermal deformations on microsystem structures as well as for the evaluation of microcracks from crack opening displacements. Some first results for residual stress release by ion milling with subsequent deformation field measurement are reported, too.

Vibration measurements on smart electronic structures by means of laser techniques

Norbert Ruemmler, Rene Schnitzer, Bernd Michel, et al.

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Knowledge of dynamical load behaviour is a basic requirement for life time optimised design of different products. This fact is especially relevant for smart electronic structures. Different non-contact working laser vibrometers (single-point and scanning) are used for vibration investigations and experimental modal analyses of such small structures. The results of this analyses show natural frequencies, vibration amplitudes and in case of scanning vibrometer also mode shapes. Based on this, structural modifications concerning a vibration optimisation can be derived. The measured results serve also as basis for numerical simulations and for FE-model validation.

Design methodology of microstructures for enhanced mechanical reliability

Olaf Wittler, Hans Walter, Dietmar Vogel, et al.

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The achievement of reliability is a major task during the design process of microsystems (i.e. MEMS: mechanical-electrical microsystems). In this respect CAD (computer aided design) simulation methods play a major role in the dimensioning of mechanical structures. It can be observed that a pure CAD approach becomes difficult because of the complexity of these systems, which originates from the large variety of integrated materials and thus a diversity of the resulting failure mechanisms. Therefore strategies dealing with these uncertainties in reliability estimates need to be incorporated in the design process. The approach presented in this paper is based on the application of simulation and advanced deformation measurement methods named microDAC (micro deformation analysis by means of grey scale correlation) and nanoDAC. It is exemplified on different detail levels of the reliability assessment, with an emphasis on fracture. The first stage consists of a parametric simulation approach, which helps to develop design guidelines for the geometry. For a more absolute quantitative analysis and for material selection in a new design the mechanical properties need to be specified and evaluated with respect to reliability. Besides, the described systematics of reliability assessment needs a profound knowledge of the failure behavior, which is analyzed by the application of microDAC/nanoDAC techniques. In the prescribed way, it becomes possible to tackle mechanical reliability problems in early design phases.

Optical full-field technique for measuring deformation on micromechanical components

Xide Li, Cheng Wei

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The rapid development of microelectromechanical system (MEMS), thin-film and material research in mechanical behaviors has provided new impetus to handle high-precision, full-filed and real-time deformation measurements. Optical methods are very useful in non-contact and full-field measurements of the deformation of an object. However, with the decrease of the dimension of the tested components, the macroscopically testing method and system in existence are not adequate to accurate measurement of the microcomponents. Furthermore, the effect of the small size of view field in the measurement makes the interferometric system hardly producing clear and stable fringe patterns, and then interpretation of the measurement results very difficult. In this paper, a Linnik microinterferometric system has been constructed to measure the full-field deformation of microcomponents. And meanwhile, the phase shifting and temporal speckle pattern interferometry are also introduced to implement the static and dynamic deformation measurements. With the interfermetric system, the characteristic size of the microcomponents can be from sub-millimeters to sever micrometers.

Measurement of blood velocity using laser Doppler method for the designing module

Guo-Liang Chen, Jen-Ai Lee, Tung-Wu Lu, et al.

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We built the Dual Beam Mode of the LDA (Laser Doppler Anemometry) frame, set the photodetector at the same side with light source which collect the scattering light of blood cell. It's proper to reduce LDA optical path and convenient for our designing module. The concentration of chicken blood in this study is about 1% and we measured the relations actually between flood velocity and the angle of beams cross on particles, temperature, and the diameter of aqueduct. We found better results while the cross angle was less than 38.8 degree, diameter of aqueduct was 6 mm, and temperature of blood was set to 36 . These parameters can also provide important basis for the LDA module kit that we are designing.

Reactive magnetron sputtering of antinomy tin oxide films on glass substrate

Chien-Cheng Liu, Wei-Chi Huang, Fei-Lung Lu, et al.

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Antinomy tin oxide (ATO) films have been widely used as a transparent conducting thin film material for application in various fields such as solar cells, opto-electronic devices, and liquid crystal displays. It has a high carrier concentration, low electrical resistivity and high transmission in the visible light range. ATO films were deposited on corning glass 1737F by low temperature reactive magnetron sputtering. The structural and surface properties of the films were determined with scanning electron microscopy, transmission electron microscopy, X-ray diffraction and atomic force microscopy. The effects of annealing temperature and atmosphere on the composition, microstructure, surface morphology, conductivity and optical properties of ATO films were investigated.

Methodology to study the effect of moisture on refractive index of optical adhesive

Shimin Lim, Anish Priyadarshi, Ranjan Rajoo, et al.

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Optical adhesives (index-matching adhesive) serve a means of structural attachment as well as provide an optical path between connecting elements. Optical properties (such as refractive index and birefringence) of these polymeric adhesives are sensitive to environmental factors, which affects optical device performance. Thus this work attempts to develop a methodology to evaluate the impact of moisture on the refractive index of an index-matching adhesive. The return loss method was employed for monitoring the moisture dependence of refractive index of an acylate-based optical adhesive. The test was performed at a wavelength of 1.55 mm. At fixed time intervals, the return loss of the sample were measured with an optical time-domain reflectometer (OTDR) during moisture desorption. The amount of moisture present in the optical adhesive at different time was calculated with the help of desorption data. Thus, a correlation between time, the amount of moisture present and refractive index was obtained. At a constant temperature of 120°C, the refractive index of the adhesive decreases as moisture content increases. However, this decrease was more drastic for small amount of moisture absorbed at -1 x 10^-4 (% moisture content)^-1 compared to -7 x 10^-6 (% moisture content)^-1 when moisture absorption exceeds 10% of the dry sample weight.

Development of an optical interferometer for micro-components inspection

Shi Hua Wang, Chenggen Quan, Cho Jui Tay, et al.

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The application of an optical interferometric system using a Mirau objective to the measurement of the surface profile of micro-components is described. The proposed system produces a uniform monochromatic illumination over the test area and introduces an interference fringe pattern localized near the test surface. Both the interference fringes and the 2D images of the test surface can be focused by an infinity microscope system consisting of a Mirau objective and a tube lens. A piezoelectric transducer (PZT) attached to the Mirau objective can move precisely along the optical axis of the objective. This enables the implementation of phase-shifting interferometry without changing the focus of a CCD sensor as the combination of the Mirau objective and the tube lens provides a depth of focus which is deep in comparison to the phase-shifting step. Experimental results from surface profilometry of the protrutsion/undercut of a polished fiber within an optical connector and of the curved surface of a micro-mirror demonstrate that features in the order of nanometers are measurable. Measurements on standard blocks also show that the accuracy of the proposed system is comparable to an existing commercial white light interferometer and a stylus profilometer.

Optimized SU-8 UV-lithographical process for a Ka-band filter fabrication

Peng Jin, Kyle Jiang, Jiubin Tan, et al.

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Rapidly expanding of millimeter wave communication has made Ka-band filter fabrication to gain more and more attention from the researcher. Described in this paper is a high quality UV-lithographic process for making high aspect ratio parts of a coaxial Ka band dual mode filter using an ultra-thick SU-8 photoresist layer, which has a potential application in LMDS systems. Due to the strict requirements on the perpendicular geometry of the filter parts, the microfabrication research work has been concentrated on modifying the SU-8 UV-lithographical process to improve the vertical angle of sidewalls and high aspect ratio. Based on the study of the photoactive property of ultra-thick SU-8 layers, an optimized prebake time has been found for obtaining the minimum UV absorption by SU-8. The optimization principle has been tested using a series of experiments of UV-lithography on different prebake times, and proved effective. An optimized SU-8 UV-lithographical process has been developed for the fabrication of thick layer filter structures. During the test fabrication, microstructures with aspect ratio as high as 40 have been produced in 1000 mm ultra-thick SU-8 layers using the standard UV-lithography equipment. The sidewall angles are controlled between 85~90 degrees. The high quality SU-8 structures will then be used as positive moulds for producing copper structures using electroforming process. The microfabication process presented in this paper suits the proposed filter well. It also reveals a good potential for volume production of high quality RF devices.

Design of micro robots with microgrippers for manipulation of micro-parts

Siew Kuan Nah, Zhaowei Zhong

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In this paper, a design of a micro-robot system with microgrippers for the purpose of manipulation of micro-parts is proposed. The methodology includes the integration of micro-actuators for micromanipulation tasks of requirements that will involve small size, low weight, high resolution, high linearity and high accuracy. The combination of micro-assembly stages and microgrippers with CNC technology will allow the fixing of a microgripper onto a CNC robot. In order to minimize the size of the microgripper, the structure is fabricated as a monolithic piece with elastic flexure hinges. The microgripper mechanism consists of flexure notch hinges and parallel movement of the gripping arms. These elements transmit the gripping force and gripping motion and realize a good mechanical advantage ratio. The compliant mechanism system of the microgrippers is analyzed using a theoretical pseudo-rigid-body model and flexural hinge equation to investigate and predict the displacement and force relationships between the inputs and the outputs. In addition, a finite element study is done on the mechanism model to compare with the theoretical results.

Fiber Bragg grating parameter estimation by using two thermally modulated intensity spectra for arbitrary distributed strain sensing

Hsu-Chih Cheng, Yu-Lung Lo

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In this paper we describe the use of a genetic algorithm and two thermally-modulated fiber Bragg grating's (FBG's) reflection intensity spectra for inversely extracting complete physical parameters. The fiber Bragg grating’s complete parameters included the grating period, grating position, grating length, chirped direction, and refractive index modulation. In this study, a uniform and chirped fiber Bragg gratings are synthesized successfully in the numerical analysis. Also, the experimental results show that the complete parameter synthesis in grating period, grating length, refractive index modulation and various grating positions from a 10 mm length uniform FBG have been recovered accurately. After finding those physical parameters, the arbitrary distributed strain sensing technique is easy to accomplish by using two fiber Bragg gratings sensing techniques.

Development of flexible force sensors using fiber Bragg grating for tactile sensing and its evaluation

Jin Seok Heo, Jung Ju Lee

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In this paper the study of development of flexible force sensor using the fiber Bragg grating is presented. This force sensor consists of a Bragg grating optical fiber and flexible silicone rubber. This sensor does not have special structure to maximize the deflection or elongation, but have good sensitivity and very flexible characteristics. In addition, this sensor has the immunity to the electro magnetic field and can be multiplexed easily, which is inherited from the characteristics of fiber Bragg grating optical fiber sensor. In the future, this sensor can be used for the tactile sensor system minimizing the sensor size with suitable fabrication method.

Simultaneous measurement of vibration and temperature with fiber Bragg grating

Nobuaki Takahashi, Hiroki Yokosuka, Satoshi Tanaka

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Simultaneous measurement of mechanical vibration and temperature are performed using a fiber Bragg grating (FBG) as a sensing element. The principle of the FBG vibration sensing is based on the fact that when an FBG is under influence of vibration, it modulates the intensity of the reflected and transmitted light if the bandwidth of the incident light is narrow and its wavelength is tuned to the slope of the FBG transmittance curve. DC component of the photocurrent produced in a photodiode by the sensor output light corresponds to the operation point of the sensor. By feeding back a part of the sensor output to the laser light source to shift the oscillation wavelength of the laser, the DC component is kept constant and the sensitivity of the vibration sensor is stabilized when the temperature varies in the environment. Its fluctuation is measured to be as small as 1 dB, though it is more than 58 dB without the stabilization. Since the oscillation wavelength has one-to-one correspondence to the environmental temperature, monitoring the laser temperature control voltage enables us to determine the temperature around the FBG sensing element.

