Proceedings Volume 3589

Process Control and Sensors for Manufacturing II

David M. Pepper
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Proceedings Volume 3589

Process Control and Sensors for Manufacturing II

David M. Pepper
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 4 February 1999
Contents: 4 Sessions, 20 Papers, 0 Presentations
Conference: Nondestructive Evaluation Techniques for Aging Infrastructures and Manufacturing 1999
Volume Number: 3589

Table of Contents

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Table of Contents

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  • Sensors
  • Process Monitoring I
  • Process Monitoring II
  • Process Monitoring III
  • Process Monitoring II
Sensors
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Integrated waveguide/thermocouple sensor for liquid properties
R. Daniel Costley, Gary Boudreaux, William G. Ramsey, et al.
A torsional and longitudinal waveguide was introduced several years ago and shown to be effective for measuring various properties of liquids, including viscosity, density and temperature. The instrument is simply a specially constructed, thin rod (waveguide), one end of which is inserted into the liquid slurry. Torsional or extensional waves are generated in the rod, via a magnetostrictive mechanism, by passing a current through a coil which fits over the dry end of the rod. Liquid properties are correlated to different attributes of the waves (e.g., speed and amplitude) that travel down the rod and reflect off the end that is inserted into the liquid. Different properties of the material can be determined using waveguides of different cross-section. Noncircular rods are used to measure density, while viscosity is measured with circular rods. Since temperature affects these same wave attributes it would be desirable to have an independent measure of the temperature. This is accomplished by using a thermocouple sheath as the sensor part of the waveguide. In this way, the influence of temperature can be decoupled from the other properties of interest. In addition, the temperature is measured at the same point where the other properties of the liquid are being measured. The basic design of the sensor will be presented along with experimental results.
Drastically simplified holographic methods well suited for in-situ monitoring and process control in a practical industrial environment
Several novel methods which drastically simplify production of holograms and holographic interferograms are presented. They relate to the holograms and holographic interferograms obtained on ultra high resolution silver halide media. The unique features of the innovative methods are: extreme simplicity, real time and quasi-real time data output, possibility to record, photoprocess and display holograms in daylight (in some cases even in direct sunlight illumination) without any interference filters; possibility to avoid any liquid baths for photoprocessing; proper color response of the reconstructed images. The novel user- friendly holographic methods can be easily allied for nondestructive optical checks in microelectronics, automotive, aerospace and other industries. They can also be applied for testing of the masterpieces of art. Corresponding examples are given. A novel supersmall holographic device is presented which suits well for in situ monitoring and process control in practical industrial environment. This device can be used as portable holographic interferometer without any lenses and no alignment problems enabling monochrome or color data output. Vast experimental data with photograph of displayed images from holograms and holographic interferograms are given. Real time in situ and quasi-real time holographic interferograms with proper color response are shown.
Homodyne detection of ultrasonic surface displacements using two-wave mixing in photorefractive polymers
Marvin B. Klein, Gerald David Bacher, Anders Grunnet-Jepsen, et al.
In recent years, a number of adaptive interferometers have been used for the remote detection of laser-generated ultrasonic waves in parts under inspection. One type of adaptive interferometer uses two-wave mixing in a photorefractive material to form a real-time hologram, or adaptive beamsplitter. In this work we describe such an interferometric receiver based on two-wave mixing in photorefractive (PR) polymers. The PR polymers have a number of very promising technical features for this application which will be described in detail. In addition, the polymer composition can be tailored to specific requirements and the materials can be processed into a variety of different shapes and forms. Finally, when compared with inorganic photorefractive crystals, the polymers are inexpensive and simple to fabricate. We have taken advantage of the above features to demonstrate homodyne detection in the PR polymers with a sensitivity that is within a factor of three of the limit for an ideal homodyne system. We have also used a laboratory receiver to detect ultrasonic waves with good signal-to-noise. In this talk we will discuss the physical features of our polymer-based receiver and describe our experiments to characterize this system.
