Proceedings Volume 4710

Thermosense XXIV

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Proceedings Volume 4710

Thermosense XXIV

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Volume Details

Date Published: 15 March 2002
Contents: 11 Sessions, 81 Papers, 0 Presentations
Conference: AeroSense 2002 2002
Volume Number: 4710

Table of Contents

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Table of Contents

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  • Radiation and Thermometry
  • Process and Product Monitoring
  • Environmental, Geological, Fire, and Surveillance
  • Building and Infrastructure
  • Predictive Maintenance
  • Biomedical and Agriculture
  • Research and Development
  • NDT I
  • NDT II
  • NDT I
  • NDT II
  • NDT I
  • Student Poster Briefs
  • Poster Session
  • Radiation and Thermometry
  • NDT I
  • Radiation and Thermometry
  • Research and Development
  • Process and Product Monitoring
Radiation and Thermometry
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High-precision blackbody sources and facilities developed at VNIIOFI, Russia
The paper contains the state-of-the-art of the precision radiometry principles based on using high temperature blackbody sources, as well as the characteristics of blackbodies (BB), developed at the All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI). A novel Medium Background Facility (MBF) intended for calibrating both IR sources and sensors has been developed at VNIIOFI. The MBF used for the calibration under vacuum conditions (10-3 Pa) and medium background temperatures includes a Ga Fixed-Point Blackbody (29.76 degree(s)C), Variable Temperature Blackbody (-60 degree(s)C ~ +80 degree(s)C) and Filter Radiometer. Both blackbody spectral radiometric calibration and effective emissivity measurement are performed in the spectral range from 2.5 micrometers to 14 micrometers for a blackbody temperature from -60 degree(s)C up to +80 degree(s)C. A brief description of the operating principles and specifications of the MBF is presented.
Spatial and angular distributions for irradiance from blackbody cavities
Amie S. Nester-, J. Robert Mahan
Blackbody cavities are commonly used in calibration of optical sensors; that is, they provoke an instrument response to a known incident flux. The so-called cavity effect produces an effective emissivity near unity so that, if a uniform temperature distribution is maintained across the cavity wall, the flux exiting the cavity approaches that of a blackbody at that temperature. The effort described here employs Monte Carlo ray-trace (MCRT) models to simulate radiation within a blackbody cavity in order to define the spatial and angular distributions of exiting flux. These models may be used to evaluate the suitability of various cavity geometries for the calibration of radiometers. The sensitivity of exiting flux properties to variations of interior surface properties and temperature may also be evaluated. Described is an effort to develop a tool that can be used to enhance the design and utilization of blackbody cavities as a calibration source.
Performance analysis of conical cavities for surface temperature retrieval with a Fourier transform infrared spectrometer
The Savannah River Technology Center (SRTC) is conducting measurements in the visible, near-infrared and infrared spectral regions of selected ground targets in support to the Department of Energy Multispectral Thermal Imager (MTI) satellite. Radiometers have been used to retrieve surface temperature from water and land targets. Surface temperature measurements of land targets are often complicated by the wavelength dependent emissivity. Conical cavities have been employed on land targets to increase the surface effective emissivity and therefore the apparent surface temperature. Surface effective emissivity values near unity offer the opportunity for absolute surface temperature retrieval. The efficacy of conical cavities for absolute surface temperature retrievals was studied with a calibrated Fourier transform infrared spectrometer (FTIR). The research paper presents the results of surface temperature retrievals of targets with low emissivity values with the aid of conical cavities.
Temperature dependence of the graybody approximation to emissivity for some common materials
Modern infrared imaging radiometric cameras typically measure over a nominal waveband within one of two atmospheric windows, 8-12 or 3-5 micrometers. As such, they must assume targets are graybodies to calculate their temperatures. The IR camera can be used to measure target emissivity, enhancing the integrity of the graybody approximation, at least near the temperature at which the emissivity was measured. For realbodies, spectrally nonuniform emitters, the graybody emissivity approximation will be temperature dependent. This paper models the graybody emissivity temperature dependence for a variety of materials whose emissivity may be easily measured near room temperature whilst the application temperatures may be several hundred degrees Celsius.
Application of IR imaging during temperature-modulated differential scanning calorimetry (TMDSC) measurements
Hsin Wang, M. Pyda, R. Androsch, et al.
In a temperature-modulated differential scanning calorimetry (TMDSC) system, temperatures are measured by thermocouples under the sample and reference furnaces. TMDSC helps to accurately measure temperature during a DSC measurement. It also helps the researcher to establish a more realistic model to calculate heat capacity of various materials. This study examined assumption of temperature gradient in TMDSC characterization. An infrared camera was used to obtain surface temperature maps of DSC cells during temperature sweeps. TMDSC units from Perkin-Elmer and TA Instrument were studied using different heating and cooling rates. Temperature gradient exists between the top and bottom of the sample. IR images showed that temperature distributions within the sample and reference cells exist. Phase lags between the top and bottom temperatures were also observed.
Relationship between MRTD and MDTD of infrared radiometer by use of FLIR collimator
Arao Kamoi, Tetsuya Kondo, Yoshizo Okamoto
As one of NDE' means, infrared radiometer (IR) has become widely used in a variety of industries. This IR method is very useful for its customers to detect invisible surface and internal flaws of material. However, there are a few standards being necessary to evaluate detection limit of the above material flaws. The IR test method for detecting the size and location of the invisible flaws has been qualitatively carried out by applying some standards, but it has become non-quantitative and inaccurate for evaluating the relation between the detection limit of the invisible flaws and detectable and resolvable characteristics of IR. Conventional IR makers are accustomed to use NETD as the resolution characteristics of IR camera, but general customers using IR camera cannot evaluate the minimum detectable size of measuring object, if they cannot evaluate MRTD and MDTD. The study of the quantitative evaluation to clarify the relationship between MRTD and MDTD is very little. This paper represents evaluating method of MDTD compared to MRTD, and their quantitative relationship by using collimator FLIR testing.
Adaptive restoration of airborne Daedalus AADS1268 ATM thermal data
Ding Yuan, Edwin L. Doak, Paul Guss, et al.
To incorporate the georegistration and restoration processes into airborne data processing in support of DOE's nuclear emergency response task, we developed an adaptive restoration filter for airborne Daedalus AADS1268 ATM thermal data based on the Wiener filtering theory. Preliminary assessment shows that this filter enhances the detectability of small weak thermal anomalies in AADS1268 thermal images.
Temperature measurement of ceramics in furnaces by 3-color thermograph
Takuya Takahashi, Miyuki Hashimoto, Kenji Yano, et al.
Temperature control in the sintering process is important to secure the quality of ceramics. We have usually controlled the sintering process indirectly by making use of the temperature of the inside of a furnace. It has been a general understanding that infrared radiometric thermograph is not suitable for measuring directly the temperature of the targets such as ceramics placed in the furnace because of emissivity dependence of the targets and because of the effect of reflection from the furnace wall. The same can be said to 2-colored thermometers because of them, too, it has been impossible to eliminate the effect of reflection for correct temperature measurement. Recently we, however, contrive two new methods for direct measurement of the surface temperature of ceramics using a 3-colored thermograph. One is to measure the indefinite emissivity of the inside of a furnace and the effect of reflection from the furnace wall. The other is to eliminate such indefinite emissivity and effect of reflection. We will report the new methods of 3-colored thermograph and the result of inspecting the said methods.
IR imaging of integrated circuit power transistors during operation
Hsin Wang, Ralph B. Dinwiddie, H. Maleki, et al.
An infrared microscope was used to study the surface temperature profiles of power transistor arrays in integrated circuits (IC) during operation. Each transistor array was set to conduct current for 20-50 microseconds. The integration time of the IR camera is adjusted to be between 2 and 10 microseconds. A thorough study of the camera's timing characteristics allows its precise synchronization to transient thermal events in the transistor arrays. Progressively adding incremental delay times to the synchronization pulses allows the complete characterization of the thermal transients as a function of time and location. The IR microscope timing characteristics were determined by imaging an incandescent lamp filament during pulsed operation. Examples of heat pulses in a lamp filament and power transistors are given.
Process and Product Monitoring
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Optimization of industrial high-temperature processes in kilns for ceramics by use of thermophysical properties
Wolfgang Bauer, Thomas Funke
Depending on temperature of the firing process many changes occur in the ceramic materials. They lead to modifications in the thermophysical properties of the materials. Depending on the temperature and the thermophysical properties, temperature-differences occur in the material and as consequence thermal stresses occur which influence the quality of the ceramics. Size and location of these stresses are not known. They can lead to a decrease in material quality or even to total damages. With the help of thermophysical measurements and the knowledge of the responsible properties of the ceramic materials a suitable simulation-model can be worked out as a simulation of the firing process, a calculation of the temperature fields and the arising thermal stresses in the material and an optimization of the process by decreasing the thermal stresses in the endangered ranges based on the simulation-results. For investigations of the critical temperature ranges and for consideration of the changes in the ceramic kiln charge and feed during heating and cooling the measurement methods of the Thermal-Analysis are used. The generated simulation-model is based on the FEM. Basis for these calculations is the knowledge of material-properties (thermal conductivity, specific heat capacity, bulk density, coefficient of linear thermal expansion, modulus of elasticity, Poisson's ratio) dependent from temperature and respective structure.