Finite element modeling and simulation of fiber optical based load cell (FOLC) sensor

N. M. Shelke, Kiran Tamadaddi, P. B. Buchade, et al.

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Optical techniques have played an important role in telecommunication, industrial instrumentation and the sensors fields. In telecommunication field, the fiber optic technology is now firmly established for voice and data transfer. Wider bandwidth, low attenuation and mechanical properties of the fiber, are among the major advantages of optical fiber systems, even in the presence of various extreme and hazardous environmental conditions. The applications of optical fibers in the field of sensors are well established. This paper reports on development, modeling and simulation of fiber optic load cell (FOLC) sensor. The sensor basically consists of a fiber optic micro-displacement sensor probe and a load sensing diaphragm which also acts as a reflector. A pan is used for keeping the weights, the load of which is transferred to the diaphragm by a pin. The geometrical information of developed sensor is translated into a 3-D model. The stresses and deformations generated in the diaphragm are calculated using finite element method. Results for loading conditions ranging from low (mg) to high (100s of kg) levels and diaphragm parameters like thickness, diameter, Young's modulus and tensile strength are obtained. The fiber optic micro displacement sensor then senses the resulting deformations. A Ray Tracing module is used to study the relation between received intensity and position of fiber probe. The simulation results match well with the experimental results. The sensor dimensional parameters, geometry and material parameters of the diaphragm are optimized and are reported in the paper. It is hoped that this non-contact Load Cell sensor will offer several benefits over the conventional strain gauge based load cells.

Laser characteristics and interferometric process and sensor applications

Otto Glatz

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Begin Fiber Bragg Gratings (FBGs) are basic elements in DWDM technology. They are produced by UV illumination. UV light sources have been steadily improved to meet the demands of FBG writing industry. We want to characterize some parameters of interest of a simple, line-narrowed excimer laser source, its improvements and contribution to interferometric non-proximity FBG writing. Parameters of interest to be discussed are the temporal and spatial coherence length, the beam stability and spectrum control of produced FBG. With a temporal coherence length of ~ 5 mm it is possible to utilize cost efficient excimer laser technology for the interferometric non-proximity FBG writing process. Correspondingly the line-narrowed Excimer laser can replace expensive frequency doubled Argon ion lasers driving interferometric FBG writing set-ups in production and R & D. Beyond it FBGs for sensor applications play an important role. They have the potential for the measurement of strain / deformation and temperature with applications including monitoring of highways, bridges, aerospace components and chemical and biological sensors. We want to discuss the requirements for excimer lasers for this application: The spatial coherence length, beam profile, pointing and energy stability.

Experimental investigation of vibration behaviors of bonded structures

Joing-Shiun Hsu, Wei-Chung Wang

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In this paper, the vibration behaviors of bonded structures were experimentally investigated by incorporating amplitude fluctuation electronic speckle pattern interferometry (AF-ESPI) and modal testing technique. A special casting procedure was employed to manufacture the naturally bonded structures to avoid the influence resulted from the adhesive. Vibration characteristics of bonded structures with different geometrical combinations of constituent adherends and the influence of presence of an interfacial crack were clarified from the distinguished vibration behaviors.

Measurement of transparent coating thickness by the use of white light interferometry

Mingzhou Li, Chenggen Quan, Cho Jui Tay, et al.

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White light interferometry is widely used to measure surface profiles in order to overcome the phase ambiguity problem, which is inevitable in the monochromatic light interferometry. In this paper, we describe a white light interferometric technique to determine the thickness of transparent coating on a silicon substrate. The layer thickness is obtained by a straightforward subtraction of two surfaces in the coated layer. The surface information is extracted by the white light interferometric surface profiler developed in the proposed system. In the surface extraction, a digital filtering technique based on fast Fourier transform (FFT) is used to retrieve the envelopes of the interferograms, and then differential operation is implemented to determine the peaks of the envelopes. Experimental work conducted on a flat mirror surface demonstrates the feasibility of the proposed method with a measuring accuracy in the order of nanometers. Results also show that by the use of the proposed method the coating thickness in the order of micrometers can be extracted satisfactorily without phase ambiguity problem.

Displacement measurement by phase-shifting digital holography with convolution technique

Hirotaka Otaki, Kenichi Sakaue, Masahisa Takashi

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Phase-shifting digital holography enables the measurement of surface displacements on an object body. In the present study, the convolution integral technique is adopted to reconstruct holographic images. The most important feature of the technique is that spatial resolution is independent on the distance of image reconstruction, and is suitable for displacement measurement of a body with depth. Also, the resolution obtained by the technique is expected to be higher than that obtained by the conventional reconstruction technique. The displacement fields are obtained using phase difference data before and after deformation. In this paper, experimental results of the case of a cantilever beam show good agreement with theory, also the algorithm developed for the convolution integral technique is shown to be effective and useful to the image reconstruction.

A combined fiber optic digital shearography and holography system for defect inspection in Si-wafers

Ganesha Udupa, Jun Wang, Bryan Kok Ann Ngoi

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The present work relates to surface and/or subsurface defects inspection system for semiconductor industries and particularly to an inspection system for a defect such as swirl defects and particles in an unpolished silicon wafer before the wafer fabrication process by a combined fiber optic digital shearography and holography technique. The dual purpose camera described in this paper gives the possibility of using either digital shearography or holography (DSPI) techniques depending on application needs. The sub-surface defects in a wafer normally create strain concentrations subjected to loading (stressing) which are translated into anomalies in the fringe pattern. A real time technique with the use of Lab view Express 7 software is developed to detect defects in Si-wafer with the application of thermal oading as a stressing method. The results obtained by applying a real time fiber optic shearography technique are described in this paper. The method described here relates specifically to semiconductor wafers, but may be generalized to any other samples.

Strain analysis on an Al-foam structure with ESPI

Ronny Wegner, Andreas Ettemeyer, Raphael Schoen, et al.

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The motivation of the study was the demand for light weight designs in automotive techniques, as well as the enhancement of the stiffness of convertible bodies and an improvement of the FEA elements and methods. Hence follow an acceleration of component design.

Electronic speckle pattern interferometry applied to the displacement measurement of sandwich plates with double fully potted inserts

Song-Jeng Huang, Hwa-Long Lin

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The construction of electronic speckle pattern interferometer (ESPI) applied to sandwich plates with double inserts has been presented in this paper. Proposed ESPI has advantages of full-field and non-destructive testing that can measures microscopic out-of-plane displacement in the elastic region and without wasting specimen. For validation purpose, the finite element method (FEM) analysis was conducted. By comparing the results of ESPI and FEM displacement at the center of the specimen that a convincing agreement is revealed, thus showing the effect of spatial interval of the double inserts on the displacement of sandwich plates under loading.

Near infrared spectroscopy based brain-computer interface

Sitaram Ranganatha, Yoko Hoshi M.D., Cuntai Guan

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A brain-computer interface (BCI) provides users with an alternative output channel other than the normal output path of the brain. BCI is being given much attention recently as an alternate mode of communication and control for the disabled, such as patients suffering from Amyotrophic Lateral Sclerosis (ALS) or "locked-in". BCI may also find applications in military, education and entertainment. Most of the existing BCI systems which rely on the brain's electrical activity use scalp EEG signals. The scalp EEG is an inherently noisy and non-linear signal. The signal is detrimentally affected by various artifacts such as the EOG, EMG, ECG and so forth. EEG is cumbersome to use in practice, because of the need for applying conductive gel, and the need for the subject to be immobile. There is an urgent need for a more accessible interface that uses a more direct measure of cognitive function to control an output device. The optical response of Near Infrared Spectroscopy (NIRS) denoting brain activation can be used as an alternative to electrical signals, with the intention of developing a more practical and user-friendly BCI. In this paper, a new method of brain-computer interface (BCI) based on NIRS is proposed. Preliminary results of our experiments towards developing this system are reported.

Noninvasive measurement of postocclusive parameters in human forearm blood by near infrared spectroscopy

K. Prahlad Rao, S. Radhakrishnan, M. Ramasubba Reddy

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Near infrared (NIR) light in the wavelength range from 700 to 900 nm can pass through skin, bone and other tissues relatively easily. As a result, NIR techniques allow a noninvasive assessment of hemoglobin saturation for a wide range of applications, such as in the study of muscle metabolism, the diagnosis of vascular disorders, brain imaging, and breast cancer detection. Near infrared Spectroscopy (NIRS) is an effective tool to measure the hemoglobin concentration in the tissues, which can discriminate optically the oxy- and deoxy- hemoglobin species because of their different near-infrared absorption spectra. We have developed an NIRS probe consisting of a laser diode of 830 nm wavelength and a PIN photodiode in reflectance mode. We have selected a set of healthy volunteers (mean age 30, range 26-40 years) for the study. The probe is placed on forearm of each subject and the backscattered light intensity is measured by occluding the blood flow at 210, 110 and 85 mmHg pressures. Recovery time, peak time and time after 50% release of the cuff pressure are determined from the optical densities during the post occlusive state of forearm. These parameters are useful for determining the transient increase in blood flow after the release of blood occlusion. Clinically, the functional aspects of blood flow in the limbs could be evaluated noninvasively by NIRS.

Use of fluorescence lifetime imaging (FLIM) for latent fingerprints detection

Peng Wang, Zhi Xia Chao, Leong Keey Seah, et al.

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Fluorescence lifetime imaging (FLIM) in frequency domain enables the mapping of the spatial distribution of fluorescence lifetimes of a specimen. FLIM can provide unique information about fluorophores and hence is widely used in biology and for medical diagnostics. In this paper, a theoretical analysis for the fluorescence lifetime determination of latent fingerprint samples is described, which is followed by the feasibility study of using FLIM in frequency domain for latent fingerprints detection. Experiments are carried out with fingerprint on green paper substrate and postcard substrate treated with certain fluorescent powder. The total phase lag and demodulation factor are calculated to determine the lifetimes pixel by pixel. The resulting fluorescence lifetime image of fingerprint revealed an improvement in the contrast, and was able to detect the latent fingerprint clearly.

Marking-dots digital image correlation and application to studies of spinal biomechanics

Jinlong Chen, Cuiru Sun, Yuwen Qin, et al.

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A method of marking-dots digital image correlation is developed to measure the biomechanics behavior of cattle spine. In the system, a video camera and personal computer are used to acquire digitized images of a random speckle pattern on the surface of a marking-dot before and after deformation. The method of making-dots digital image correlation can immediately measure the transformation by tracking the gray value pattern in small local neighborhoods commonly referred to as subsets. In the experiment, a specimen was selected from the cattle's spine that was covered with some muscles and tissues. It is apparent that the covering muscles and tissues cannot be treated as the information carrier, for they must be kept active and moist curing by the physiological brine in the course of the experiment. In order to solve the problem, the marking-dots were fixed into the vertebrae, and the front surface of a marking-dot was coated with a thin layer of white paint and splattered with black spot so as to create a random black-on-white speckle pattern. Experimental results have shown that the marking-dots digital image correlation method can be applied to the measurement of the biomechanical behavior of cattle spine, and offer an effective measurement tool to research the range of motion of the adjacent segment in spine under intervertebral fusion.

Image enhancement for radiography inspection

Xin Wang, Brian Stephen Wong, Tui Chen Guan

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The x-ray radiographic testing method is often used for detecting defects as a non-destructive testing method (NDT). In many cases, NDT is used for aircraft components, welds, etc. Hence, the backgrounds are always more complex than a piece of steel. Radiographic images are low contrast, dark and high noise image. It is difficult to detect defects directly. So, image enhancement is a significant part of automated radiography inspection system. Histogram equalization and median filter are the most frequently used techniques to enhance the radiographic images. In this paper, the adaptive histogram equalization and contrast limited histogram equalization are compared with histogram equalization. The adaptive wavelet thresholding is compared with median filter. Through comparative analysis, the contrast limited histogram equalization and adaptive wavelet thresholding can enhance perception of defects better.