Noncontact characterization of static paper materials using a photorefractive interferometer
Emmanuel F. Lafond, Joseph P. Gerhardstein, Pierre H. Brodeur
Laser-Based Ultrasound (LBU) systems are now entering their maturity years by penetrating the factory in both the areas of non-destructive testing and process control. A LBU system can be used for the on-line characterization of a paper web in a paper mill. Compared to contact techniques, LBU is able to generate and detect on a paper web both symmetric and antisymmetric waves with a non-contact tool which is the spot of the generation laser. This provides all at once a rich amount of data about the stiffness properties of the sheet. To demonstrate this concept we made some experiments on static paper first, our ultimate goal being to monitor the stiffness properties of a paper web, on-line, at industrial speeds. A photorefractive interferometer using the two-wave mixing method with a continuous electric field applied to a BSO crystal has been built for ultrasound detection. Results are presented on different paper grades, using a Nd:YAG laser for generation. Both A0 (anti- symmetric) and S0 (symmetric) modes of Lamb waves have been detected with acceptable signal to noise ratio in single laser shot. The dispersive nature of A0 wave is clearly visible as well as the higher frequency content of S0 wave.
Process Monitoring I
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Laser-EMAT system for ultrasonic weld inspection
Stephen Dixon, Christopher Edwards, Stuart B. Palmer
The non-destructive testing of welded metal components is an area where significant savings in test cost can be made if preparation costs can be minimized. The biggest cost associated with preparation is grinding off the weld cap in order to facilitate the detection of defects that may be present just under the cap. In addition there are also potential savings to be made if the actual testing time can be reduced or if the tests can be performed at temperatures above which conventional contacting ultrasonic techniques cannot be used. This paper describes a non-contact ultrasonic method that uses a pulsed laser as generator and an electromagnetic acoustic transducer as detector which has the potential to interrogate the entire cross section of a weld.
Noncontact ultrasonic liquid-level measurement of drink cans
Stephen Dixon, Christopher Edwards, Stuart B. Palmer
This paper describes a non-contact ultrasound system that has been used to measure liquid level in beverage containers at rates of up to 20 per second. The system is both a more accurate and environmentally friendly alternative to the existing gamma-ray based inspection systems. A viable non- contact on-line ultrasonic technique is demonstrated which has potential applications outside the packaging industry.
In-situ microwave characterization of planar/nonplanar specimens
Microwave Nondestructive Evaluation (NDE) offers an attractive alternative to ultrasonic NDE. Using the free space spot focused antenna system developed by CEEAM, it is possible to perform non-contact, non-destructive evaluation of homogeneous, inhomogeneous, composite and anisotriophic materials as a function of frequency and temperature. Vary little sample preparation is required and the technique presented here leads itself to in situ process monitoring during manufacture and quality control of finished products. The material being evaluated may be planar or nonplanar. Reflection and/or transmission measurements may be used to reconstruct the material property tensors. Although microwaves cannot pass through metals, this technique has been used very successfully to evaluate the surface resistivity/conductivity of thin film metal coatings. Unlike ultrasonic measurements which may be limited by temperature, the free space microwave system has been used successfully temperature up to 1000 degree(s)C. In this respect, the free space microwave NDE system is a far cry from conventional methods such as coaxial and waveguide methods as well as the cavity resonance technique, all of which require sample preparation and hence, cannot be used for in situ inspection. Being a noncontact method this system can be used to characterize both liquids and solids. In this paper, the technique and the system will be described and the results will illustrate the versatility and user friendliness of the free space microwave system. In a comparison paper, we describe how this system can be adapted as a non-destructive point to point inspection system for locating flaws, manufacturing defects, delamination and disbonding, accurate thickness measurements, surface profiling, etc. of materials in sheet form or objects of complex shape.