Infrared line cameras based on linear arrays for industrial temperature measurement
Peter Drogmoeller, Guenter Hofmann, Helmut Budzier, et al.
The PYROLINE/ MikroLine cameras provide continuous, non-contact measurement of linear temperature distributions. Operation in conjunction with the IR_LINE software provides data recording, real-time graphical analysis, process integration and camera-control capabilities. One system is based on pyroelectric line sensors with either 128 or 256 elements, operating at frame rates of 128 and 544 Hz respectively. Temperatures between 0 and 1300DGRC are measurable in four distinct spectral ranges; 8-14micrometers for low temperatures, 3-5micrometers for medium temperatures, 4.8-5.2micrometers for glass-temperature applications and 1.4-1.8micrometers for high temperatures. A newly developed IR-line camera (HRP 250) based upon a thermoelectrically cooled, 160-element, PbSe detector array operating in the 3 - 5 micrometers spectral range permits the thermal gradients of fast moving targets to be measured in the range 50 - 180 degree(s)C at a maximum frequency of 18kHz. This special system was used to measure temperature distributions on rotating tires at velocities of more than 300 km/h (190 mph). A modified version of this device was used for real-time measurement of disk-brake rotors under load. Another line camera consisting a 256 element InGaAs array was developed for the spectral range of 1.4 - 1.8 micrometers to detect impurities of polypropylene and polyethylene in raw cotton at frequencies of 2.5 - 5 kHz.
Nondestructive control of glass components by means of thermography
Umberto Galietti, Andrea Cavicchia, Leonardo Spagnolo
The aim of this work is to demonstrate the possibility to develop and test a specific control procedure based on the use of thermography, for hot forging of glass components. A methodology for the analysis and the control of the process, in terms of amount of wastes, has been implemented, through the control of some easily measureable features, such as the temperature of the forge or of the component itself.
Thermographic measurements of high-speed metal cutting
Bernhard Mueller, Ulrich Renz
Thermographic measurements of a high-speed cutting process have been performed with an infrared camera. To realize images without motion blur the integration times were reduced to a few microseconds. Since the high tool wear influences the measured temperatures a set-up has been realized which enables small cutting lengths. Only single images have been recorded because the process is too fast to acquire a sequence of images even with the frame rate of the very fast infrared camera which has been used. To expose the camera when the rotating tool is in the middle of the camera image an experimental set-up with a light barrier and a digital delay generator with a time resolution of 1 ns has been realized. This enables a very exact triggering of the camera at the desired position of the tool in the image. Since the cutting depth is between 0.1 and 0.2 mm a high spatial resolution was also necessary which was obtained by a special close-up lens allowing a resolution of app. 45 microns. The experimental set-up will be described and infrared images and evaluated temperatures of a titanium alloy and a carbon steel will be presented for cutting speeds up to 42 m/s.
Infrared technique for decoding of invisible laser markings
Heinz Haferkamp, Peter Jaeschke, Johannes Stein, et al.
Counterfeiting and product piracy continues to be an important issue not only for the Western industry, but also for the society in general. Due to the drastic increase in product imitation and the request for plagiarism protection as well as for reducing thefts there is a high interest in new protection methods providing new security features. The method presented here consists of security markings which are included below paint layers. These markings are invisible for the human eye due to the non-transparency of the upper layers in the visible spectral range. However, the markings can be detected by an infrared technique taking advantage on the partial transparency of the upper paint layers in the IR-region. Metal sheets are marked using laser radiation. The beam of a Nd:YAG-laser provides a modification of the surface structure, resulting in dark markings due to the annealing effect. After coating of the laser-marked material, the markings are invisible for the bare eye. In order to read out the invisible information below the coating, an infrared reflection technique is used. The samples are illuminated with halogen lamps or infrared radiators. Many coating materials (i. e. paints) show a certain transparency in the mid-infrared region, especially between 3 - 5 micrometers . The reflected radiation is detected using an IR-camera with a sensitivity range from 3.4 - 5 micrometers . Due to the different reflection properties between the markings and their surrounding, the information can be detected.
Condition monitoring of paper machine with thermal imaging
This technical paper describes the requirements to effectively use thermal imaging as a means of monitoring rotating machine components in a paper machine. The present efforts are focused mainly on monitoring polymer-covered rolls in paper machine calenders, but the studies will be expanded in the future to monitoring the temperature profiles of paper machine press fabrics and press belts in shoe presses. The main challenges in these areas are the high speeds of the target surfaces, obtaining adequate temperature difference resolution at relatively low surface temperatures and challenging environmental conditions. Adaptive triggering is discussed as a synchronization method for obtaining an adequate number of images from the target. Also some image processing techniques, test results and required qualities of infrared camera technology are presented.
Environmental, Geological, Fire, and Surveillance
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Airborne wildfire intelligence system: a decision support tool for wildland fire managers in Alberta
Doug Campbell, Wally G. Born, Judi Beck, et al.
The Airborne Wildfire Intelligence System (AWIS) defines the state-of-the-art in remotely sensed wildfire intelligence. AWIS is a commercial, automated, intelligence service, delivering GIS integrated fire intelligence, classified interpretive and analysis layers, and higher level decision support products for wildfires in near real time via the Internet. The AWIS effort illustrates flexible and dynamic cooperation between industry and government to combine technology with field knowledge and experience into an effective, optimized end-user tool. In Alberta the Forest Protection Division of the department of Sustainable Resource Development uses AWIS for several applications: holdover and wildfire hotspot detection, fire front and burned area perimeter mapping, strategic and tactical support through 3D visualization, research into the effects of fire and its severity and to document burn patterns across the landscape. A discussion of all of the scientific themes behind the AWIS is outside the scope of this paper, however, the science of sub-element detection will be reviewed. An independent study has been conducted by the Forest Engineering Research Institute of Canada (FERIC) to investigate the capability of a variety of thermal infrared remote sensing systems to detect small and subtle hotspots in an effort to identify the strengths and weaknesses thereof. As a result of this work, method suitability guidelines have been established to match appropriate infrared technology with a given wildfire management objective.
Measuring important parameters for air-sea heat exchange
The heat transfer between the ocean and the atmosphere is one of the most important parameters governing the global climate. Important parameters include the heat transfer velocity and the net heat flux as well as parameters of the underlying transport model. However, the net heat flux is hard to measure since processes take place in the thermal boundary layer, that is the topmost layer of the ocean less than 1 mm thick. Current techniques rely on three independent measurements of the constituent fluxes, the sensible heat flux, latent heat flux and radiative flux. They depend on indirect measurements of meteorological parameters and rely on a combination of data from different sensors using a number of heuristic assumptions. High relative errors and the need for long temporal averaging reduce the practicability of these techniques. In this paper a novel technique is presented that circumvents these drawbacks by directly measuring the net heat flux across the air-water interface with a single low-NETD infrared camera. A newly developed digital image processing technique allows to simultaneously estimating the surface velocity field and parameters of the temporal temperature change. In particular, this technique allows estimating the total derivative of the temperature with respect to time from a sequence of infrared images, together with error bounds on the estimates. This derivative can be used to compute the heat flux density and the heat transfer velocity, as well as the probability density function of the underlying surface renewal model. It is also possible to estimate the bulk-skin temperature difference given rise to by the net heat flux. Our technique has been successfully used in both laboratory measurements in the Heidelberg Aeolotron, as well as in field measurements in the equatorial pacific during the NOAA GasExII experiment this spring. The data show that heat flux measurements to an accuracy of better than 5% on a time scale of seconds are feasible.
MODIS land surface temperatures and their relationship with hydroclimatological parameters
Sunyurp Park, Johannes J. Feddema, Stephen L. Egbert
Daily land surface temperatures (LST) of Moderate Resolution Imaging Spectroradiometer (MODIS) data were analyzed to determine how the data were correlated with climatic water budget variables. Using a climatic water budget program, four daily water budget factors were calculated at six weather stations across the state; percent soil moisture, AE/PE, water deficit, and water deficit/PE. Land surface temperature deviations standardized with air temperature were expected to have a significant correlation with the water budget factors. To do correlation analyses on a weekly basis, daily MODIS data were integrated into three different types of weekly composites, including maximum temperature, driest-day, and combination composite data sets. Results showed that the maximum composite data set had the highest, and the driest-day composite had the lowest, correlation with the climatic water budget on average. Percent soil moisture, AE/PE, and Def/PE consistently had a high correlation with the LST deviation, whereas water deficit values showed inconsistent relationships from place to place. Time-integrated, or cumulative values of the LST-meanTair showed even stronger relationships with the water budget factors, increasing the correlation coefficients by 33.4% on average. The absolute values of their correlation coefficients ranged from 0.618 to 0.823.