Fatigue properties of rolled stainless steels

Priyo Tri Iswanto, Shin-ichi Nishida, Nobusuke Hattori, et al.

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In this present study, rotating bending fatigue tests and compressive tensile fatigue tests had been performed on notched martensitic stainless steel and austenitic stainless steel specimens, respectively. Fatigue limit tests were done on notched non-deformed and notched deformed specimens in order to evaluate the effect of plastic deformation due to roller-working on fatigue behavior of notched deformed specimens. The result showed that according to increase of deformation value on surface layer of martensitic stainless steel specimens from 0, 0.5 and 1.0 mm, the fatigue limit of those specimens also increase to 485, 730 and 800 MPa, respectively. In case of austenitic stainless steel specimen, the fatigue limit of 0, 0.5 and 1.0 mm deformed specimens are 260, 470 and 500 MPa, respectively Fatigue limit of rolled specimens does not linearly increase with increase in plastic deformation value. Hardness number improvement and notch root residual stress are the most responsible in fatigue strength improvement of the rolled specimens.

Industrial applications of shearography for inspection of aircraft components

Rene Krupka, Thomas Walz, Andreas Ettemeyer

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Shearography has been validated as fast and reliable inspection technique for aerospace components. Following several years phase of evaluation of the technique, meanwhile, shearography has entered the industrial production inspection. The applications basically range from serial inspection in the production line to field inspection in assembly and to applications in the maintenance and repair area. In all applications, the main advantages of shearography, as very fast and full field insection and high sensitivity even on very complex on composite materials have led to the decision for laser shearography as inspection tool. In this paper, we present some highlights of industrial shearography inspection. One of the first industrial installations of laser shearography in Europe was a fully automatic inspection system for helicopter rotorblades. Complete rotor blades are inspected within 10 minutes on delaminations and debondingg in the composite structure. In case of more complex components, robotic manipulation of the shearography camera has proven to be the optimal solution. An industry 6-axis robot give utmost flexibility to position the camera in any angle and distance. Automatic defect marking systems have also been introduced to indicate the exact position of the defect directly on the inspected component. Other applications are shearography inspection systems for abradable seals in jet engines and portable shearography inspection systems for maintenance and repair inspection in the field. In this paper, recent installations of automatice inspection systems in aerospace industries are presented.

Development of an automated ultrasonic testing system

Jiao Shuxiang, Brian Stephen Wong

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Non-Destructive Testing is necessary in areas where defects in structures emerge over time due to wear and tear and structural integrity is necessary to maintain its usability. However, manual testing results in many limitations: high training cost, long training procedure, and worse, the inconsistent test results. A prime objective of this project is to develop an automatic Non-Destructive testing system for a shaft of the wheel axle of a railway carriage. Various methods, such as the neural network, pattern recognition methods and knowledge-based system are used for the artificial intelligence problem. In this paper, a statistical pattern recognition approach, Classification Tree is applied. Before feature selection, a thorough study on the ultrasonic signals produced was carried out. Based on the analysis of the ultrasonic signals, three signal processing methods were developed to enhance the ultrasonic signals: Cross-Correlation, Zero-Phase filter and Averaging. The target of this step is to reduce the noise and make the signal character more distinguishable. Four features: 1. The Auto Regressive Model Coefficients. 2. Standard Deviation. 3. Pearson Correlation 4. Dispersion Uniformity Degree are selected. And then a Classification Tree is created and applied to recognize the peak positions and amplitudes. Searching local maximum is carried out before feature computing. This procedure reduces much computation time in the real-time testing. Based on this algorithm, a software package called SOFRA was developed to recognize the peaks, calibrate automatically and test a simulated shaft automatically. The automatic calibration procedure and the automatic shaft testing procedure are developed.

Residual stress analysis of welded joints by the variational eigenstrain approach

Alexander M. Korsunsky, Gabriel Regino, David Nowell

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We present the formulation for finding the distribution of eigenstrains, i.e. the sources of residual stress, from a set of measurements of residual elastic strain (e.g. by diffraction), or residual stress, or stress redistribution, or distortion. The variational formulation employed seeks to achieve the best agreement between the model prediction and some measured parameters in the sense of a minimum of a functional given by a sum over the entire set of measurements. The advantage of this approach lies in its flexibility: different sets of measurements and information about different components of the stress-strain state can be incorporated. We demonstrate the power of the technique by analysing experimental data for welds in thin sheet of a nickel superalloy aerospace material. Very good agreement can be achieved between the prediction and the measurement results without the necessity of using iterative solution. In practice complete characterisation of residual stress states is often very difficult, due to limitations of facility access, measurement time or specimen dimensions. Implications of the new technique for experimental analysis are all the more significant, since it allows the reconstruction of the entire stress state from incomplete sets of data.

Fatigue mechanism of elemental alloyed and nitrided ultra-low carbon steel sheets

Tuan Suhaimi Salleh, Shin-ichi Nishida, Nobusuke Hattori

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Ultra-low carbons steels, commonly known as interstitial free steels are widely used especially for automobile plates because of their excellent deep-draw ability and low deformation resistance has been studied. The influence of alloy elements and nitriding on fatigue properties of ultra-low carbon steel have been investigated using 4 kinds of materials of non-nitrided specimens and nitrided ones, respectively. For non-nitrided specimens, fatigue strength at 1x10⁷ cycles of material added with Niobium element is greater compared to the material added with Titanium element. In addition, the fatigue strength of nitrided specimens is generally higher than that of non-nitrided specimens. This is related to the hardness distribution of the specimens. In the case of the nitrided specimen, the maximum hardness is recorded at the surface and decreased gradually toward the center of the specimen. Accordingly, the fatigue limit and strength of the nitrided specimens are determined by internal properties of the materials due to the influence of nitriding processes to the hardness properties at the surface as well as internal layer. For non-nitrided and nitrided specimens, none of the microcracks are emanated at the curve root but from the inside of specimens and surface crack growth for non-nitrided specimens revealed irregularities. However, in the case of the nitrided specimens, it is difficult to observe the cracks from the surface as the microcrack initiated internally.

Novel calibration method for 3-D measurement system based on fringe projection

Mingyi Chen, Haitao He, Hongwei Guo

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A novel calibration method for fringe projection 3-D measurement system is presented. To get the data serving the calibration, a calibration gauge with white-black checker pattern is transferred to different positions with known depths. At each position, the phase values in the black squares are regarded as invalid data for their lower modulation, and the phase distribution of the whole calibration gauge is obtained by the least-square fitting to the phases in the white squares according to the theoretical distribution function. The phase-to-depth and pixel to lateral coordinate mapping relationship are simultaneously calibrated. The validityof the proposed method is demonstrated by experimental results.

Profile measurement of microwave antenna using close range photogrammetry

Naiguang Lu, Wenyi Deng, Yongqiang Wang, et al.

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A digital close range photogrammetric method for space deployable microwave antenna is presented. The planning of multi-camera stations, 3D data connection of images of different view field and the calibration of the cameras are discussed. The procedure of calibration has two steps: direct linear transformation and the bundle adjustment. The measurement error resulted from lens distortion can be corrected. The relative accuracy of 1 part in 1000 can be achieved using on site automatic calibration during measurement. The profile of the space deployable microwave antenna was obtained through the least squares fitting of the adjusted observations.

Ultrasonic field modeling for arbitrary non-contact transducer source

Xiaoming Jian, Steve Dixon, Rachel S. Edwards

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We present a model for transient ultrasonic wave generation by Electromagnetic Acoustical Transducers (EMATs). Analytical solutions are currently available only for few kinds of sources and our model combines these analytical solutions and numerical computation to predict the ultrasonic field generated by arbitrary sources. This model can be used to calculate bulk waves within samples as well as surface waves on sample surfaces with the advantages of explicit physical meaning and quick processing speed over pure numerical calculations such as the Finite Element Method (FEM). We use the model to explain how static and dynamic magnetic fields generate ultrasonic waves in a sample. We wish to characterize the EMAT source in detail in order to tailor sources for optimal configuration for specific NDE applications. A Michelson laser interferometer is used to measure out of plane surface displacement of sample, and results agree well with the modelling simulation. The modelling can be used for arbitrary source.

A fundamental study of an inspection method for thin-walled structures using lamb waves induced by chirp signals

Yoshihiro Mizutani, Satoshi Inokawa

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In this study, a new NDT-method is proposed for inspecting delaminations in the composite plates (1mm-thickness CFRP layer with 1mm-thickness aluminum liner) Lamb waves (plate waves) generated by chirp signals (250-1000 kHz, 4Vp-p) were used for the inspection. We first studied characteristics of excited signals from the pulser when the chirp signal is used as an input signals. The amplitude of the excited signal from the pulser is changed with frequency due to the resonant characteristics of the transducer, although, wide range of the frequency components can be generated by using chirp signals. Two transducers were mounted on the composite plate, and inspection was conducted by using lamb waves. The amplitude, velocity and scattering of lamb waves on damaged and sound zone were compared. When the transducer is on the delamination area, low frequency components of the lamb wave drastically attenuated and could easily detect the delaminations. While, when the delamination is between two transducers, characteristics of lamb waves are similar to those on the sound area and difficult to separate each other with reasonable accuracy. Further modification of experimental method is needed to accomplish new inspection method.

Ultrasonic weak bond evaluation in IC packaging

Xiaoming Jian, N. Guo, Steve Dixon

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Air gap such as disbond and crack can be successfully detected by ultrasonic testing. But imperfect interface evaluation is still a challenge. The challenge arises from the uncertainty of formation mechanism, boundary condition and acoustical response. In the paper, samples of structure silicon/adhesive/lead-frame, typical in IC packaging, are fabricated with two adhesives, degraded through thermo cycling, examined by acoustical waveform and C-imaging, and compared to the measured optical microscopy image and the measured failure shear strength.

Time of flight diffraction: an alternate non-destructive testing procedure to replace traditional methods

K. G. Prabhakaran, Brian Stephen Wong, Yeo Yan Teng

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Time-of-flight-diffraction Technique (TOFD) is considered as one of the fastest methods of Non-destructive testing (NDT) since a weld can be characterized to a certain degree with one single scan along its length with two probes. An image of the complete weld is created showing component and, more importantly, any defect information. In this paper a comprehensive review of the TOFD technique covering many aspects, e.g. accuracy, coverage, resolution, repeatability, and last not least speed where the real value of TOFD lies-despite its few inherent limitations is presented. This paper presents the results of experimental investigations carried out using various NDT techniques including TOFD on specimens such as welds with various types of defects. The results of these investigations are compared and the feasibility of using TOFD as an alternative NDT procedure to replace the traditional NDT methods of inspecting fabricated pressure vessel components are examined.

Ultrasonic attenuation studies in high Tc superconductors

Zhong Cheng Shen, Zuo Jiang

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In this paper a great number of mechanical relaxation spectrum experiment results in the mixed state of high Tc superconductors have been summarized. A new low frequency mechanical relaxation spectrum apparatus have been shown. We pointed out that the mechanical relaxation peaks are attributed to anelastic relaxation processes and the transition of rigidly pinned FLL into a depinned state.

In-plane displacements measurement by gradient-based digital image correlation

Bing Pan, Peng Cheng, Boqin Xu

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The basic assumption of gradient-based DIC method is the rigid body translation of the interrogated subset. However, this is in contradiction to the real circumstances where displacement gradients exist. In this paper the theoretical error analysis shows that the assumption of subset rigid body translation in gradient-based DIC and the linear approximation of the deformation mapping in N-R method yield identical subset center displacements. Then four real experiments are designed to explore the feasibility and sensitivity of this algorithm. The experiment of uniform uniaxial tension test of aluminum specimen is also investigated as a state when strains exist. The results show that the experimental data of the two algorithms are in good agreement, but the proposed algorithm is much faster than N-R method.