In-situ noncontact nondestructive point-to-point microwave inspection system
Vasundara V. Varadan, Richard D. Hollinger, Anikumar R. Tellakula, et al.
Discontinuities and manufacturing flaws affect system performance. The accurate location of flaws and defects is sometimes more important than its precise characterization. For mechanical structures, similarly sized flaws in certain locations are more critical than at other locations. Non- contact microwave inspection systems offer many advantages relative to traditional NDE techniques complex and nonplanar samples as well as composite or anisotropic materials, except where transmission through a metallic object is required. Using spot focused horn antennas, it is possible to detect, locate and identify the inhomogeneities inside dielectric materials with local resolution approaching one wavelength. The system can be completely automated under computer control. Inspection can be done purely in the reflect mode using only one antenna or in the transmission mode using two antennas. The antennas can move on a robotic arm or the system under inspection can move or rotate under the antenna. Surface profiling, shape profiling, and accurate non-contact thickness measurements can be performed in addition to locating flaws and delaminations. Inspection can be done in situ even in high temperature environments since this a non-contact method. Several different examples are presented to illustrate the efficacy of the method as an attractive, user friendly NDE tool.
Process Monitoring II
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Noncontact real-time measurement of surface roughness inside cylinders
John N. Pike, Yogesh Mehrotra
The MLS method for measuring surface roughness (rms roughness RQ in the range 1 - 200 microns) is reviewed for the usual case of a nominally planar target surface. Application is then made to surfaces with cylindrical curvature, as would be found typically in examining the inner surfaces of bored or drawn cylinders. It is shown that the MLS algorithm for determining RQ from image data needs no geometrical correction in the often desired special case when the MLS instrument's Ronchi ruling has its grid lines oriented tangential to the cylinder's curvature (i.e., lines perpendicular to the cylinder's axial direction). Corrections for other cases are small for cylinders with inside diameters greater than 50 mm, and are easily handled in software. Folding of the optical system of the MLS method is illustrated, to provide a surface sensing probe that can be inserted in rough cylinders, e.g., for monitoring the progress of grinding operations.
Industrial monitoring and controlling system for an integrated single-chip computer with a linear CCD image sensor
Jinghui Wang, Anhua Mei
This paper presents a monitoring and controlling system which integrated single chip computer with linear CCD image sensor for measuring the length of automobile screws in industrial automatic line. The system consists of hardware and software. There are five parts in the hardware setup. They are optical part machinery, linear CCD image setup and its driving circuit, binarilizing circuit and 8098 user setup. The measuring range is adjustable because single end measurement is used. Minnum bi--multiplication is applied in the software to correct system deviation and increase system precision. Experiment has proved that the system is highly effective, nontouch, nondestructive and economical.
Open architecture framework for distributed real-time fault diagnosing
Hongan Wang, Guozhong Dai
Fault diagnosing has recently received considerable attention. Its applicability is severely restricted by the computational complexity involved in the diagnosing process. In this paper, it is presented an open architecture framework for distributed real-time fault diagnosing in an industrial environment. Within this framework, all work units comprising the manufacturing system are modeled using intelligent agents. Each agent has autonomous and cooperative functions, observing the local fault diagnosing process via the combination of model-based qualitative and heuristic reasoning with learning techniques; and cooperatively reporting the primary diagnosis result to the diagnosis manager, which supervises the global fault diagnosing process using the constraint propagation technology. To fast the constraint propagation, a matrix- based constraint parallel propagation method is discussed, which greatly reduces the computational overhead. Also, a formal description method for agent's structure is given, which can be used to describe agents and verify their functions.
Process Monitoring III
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Fiber optic sensor for composite cure monitoring
Joseph L. Lenhart, John H. van Zanten, Joy P. Dunkers, et al.