Mapping quartz, carbonate minerals, and mafic-ultramafic rocks using remotely sensed multispectral thermal infrared ASTER data
ASTER sensor aboard Terra satellite has a capability of spectral measurement in the thermal infrared (TIR) region with a spatial resolution adequate for geological applications. This paper attempts mapping quarts, carbonate minerals and bulk SiO2 content in silicate rocks with the indices defined for ASTER TIR multispectral data. Silica minerals represented by the commonest mineral on earth, quartz, have a unique spectral property in TIR. They have lower emissivity in ASTER band 10 and band 12 spectral regions than in band 11. All the common carbonate minerals represented by calcite and dolomite have another unique spectral feature. They have low emissivity in ASTER band 14 spectral region, and high emissivity in ASTER band 10 to 13 spectral region. In silicate rocks, the wavelength at trough in TIR emissivity spectra systematically moves to longer wavelength as the rock type changes from felsic to ultramafic. The emissivity in band 12 is lower than in band 13 for felsic rocks, and higher for ultramafic rocks. Using the spectral features described above, several indices are defined. They are applied to ASTER Level 1B data in the study areas. The results are compared with the information from the field and the laboratory geological investigations including the TIR spectra of the rocks collected at the site and published geological maps. Potential ability of the indices in mapping quarts, carbonate minerals and silicate rocks is suggested.
Airborne thermography applications in Argentina
Eduardo H. Castro, Eduardo Jorge Selles, Marcelo Costanzo, et al.
Forest fires in summer and sheep buried under the snow in winter have become important problems in the south of our country, in the region named Patagonia. We are studying to find a solution by means of an airborne imaging system whose construction we have just finished. It is a 12 channel multispectral airborne scanner system that can be mounted in a Guarani airplane or in a Learjet; the first is a non- pressurized aircraft for flight at low height and the second is a pressurized one for higher flights. The scanner system is briefly described. Their sensors can detect radiation from the ultra violet to the thermal infrared. The images are visualized in real time in a monitor screen and can be stored in the hard disc of the PC for later processing. The use of this scanner for some applications that include the prevention and fighting of forest fires and the study of the possibility of detection of sheep under snow in the Patagonia is now being accomplished. Theoretical and experimental results in fire detection and a theoretical model for studying the possibility of detection of the buried sheep are presented.
Flight testing the infrared eye prototype
Benoit Ricard, Paul C. Chevrette, Mario Pichette
The Infrared (IR) Eye was developed with support from the National Search-and-Rescue Secretariat (NSS), in view of improving the efficiency of airborne search-and-rescue operations. The IR Eye concept is based on the human eye and uses simultaneously two fields of view to optimize area coverage and detection capability. It integrates two cameras: the first, with a wide field of view of 40 degree(s), is used for search and detection while the second camera, with a narrower field of view of 10 degree(s) for higher resolution and identification, is mobile within the wide field and slaved to the operator's line of sight by means of an eye-tracking system. The images from both cameras are fused and shown simultaneously on a standard high resolution CRT display unit, interfaced with the eye-tracking unit in order to optimize the man-machine interface. The system was flight tested using the Advanced System Research Aircraft (Bell 412 helicopter) from the Flight Research Laboratory of the National Research Council of Canada. This paper presents some results of the flight tests, indicates the strengths and deficiencies of the system, and suggests future improvements for an advanced system.
Spawning migration and intraspecies differentiation of pink salmon from northwestern Sakhalin waters
Alexander N. Ivanov, Alexej Shershnev, Nina Ph. Kaplanova, et al.
Pacific salmon fishery near the northwestern Sakhalin coast is based on fish spawning both in the island and continental rivers. Salmon fishery near the Sakhalin coast of Amur Estuary has significantly lost contact with the main salmon rivers of the region. Pink salmon is the most abundant salmon species of the region rivers. Biology of the northwestern Sakhalin pink salmon is less studied of all the fishery regions on the island. So far, their migratory ways from feeding and wintering areas to the spawning rivers have not been ascertained. The results of monitoring for pink salmon have shown that by some biological indices, commercial-statistic data, and also by the data of satellites NOAA-10, NOAA-12, NOAA-14, their commercial catches near the northwestern Sakhalin are formed by fish groups migrating both through the Amur Estuary from the south, and through the Sakhalin Bay from the north. The base of spawning fish in rivers of northwestern Sakhalin is formed by the summer pink salmon migrating from the north. A preliminary computation of distinguished pink salmon groups (summer southern and northern autumn) shows a ratio 0.1:5.7:1 in odd years and 1:2:1 in even years.
Cloud effects on thermal downwelling sky radiance
Mark A. Goforth, George W. Gilchrist, Joseph D. Sirianni
Total sky irradiance onto the Earth's surface includes contributions from solar (or shortwave) radiation as well as thermal (longwave) radiation. Whereas shortwave downwelling is only present during daylight hours, thermal downwelling radiation is present throughout the day and night. Sky thermal irradiance on the Earth's surface has been described in other references as a function of surface ambient temperature and relative humidity. In this study, we show that with the introduction of low overcast clouds (altitude less than 2km and 100% cloud cover), thermal downwelling sky irradiance increases 34%. A comprehensive model was developed to compute the thermal downwelling sky irradiance as a function of temperature, relative humidity, cloud height, and percent cloud cover. Based on ground truth measurements collected in Reston, Virginia, we propose coefficients to model the total thermal downwelling irradiance including cloud effects with an operational error of 9.7%.
Multispectral back-scattering spectrometer for water quality measurement
Mohammad Zubir Mat Jafri, Khiruddin Abdullah, Mohammed Noordin Abu Bakar, et al.
The conventional method used to measure the pollution level of water is by collecting samples and analyzing them in the lab. This method is not efficient and cannot provide a real-time result, whereas, digital image processing and remote sensing techniques have been widely used in estimating and mapping water pollution levels in vast areas. Various algorithms have been developed and used for the measurement of the water pollution level. In this work, an algorithm developed for remote sensing techniques is used. The technique employed involves radiating the samples with a laser and then correlating the backscattering with water pollution level. A laser emitting multiple wavelengths are radiated into the water sample and backscattering radiations for every wavelength are analyzed and correlated with the pollutant concentration. The backscattering radiation is then analyzed and the proposed water quality algorithm is calibrated for measuring the pollution level of the samples.
Building and Infrastructure
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Mapping hidden wall structures by quantitative IR thermography
Knowledge of an historic monument can be substantially improved by locating hidden structures, openings and the wall bonding beneath the plaster. When restoring buildings, the physical connection between the walls must be known in order to predict the risk areas for structural weakness. IR Thermography produces remarkable results, especially by means of the quantitative approach. The temperature pattern detected by thermography and analyzed in space and time maps the hidden structure of the wall. Thick walls exposed to the weather represent a challenge in detecting hidden structures by means of thermography. Frequently output is very poor because testing conditions are not optimized. Hence, appropriate testing requires careful analysis of the wall system before and after taking the thermograms. Otherwise, false alarms render the images useless. This paper describes a general procedure applied to see the hidden wall structure. It works in three steps: a) a mathematical simulation of the real test by a dedicated software, implementing the 3D thermal problem; b) a transient thermographic test, delivering a suitable heating flux on the surface for the proper time; c) processing test data, including a thermogram sequence and air temperature analysis. Here, are reported tests achieved on a XV-XVIIth century Palace at Cremona (Italy) and in the Westcott House in Springfield (OH).
Thermal performance of windows by means of thermography and heat-flux meters
The replacement of windows is the most common renovation measure in Finland. There are also problems in new buildings especially with new thin light metal-framed windows, even though the U-value of the pane would be acceptable. The minor defects in the installation may cause IAQ-problems - because of seam leaks and thermal bridges. There is no general procedure for condition survey of windows based on measurements. In this paper a procedure for testing windows in in-situ conditions is presented based on case studies. Thermal performance of windows can be measured using thermography and supporting methods, like heat-flux measurements and air leak tests. Even though the absolute results may include interfering factors, we can compare the windows with each other (depending on the conditions) and make decisions on the quality of the installation work and the thermal performance of windows.
Unique thermal problem found in certain double-glazed windows
Robert W. Spring, John R. Snell Jr.
Thermography has been used with great success for number of years to inspect building fenestration, both during design and production, as well as after installation.1 Typically double-glazed windows exhibit a well-understood pattern of increased heat loss around the perimeter, due mainly to thermal bridging or edge-effect losses. In this paper we present the findings of an investigation about a very different, and unusual, thermal pattern discovered on windows in the home of one of the authors. The pattern was first illuminated by condensation in the central portion of the window. This thermal pattern was verified with a radiometric thermal imaging camera as well as thermal contact probes. After additional investigation we found the cause of this anomalous pattern is related to the loss of some of the insulating argon gas installed in the window during manufacturing. We also discovered the problem was a not uncommon for certain types of windows. As these windows age, the problems usually become more pronounced and, in some cases, a total failure of the window by implosion results. We hope that publication of this information will rove useful to others who may have been mystified after seeing similar patterns.
Role of emissivity in infrared thermographic imaging and testing of building and structural materials
Antonia Moropoulou, Nicolas P. Avdelidis
Emissivity can be defined as an expression that describes the optical properties of a material in sense of the extent of energy emitted with regard to an ideal black body. Since there is no infrared camera that can read temperature directly, correct emissivity values ought to be measured with the intention of interpreting thermal images obtained from thermographic surveys. In the present work, the emissivity values of numerous building and structural materials, such as stones, plasters, mortars, marbles and mosaics' tesserae, were calculated in accordance with the relevant ASTM standard approach or by the use of an empirical laboratory developed approach. The obtained emissivity values were discussed and explained in terms of the approach used, the wavelength effect, as well as the materials surface condition.