Improvement of accuracy of shape measurement using DMD reflection-type CCD camera

Motoharu Fujigaki, Yoshiharu Morimoto, Shien Ri

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We previously developed a DMD(Digital Micro-mirror Device) reflection-type CCD camera that we call 'DMD camera' and we applied the DMD camera to shape measurement. In this former method, the integral values at a point are obtained by the averaging with the surrounding 9 pixels. This method, therefore, causes a problem that errors are caused by misalignment between the CCD pixel and the DMD pixel. In this paper, we propose a method to improve the algorithm to obtain the phase of a projected grating by phase-shifting method using correlation. The transferred on/off pattern to the DMD are modified and the integral values at a point are obtained by the averaging with the vertical 4 pixels. The accuracy of the shape measurement is improved using the proposed method. The principle, an experimental result, and a comparison of the accuracy between the former method and the proposed method are shown.

Temporal wavelet analysis for deformation measurement of small components using micro-ESPI

Yu Fu, Cho Jui Tay, Chenggen Quan, et al.

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Measuring continuous deformation of specimens whose dimensions are in the range of sub-millimeter introduces a number of difficulties using laser speckle interferometry. During deformation, the speckle patterns recorded on a camera sensor change constantly. These time-dependent speckle patterns would provide the deformation history of the object. However, compared to large objects, noise effect is much more serious due to the high magnification. In this study, a series of speckle patterns on small objects are captured during deformation by high speed camera and the temporal intensity variation of each pixel is analyzed by a robust mathematical tool --- complex Morlet wavelet transform instead of conventional Fourier transform. The transient velocity and displacement of each point can be retrieved without the need for temporal or spatial phase unwrapping process. Displacements obtained are compared with those from temporal Fourier transform, and the results show that wavelet transform minimize the influence of noise and provide better results.

Uncertainty principle and fringe image processing

Bing Zhao, Huimin Xie, Anand Asundi

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Fringe detection technique is discussed with information theory and signal processing approaches. Uncertainty principle for fringe signal detection is set up. Its application on the effect of signal length, phase measurement, and strain or slope measurement is discussed. The relationship between the accuracy and spatial resolution for measurand is investigated.

Holographic particle sizing by using absolute values of the wavelet transform

Joewono Widjaja, Siriwat Soontaranon, Toshimitsu Asakura

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A new method for sizing particle from in-line Fraunhofer holograms by using absolute values of the wavelet transform is proposed. The method gives zero-crossing points of an envelope function of the hologram which are determined by the particle size. Since the resultant zero-crossing points are functions of the dilation parameter, the frequencies of the fringes at the zero-crossing points are measured. The particle size can be finally calculated from the relationship between the frequencies with the positions of the zero-crossing points. The experimental results agree well with the theory.

Effect of wavefront divergence in the quantitative measurement analysis of electronic speckle pattern shearing interferometry (ESPSI)

W. S. Wan Abdullah, Jon N. Petzing, John Raymond Tyrer

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ESPSI or shearography has been successfully used in non-destructive testing (NDT) for measuring the derivative out-of-plane displacement, w/x and/or w/y, and recently a few investigations of derivative in-plain displacement, u/x, v/y, u/y and v/x have been reported. The demand of quantitative measurement has encouraged manufacturers to produce a quantitative shearography system. However, errors arising from numerous sources, including wavefront divergence and object geometry are not taken into account when calculating the interferometer fringe function and quantifying the data. In this paper the novel approach in quantified error that propagates from the divergence illumination wavefront is presented. The theoretical error is formulated by means of mathematical approach that comprises of three dependent variables, the inspected object distance, the object size (field area covered by the CCD camera) and the illumination angle. The error defined by the difference of phase data using divergence illumination object wavefront compared to phase data that is measured by using collimated illumination wavefront. Theoretical analysis and experimental validation indicates that the magnitude of the maximum phase change difference due to the divergence of illumination wavefront to exceed 10% for out-of-plane and 40% for in-plane analysis.

A new phase shifting shadow moiré method for out-of-plane displacement measurement

Fujun Yang, Wei Sun, Chengjun Gu, et al.

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It is well known that the introduction of a phase-shifting procedure may give a better resolution in optical techniques. This paper presents a new digital shadow moire method with phase-shifting based on liquid crystal display (LCD) projector. The first one of four computer-generated phase-shifting fringe patterns is projected on the surface of testing object while all fringe patterns are sequentially projected on a planar plate for generating phase-shifting moire fringes, which are formed by the projected phase-shifting fringe patterns subtracting with the deformed fringe pattern in sequence. This new method provides many advantages in performing topography and out-of-plane displacement measurement. First, the spatial line period and phase step is readily adjusted to suit the measurement precision. Second, the measuring speed is relatively fast and suit for dynamic testing because the digital phase shifting is no time-consuming comparing with other phase-shifting techniques. The experimental performance on out-of-plane displacement measurement of a cantilever beam well demonstrates the validity of the new method.

High-speed imaging for evaluation of silicon wafer defects

Jun Wang, Ganesha Udupa, Bryan Kok Ann Ngoi

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A speckle shearing interferometric system is proposed for real-time inspecting sub-surface defects of unpolished silicon wafer. Under dynamic thermal loading, derivative distribution of out-of-plane displacement along a shear direction is measured and homogeneity and regularity of the distribution is indicator of whether impurities or voids exist under the wafer surface. During a continuous thermal stressing, a sequence of speckle patterns are obtained and phase analysis is implemented in time domain. In this paper, the validity of the method for non-destructive testing of sub-surface defects of silicon wafers has been demonstrated.

Phase shifting calibrated with digital image correlation method

Ming Jiang, H. Y. Tam, Xiao Yuan He

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Three-dimensional (3D) shape measurement can be accurately performed using sinusoid grating projection. However, the projection technique requires very accurate phase shifting of the grating. A method for phase shifting calibration which utilizes gray value correlation of image patterns is presented. The method enables calibration to be performed at sub-pixel accuracy. Experiments were carried out to verify the proposed calibration method.

Cells and gels: implications for mechanics

Gerald H. Pollack

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That the cell is a gel has been well established. If so, then a logical approach to the understanding of cell function may be through an understanding of gel function. Great strides have been made recently in understanding the principles of gel dynamics. It has become clear that a central mechanism in biology is the polymer-gel phase-transition: a major structural change prompted by a subtle change of environment. Phase-transitions are capable of doing mechanical work, and such mechanisms could be responsible for much of the mechanical work of the cell. Here, we consider this approach. We set up a polymer-gel-based foundation for cell function, and explore the extent to which this foundation explains how the cell goes about its business, with an eye toward mechanics.

Characterization of microscopic deformation in polymeric thin films using particle image velocimetry

Manish Soni, Moiz Diwan, Abhijit P. Deshpande

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The effectiveness of a technique based on particle image velocimetry (PIV) for measuring the instantaneous deformation field in planar polymeric films is investigated. Detailed deformation of polymeric films under complex stretching conditions will be very useful in characterization as well as optimization of mechanical properties. PIV is a method for measuring velocity fields in many fluid mechanics applications. In this technique, light scattering from glass micro-particles is used for estimating flow fields. In this work, the particles are spread on the surface of a polymeric film. The film is kept in a laser sheet while the deformation takes place. Two consecutive images of areas as large as 100 cm² are taken, separated by small time interval Δt. Displacement of seed particles over this time interval is estimated using cross-correlation. The polymer film was stretched uniaxially at constant rates. The deformation fields in the thin films over the time of stretching were evaluated. Films with introduced defects were also investigated for the measurement of the planar deformation fields. It is shown that the technique has potential to quantify the instantaneous deformation rate and strain fields for a large area in the plane of a film.

Elastic-plastic stress analysis near the crack tip by the 2-dimensional elastic-plastic hybrid method and digital image correlation

Kenji Machida, Kensaku Morita

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In a previous study, the authors have developed the intelligent hybrid method for 2-D elastic stress analysis. In this study, we have analyzed about the elastic-plastic singular stress field near the crack tip by digital image correlation and the elastic-plastic intelligent hybrid method. The surface images of an object before and after the deformation were taken by a CMOS camera. From these images, the displacement data corresponding to the 2-D mesh pattern were calculated by digital image correlation. The displacement data obtained from the experiment were including large error, so it is difficult to evaluate the stress and the strain with high accuracy using raw displacement data. Therefore, displacement data were smoothed by 2-D FFT filtering and the least squares method. After that we applied the elastic-plastic intelligent hybrid method proposed by Nishioka et al. Evaluation of the stress and strain fields and a fracture mechanics parameter can be carried out by this. In the experiment, the mode I loading was applied to CT specimen with a fatigue crack, and the image near the fatigue crack-tip in an elastic-plastic deformation process was taken by the CMOS camera. The speckle pattern on a specimen surface was made using five kinds of colour sprays. The 3-D finite element method was performed about the same specimen as the experiment, and the validity of this approach was discussed from the comparison of the experiment and 3-D finite element method.

Feasibilty of modulated optical deflection sensing in atomic force microscopy

Tuck Wah Ng, W. S. Lee, Osami Sasaki

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Optical deflection sensing is perhaps the most widely used scheme in atomic force microscopy. In this technique, the sensor is a quadrant photodiode. Position detection is essentially achieved using voltage differencing between the photodiode outputs. To improve data throughput, this is often done using operational amplifiers in the differencing mode. The measurement sensitivity is affected by environmental noise. Intensity modulation is a simple method of overcoming environmental noise. When this scheme is applied to the optical deflection sensor technique, random chaotic signals were found to form. Unless expensive filtering methods are introduced, the efficacy of using intensity modulation to reduce the effects of environmental noise in the optical deflection sensing method is limited.

Influences of strain rate on yield strength aluminum alloys

Samsul Rizal, Hamdani Teuku Firdaus, Razali Thaib, et al.

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The simulation of aircraft has often been performing by implementing finite element code on supercomputers. The reliability an accuracy of simulation depends mainly on the material model as well as on structural model used in calculations. Consequently, an accurate knowledge of mechanical behavior of materials under impact loading is essential for safety performance evaluation of structure. Impact tension tests on specimens for aircrafts and automotive structural applications are conduct by means of the split Hopkinson bar apparatus. Small specimens having diameter 4 mm are use in the test. Tensile stress-strain relations at strain rates of 10² s^-1 to over 10³ s^-1 are present and compared with those obtained at quasi-static strain rates. The limitations on the applicability of apparatus are also discusses. The other importance of the reference of strain, while studying void growth in elastic-viscoplastic material, is emphasized. In the present paper, a simplified plane-symmetrical two-dimensional finite element model for a SHPB with a plate specimen made of an elastic material is first established. The used of strain gage mounted at the specimens to be monitored strain during the course of impact test. Comparisons may then be made between the numerical predicted and experimentally observed of load and a specimen strain. This report also describes the apparatus and instrumentation, and also be discusses the advantages and limitations of experimental technique. Fractograph is taken by scanning electron microscope on the center of the specimens for judgment of the fracture mechanism and strain rates influences on the materials.

Dynamic testing of micro devices using PZT base excitation

Min Hu, Jin Xie, Shih-Fu Ling, et al.

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Dynamic testing of micro devices by lead zirconate titanate (PZT) base excitation is presented in this work. Followed with a brief discussion of base excitation principle, the suitability of piezoelectric plate for high bandwidth vibration excitation is revealed. To compare the dynamic testing results based on this method, a 1.21mm (L) by 0.52mm (W) PZT micro cantilever with self-exciting capability is designed and fabricated by a sol-gel process. The fabricated PZT micro cantilever beam is then attached to a 10mm by 10mm by 1 mm piezoelectric plate (PI piezoceramic). A Polytech scanning laser Doppler vibrometer (SLDV) system is used to measure the resonance frequencies and corresponding modal shapes of the micro cantilever beam under the piezoelectric plate base excitation and the PZT micro cantilever self-excitation, respectively. It is found that piezoelectric plate base excitation would be more powerful than self excitation to stimulate the mode shapes of a micro device under testing.