The fiber/resin interface is critical to the final mechanical properties of a fiber reinforced composite material. To directly study this region, Robello siloxane (RBS) was grafted to glass surfaces. RBS contains a dimethylaminonitrostilbene fluorophore tethered to a isocyanatopropyltriethoxysilane coupling agent. Silane coupling agent chemistry was used to deposit small amounts of RBS to glass surfaces in a mixed silane layer with a diluting coupling agent. The fluorescence response of grafted RBS was sensitive to the chemical functionality of the diluting coupling agent. A blue shift in fluorescence from the grafted RBS dye can be followed during cure of an epoxy resin over layer, giving the technique potential to monitor cure in the interfacial region.
Feedback control of the vacuum-assisted resin transfer molding (VARTM) process
Dirk Heider, A. Graf, Bruce K. Fink, et al.
The Vacuum Assisted Resin Transfer Molding (VARTM) technique is a liquid-molding process that offers the potential to significantly reduce fabrication costs for large-scale composite structures. The VARTM workcell is used to evaluate control strategies and sensors such as SMARTweave to provide feedback for an intelligent control system. Current VARTM systems lack automated control systems resulting in part to part variability. This research presents a continuously controlled vacuum actuator system and the influence of vacuum gradients on resin flow front control.
Fiber optic Raman backscatter temperature monitoring in composites
John H. Belk, Erwin W. Baumann, Michael L. Vandernoot
Fiberoptic Raman backscatter based distributed temperature measurement systems have been available for several years. Recent efforts at Boeing have focused on developing methods to apply this equipment to monitoring the temperature of composite parts during manufacture, laboratory testing, and on-board application for health monitoring. A number of these applications involve embedding the temperature-sensing fiber directly into or onto composite parts. Several examples are given and lessons learned are discussed, including effects of microbending losses and how they are being addressed.
Pitch catch ultrasonic bond sensor for the in-situ tow placement consolidation of thermoplastic laminates
Benjamin Zurn, Susan C. Mantell
A nondestructive sensor for on-line inspection of laminated composites was developed. In particular, we have developed a repeatable, low cost method for sensing poorly bonded plies as a thermoplastic laminated composite part is formed. The sensor consists of two piezoelectric transducers mounted in a `pitch catch' arrangement. One transducer transmits an ultrasonic signal and the other receives the signal. Each transducer is mounted on a Acrylic wedge. The Acrylic wedge, in turn, is mounted on a steel wedge. The Acrylic wedge angle is selected so as to excite a Rayleigh wave in the steel wedge. The steel wedge introduces the Rayleigh wave into the composite via Hertzian contact. There is no couplant at the composite surface. Received signals have been analyzed for frequency shift, frequency filtering, attenuation and changes in wave speed. Of these signal analysis methods, the most consistent indicators of poorly bonded regions are signal attenuation and wave speed. Selected results from an extensive experimental study are described. These results indicate that the Rayleigh wave speed and amplitude are indicative of the bond strength of a ply near the surface of the composite.
Intrinsic fiber optic Sagnac ultrasound sensor for process monitoring in composite structures
In this paper, we report the development of an intrinsic fiber-optic Sagnac-type ultrasound sensor for cure monitoring. The Sagnac ultrasonic sensor consists of a Sagnac demodulation unit and a sensing segment which can be embedded in a composite structure. The Sagnac optical demodulator is common-path and hence self-stabilized and much simpler than the alternate Fabry-Perot or Michelson type sensors which require external stabilization. Any phase variations that the sampling beams experience due to ultrasound impinging on the sensing segment are demodulated by the Sagnac sensor to produce a signal proportional to ultrasonic signal. The sensing fiber segment of the Sagnac is placed within the composite at the time of manufacture. As the composite is cured, this sensor detects ultrasound that is generated by a laser source or a pzt-transducer. The wavespeed and attenuation of the ultrasound are measured as the cure process proceeds, and these provide information on the state of cure of the composite. We discuss the details of the above intrinsic Sagnac sensor, as well as report on its characteristics including frequency response, sensitivity, and directionality. Results of a cure monitoring are also presented.