Verification of dynamic buffer zone (DBZ) wall assembly performance using infrared thermography
Antonio Colantonio, Rick Quirouette
A new type of exterior building enclosure called the dynamic buffer zone (DBZ) system is being designed and built for both new projects and retrofit of existing buildings. Dry conditioned air is forced into and out of interstitial exterior wall cavities by means of dedicated mechanical systems in such a manner as to constantly ensure positive pressure within the cavities relative to interior environments. The primary reason for implementation of this type of design solution is to ensure elimination of moisture accumulation from either interior or exterior sources within the enclosure assemblies. Enclosure cavities are maintained at such low absolute humidity that the cavity air maintains a dew point temperature below the outdoor temperature for most of the time during winter. Since these types of building enclosures rely on mechanical systems, performance verification and commissioning are key components to the success of the assembly to achieve its objectives. Pressure differential, relative humidity and temperature sensors are necessary to ensure effective operation of these types of assemblies but they cannot determine the performance of all areas of exterior assemblies. Infrared thermography is used in combination with data from these sensors to determine the hygrothermal performance of all areas of enclosure assemblies. This paper will discuss the methodology of DBZ wall commissioning and some of the issues related to detection of improper wall assembly performance.
Practical utilization of thermography in road construction and in waterproofing systems
An overview of the damages, which can be detected by thermography in road and bridge paving, is given. Emphasis is placed on the detection of blisters in waterproofing membranes and bridge decks, as those disturb the heat flow. This system may be used both during construction and after deployment. Data collected during the construction (such as temperature of mixture during paving, temperature of the underground or temperature during flame up of waterproofing membranes) influence the quality of the building, suggesting the addition of thermograms to the building documentation. Some challenges in the analysis of thermograms due to patching on the roads are exposed and possible evaluation tools are presented. The currently utilized thermography is a passive system with seasonal and weather employment limitations; preliminary results of a test to assess the use of microwaves as heat source are presented.
Quantification of incident radiation on building wall surfaces by means of infrared thermography
Stefan Datcu, Laurent Ibos, Simone Mattei, et al.
By using quantitative thermal scanning of building surface structures, it is possible to access to the temperature field. For the further calculation of the heat flux exchanged by these structures with the environment, one must quantify as finely as possible the temperature field on the bodies' surfaces. For this purpose we have to take into account the fact that real bodies are not black which implies that a parts of the radiant energy received by the infrared camera detectors is reflected radiation. In this paper, we present a method to quantify the energy issued by all the bodies placed into e virtual hemisphere surrounding the thermal scene. The target body is a multi-layers wall, which represent a simplified version of a real building structure. In order to validate the method, we have compared the results obtained by thermocouple measurements and by computer simulation of the body with the corrected temperature field.
Thermographic NDT of building envelopes utilizing in-door heating systems
Tatsuhito Komiyama, Yonezou Nakano, Yasuo Tanigawa
The deterioration of concrete structures due to drastic changes in environment or due to poor workmanship has become very serious in Japan recently. In particular, since buildings are finished with render or tile on their facades in order to improve durability and appearance in many cases, the number of accidents resulting in injury or death caused by the fall of these finishing materials in increasing continuously. As a method of detecting delaminations of finishing materials, the thermographic survey using thermal imager is widely used because of the advantages of easiness, rate of data sampling and safeness. However, since this method is based on the difference of surface temperature between delaminated areas and sound areas generated by solar radiation, the method cannot be used under cloudy weather. It is a big difference between the construction field and other fields like metals, ceramics and plastics, which can do artificial heating or cooling easily. In order to improve the applicability and limitations of the method, a study was carried out. In ths study, instead of exposing an external wall to the sun, a method of heating the rear side of the wall by using the indoor heating system of the building was discussed and tested. As a result, it was proved that below-surface defects of building facades could be located without solar radiation by controlling the room temperature appropriately. This paper outlines the procedure and results of the study.
Detection of moisture in porous materials by infrared thermography
Antonia Moropoulou, Nicolas P. Avdelidis, Georgios Haralampopoulos, et al.
Frequently, damages in porous materials arise as a direct or indirect consequence of moisture concentration and transport. Usually, detection of the existing moisture in porous materials is fundamentally necessary, in order to identify the actual damage, as well as their deterioration rate. There have been numerous reports about moisture detection in porous media, employing various direct techniques. In this research work, infrared thermography was employed with the intention of assessing moisture concentration in reference porous materials in the laboratory. Untreated and consolidated porous stones were subjected to capillary rise moisture tests, whilst infrared thermography was used for the monitoring of these laboratory tests. The performance of the investigated porous materials, in order to interpret the moisture phenomena studied and the obtained thermographs, was also examined in terms of their microstructure (mercury intrusion porosimetric results) and isothermic behavior (water sorption curves). The results of this work indicate that thermography ought to be considered as a nondestructive assessment tool for the detection of moisture in porous materials.
Predictive Maintenance
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Infrared inspection applied to offshore platforms: Petrobras experience at Campos Basin
Edson Andre Verdini, Attilio Bruno Veratti
Bacia de Campos (Rio de Janeiro - Brazil) is one of the biggest offshore petroleum fields in the world today. In June 2001, Bacia de Campos, having more than 490 oil wells, 34 offshore platforms and 7 modified ships in operation, reached 1,3 million barrels/day. If compared to OPEP countries only nine of them got an average production higher than 1 million barrels/day in 2000, which means it can be placed on the 10th position in the rank of oil producers. In this context this work aims not only to show the results achieved within the introduction of thermographic inspections in offshore oil production (platforms and ships), but also the financial results (ROI - Return of Investment) considering the use of this particular technique. Bacia de Campos got a ROI around 7 million dollars in the last 4 years, which means a hundred times higher than the total cost of thermographic services in the same period. As far as we know this is one of the best results already reported in the world. We also present the methodology applied to analyze thermal anomalies in electrical components and data management software, including advanced Digital Reports sent via Internet.
Developing a comprehensive training curriculum for integrated predictive maintenance
On-line equipment condition monitoring is a critical component of the world-class production and safety histories of many successful nuclear plant operators. From addressing availability and operability concerns of nuclear safety-related equipment to increasing profitability through support system reliability and reduced maintenance costs, Predictive Maintenance programs have increasingly become a vital contribution to the maintenance and operation decisions of nuclear facilities. In recent years, significant advancements have been made in the quality and portability of many of the instruments being used, and software improvements have been made as well. However, the single most influential component of the success of these programs is the impact of a trained and experienced team of personnel putting this technology to work. Changes in the nature of the power generation industry brought on by competition, mergers, and acquisitions, has taken the historically stable personnel environment of power generation and created a very dynamic situation. As a result, many facilities have seen a significant turnover in personnel in key positions, including predictive maintenance personnel. It has become the challenge for many nuclear operators to maintain the consistent contribution of quality data and information from predictive maintenance that has become important in the overall equipment decision process. These challenges can be met through the implementation of quality training to predictive maintenance personnel and regular updating and re-certification of key technology holders. The use of data management tools and services aid in the sharing of information across sites within an operating company, and with experts who can contribute value-added data management and analysis. The overall effectiveness of predictive maintenance programs can be improved through the incorporation of newly developed comprehensive technology training courses. These courses address the use of key technologies such as vibration analysis, infrared thermography, and oil analysis not as singular entities, but as a toolbox resource from which to address overall equipment and plant reliability in a structured program and decision environment.
New detection method of faulty distribution power apparatus using thermal images
In automatic diagnosis of a power distribution apparatus is utilizing thermal images problems arise in that there are problems, that there are many thermal patterns similar to the thermal pattern of the target apparatus and that the temperature around the apparatus influences the diagnosis. In order to solve these problems, we developed a new method whereby images of the apparatus are extracted by an image processing technique based on high-order local autocorrelation features, the attachment pattern on a pole, and a disparity map; a faulty apparatus is identified based on the local temperature gradient. In the extraction method, the distance information provided by the disparity map narrows the search area of the apparatus. The search is conducted according to the rule that an apparatus feature that is defined by high-order local autocorrelation features appears at certain intervals, according to the attachment pattern on a pole, in the search area. The local temperature gradient detects local heat in the form of leakage current on the faulty apparatus. Experiments using the proposed method were conducted under different weather conditions, at different times and seasons. An error rate of 3% was obtained from experiments on the extraction of an apparatus, and an error rate of 17% was obtained from experiments on the detection of a faulty apparatus. The proposed method can extract and detect faulty apparatuses, such as a pin insulator, a section switch and a strain insulator, except in the case where the distance between the pole and the infrared camera is so large that the sensitivity is insufficient.
Load and torque: what is the infrared connection?