Femtosecond laser for glaucoma treatment: the comparison between simulation and experimentation results on ocular tissue removal

Dong Xia Hou, Bryan Kok Ann Ngoi, Sek Tien Hoh, et al.

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In ophthalmology, the use of femtosecond lasers is receiving more attention than ever due to its extremely high intensity and ultra short pulse duration. It opens the highly beneficial possibilities for minimized side effects during surgery process, and one of the specific areas is laser surgery in glaucoma treatment. However, the sophisticated femtosecond laser-ocular tissue interaction mechanism hampers the clinical application of femtosecond laser to treat glaucoma. The potential contribution in this work lies in the fact, that this is the first time a modified moving breakdown theory is applied, which is appropriate for femtosecond time scale, to analyze femtosecond laser-ocular tissue interaction mechanism. Based on this theory, energy deposition and corresponding thermal increase are studied by both simulation and experimentation. A simulation model was developed using Matlab software, and the simulation result was validated through in-vitro laser-tissue interaction experiment using pig iris. By comparing the theoretical and experimental results, it is shown that femtosecond laser can obtain determined ocular tissue removal, and the thermal damage is evidently reduced. This result provides a promising potential for femtosecond laser in glaucoma treatment.

Force microscopy: application to soft matter

Mounir Maaloum, Raphaël Levy

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Atomic force microscopy (AFM) has been shown to be a good means of investigating matter at the nanometer scale. Here, we use it on one hand to determine the structure of adsorbed biological macromolecules such as DNA at high resolution on solid surfaces in liquid, and on the other hand as a force probe. In this case, we try to extract the relevant information from the complicated force profiles. We have studied the characterisation of specific molecular interactions. Our study reveals that in the presence of multiple parallel bonds with high rebinding probability, the force increases with decreasing speed velocity. We propose that the rebinding via the fluctuation of the linker is responsible for the observed behaviour.

Cheap color evaluation of dye-based pressure sensitive films for plantar studies

W. K. Yeong, Tuck Wah Ng

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Dye-based pressure sensitive films are advantageous in plantar pressure studies due to their of ease of use, costeffectiveness, and ability to produce measurements within the shoe. To circumvent the use of proprietary equipment and software to relate the dye stained film to load, an alternative approach of using a conventional flatbed scanner and generic image processing software is attempted here instead. The technique revealed high linear increasing and decreasing trends for the respective red and blue normalized intensities (correlation coefficient > 0.95) and low standard deviation in all readings (< 0.06) overall. By subtracting the blue from the red normalized intensity, it was discovered that the measurement sensitivity could be doubled. The results here confirm the viability of using a conventional flatbed scanner and generic image processing software to relate the dye stained pressure films to load. The adoption of this approach promises substantial cost savings.

Towards an ideal polymer scaffold for tendon/ligament tissue engineering

Sambit Sahoo, Hong Wei Ouyang, James Cho-Hong Goh, et al.

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Tissue engineering holds promise in treating injured tendons and ligaments by replacing the injured tissues with "engineered tissues" with identical mechanical and functional characteristics. A biocompatible, biodegradable, porous scaffold with optimized architecture, sufficient surface area for cell attachment, growth and proliferation, faborable mechanical properties, and suitable degradation rate is a pre-requisite to achieve success with this aproach. Knitted poly(lactide-co-glycolide) (PLGA) scaffolds comprising of microfibers of 25 micron diameter were coated with PLGA nanofibers on their surfaces by electrospinning technique. A cell suspension of pig bone marrow stromal cells (BMSC) was seeded on the scaffolds by pipetting, and the cell-scaffold constructs were cultured in a CO₂ incubator, at 37°C for 1-2 weeks. The "engineered tissues" were then assessed for cell attachment and proliferation, tissue formation, and mechanical properties. Nanofibers, of diameter 300-900 nm, were spread randomly over the knitted scaffold. The reduction in pore-size from about 1 mm (in the knitted scaffold) to a few micrometers (in the nano-microscaffold) allowed cell seeding by direct pipetting, and eliminated the need of a cell-delivery system like fibrin gel. BMSCs were seen to attach and proliferate well on the nano-microscaffold, producing abundant extracellular matrix. Mechanical testing revealed that the cell-seeded nano-microscaffolds possessed slightly higher values of failure load, elastic-region stiffness and toe-region stiffness, than the unseeded scaffolds. The combination of superior mechanical strength and integrity of knitted microfibers, with the large surface area and improved hydrophilicity of the electrospun nanofibers facilitated cell attachment and new tissue formation. This holds promise in tissue engineering of tendon/ligament.

Cyclic uniaxial strains on fibroblasts-seeded PLGA scaffolds for tissure engineering of ligaments

Kyaw Moe, Tong Earn Tay, James Cho Hong Goh, et al.

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Mechanical strain regulates the structure and mechanical properties of the engineering tissue. Previous studies showed that cyclic mechanical strain affect in development and function of cells in tissue formation on various three-dimension scaffolds. In this study, the effect of cyclic uniaxial tensile straining on cell morphology was investigated. The objective of this research is to investigate the effect of cyclic uniaxial strain on cells' growth on knitted PLGA (Poly-Lactide-co-glycolide) scaffolds. A biocompatible cyclic uniaxial tensile straining device (bioreactor) was developed. Cyclic uniaxial straining was applied at 1.8% strain for 4 hours daily. To study the effect of cyclic frequency on cells' growth, two sets (1Hz and 0.1 Hz) of frequencies were used. After two weeks stimulation, the cell morphology was studied with the aid of Hematoxylin & Eosin staining using paraffin sectioning. In both frequency sets the mean nuclei length are longer than unstrained specimens. The cell population also tended to orientate parallel to the straining axis. In 0.1Hz frequency straining, more cell population are aligned in the straining direction than in 1Hz frequency. This study has demonstrated that cyclic uniaxial strain affect on cell morphology and mechanical properties of engineering tissue.

Structure analysis of the wing of a dragonfly

Kenji Machida, J. Shimanuki

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It is considered that wing corrugation increases not only the warping rigidity but also the flexibility. The wing of a dragonfly has some characteristic structures, such as "Nodus", "Stigma". Nodus is located in the center of the leading edge, and stigma like a mark is located near the end of the wing. It is considered that these structures not only increase the flexibility of the wing, but also prevent fatigue fracture of wings. Therefore, to investigate the mechanism of dragonfly's wing, the configuration of wing used for analyses was measured using an optical coordinate profile measuring machine and a laser microscope. Moreover, several 3-D models of the dragonfly's wing were made, and calculated by the 3-D finite element method.

Biomechanical study of patellofemoral joint instability

Wongwit Senavongse

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Patellofemoral joint instability is a complex clinical problem. It may be a consequence of pre-existing anatomical abnormality or trauma. The objectives of this study were to use experimental mechanics to measure patellar stability and to quantify the effects of pathological abnormalities on patellar stability in vitro. Eight fresh-frozen cadaver knees were studies. The patellar stability was measured using an Instron material testing machine. A total load of 175N was applied to the quadriceps muscles. Patellar force-displacement was tested at different knee flexion angles as the patella was cyclically displaced 10mm laterally and medially. Three pathological abnormalities were applied; VMO malfunction, flat lateral trochlea, and medial retinacular structure rupturing. For the first time, this study has shown comparative and quantitative influence of pathological abnormalities on patellar stability. It was found that a flat lateral trochlea has greater effect than the medial retinacular rupturing whereas the medial retinacular rupturing has greater effect than VMO malfunction on patellar lateral stability. These results are important for future investigations on the treatment of patellofemoral instability.

Analysis of dynamic foot pressure distribution and ground reaction forces

F. R. Ong, T. S. Wong

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The purpose of this study was to assess the relationship between forces derived from in-shoe pressure distribution and GRFs during normal gait. The relationship served to demonstrate the accuracy and reliability of the in-shoe pressure sensor. The in-shoe pressure distribution from Tekscan F-Scan system outputs vertical forces and Centre of Force (COF), while the Kistler force plate gives ground reaction forces (GRFs) in terms of F_z, F_x and F_y, as well as vertical torque, T_z. The two systems were synchronized for pressure and GRFs measurements. Data was collected from four volunteers through three trials for both left and right foot under barefoot condition with the in-shoe sensor. The forces derived from pressure distribution correlated well with the vertical GRFs, and the correlation coefficient (r²) was in the range of 0.93 to 0.99. This is a result of extended calibration, which improves pressure measurement to give better accuracy and reliability. The COF from in-shoe sensor generally matched well with the force plate COP. As for the maximum vertical torque at the forefoot during toe-off, there was no relationship with the pressure distribution. However, the maximum torque was shown to give an indication of the rotational angle of the foot.

Fluorescence photon migration techniques for the on-farm measurement of somatic cell count in fresh cow's milk

Geoffrey Khoo, Rainer Kuennemeyer, Rod W. Claycomb

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Currently, the state of the art of mastitis detection in dairy cows is the laboratory-based measurement of somatic cell count (SCC), which is time consuming and expensive. Alternative, rapid, and reliable on-farm measurement methods are required for effective farm management. We have investigated whether fluorescence lifetime measurements can determine SCC in fresh, unprocessed milk. The method is based on the change in fluorescence lifetime of ethidium bromide when it binds to DNA from the somatic cells. Milk samples were obtained from a Fullwood Merlin Automated Milking System and analysed within a twenty-four hour period, over which the SCC does not change appreciably. For reference, the milk samples were also sent to a testing laboratory where the SCC was determined by traditional methods. The results show that we can quantify SCC using the fluorescence photon migration method from a lower bound of 4x10⁵ cells mL^-1 to an upper bound of 1 x 10⁷ cells mL^-1. The upper bound is due to the reference method used while the cause of the lower boundary is unknown, yet.

Use of reflectance spectroscopy for early detection of calcium deficiency in plants

Bingqing Li, Liew Oi Wah, Anand Krishna Asundi

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This article investigates calcium deficiency symptoms of the plants grown under hydroponics conditions. Leaf reflectance data were collected from plants, and then transformed to L*, a*, b* values, which provide color information of the leaves. After comparing the color information of deficient plants to control plants, a set of deficiency criterion was established for early detection of calcium deficiency in the plants. Calcium deficiency could be detected as early as two days from the onset of stress in mature plants when optical data were collected from terminal young leaves. Young plants subjected to calcium stress for 9 days could not be distinguished from nutrient sufficient plants.

On-line milk spectrometry: analysis of bovine milk composition

Kyle Spitzer, Rainer Kuennemeyer, Murray Woolford, et al.

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We present partial least squares (PLS) regressions to predict the composition of raw, unhomogenised milk using visible to near infrared spectroscopy. A total of 370 milk samples from individual quarters were collected and analysed on-line by two low cost spectrometers in the wavelength ranges 380-1100 nm and 900-1700 nm. Samples were collected from 22 Friesian, 17 Jersey, 2 Ayrshire and 3 Friesian-Jersey crossbred cows over a period of 7 consecutive days. Transmission spectra were recorded in an inline flowcell through a 0.5 mm thick milk sample. PLS models, where wavelength selection was performed using iterative PLS, were developed for fat, protein, lactose, and somatic cell content. The root mean square error of prediction (and correlation coefficient) for the nir and visible spectrometers respectively were 0.70%(0.93) and 0.91%(0.91) for fat, 0.65%(0.5) and 0.47%(0.79) for protein, 0.36%(0.49) and 0.45%(0.43) for lactose, and 0.50(0.54) and 0.48(0.51) for log10 somatic cells.