On-machine characterization of moving paper using a photo-emf laser ultrasonics method
Bruno F. Pouet, Emmanuel F. Lafond, Brian Pufahl, et al.
Stiffness properties of paper materials can readily be characterized in the laboratory using conventional ultrasonic techniques. For on-line inspection on a paper machine, due to the high translation velocity and the somewhat fragile nature of the moving paper web, contact ultrasonic techniques using piezoelectric transducers are of limited use. To overcome this limitation, non-contact laser- based ultrasonic techniques can be used. Due to the rough surface of the paper, the reflected light is composed of many speckles. For efficient detection, the receiver must be able to process as many speckles as possible. Adaptive receivers using the photorefractive or photo-emf effects are characterized by a large etendue, and thus, are well suited for detection on paper and paperboard. Moreover, the translation velocity of the moving web implies that the detection system must adapt extremely quickly to the changing speckle pattern. In this work, a photo-emf receiver was used to detect Lamb waves excited using a pulsed Nd:YAG laser in moving paper. Experiments were performed using a variable-speed web simulator at speeds much higher than 1 m.s-1. Results corresponding to various translation speeds are shown, demonstrating the feasibility of laser- based ultrasound for on-machine inspection of paper and paperboard during production.
Acoustic emission monitoring of fiber breakage during TMC consolidation
Roderick Rowland, Gareth Munger
Fiber breakage during consolidation processing is a significant problem which leads to a reduction in the composites strength in the axial and transverse direction. Past research and development projects have been restricted to measurement of fiber fracture after consolidation and to modeling the process during the consolidation cycle, however, no direct or indirect method has been developed to measure fiber breaks during the consolidation. This method successfully incorporates acoustic emission sensor technology capable of measuring fiber breaks inside of a hot isostatic press during the consolidation of metal matrix composites.
Process Monitoring II
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Effects of drilling conditions, drill material, and point angle on acoustic emission and exit hole delamination in drilling advanced fiber-reinforced composites
Anthony Chukwujekwu Okafor, Scott R. Birdsong
A 1/3 fractional factorial design of experiment with four factors at three levels was used to investigate drilling of multi-directional AS4/PEEK composites. The design of experiment was conducted to determine the main effects and two factor interactions of drill point angle, cutting speed, feed rate, and drill material on acoustic emission generated in drilling and drilled hole exit delamination. Drill material, feedrate, cutting speed, and drill point angle were found to have statistically significant effects on total and average acoustic emission energy generated which also depends on the location of the acoustic emission spectra (on the workpiece or on the drilling fixture). Drill material was found to have the most significant effect on exit hold delamination, and accounted for over 50% of the variation in the measured exit hole delamination. Carbide drills were found to produce the least amount of exit hold delamination throughout the range of speeds investigated followed by Polycrystalline Diamond drills, while High Speed Steel Cobalt drills were found to produce holes with the greatest amount of exit hold delamination.
Monitoring drilling of advanced composites, drill wear, and exit hole delamination using wave-based acoustic emission
Anthony Chukwujekwu Okafor, Scott R. Birdsong
An experimental investigation was performed to study drill wear and its effect on acoustic emission and drilled hole exit delamination for both carbide and PCD drills when drilling in advanced composites (AS4/PEEK). Drilling conditions were selected to minimize exit hole delamination for the carbide drill and a series on 80 holes were drilled with both carbide and PCD drills. Acoustic emission signals were acquired and flank wear width were measured after every fifth hole. Carbide drill material was found to wear more than the PCD drill. Exit hole delamination increases with tool wear for both carbide and PCD drills as shown from measurements and SEM micrograph images of drilled holes. The average acoustic emission (AE) energy per event as well as total AE energy were found to decrease with tool wear. The results show that acoustic emission could be used successfully for real-time monitoring and prediction of drill wear and exit hole delamination.