To see the spark of a short circuit in an electrical component is a human ability. To detect the hot spot in a faulty electrical connection long before the component reaches a failure state is an ability which infrared thermography is noted for throughout the inspection community. Over the years, the inspection industry has developed various guidelines for different fault categories as it relates to measured surface temperatures. These temperature categories indicate the electrical connection's severity and in turn equate to a repair schedule. Typically during an electrical thermographic inspection the component's phase loading should be obtained by an electrician. However, quite often this is not achievable. In the absence of phase loading measurements, the thermographer must diagnose thermal patterns to accurately identify the fault type, i.e. loose, overload, etc.. More times than not, this predictive maintenance tool detects loose connections. Unfortunately, the phase connection's torque value is not obtainable during an infrared inspection to see how loose or tight the connection really is. Therefore, to measure the phase loading is only one aspect. Knowing the connections' torque value is another. This paper is intended to reveal the infrared relationship between variable phase loading, variable lug torque and the associated surface temperatures.
Biomedical and Agriculture
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Progress in theoretical, experimental, and computational investigations in turbid tissue phantoms and human teeth using laser infrared photothermal radiometry
This paper reviews and describes the state-of-the-art in the development of frequency-domain infrared photothermal radiometry (FD-PTR) for biomedical and dental applications. The emphasis is placed on the measurement of the optical and thermal properties of tissue-like materials using FD-PTR. A rigorous three-dimensional thermal-wave formulation with three-dimensional diffuse and coherent photon-density-wave sources is presented, and is applied to data from model tissue phantoms and dental enamel samples. The combined theoretical, experimental and computational methodology shows good promise with regard to its analytical ability to measure optical properties of turbid media uniquely, as compared to PPTR, which exhibits uniqueness problems. From data sets obtained with calibrated test phantoms, the reduced optical scattering and absorption coefficients were found to be within 20% and 10%, respectively, from the independently derived values using Mie scattering theory and spectrophotometric measurements. Furthermore, the state-of-the-art and recent developments in applications of laser infrared FD-PTR to dental caries research is described, with examples and histological studies from carious dental tissue. The correlation of PTR signals with modulated dental luminescence is discussed as a very promising potential quantitative methodology for the clinical diagnosis of sub-surface incipient dental caries. The application of the turbid-medium thermal-wave model to the measurement of the optical absorption and scattering coefficients of enamel is also presented.
Effects of peripheral dynamic movements on the lower-limb circulation assessed by thermography: three one-group studies
Anne Kaerki, Matti Laehdeniemi
Peripheral dynamic movements are used as part of postoperative protocols and for preventing vascular complications during bed rest. The effects of peripheral movements have not been studied. The purposes of these studies were to explain the effects of peripheral dynamic movements on lower limb circulation. The aim was also to explain how other factors like sex, age, BMI, medication, smoking, sports activity etc. affect the circulation. Healthy young subjects (N=19), healthy elderly subjects (N=19) and diabetic subjects (N=21) participated in the studies between 1997 and 1999. The study design was the same in each study. Infrared technology and image processing belong to our focus fields of applied research and IR is widely used in our real time industrial applications including also ongoing research of new possibilities. This paper presents the results of our newest application of IR thermography, where it was used to measure the skin temperature over the soleus muscle during and after dynamic ankle movements. The results showed that the skin temperature increased further during the recovery period after movements, and temperature was highest after 3- 5 minutes. Diabetic male subjects were the only subgroup that had immediate decrease during recovery period. The studies showed that smoking had a negative effect on circulation. BMI had also negative correlation (-0,356), showing that subjects with higher BMI had less increase. The results proved that peripheral movements were effective for increasing circulation in the soleus muscle and the effect was still seen after 15 minutes.
Response of the oscillator systems resident in biological cells to changes in temperature
Oscillating polar entities, such as protein molecules embedded in the cell's membrane or microtubules in the cell's interior are, as theoretically predicted and empirically demonstrated, sources of electromagnetic fields with frequencies ranging from far infrared to the MHz domain. The preliminary results obtained in our laboratory suggest connection of the characteristics of observed electromagnetic signals with the phases of the mitotic cycle. Such techniques, if adequately developed, could form a basis of new diagnostic methods in cytology. The present contribution examines the influence of temperature changes (within the physiologically acceptable limits) on properties of the oscillator ensembles, in particular on dependences of the occupation numbers versus the energy pumping rate.
Infrared thermography: a tool to map temperature anomalies of plants in a greenhouse heated by gas fired infrared heaters
Sven-Ake Ljungberg, Owe Joensson
A successful production of plants in a greenhouse requires a microclimate adapted to the needs of each specific type of plant produced. Ambient temperature and humidity are two important parameters. This paper describes preliminary results from a field study using infrared thermography to map the temperature distribution pattern of tables for plant production, gas heated infrared radiation tubes, and of plants at different stages of growth. Comparative studies are performed for one gas-IR heated greenhouse and one reference greenhouse with a conventional water based heating system. Preliminary results indicate that infrared thermography is an efficient way to detect temperature anomalies of the heating systems and of the heat distribution systems of a greenhouse. Thermography could also be used as a tool when calibrating and evaluating the function of greenhouse heating systems, and to indicate anomalies in the growth process of the plants.
Thermographic measurements on plant leaves
Christoph Garbe, Ulrich Schurr, Bernd Jaehne
An important process of plant physiology is the transpiration of plant leaves. It is actively controlled by pores (stomata) in the leaf and the governing feature for vital factors such as gas exchange and water transport affixed to which is the nutrient transport from the root to the shoot. Because of its importance, the transpiration and water transport in leaves have been extensively studied. However, current measurement techniques provide poor spatial and temporal resolution. With the use of one single low-NETD infrared camera important parameter of plant physiology such as transpiration rates, heat capacity per unit area of the leaf and the water flow velocity can be measured to high temporal and special resolution by techniques presented in this paper. The latent heat flux of a plant, which is directly proportional to the transpiration rate, can be measured with passive thermography. Here use is made of the linear relationship between the temperature difference between a non transpiring reference body and the transpiring leaf and the latent heat flux. From active thermography the heat capacity per unit area of the leaf can be measured. This method is termed active, because the response of the leaf temperature to an imposed energy flux is measured. Through the use of digital image processing techniques simultaneous measurements of the velocity field and temporal change of heated water parcels traveling through the leaf can be estimated from thermal image sequences.
Visualization of early stress responses in plant leaves
Laury Chaerle, Martin J. vandeVen, Roland L. Valcke, et al.
Plant leaves possess microscopic valves, called stomata, that enable control of transpirational water loss. In case of water shortage, stomata close, resulting in decreased transpirational cooling. The ensuing temperature increase is readily visualized by thermography. Salicylic acid, a central compound in the defense of plants against pathogens, also closes stomata in several species. In previous work, thermography permitted to monitor an increase in temperature after infection of resistant tobacco by tobacco mosaic virus, before visual symptoms appeared. Furthermore, cell death was visualized with high contrast in both tobacco and Arabidopsis. In addition to transpiration, photosynthetic assimilation is a key physiological parameter. If the amount of light absorbed by chlorophyll exceeds the capacity of the photosynthetic chain, the surplus is dissipated as light of longer wavelength. This phenomenon is known as chlorophyll fluorescence. If a plant leaf is affected by stress, photosynthesis is impaired resulting in a bigger share of non-utilized light energy emitted as fluorescence. The potential of an automated imaging setup combining thermal and fluorescence imaging was shown by monitoring spontaneous cell death in tobacco. This represents a first step to multispectral characterization of a wide range of emerging stresses, which likely affect one or both key physiological parameters.
Optimized laser application in dermatology using infrared thermography
Roderick A. Thomas, Kelvin E. Donne, Marc Clement, et al.
Infrared thermography can be used to optimize the application of lasers in dermatology with particular reference to the treatment of certain skin disorders such as vascular lesions and depilation. The efficacy of treatment is dependent upon a number of factors including: Optimization and correct selection of laser parameters such as wavelength and spot size. Human factors, such as laser operator skill, patient's skin type and anatomical location. By observing the thermal effects of laser irradiation on the skins surface during treatment results in improved efficacy and minimizes the possible threshold to skin damage, reducing the possibility of burning and scarring. This is of particular significance for example, in the control of purpura for the treatment of vascular lesions. The optimization is validated with reference to a computer model that predicts various skin temperatures based on two different laser spot sizes.
Research and Development
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Thermography detection of damage initiation during fatigue tests
Jean-Claude Krapez, Didier Pacou
The design of mechanical structures that are subject to repeated loads relies upon the knowledge of the fatigue limit of the constitutive materials. Conventional methods for the fatigue limit evaluation are lengthy and therefore expensive. We propose a new approach for this problem. It is based on the detection of a modification of the thermomechanical couplings occurring together with the damage onset. A specific synchronous demodulation thermography approach was devised which provides a map of the two first harmonics of temperature and a map of the temperature mean rise. Experiments performed on steel XC48, 316L and on Al 7010, Al 2024 show the high potential of this method.
Emerging applications for high-performance near-infrared imagers
Recent advances in ultra-high performance InGaAs focal plane array (FPA) technology has enabled many new imaging applications in diverse fields. This paper briefly describes the InGaAs FPA technology developed by Indigo Systems Corporation, outlines the performance specifications of a new camera based on this InGaAs FPA, and highlights some of the applications for this technology, including laser beam and material characterization and NIR imaging spectroscopy.