Use of LANDSAT-7 ETM+ with ancillary data for soil salinity mapping in northeast Thailand

Roengsak Katawatin, Wilaiwan Kotrapat

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Soil salinity is a major environmental constraint in Northeast Thailand. Sustainable land use and management in this region require careful mapping of the salinity status. This study was conducted to investigate performances of some digital classification techniques for soil salinity mapping in the Northeast. The techniques investigated were based on the use of LANDSAT-7 ETM+ with different combinations of three kinds of ancillary data (i.e., topography, geology, and underground water quality). In this study, the Maximum Likelihood classification method was employed. Statistics including KAPPA analysis and Z-statistic, overall accuracy, producer's accuracy, and user's accuracy, were used as the bases for assessments of mapping accuracies and, in turn, performances of the classification techniques. Results have shown that the use of ETM+ data bands 4,5 and 7, with the combination of all three kinds of the ancillary data yielded the most accurate soil salinity map with 83.6 % overall accuracy. The same subset of ETM+ data when used with any combination of two kinds of the ancillary data could serve as well. Other classification techniques yielded significantly less accurate results. It was, therefore, concluded that techniques based on the use of the selected ETM+ data subset with combinations of two or three kinds of the ancillary data were promising.

Spectroscopic detection of fluorescent protein marker gene activity in genetically modified plants

O. W. Liew, Jenny P. C. Chong, Anand K. Asundi

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This work focuses on developing a portable fibre optic fluorescence analyser for rapid identification of genetically modified plants tagged with a fluorescent marker gene. Independent transgenic tobacco plant lines expressing the enhanced green fluorescence protein (EGFP) gene were regenerated following Agrobacterium-mediated gene transfer. Molecular characterisation of these plant lines was carried out at the DNA level by PCR screening to confirm their transgenic status. Conventional transgene expression analysis was then carried out at the RNA level by RT-PCR and at the protein level by Western blotting using anti-GFP rabbit antiserum. The amount of plant-expressed EGFP on a Western blot was quantified against known amounts of purified EGFP by scanning densitometry. The expression level of EGFP in transformed plants was found to range from 0.1 - 0.6% of total extractable protein. A comparison between conventional western analysis of transformants and direct spectroscopic quantification using the fibre optic fluorescence analyser was made. The results showed that spectroscopic measurements of fluorescence emission from strong EGFP expressors correlated positively with Western blot data. However, the fluorescence analyser was also able to identify weakly expressing plant transformants below the detection limit of colorimetric Western blotting.

A new method to measure the distance between the micro-device and the substrate

Satoshi Kishimoto, George C. Johnson

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A technique for measuring the distance between the micro-device and substrate is developed. An electron beam scan of a scanning electron microscope used for this method. A micro-device is placed over the substrate and obstructs the back-scattered electrons from the substrate. Therefore, the shadow image of the micro-device is observed in the SEM image. The distance between the micro-device and the substrate can be calculated using the width of the shadow, dimension of the detectors for the back-scattered electrons and the dimension of the micro-devices. This method makes it possible not only to measure the distance between the micro-device and the substrate and also detect the form of the specimen surface. In addition, observation of the micro-devices and measuring the distance between the micro-device and the substrate can perform at the same time. As a demonstration, the distance between the micro-bar and the substrate and the shape of the micro-hardness tester's indent mark is measured.

Laser interferometry method for measuring displacement field of crack tip of bimetal hot-dip specimen

Jiyong Chen, Anand Asundi

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The U and V distortion fields at the interface of cracked zinc alloy ZAS35/carbon steel have been obtained by means of a laser moire interferometry. The optimum cast preheating temperature has been decided based on the experimentally determined shear strength. The microstructure of the interface of bimetal composite of zinc alloy ZAS35/carbon steel is analyzed and studied using X-ray diffraction and Scanning Electron Microscope (SEM). The phase component of the metallic interface bond of the alloy has been determined and the results of interface distribution of elements Fe and Zn have been obtained with dip coating at a temperature of 700°C. The above theory, the experimental technology and the results will be introduced and analyzed in this paper.

Moiré interferometric investigation on the role of hydration in the mechanical behavior of dentine

Anil Kishen, Anand Asundi

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This study was conducted to investigate the mechanical behavior of dehydrated and rehydrated dentine using a digital moire interferometry. It was observed from this experiment that structural dentine demonstrated distinct strain gradients in the direction parallel and perpendicular to the dentinal tubules. During compressive loading, the rehydrated dentine displayed strain response characteristic of a tough material, while the dehydrated dentine showed strain response characteristic of a brittle material. Dehydration resulted in higher stiffness and reduced toughness in dentine structure. These experiments highlighted that the presence of water considerably influenced the mechanical behavior of structural dentine.

Micro/nano grating and its application to moiré measurement

Huimin Xie, Zhanwei Liu, Haixia Shang, et al.

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In this paper, some novel micro/nano- moire grating fabricating techniques are introduced. The gratings are produced by the SPM lithography, FIB lithography, and molecular beam epitaxy (MBE) method. The moire patterns formed with these gratings are also introduced. The gratings are successfully to be used to measure the residual deformation in the surface around a step edge of the Al/Si artificial nanocluster with the moire methods. The successful experimental results verify the feasibility of these methods.

New optical strain method of three-beams interferometry and digital image processing

L. A. Li, Z. Y. Wang, S. B. Wang, et al.

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Based on the optical diffraction and interference, a new method of digital image processing is presented for the in-plane strain measurements in macro and micro-zone. The principle of the improved moire interferometry and the algorithm are presented in this paper. In this study, the cross grating of the frequency of 1200 l/mm is replicated on the specimen surface. Three coherent laser beams are used to obtain the U+V and U-V fringe patterns. Combining the FFT phase shift technique and subpixel technique, the displacement components U and V are calculated with the high precision. The new method has some advantages, such as simple optical arrangement, direct calculation of U and V fields with higher precision. Using this method, the displacement and strain fields on the free-edge of the thermo-plastic composite laminates AS4/PEEK[0/±45/90]7S (56-ply) under three-point bending have been measured. The corresponding numerical simulation has been carried out using three-dimensional orthotropic elastic finite element model method. It is believed that this method will be a powerful tool in characterizing the mechanical properties of materials.

Nanocharacterization of bio-silica using atomic force and ultrasonic force microscopy

Vinaypreet S. Gill, Kevin P. Hallinan, N. S. Brar

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Nanotechnology has become central to our research efforts to fabricate relatively smaller size devices, which are more versatile than their older and larger predecessors. Silica is a very important material in this regard. Recently, a new biomimetically inspired path to silica production has been demonstrated. This processing technique was inspired from biological organisms, such as marine diatoms, which produce silica at ambient conditions and almost neutral ph with beautiful control over location and structure. Recently, several researchers have demonstrated that positional control of silica formed could be achieved by application of an electric field to locate charged enzymes responsible for the bio catalytic condensation of silica from solution. Secondly, chemical and physical controls of silica structural morphology were achievable. Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) techniques are employed for the first time to provide both substantially improved resolution of the morphology and relative measurement of the modulus of elasticity of the structures. In particular, these measurements reveal the positive impact of a shear flow field present during the silica formation on both the "ordering" of the structure and the mechanical properties.

Preliminary work of a smart needling project

Kaiguo Yan, Tien-I Liu, Keck Voon Ling, et al.

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Precise needle placement is vital for the success of a wide variety of percutaneous surgical procedures. Insertions into soft tissues can be difficult to learn and to perform, due to tissue deformation, needle deflection and limited visual feedback. Little quantitative information is known about the interaction between needles and soft tissues during puncture. We are carrying out a "smart needling" project in which a fairly long, but slender biopsy needle will be controlled to hit the target that is inside human body, automatically and precisely. This paper reports the preliminary work which is to prove that translational oscillation of the needle can reduce target movement, and at the same time to find the optimal settings of the important factors that will produce the least target movement. The experiment platform comprises of an oscillatory needle restricted to translate horizontally. A position-trackable catheter was embedded in the phantom to act as the target. Two-Level factorial design was adopted and an exploratory data analysis (EDA) approach was used for analysis. The final results showed that oscillation at high frequency band from 2kHz to 20kHz can reduce target movement. Translation speed, oscillation frequency and amplitude are all important factors. But phantoms with different elasticities may have different best settings of these factors. For example, for soft phantoms, lower frequency, higher speed and smaller amplitude are desired for minimal target movement. Optimization searching engine will be designed correspondingly to control the needle in optimal working conditions that can produce minimal target movement.

Finite element modeling of the micropipette aspiration of malaria-infected red blood cells

E. H. Zhou, C. T. Lim, K. S. W. Tan, et al.

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Micropipette aspiration is one of the most widely used techniques for measuring the mechanical properties of single cells. The homogeneous linear elastic half-space model has been frequently applied to characterize the micropipette aspiration of chondrocytes and endothelial cells. However, the linear elastic model is limited to small deformation and the half-space assumption is frequently invalidated when moderately large micropipettes are used. In this work, the linear elastic constitutive model is extended to the neo-Hookean constitutive model and the geometry is simulated more realistically by considering the cell as a sphere. The large-deformation contact mechanics problem is solved using dimensionless axisymmetric finite element analysis. The effects of pipette diameter and fillet radius on the cellular rheological behaviour are also systematically studied. Based on the finite element simulation, empirical relationships have been derived for the direct interpretation of the elastic mechanical parameters from the micropipette aspiration experiments. Micropipette aspiration of late-stage malaria-infected red blood cells (schizonts) is conducted. The infected cells are found to exhibit elastic solid behavior in contrast to the liquid drop behavior of healthy red blood cells. The apparent shear modulus of the schizonts, interpreted from the elastic solid model, is found to be 119±62 Pa.

3-dimensional orthodontics visualization system with dental study models and orthopantomograms

Hua Zhang, S. H. Ong, K. W. C. Foong, et al.

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The aim of this study is to develop a system that provides 3-dimensional visualization of orthodontic treatments. Dental plaster models and corresponding orthopantomogram (dental panoramic tomogram) are first digitized and fed into the system. A semi-auto segmentation technique is applied to the plaster models to detect the dental arches, tooth interstices and gum margins, which are used to extract individual crown models. 3-dimensional representation of roots, generated by deforming generic tooth models with orthopantomogram using radial basis functions, is attached to corresponding crowns to enable visualization of complete teeth. An optional algorithm to close the gaps between deformed roots and actual crowns by using multi-quadratic radial basis functions is also presented, which is capable of generating smooth mesh representation of complete 3-dimensional teeth. User interface is carefully designed to achieve a flexible system with as much user friendliness as possible. Manual calibration and correction is possible throughout the data processing steps to compensate occasional misbehaviors of automatic procedures. By allowing the users to move and re-arrange individual teeth (with their roots) on a full dentition, this orthodontic visualization system provides an easy and accurate way of simulation and planning of orthodontic treatment. Its capability of presenting 3-dimensional root information with only study models and orthopantomogram is especially useful for patients who do not undergo CT scanning, which is not a routine procedure in most orthodontic cases.

Simple optical characterisation for biomimetic micromachined silicon strain-sensing structure

Dedy H. B. Wicaksono, Gregory Pandraud, Patrick J. French

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This paper presents an on-going work to develop micromachined silicon-based strain sensor inspired from the campaniform sensillum of insects. We present simple optical setup for the characterisation of a membrane-in-recess structure as an early stage in mimicking the natural sensor. The microstructure is a 500 nm-thick SiO₂/SiN circular membrane, burried 13 μm from the surface of a 3x3 mm, 525 μm thick Si-chip. The chip was attached to a 45x10x0.525 mm Si beam. The simple optical characterisation setup is based on imaging the reflected laser beam from the biomimetic structure. Since an optical cavity between the membrane and the Si beams beneath was formed, ideal flat-parallel Fabry-Perot interferometer equation was applied to interpret the results semi-quantitatively. We obtained 2-D interference fringe pattern having 3 orders of maxima from the middle to the edge of the circular apperture, as a result of an initial internal membrane stress. The pattern changed non-linearly as we applied flexural strain from behind the beam up to 50 μm, most probably caused by nonlinear deflection of the membrane (i.e. the membrane did not deflect similarly as the beam beneath it). This phenomena might explain one of the strain-amplifying properties of this biomimetic strain sensing microstructure.

A stroboscopic structured illumination system used in dynamic 3D visualization of high-speed motion object

Xianyu Su, Qican Zhang, Yong Li, et al.

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A stroboscopic structured illumination system, which can be used in measurement for 3D shape and deformation of high-speed motion object, is proposed and verified by experiments. The system, present in this paper, can automatically detect the position of high-speed moving object and synchronously control the flash of LED to project a structured optical field onto surface of motion object and the shoot of imaging system to acquire an image of deformed fringe pattern, also can create a signal, set artificially through software, to synchronously control the LED and imaging system to do their job. We experiment on a civil electric fan, successful acquire a serial of instantaneous, sharp and clear images of rotation blade and reconstruct its 3D shapes in difference revolutions.

The unbalanced signal measuring of automotive brake drum

Xiao-Dong Wang, Sheng-Hua Ye, Bang-Cheng Zhang

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For the purpose of the research and development of automatic balancing system by mass removing, the dissertation deals with the measuring method of the unbalance signal, the design the automatic balance equipment and the software. This paper emphases the testing system of the balancer of automotive brake drum. The paper designs the band-pass filter product with favorable automatic follow of electronic product, and with favorable automatic follow capability, filtration effect and stability. The system of automatic balancing system by mass removing based on virtual instrument is designed in this paper. A lab system has been constructed. The results of contrast experiments indicate the notable effect of 1-plane automatic balance and the high precision of dynamic balance, and demonstrate the application value of the system.

Influence of the radius of curvature of crack-tip on the mixed mode stress intensity factor by infrared hybrid method

Kenji Machida, M. Sato

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The seven kinds of mixed-mode loading of the CNS specimen were carried out using the thermography and servopulser, and the data of the sum of the principal stresses were obtained. After estimating the nodal forces from the sum of the principal stresses by an inverse problem, the error included in the experiment field was modified by the intelligent hybrid method. The stress intensity factor was evaluated by the virtual crack extension method and the displacement extrapolation, and the validity was discussed as comparing with the 3-dimensional finite element analysis. The relative error to the stress intensity factor obtained by the 3-dimensional finite element analysis increases as a load application angle increases. The stress distribution obtained from the infrared thermography differed from the finite element method greatly, and it became clear that the influence of thermal conduction cannot be disregarded. Therefore, thermal-conduction inverse problem analysis is needed to estimate a true stress field.

A new method for the determination of essential work of necking and tearing

Alexander M. Korsunsky, Kyungmok Kim, Colin Chiu

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We introduce a new technique for the determination of the material property characterizing the resistance to ductile fracture from a single tensile test on an unnotched specimen. The property known as the essential work of fracture (EWF) is usually associated with the specific energy, per unit cross sectional area, consumed during ductile fracture in a double edge notched tensile (DENT) specimen. This energy is referred to as 'essential' in order to distinguish it from the non-essential energy consumed on distributed plastic deformation accompanying fracture, but not required for material separation. In the present study we consider tensile tests carried out on unnotched dog-bone (DB) tensile specimens carrying large numbers of markers and incorporating continuous measurement of elongation between any two markers using a laser scanning extensometer. In a single test it is therefore possible to obtain multiple load-elongation curves for a large number of tensile specimens. This data is analyzed by separating contributions to specimen elongation made by distributed (pre-softening) and localized (post-softening) plastic deformation. We demonstrate on a series of tests the evaluation of essential and non-essential work of necking and tearing for an aluminum alloy subjected to different heat treatments, and compare the results with those obtained from conventional DENT tests.

Effect of mean stress and residual stress on fatigue strength improvement of ferritic stainless steel

Priyo Tri Iswanto, Shin-ichi Nishida, Nobusuke Hattori

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This paper covers investigations of the effect of compressive mean stress on fatigue properties of non-deformed specimens and the effect of compressive residual stress on fatigue properties of plastically deformed specimens of ferritic stainless steel by roller-working. Tensile-compressive fatigue test and rotating banding fatigue test have been performed on these specimens. The results showed that according to increase of the compressive mean stress the fatigue strengths of these specimens increase. Compressive mean stress delays crack initiation and suppresses fatigue crack propagation properties. In case of tensile mean stress, this kind of mean stress decreases the fatigue strength. The fatigue limits of plastically deformed specimen are much higher than that of non-deformed specimen and does not linearly increase with an increase of plastic deformation value. The fatigue limit improvement of deformed specimens would be caused by notch root compressive residual stress and work-hardening due to roller working.

Magnetomechanical hysteresis damping in Fe-Al alloys

Z. C. Zhou, Z. C. Shen, Z. Jiang, et al.

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The magnetomechanical hysteresis damping of Fe-Al alloys has been investigated using a computer-controlled automatic inverted torsion pendulum. It has been shown that Al content and heat treatment have a significant effect on the magnetomechanical hysteresis damping of the alloys. The Fe-10.5 (at.%)Al alloy has an optimal damping capacity after it was air-cooled from 900°C and the Fe-Al alloys with 29(at.)%Al and 38(at.)%Al exhibit rather low damping capacity after undergoing the same heat treatment because of decreasing magnetism. The water-quenched or as-cast specimens cannot form high damping due to high internal stress. An appropriate heating temperature in heat treatments is essential to obtain high damping.

Experimental analysis of stress intensity factor of a high polymer having a crack and a circular hole or an inclusion by tensile load

Syuutei Sasaki, Tsutomu Ezumi

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In recent society, various large structures such as large buildings, ships, bridges etc., have been constructed using metal, polymers and polymer alloys. Many other new materials are being developed and invented in the world. These materials are made on automatic line systems in factories. These are tested under the rigorous and sever conditions, and shipped on demand. After testing, however, materials often contain cracks, holes or inclusions. The intensity stress generates on top of the crack and may cause the accidents. Holes or inclusions in the material have negative effects on the rigidity and the safety. Many researchers are about cracks analyzing the use of polycarbonate to soleve the problem. The authors think that the various problems about cracks, holes and includes are not studied enough. They tried to examine the relation ship of the details of stress intensity factor of the high polymer materials through the caustic method and the photoelastic method. This paper discusses the causes and effects of mutual interference of cracks, holes and inclusions in the materials.

Fracture properties of bioabsorbable HA/PLLA/PCL composite material

S. D. Park, M. Todo, K. Arakawa, et al.

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Hydroxyapatite particle filled poly(L-lactic acid)/poly(e-caprolactone) blend (HA/PLLA/PCL) composite materials were developed by melt-mixing, and their bending mechanical properties and fracture toughness were examined. It was found that the fracture absorbed energy and fracture toughness are maximized with the PCL content of 5wt%. Local plastic deformation of PLLA/PCL matrix is the main mechanism of energy dissipation during fracture. This ductile deformation is considered to be initiated in the surroundings of voids formed due to interfacial debonding at HA/matrix interfaces and phase separation of PLLA and PCL. On the other hand, fracture toughness of HA/PLLA/PCL with the PCL contents of 10 and 15wt% becomes lower than that of HA/PLLA. In these composites, void formation causes severe local stress concentration and therefore degrades the materials rather than improving the fracture resistance.

The positional capture experiments of the LCM using near field fiber probe

Chi-Fu Yen, Jen-Ai Lee, Chien-Ming Chen

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Laser Capture Microdissection (LCM) is a technique that permits rapid and reliable procurement of pure population of cells from tissue sections. We created the LCM system with a near field fiber probe to transmit the laser light (808 nm) to heat the thermoplastic polymer film which was placed above the tissue section. Laser spots in nano-dimension cause the film to be melted and fused with the underlying target of choice. In the study, we set the fiber probe on a two-dimensional nanometer PZT to do precisely capture. The aperture of fiber probe we used is 100 nm through which light can be focused. We used 20 nm spread gold particles to be captured in these experiments instead of tissue sections. By moving the probe in X direction to melt spots in different distances, we can know more molecular properties of the thermoplastic polymer film especially in its resolving power. When the film is removed, the chosen particles remain bound to the film, while the rest of the tissue or particles are left behind. According to the results of this study, we can know how close the melted spots can reach to, and it is also helpful to the operation of this new LCM system.

Nanomechanical testing of polymeric nanofibers

E. P. S. Tan, C. T. Lim

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Biodegradable polymeric nanofibrous scaffold comprises individual nanofibers where their stiffnesses can promote or undermine the various cellular functions as well as structural integrity of the scaffold. As such, there is a need to investigate the nanomechanical properties of these individual nanofibers. However, conducting mechanical tests of individual fibers at the nanometer scale can pose great challenges and difficulties. Here, we present novel techniques to perform nanomechanical testing of individual polymeric nanofibers. For demonstration of the nano tensile tests, polycaprolactone (PCL) nanofibers were produced via electrospinning. These fibers were deposited across two parallel edges of a cardboard frame so that a single nanofiber can be isolated for tensile test using a nano tensile tester. For nanoscale three-point bend test, a Poly (L-lactic acid) (PLLA) nanofiber was suspended across a microsized groove etched on a silicon wafer. An atomic force microscope (AFM) tip was then used to apply a point load on the mid-span of the suspended fiber. Beam bending theory was then used to calculate the elastic modulus of the nanofiber. For nanoindentation test, a PLLA nanofiber was deposited on a mica substrate and an AFM tip used to indent the nanofiber. Modified Hertz theory for normal contact was then used to evaluate the elastic modulus of the nanofiber.

Automatic extraction of isotropic points using min-max scanned photoelastic images

Terry Yuan-Fang Chen, Yu-Hsiang Fang, Han-Sheng Lin

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A robust and accurate method is proposed to extract the isotropic points from min-max scanned photoelastic images automatically. The method uses a multiple layered window with four-change condition to extract the isotropic points. Test of this method on both the simulated and experimental obtained isoclinic images and direction images is shown. An exact position was found for the simulated images and a difference of about 1.4 pixels is achieved for the experimental ones. The whole scheme is very simple, fast, and effective to extract the isotropic point for structural design purpose.

Application of digital photoelasticity to determine stress in beam due to shear/flexural crack

Dulal Goldar

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Conventional diffused light polariscope was utlized to capture images by a digital camera, which were transferred online to a personal computer. Further, a software was developed to identify Isochromatic and Isoclinic fringes in the beam to study stress distribution. The algorithm was written in Turbo C++.

Ultrasonic stress analysis of a strip by the time-averaged photoelastic method

Wei-Chung Wang, Ying-Huang Tsai

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Based on the time-averaged technique, a digital photoelastic system was employed to observe the stress distribution generated by an ultrasonic wave impinged at the edge of a strip. According to the classical photoelastic theory, light intensities emerging from the analyzer were formulated and expressed in the form of 1-J_O(Δ), where Jo is the zeroth-order Bessel function. This new technique is called the time-averaged photoelastic method. To verify the proposed theory, the distribution of 1-J_O(Δ) was superimposed onto the distribution of gray level of the experimentally obtained photoelastic fringe pattern. Except regions near the edges and the center of fringes, qualitatively well-matched results were found.

The measurement of the flight gesture and the wing deformation of dragonfly in free flight

Peng Cheng, Jinsong Hu, Guofeng Zhang, et al.