Applications for high-performance thermal imaging cameras
High-performance thermal imaging cameras based on indium antimonide (InSb) focal plane arrays (FPAs) offer excellent sensitivity in the midwave infrared band, notably in the 3-5 micron waveband. Noise levels below 20 mK enable detection of surface temperature differences of 0.1 C, and the high-speed response of the InSb photodetectors enablesv the capture of events on time scale as short as 5 microseconds.
Energy analysis of fatigue damage by thermographic technique
Anna Eva Morabito, Vito Dattoma, Umberto Galietti
The main aims of this paper are to describe the thermographic methodologies currently used in Italy for the rapid evaluation of the fatigue limit and to describe the local energy approach actually under development by the authors. Thermographic methodologies currently used in Italy for the rapid evaluation of the fatigue limit were applied to two stainless steels (AISI 304 and AISI 409). All the experimental results here obtained are in good agreement with the respective values reported in literature. An experimental program for the local energy approach is under development: its main characteristic consists in doing, besides the usual thermal measurements made by thermography, mechanical measurements in order to evaluate the mechanical energy locally dissipated inside the material. This experimental research is part of an interuniversity research program and it is made on stainless steel (AISI 304) notched specimens.
Passive gas imaging: preliminary results from gas leak simulations-a field study performed under real-world conditions
Sven-Ake Ljungberg, Owe Joensson
The set up for a field test site for simulation and detection of methane gas leaks is described. The problems of detecting gas leaks in real world conditions are discussed. Results from interpretation of images from passive gas imaging surveyed during different delta T, gas flow, and wind conditions are presented and analyzed. The continuation of the research project and its connection to ongoing international research of passive and active gas imaging is described.
Thermoelastic and thermoplastic effects investigated in steel, polyamide, and shape memory alloys
Elzbieta Pieczyska, Stefan Gadaj, Wojciech Nowacki
This research is an experimental confirmation of the theoretical model, presented by M.G. Beghi, C.E. Bottani and G. Cagliotti, realized due to the contact less method of temperature measurement and conversion. The effects of thermomechanical coupling occurring in austenitic steel, polyamide and shape memory alloys were examined. The change of character of the samples temperature was applied as a criterion for the limit between the elastic and plastic regimes. The thermal effects concomitant with thermoelastic unloading were also quite precisely evaluated. The obtained results indicate on both qualitative and quantitative differences between thermomechanical behaviors of the materials subjected to deformation. TiNi shape memory alloy was tested both at room and at elevated temperatures. The temperature distribution on the surface of specimen examined at ambient temperature was uniform, while for the specimen deformed at elevated temperature the areas of higher temperature were registered. There are probably the regions of creation and developing of the new - martensite phase.
NDT I
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Infrared detection of thermomechanical coupling in solids
Minh Phong Luong
The thermal effects due to thermomechanical coupling in solids have been identified within the general framework of the thermodynamics of irreversible processes based on internal variables. The paper aims to illustrate the use of infrared thermography as a nondestructive, real-time and noncontact technique to detect, observe and evaluate the evolution of temperature changes caused by the diverse processes of irreversible physical phenomena. The results obtained highlight the advantages of differential infrared thermography. This technique minimizes the thermal noise in real or industrial environments and thus facilitates the detection, discrimination and interpretation of the diverse dissipative phenomena involved in these nonlinear coupled thermomechanical effects within the framework of a consistent theoretical background. Stress and strain concentrations in loaded materials and structural components occur and result in localized forces that are sufficient to promote plasticity and/or inelasticity. At the structural level, breakdown appears as microcracking and possibly slippage at component interfaces. In addition to traditional techniques of mechanical strength evaluation, it provides a ready evaluation of a limit of acceptable damage under service loading beyond which the material will be rapidly destroyed, or of fatigue resistance under cyclic excitations or dynamic solicitations. Finally this paper suggests various potential applications of the thermal scanning technique in diverse engineering domains: detection of fluid leakage, nondestructive testing using thermal conduction phenomena, elastic stress measurements, localization of dissipative phenomena and rapid evaluation of fatigue limit for industrial materials.
Advanced modeling of thermal NDT problems: from buried landmines to defects in composites
Advanced thermal models that can be used in the detection of buried landmines and the TNDT (thermographic nondestructive testing) of composites are discussed. The interdependence between surface temperature signals and various complex parameters, such as surface and volumetric moisture, the shape of a heat pulse, material anisotropy, etc., is demonstrated.
Genetic algorithm for flaw characterization based on thermographic inspection data
A genetic algorithm is applied to the task of aw characterization based on active thermal inspection data. Experimental observations pertaining to test samples with axisymmetric inclusion aws are used to validate the approach, with encouraging results. Errors in identification are discussed and can, at least in part, be attributed to the use of a relatively primitive fitness function formulation and the assumption in the heat-transfer model of negligible heat-loss through convection and radiation. The general approach however appears sound and can be modified to include important heat-transfer mechanisms and alternative fitness function formulations.
Enhancement and reconstruction of thermographic NDT data
Steven M. Shepard, James R. Lhota, Bruce A. Rubadeux, et al.
Visualization and analysis of pulsed thermographic data for NDT has generally been based on simple image averaging, subtraction or slope operations. Quantitative contrast methods, based on comparison to a defect free reference point or region, have also been used to a lesser extent. Despite their widespread use, all of these methods are highly susceptible to noise, nonlinearity of the IR camera response, and the presence of surface features on the sample. More importantly, the ability of any of these methods to significantly improve the ability to retrieve deep or weak subsurface features beyond the original unmodified image is limited. In a previous paper, we introduced the concept of Thermographic Signal Reconstruction (TSR) as a means of enhancing defect to background contrast while reducing the amount of data that must be stored by an order of magnitude. The TSR method increases the depth range over which pulsed thermography can be applied, and also reduces the amount of blurring due to lateral diffusion that is typical of thermographic imaging. In this paper we compare TSR with conventional thermographic approaches and consider the mechanisms for the resulting performance improvements.
Single-sided thermal diffusivity imaging in composites with a shuttered thermographic inspection system
A measurement configuration is discussed where shutters are placed in front of the imager and the flash lamps. Proper timing for the opening and closing of the shutters eliminates a direct interaction between the imager and flash lamps for a single sided measurement, enabling accurate measurement of the thermal response of a specimen. The time dependence of the thermal response is analyzed to produce an image of the effective diffusivity of the specimen.
Inspection of high-performance peltier coolers using lock-in thermography
Peltier cooling devices are used on the Hubble Space telescope for temperature control of various detector packages. A typical construction of these devices involves sandwiching an array of Bismuth-Tellurium (Bi2Te3) posts between two ceramic plates. When a DC current is applied to the device heat is moved from one side of the device to the other, depending on the polarity of the current. Because these devices can change temperature very rapidly, there is the potential for damage due to thermal expansion and contraction of the constituents. A failure in the bonding of the Bi2Te3 to the ceramic sheet can lead to reduced efficiency or failure of the device. NASA Langley Research Center has developed a nondestructive thermal imaging technique to determine the integrity of the Bi2Te3 posts through the ceramic surface of the peltier device. By driving the peltier device with a time varying DC current, a corresponding temperature rise and fall can be observed on the surface of the device using a commercial infrared camera. Lock-in thermography can then be used to construct both phase and amplitude images of the front surface temperature. It has been found that failure of Bi2Te3 posts results in a measurable change in both the amplitude and phase. This paper will describe an inspection method that has been developed and show results of the inspection of the extremely small Bi2Te3 posts whose dimensions are 0.81mm by 0.81mm and approximately 1.45mm tall.
NDT II
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Application of lock-in data processing for thermographic NDT of concrete structures
Takahide Sakagami, Shiro Kubo, Shiro Nakamura, et al.
A new quantitative nondestructive testing technique for delamination defects in concrete structures was developed based on the phase delay measurement using a lock-in infrared thermography under the application of periodical heating. The lock-in thermography technique was developed based on the thermal insulation method thermographic NDT. Experimental studies were made on the applicability to the detection of artificial delamination defects in concrete blocks. Concrete blocks were periodically heated by quartz lamps combined with the light dimmer controller. The controller was operated by the same reference signal for the lock-in thermography. It was found that the delamination defects were detected by the localized contrast change in the phase delay images. It was also found that the location and size of the delamination defects can be estimated by the area of contrast change in the phase delay images which was clearly observed compared with conventional thermography techniques. The relationship between the values of phase delay and heating period was examined for several defect depths and several heating periods. It was found that the phase delay curve for certain defect depth shows the peak of the contrast in phase delay image at certain heating period and the depth of the delamination defects can be estimated from this relationship. Finally, the proposed lock-in thermographic NDT technique was applied for the quantitative measurement of the actual delamination defects found under railway bridge. It was fund that the depths of the delamination defects can be estimated using the master curve of the relationship between the values of phase delay and heating period made by the experiments for artificial delamination defects.
NDT I
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Dielectric constant measurements by IR thermography in microwave heating
Gennaro Cuccurullo, Vincenzo Pierro
In this paper a technique based on microwave heating and IR thermography measurement for dielectric constant estimation is proposed. The effect of the propagating EM wave on the temperature distribution inside the sample under test is studied for short observations time. A model was derived and a suitable data reduction is accomplished. Preliminary results are presented and discussed for the pure water case.