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Using the phase shifting and the grating projection method, the kinematical parameters of dragonfly in free flight were measured. In our experiment, during projecting parallel sine fringes on the dragonfly's wings with a projector, the high speed CCD TV camera (1000 frames per second) recorded the dragonfly and the fringes projected on the dragonfly's wing , then the shape of the dragonfly's wings in every frame could be gutted using SCPM (Spatial-Carrier Phase Measurement) method. According to this data, we designed a program which can show the change of the gesture of the dragonfly's wing, the 3-D figure, the contour line and the curve of any transversal of the dragonfly's wing at any given time. From the figures of the 3-D deformation, we also can see that the deformation is not completely negative, it must could be control by the dragonfly via the veins on the wing.

The effect of illumination volume in underwater camera image

Lin Xu, Gerald Seet, Duo-Min He

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Video cameras are standard equipment on, practically, all of today's underwater robotics vehicles. As a part of a camera system setting, the arrangement of active illumination affects the quality of acquisition, particularly in turbid water environment. Large illumination volume helps to increase image brightness but depresses modulated contrast. This paper elaborates on the effects of illumination volume due to the forward and backward scattering progresses. An intensity model is proposed to include the geometrical parameters of the illumination setup. This model is based on the volume scattering function (VSF) and Lambertian reflection effects. The distribution of scattering noise in the image is predicted for different size of light beam. Experiments were conducted in a short water tank using a continuous wave, 532nm laser light source with an adjustable parallel beam output. In application, as laser beam scanning is a well-known method to improve underwater visibility, the theoretical model helps in determining the optimum illumination setting in different water conditions, and accordingly reducing the time of photomosaicing.

Finite element study of flip chip on board in drop test

Siew Kuan Nah, Zhaowei Zhong

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The reliability of electronic packages in mechanical drop tests is critical especially for portable electronic devices as these electronic packages are very vulnerable to solder joint failures caused by the mechanical shock and the PCB warping upon impact. Drop test studies are performed to investigate the solder joints mechanical failure in electronic packages. In this paper, the mechanical impact on the solder joints of a flip chip in a simulated drop test is investigated. The drop test simulation consists of a typical flip chip on board (FCOB) that has 48 peripheral eutectic solder bumps modeled in CAD/CAM software. The flip chip solder joint reliability under mechanical shock is studied using 3D finite element simulation. Comprehensive design analyses are performed to study 3 different models. The design models are varied in the substrate dimensions and the addition of encapsulation. The results of the stresses and strains in the solder joints are obtained using finite element analysis in the drop test. The findings indicate that the stress on the flip chip corner solder joint decreases if the substrate is larger in dimension. In addition, the introduction of an encapsulation helps to reduce the stress experienced by the solder joint.

Three-dimensional shape visualization of balloon hull in quick deflation

Qican Zhang, Xianyu Su, Liqun Xiang, et al.

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In this paper we proposed a method for three-dimensional (3D) shape measurement and visualization of balloon hull during quick deflation based on Fourier transform profilometry (FTP). A sequence of dynamic deformed fringe images can be grabbed by high-speed CCD camera and saved on disk rapidly. By Fourier transform, filtering, inverse Fourier transform and unwrapping these phase maps in 3D phase space, we can obtain the shape of the rapid deflating balloon in different times. Based on the phase difference between two neighborhood frames, we propound a 3D phase unwrapping algorithm, which will be of great benefit to 3D phase unwrapping in speed and accuracy. The results of our experiment indicate that the method, presented in this paper, can efficiently deal with the surface shape measurement for rapid motion object and will be a promising one with the development of high-speed frame grabber.

A frequency encoding method for fringe projection profilometry

Hongwei Guo, Mingyi Chen, Haitao He

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A frequency encoding approach for fringe projection profilometry is proposed. First, a series of fringe patterns are generated in computer where the pixels are encoded with the temporal frequencies. Second, the patterns are cast on the object surface by an LCD projector and then the distorted patterns are captured by a CCD camera. Third, a least squares algorithm based on a linear prediction is deduced to estimate the frequencies, and then the depth map is further reconstructed by using the mapping relationship between the temporal frequency and the depth of the object surface. Experimental results are presented to demonstrate the validity of this technique.

The signal extraction of fetal heart rate based on wavelet transform and BP neural network

Xiao Hong Yang, Bang-Cheng Zhang, Hu Dai Fu

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This paper briefly introduces the collection and recognition of bio-medical signals, designs the method to collect FM signals. A detailed discussion on the system hardware, structure and functions is also given. Under LabWindows/CVI,the hardware and the driver do compatible, the hardware equipment work properly actively. The paper adopts multi threading technology for real-time analysis and makes use of latency time of CPU effectively, expedites program reflect speed, improves the program to perform efficiency. One threading is collecting data; the other threading is analyzing data. Using the method, it is broaden to analyze the signal in real-time. Wavelet transform to remove the main interference in the FM and by adding time-window to recognize with BP network; Finally the results of collecting signals and BP networks are discussed. 8 pregnant women's signals of FM were collected successfully by using the sensor. The correctness rate of BP network recognition is about 83.3% by using the above measure.

Fiber optic interferometric sensors for micro-positioning applications

Kai-Yu Cheng, Yu Yi Su, Yen-Liang Chen, et al.

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The precision displacement control in high-resolution instrument is influenced by non-linearity effects of PZT actuators. The capacitive sensor within PZT actuator is often used as a displacement sensor for feedback control, but the calibration and traceability of capacitive sensor are hardly to be accomplished. The optic fiber sensor is a useful high-resolution displacement sensor to perform the measurement in space-limited instrument, and it’s also capable of a non-contact function. In this paper, the structure of an optic fiber sensor was introduced, and the hysteresis characteristic of PZT actuator was evaluated. In addition, the performance of the capacitive sensor within PZT actuator for close-loop control was compared with those of the optic fiber sensor, and the differences ratio between both was less than 0.12 %. Following the scanned images by interference microscope, the images have some distortions before applying the compensated curve function for non-linearity. Thus, the optic fiber sensor could be provided a calibration service for displacement measurement of interference microscope.

Experiment and analysis of the fiber shape of curculionidae cuticle

B. Chen, X. Peng, J. G. Wang, et al.

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Most structural materials existing in nature take the form of composite. After centuries' evolution and modification, these natural materials gain highly optimized structures and prominent performances. The SEM observation on the cuticle of curculionidae shows that the cuticle is a biocomposite reinforced with chitin fibers. The chitin fibers are embedded in a protein matrix of the cuticle in the form of layers. A kind of revolving fiber layup was found. Observation also shows that there is a kind of special spinous fiber consisting of a long fiber and many short fibers. The maximal pullout force of the spinous fiber is analyzed. The results show that the maximal pullout force of the spinous fiber is distinctly larger than that of ordinary straight fiber.

Shock characteristics obtained by nanosecond analyses for aerospace materials

Yasuhisa Sato, Taku Ueno

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For numerical designs of safety cabin and seats to maintain a survivable environment for passengers and crew in a crash occurrence, very high-strain-rate characteristics of many kinds aerospace materials are indispensable. So, stress-time histories are obtained in two glassy polymers (polymethyl methacrylate: PMMA and polycarbonate: PC) and two kinds of light metals (commercially pure aluminum: A1100-H14[JIS] and super duralumin: A2024-T3[JIS]) at impact velocity 600 to 700 m/s using polyvinylidene fluoride (PVDF) gauges in a plate impact testing by a powder gun. Nanosecond analyses are used to extract strain-time histories from experimental stress data. Then, stress-strain curves at very high-strain-rates (10⁶ to 10⁷ [1/s]) in shock wave region under conditions of uniaxial strain. A drop-hammer compression test is also used to determine stress-strain curves at medium strain rates (10² [1/s]) under conditions of uniaxial stress by using an extrapolation method. For low strain rates (ca. 10^-4 [1/s]), stress-strain curves are determined under conditions of uniaxial stress by a universal testing machine combined with the extrapolation method. Power law relations between stress and strain-rate are observed with the glassy polymers under uniaxial strain conditions in a very wide strain-rate range.

Electronic speckle pattern interferometry of residual stress measurement using hole-indentation method

C. N. Sim, Cho Jui Tay, L. Cheng

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Residual stresses is measured using a new technique combining hole indentation with Electronic Speckle Pattern Interferometry (ESPI). The technique is superior to conventional methods such as the widely used rosette strain-gage hole drilling technique in the ease of experimental set up and the use of optics in strain measurement allows results to be displayed in real-time. The technique is fast, simple, less destructive and has great potential to be developed into a quality inspection tool in the production/field environment.

A compact remote controlled interferometer for photomechanics applications

Zhong Ming, Low Kelvin, Nadirah Mohamed, et al.

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The paper describes a portable, remote controlled Michelson interferometer using a laser pointer. The mirror on one of the arms was mounted on an encoded stepper motor. A motor driver controller circuit has also been fabricated, which is interfaced with a personal computer and that can be controlled through Web.

Experiment and analysis on the aragonite layer of clam shell

B. Chen, X. Peng, J. G. Wang, et al.

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Molluscan shell is strong, stiff, tough and shows a erose fracture surface when it is broken. In this paper, the SEM observation on a clam's shell shows that the shell is composed of aragonite layers and organic matrix. Each aragonite layer is parallel to the surface of the shell and consists of many thin aragonite sheets. These aragonite sheets are perpendicular to the layer where they are located. The observation also shows that the direction of the sheets in different layer is various and a kind of herringbone arrangement is found. The maximum pullout force of the herringbone arrangement is analyzed based on its representative model, and it shows that the herringbone arrangement can markedly increase the pullout force of the arrangement and improve the fracture toughness of the shell.

Enantiomeric determination of D-, L-lactate in diabetic rat urine using a column-switching HPLC

Chien-Ming Chen, Yih-Chiao Tsai, Takeshi Fukushima, et al.

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A highly sensitive method for the determination of D-lactate in rat urine was developed by using a high-performance liquid chromatography (HPLC) with an octadecylsilica (ODS) connected to a chiral column. At first, (D+L)-lactate in the urine were derivatized with a fluorescent reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ), and separated on the ODS column and determined fluorimetrically at 547 nm with 491 nm of excitation wavelength. During the separation step on the ODS, the peak fraction of (D+L)-lactate derivative was introduced directly to an amylose tris (3,5-dimethylphenylcarbamate) (Chiralpak AD-RH) chiral column by changing the flow of the eluent via 6-port valve. Then, D-lactate derivative was separated enantiomerically from L-lactate derivative, and the enantiomeric ratio was determined from the chromatogram. The accuracy values for the determination of D-lactate in 20 μL of rat urine were 96.93% - 104.85%. The intra- and inter-day precision values were within 0.80% and 14.44%. The proposed method was applied to the urine of diabetic rats induced by intraperitoneal administration of streptozotocin, and the significant increases of D-lactate was observed in the diabetic rats as compared to the normal rats.

Template based nanofabrication: mechanical characterization of film-substrate interface

Biswajit Das, Pavan Singaraju

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This paper presents the results of investigations of thin film alumina templates fabricated on silicon and other substrates. Such templates are of significant interest for the low-cost implementation of semiconductor and metal nanostructure arrays. In addition, thin film alumina templates on silicon have the potential for nanostructure integration with silicon electronics. Formation of thin film alumina templates on silicon substrates was investigated under different fabrication conditions, and the dependence of pore morphology and pore formation rate on process parameters was evaluated. In addition, process conditions for improved pore size distribution and periodicity were determined. The template/silicon interface, important for nanostructure integration on silicon, was investigated using different techniques. Thin film alumina templates on non-silicon substrates such as glass, indium-tin-oxide-coated glass and silicon carbide were also investigated.

Third International Conference on Experimental Mechanics and Third Conference of the Asian Committee on Experimental Mechanics

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