Detection of foreign substances in food using thermography
Peter Meinlschmidt, Volker Maergner
This paper gives a short introduction into the possibility of detecting foreign bodies in food by using IR thermography. The first results shown for combinations of cherries and chocolate and berries contaminated with leaves, stalks, pedicel and thorns could be easily evaluated manually. Therefore the differing emissivity coefficients or the different heat conductivities and/or capacities are used for differentiation. Applying pulse thermography, first heat conductivity measurements of different food materials are performed. Calculating the contrast of possible food / contaminant combinations shows the difficulty of differentiating certain materials. A possible automatic evaluation for raisins contaminated with wooden sticks and almonds blended with stones could be shown. The power of special adapted algorithms using statistical or morphological analysis is shown to distinguish the foreign bodies from the foodstuff.
NDT II
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Burst phase-angle thermography with elastic waves
Alexander Dillenz, Thomas Zweschper, Gerhard Busse
Defect selective non-destructive testing methods are increasingly being used for safety relevant applications in aerospace and related fields. The main advantage is the clarity in interpretation of such methods: defects are revealed while non- relevant structural information is suppressed. One way to achieve defect selectivity is the combination of mechanical load to generate heat inside a sample and thermography to detect the resulting thermal waves. Ultrasound Lock-in thermography is one example of an established defect selective testing method described previously. In this paper, several kinds of excitation sources and modulation shapes are discussed.
Portable combined thermography/shearography NDT system for inspecting large composite structures
The use of a combination TNDT/SNDT (Thermographic nondestructive testing/ Shearographic nondestructive testing) system for the inspection of large composite structures is discussed. While each of the techniques may find defects on a particular composite structure, each may show types or sizes of defects that the other does not. The two methods complement one another well. A combination TNDT/SNDT system would provide the benefits of both techniques.
NDE of porosity in CFRP by multiple thermographic techniques
Non Destructive Testing on aerospace components is continuously changing due to the developments in materials and manufacturing processes. Thermography, if compared with other methods is gaining a role that mainly depends on findings reliability. Furthermore, dedicated procedures to particular component-defects couples are devised using advanced tools. This paper is devoted to the identification of porosity anomalous level on composite structures by thermography. Porosity is normally investigated by ultrasound techniques that, on the other hand, under usual conditions, are not always able to distinguish voids from resin starved zones (which they are themselves defects under some circumstances). The continuous behavior of this kind of defect makes ordinary controls very difficult. The thermal properties mapping evaluation of local diffusivity and effusivity is used for this purpose. Both measures are sensible to the principal thermal properties variation, but the combination allows increasing considerably reliability of the result. Experimental results obtained on a real aeronautic part in different experimental conditions are reported and compared with findings given by Ultrasounds. Numerical modeling of the various conditions helps to select suitable heating devices. A principal goal is the fast testing of a whole component in a one shot. A significative time saving is added to an easier interpretation of data.
Hybrid procedure to characterize hidden defects in composite materials
Umberto Galietti, Sebastiano Ladisa, Carmine Pappalettere, et al.
Among the non destructive methods used for the control of composite material, the infrared thermography is being given more and more attention since it enables to analyze the effects induced by the anomalies on the thermal behavior of the material. In particular the Lock-in and the Pulse techniques can provide information about the dimension and the depth of the defects. The present work aims at exploit the results given by the thermographic analysis, after a continuous heating by means of a microbolometric thermocamera, by defining a hybrid procedure, numerical and experimental. The main purposes of the hybrid procedure are: Determining the characteristics (in terms of dimensions and depth) necessary in order to make a certain type of defect detectable inside a laminate of composite material; Discovering the minimum prerequisites which a thermographic detection system should have.
Quantitative thermal nondestructive evaluation using an uncooled microbolometer infrared camera
Recent advances in uncooled microbolometer detector arrays has resulted in low cost, small size/weight, and low power consumption infrared cameras. The purpose of this paper is to assess the capabilities of the new microbolometer infrared cameras for quantitative thermal nondestructive evaluation. The camera assessed is a 160 x 128 uncooled microbolometer sensor array operating in the long wavelength infrared band (7.5 to 13.5 microns). The camera size is 4.32 H x 4.32 W X 10.92 L centimeters. Quantitative thermal diffusivity and thickness images obtained by minimizing the squared difference between the data and a thermal model on samples with fabricated defects are presented. The results are compared to conventional thermal imaging cameras using cooled focal plane array detectors. The advantages of a synchronized electronic shutter system (SESS) to remove the heat lamp influence during and after flash heating will also be discussed for these uncooled microbolometer detector arrays.
NDT I
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Heat pulse optimization by SPICE simulation for transient thermography in silicon
Rajesh Gupta, Suneet Tuli
Silicon, apart from conventional integrated circuits, is also the basis for fabricating miniaturized 3-dimensional (3-D) mechanical structures. This paper presents a technique for the optimization of time duration of heat pulse required for transient thermography in silicon wafers. In the present work, a silicon diaphragm fabricated on one surface of a silicon wafer has been electro-thermally modeled as a 3-D Resistance Capacitance (RC) network. The region below the diaphragm was treated as a defect. Heat transfer by all three modes: conduction, convection and radiation has been taken into account. A C++ program generates the equivalent electrical circuit of the given sample, which was then directly simulated by SPICE (Simulation Program with Integrated Circuit Emphasis), a popular electrical circuit simulator. Experimental verification was performed on the silicon diaphragm sample. Prediction of a time duration in which temperature contrast of the sample reaches its maximum (saturation) value with minimum rise of sample temperature, is experimentally verified. This could be very useful in thermography situations where temperature rise should be no more than necessary to avoid potentially dangerous thermal stresses. Another possible use of the technique is for finding the heat flux of very short-pulsed heat sources.
Student Poster Briefs
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University of Virginia suborbital infrared sensing experiment
Stephen Holland, Clayton Nunnally, Sarah Armstrong, et al.
An Orion sounding rocket launched from Wallops Flight Facility carried a University of Virginia payload to an altitude of 47 km and returned infrared measurements of the Earth's upper atmosphere and video images of the ocean. The payload launch was the result of a three-year undergraduate design project by a multi-disciplinary student group from the University of Virginia and James Madison University. As part of a new multi-year design course, undergraduate students designed, built, tested, and participated in the launch of a suborbital platform from which atmospheric remote sensors and other scientific experiments could operate. The first launch included a simplified atmospheric measurement system intended to demonstrate full system operation and remote sensing capabilities during suborbital flight. A thermoelectrically cooled HgCdTe infrared detector, with peak sensitivity at 10 micrometers , measured upwelling radiation and a small camera and VCR system, aligned with the infrared sensor, provided a ground reference. Additionally, a simple orientation sensor, consisting of three photodiodes, equipped with red, green, and blue light with dichroic filters, was tested. Temperature measurements of the upper atmosphere were successfully obtained during the flight. Video images were successfully recorded on-board the payload and proved a valuable tool in the data analysis process. The photodiode system, intended as a replacement for the camera and VCR system, functioned well, despite low signal amplification. This fully integrated and flight tested payload will serve as a platform for future atmospheric sensing experiments. It is currently being modified for a second suborbital flight that will incorporate a gas filter correlation radiometry (GFCR) instrument to measure the distribution of stratospheric methane and imaging capabilities to record the chlorophyll distribution in the Metompkin Bay as an indicator of pollution runoff.
Current source modeling of radiative heat source in transient thermography simulation by SPICE
Rajesh Gupta, Suneet Tuli
This paper presents modeling of transient thermography in terms of equivalent electrical parameters, its simulation using a popular circuit simulator SPICE (Simulation Program with Integrated Circuit Emphasis), followed by experimental verification. A novel current source based electro-thermal modeling of radiative heat sources is introduced. Analytic comparison of thermal and electrical circuits forms the basis for modeling and simulation of transient thermography experiments, in which the current source (modeling rate of incident radiative energy) drives a 3-dimensional (3-D) Resistance-Capacitance (RC) network (modeling heat conduction in the material). The current source value was derived from pyranometer-based measurements of the heat flux from the source. A mild-steel sample with a blind hole below the front surface, irradiated by a heat pulse, has been modeled by the proposed technique. SPICE then simulates the absolute thermal contrast of the surface as a function of time, in moderate computing time (seconds). The simulations compare well with experimental observations and similar to generally reported results. Current source approach, allows estimation of radiative heat flux necessary, to view sub-surface defects in a given material, at different depths, in general, and to predict time and magnitude of surface temperature over the defect and non-defect region in particular.
Infrared imaging and measurement of tropospheric carbon monoxide using gas filter correlation radiometry
Jenna E. Bourne, Megan Clark, Stefanie Bourne, et al.
The purpose of this project is to quantify tropospheric carbon monoxide (CO) concentrations by utilizing a system that applies infrared imaging and gas filter correlation radiometry (GFCR). GFCR offers a differencing method of remote sensing of atmospheric gas concentrations over a large area. A modified, ground-based version for GFCR is used for this project using the moon as our emitting reflected infrared source. The measurement is made by differencing a radiance stream obtained from the moon as passed through an evacuated cell or a cell containing a predetermined concentration of CO. With this measurement, our model is used to correlate this data to real CO concentrations in the troposphere. An ancillary purpose of this project is to calculate the responsivity of the infrared imager used in our measurements by determining the power that is equivalent to the outputted data number.
Noncontact temperature measurement of aluminized polymer for space applications
William Pollard Jr., Benjamin Hannas
An existing fiber-optic/infrared (F-O/IR) temperature measurement system was adapted to measure the surface temperature of a thin-film aluminized polymer. The polymer under study, Kapton by Dupont, is used commonly in the aerospace industry for applications such as solar sails and solar shields. A cold plate was developed and implemented to control environmental effects on infrared data. Spectral characterization of the optical properties of Kapton was conducted to improve measurement accuracy. The instrument provides a non-contact means for accurate temperature measurement of very thin polymer membranes without distorting surface contour.
Development and testing of gas filters used in correlation radiometry for carbon monoxide measurement
Danielle Rockwood, Jared T Fravel
The design and manufacture of gas filters is critical in Gas Filter Correlation Radiometry (GFCR). Gas cells are either evacuated or back-filled with carbon monoxide (CO) and serve as high-resolution optical filters. The filters must be able to maintain a sustained vacuum for several days and feature optics transmissive in the infrared (IR). GFCR is applied to measure concentrations of carbon monoxide in the troposphere using the moon as a radiance source. The filters are an important component in this experimental effort. The design and manufacturing process associated with the filters is presented and test results described. In order to test the gas filters for functionality, two processes are employed. The first is a simple pressure versus time experiment that shows how well the cells operate under vacuum pressure. The second utilizes a Fourier Infrared Spectrometer that shows the absorption spectra within the gas filter. The latter analysis reveals whether outside air leaks into the gas filter. Initial testing shows that the latest generation of the filters is effective in maintaining vacuum pressures.
Poster Session
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Capacitance sensitivity distributions model and image reconstruction in electrical capacitance tomography
Deyun Chen, Guibin Zheng, Xiaoyang Yu
In this paper a software method for electrical capacitance sensor design of electrical capacitance tomography system is presented by using finite element analysis techniques. Electrical capacitance sensor theory model is established, and capacitance sensitivity field distribution and structure parameters of the sensor to measurement effect are analyzed by the method. The optimized design and simulation of electrical capacitance sensor is based on the method, and performances of electrical capacitance sensor are improved clearly, satisfactory images can be reconstructed by using the capacitance sensitivity distributions as a priori information. It provides powerful support for further application research.
IR temperature measurements in monomode microwave cavity for soot-trap filter regeneration
Anna Angela Barba, Gennaro Cuccurullo, Matteo d'Amore
The study of microwaves assisted soot-trap filter regeneration has been performed in a single mode microwave cavity by use of an IR thermographic system. The thermal history of the soot loaded filter during the microwave treatment has been followed on line. A simple one-dimensional transient mathematical model has been proposed, which takes into account the generation term due to the interactions between matter and electromagnetic field.
Thermographic inspection of cracked solar cells
M. Pilla, Francois Galmiche, Xavier P. Maldague
In this paper, a report is presented about the thermographic inspection of photovoltaic solar cells in search for cracks. Theoretical and practical application including experimental results and image processing are included.
Catalyzed growth of doped TGS single crystals for infrared applications
Jan Novotny, J. Zelinka, Z. Podvalova
Single crystals of triglycine sulphate (TGS) doped with Pr3+ Sm3+, Pd2+, Co2+, Pt4+ and PO43- with L-alanin were grown from aqueous solutions by means of the slow cooling method. Surface morphology, domain structure and P-E hysteresis loops have been investigated. The model of catalyzed growth of {001}and{101}crystal pyramids on the basis of metal-glycine complexes has been suggested. We have found on the basis of experimental results that TGS single crystals doped with Pt4+ and L-alanin are excellent materials for construction of infrared detectors.
Wireless temperature measurement utilizing the temperature-frequency character of crystal
Usually, the situation should be avoided that the resonant frequency of crystal changes with temperature. However because the precision of the crystal resonance frequency is quite high, the temperature measurement can be realized by utilizing the relation between the resonant frequency and temperature. Its principle, measuring method are discussed and the experimental results are demonstrated in this paper.
Ultrasensitive polarimetric torque sensor
Nicolas Javahiraly, Ayoub Chakari, Lionel Calegari, et al.
We propose the study and the design of an ultra sensitive polarimetric torque sensor. The principle is based on the measurement of the torsion angle (theta) induced on the shaft when a torque T is applied on it. This optical torque sensor has been tested for aluminum, steel and Plexiglas shafts with different geometries. The torsion angle has been measured with 0,001 degree(s) accuracy. The torsion angle is then studied as a function of the applied torque. The comparison between the theoretical and the experimental results give us respectively 4,33%, 1,30% and 1,24% for the Plexiglas, the aluminum and the steel shafts. These results permit us good perspectives for our applications.
Radiation and Thermometry
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Concept of partially overlapping multiple beams for spatial determination of solar bursts time transients at submm-IR wavelengths
The concept of partially overlapping multiple beams, produced by focal plane arrays in large antennas, has been used successfully at mm-waves to detect instantaneously spatial positions of rapid spikes produced by solar flares. The technique has been used at mm-waves and was recently applied to the Solar Submillimeter-wave Telescope, which operates at 212 and 405 GHz. We present the basic description of the concept and the results obtained. New applications are being considered for shorter submm-IR wavelengths, with the use of focal plane arrays of bolometers, which spatial angular accuracy will strongly depend on the knowledge of the beamshapes of the individual beams produced.
NDT I
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Neural network and statistical modeling techniques for electronic stress prediction
Electronic components are constantly under stress due to factors such as signal density, temperature, humidity, and high current and voltage. There has been relatively little emphasis on stress level prediction under voltage stress. The purpose of this study was to develop an electronic temperature profile model for stress level prediction utilizing neural network and statistical approaches, such as multivariate regression models. Electronic components were removed from boards, subjected to different levels of stress, then replaced. An infrared camera was then used to capture information about component temperature changes over time under normal operating conditions. Neural network and statistical approaches were used to model temperature change profiles for components that had been stressed at different levels, and their predictive ability was compared. Separate data sets were used for model development and model verification. Neural network prediction rates were around 70%, compared to 30% for the statistical approach. Experiments were also conducted to evaluate the noise-tolerance of the neural network model. The neural network accommodated the presence of noise much more easily than statistical approaches. Resilient back propagation learning functions performed better than functions studied. A 3-2-1 topology performed better than 3-3-1 or 3-2-2-1 topologies.
Radiation and Thermometry
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Temperature and wavelength dependent emissivity of a shocked surface: a first experiment
Peter Poulsen, David E. Hare
We have conducted an experiment in which the temperature and the wavelength dependent emissivity of a shocked surface has been measured. In the past, only the thermal emission from the shocked surface has been measured. The lack of knowledge of the emissivity as a function of wavelength leads to uncertainty in converting the measured emission spectrum into a surface temperature. We have developed a technique by which we are able to calculate both the emissivity of the shocked surface over a range of relevant wavelengths and the temperature of the surface. We use a multi-channel spectrometer in combination with a pulsed light source having a known spectrum of infrared radiation. Two separate techniques using a pulse of reflected radiation are employed and described. Both give the same result: An initially polished molybdenum surface that is shocked and partially released has a temperature of 1040 degrees Kelvin and a wavelength ((lambda) ) dependent emissivity of 0.16 ((lambda) =1.2micrometers ), 0.10 ((lambda)
Research and Development
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Optical mirrors for cryogenic IR systems
Sergey V. Ljubarsky
Surveyed are resylts of development, design, fabrication and thermal-optical test of optical mirrors out of vatious materials for space IR systems operating at cryogenic temperatures. Results are presented showing feasibility of optical mirrors having diameters to 900 mm and wavefront errors RMSWFE=0,05(lambda) (at (lambda) =200 nm) operating in systems and instruments at 10-15K. Results of thermal-optical tests are given.
Process and Product Monitoring
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Resolution enhancement of infrared imaging by triggered image acquisition with ultrashort integration time
Oliver Schreer, Monica Lopez Saenz, Ch. Peppermueller, et al.
Infrared cameras are sometimes not fast or sensitive enough when short events with low temperature dynamics have to be measured. Thermal imaging systems sensitive at 3micrometers - 5micrometers usually operate with integration times of 1 ms and more for room temperature scene measurements. Thus very short events with low dynamics cannot be resolved with sufficient temporal and thermal resolution. Advanced measurement techniques which make use of triggering, summing or even lock-in must be used then. We present an infrared imaging system, based on a high quantum efficiency 384x288 pixel HgCdTe FPA detector, for temperature measurements of gasoline sprays ejected out of injection nozzles for automobile motors. The temperature distribution of the gasoline jet while ejected out of a injection nozzle (the process is finished after 2 ms) is urged to be known with high accuracy at high temporal and spatial resolution. With highly advanced instrumentation we are able to measure with both high temporal and temperature resolution. The system described here helps automotive engineers to better understand and improve the combustion process in modern motors.