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Showing papers on "Thermography published in 1989"


01 Apr 1989
TL;DR: In this paper, a chromatic image analysis system and temperature sensitive coatings are used for thermal mapping and surface heat transfer measurements on aerothermodynamic test models in hypersonic wind tunnels.
Abstract: Thermal imaging techniques are introduced using a chromatic image analysis system and temperature sensitive coatings. These techniques are used for thermal mapping and surface heat transfer measurements on aerothermodynamic test models in hypersonic wind tunnels. Measurements are made on complex vehicle configurations in a timely manner and at minimal expense. The image analysis system uses separate wavelength filtered images to analyze surface spectral intensity data. The system was initially developed for quantitative surface temperature mapping using two-color thermographic phosphors but was found useful in interpreting phase change paint and liquid crystal data as well.

60 citations



Proceedings ArticleDOI
21 Mar 1989
TL;DR: In this paper, the authors describe a phase-locked infrared imaging system for the detection of micro-cracks in Cu foils deposited on polyimide substrates, where the images are phaselocked with the periodic thermal radiation used as source of illumination.
Abstract: Phase-locked detection is a very useful instrumentation technique. It can be used whenever the desired signal is phase-coherent with another reference signal. Very frequently, the reference signal is, or can be derived from, the periodic external stimulus which is responsible for the signal in the first place. Typically the use of a lock-in amplifier can improve the signal-to-noise ratio by several orders of magnitude. We describe a successful implementation of an infrared imaging system in which the images are phase-locked with the periodic thermal radiation used as source of illumination and we also report the application of this phase-locked infrared imaging technique to the detection of microcracks in Cu foils deposited on polyimide substrates.

33 citations


Journal ArticleDOI
TL;DR: A highly sensitive infrared thermographic camera was evaluated in a variety of physiologic and pathologic conditions associated with the head and neck, and wide variations in normal values were noted that any standardization was extremely difficult.

22 citations


Journal ArticleDOI
TL;DR: The infrared thermographic camera could provide a method of testing tooth vitality based on blood supply rather than nerve supply, but after cooling with cold air, nonvital teeth were slower to rewarm than vital teeth.

21 citations


01 Jan 1989
TL;DR: In this paper, infrared thermography was used as a sensor to control the position of the arc and the penetration depth of the weld, and image analysis techniques were developed to quantify the changes in the surface tempera-ture distribution of the plates being welded.
Abstract: Adaptive welding enables dy­ namic altering of the welding parameters to compensate for changing environment. Sensors providing process status informa­ tion in real time are an integral part of such an adaptive system. In this investigation, infrared thermography was used as a sen­ sor to control the position of the arc and the penetration depth of the weld. Pre­ liminary work on infrared thermography showed that variation in these parameters produces a change in the surface temper­ ature distributions of the plates being welded. Subsequently, to achieve com­ puter control of these variables, image analysis techniques have been developed to quantify the changes in the tempera­ ture distribution.

15 citations


Journal Article
TL;DR: In this article, the use of infrared thermography to perform an inspection of a concrete and asphalt overlaid deck on a bridge in the Mississippi River in St Louis is described, using an infrared scanner system utilizing temperature differentials caused by a sewer void to produce a picture of that void from above ground without boring.
Abstract: Remote sensing infrared thermography, which can locate voids before structural failure, is an important tool in preventive maintenance. The high resolution, custom designed infrared thermographic scanning systems can be used to measure thousands of surface temperatures simultaneously in real time. The resulting data is displayed as computer images with areas of differing temperatures, designated either by differing gray tones on a black and white image or by various colors in a color image. The use of infrared thermography to perform an inspection of a concrete and asphalt overlaid deck on a bridge in the Mississippi River in St Louis is described. The use of an infrared scanner system utilizing temperature differentials caused by a sewer void to produce a picture of that void from above ground without boring is also described. Since emergency repairs cost more than preventive maintenance, indentifying sewer problems before a cave-in can be crucial

14 citations


01 Jan 1989
TL;DR: In this paper, a thermographic technique is presented which is able to detect subsurface delamination using one of several heat sources (such as hot water, hot air, IR lamps, etc.).
Abstract: The presence of disbonds significantly decreases the integrity of many laminated structures used in aerospace applications. A thermographic technique is presented which is able to detect subsurface delamination. The technique uses one of several heat sources (such as hot water, hot air, IR lamps, etc.) to increase the surface temperature of the structure. The subsequent temperature profiles of the surface are detected with an IR camera. A novel spatial filter developed at NASA-Langley eliminates the effects of uneven heating to give clear images of the subsurface delaminations. Defects are detectable in samples as diverse as solid rocket motor samples and laminated wood for wind tunnel blades. Numerical simulations are presented for comparison with experiment results.

13 citations


Journal ArticleDOI
TL;DR: In this article, a simple one-dimensional analysis of heat diffusion in a defective test piece is presented, which shows that the most effective form of noncontact heating is flux profiled so that the temperature of the front surface of the specimen is maintained at a constant high value.
Abstract: Thermographic NDT is potentially a very useful technique for rapidly locating flaws in large structures without physical contact. The fundamental factors limiting thermography are discussed, and recommendations for the achievement of high-contrast thermograms are formulated based upon a simple one-dimensional analysis of heat diffusion in a defective test piece. The analysis shows that the most effective form of noncontact heating is flux profiled so that the temperature of the front surface of the specimen is maintained at a constant high value. A three-dimensional numerical model has also been developed and some predictions are presented. The model is used to calculate the size and depth of a perfectly insulating defect which can be detected thermographically under ideal experimental conditions.

13 citations


Dissertation
01 Jan 1989
TL;DR: In this article, a Dicke configuration radiometer receiver and a cylindrical low-impedance waveguide antenna are used to estimate the temperature distribution in the human breast.
Abstract: Microwave thermography obtains information about the temperature of internal body tissues by a spectral measurement of the intensity of the natural thermally generated radiation emitted by the body tissues. At the lower microwave frequencies radiation can penetrate through tissue for distances useful for a range of medical applications. Radiation from inside the body may be detected and measured non-invasively at the skin surface by a microwave thermography system consisting of a suitable antenna to detect the radiation and a radiometer receiver to measure its intensity. In the microwave region the radiative power emitted per unit bandwidth is proportional to the temperature of the emitting tissue and the total radiative power received from the body tissues, P, is a weighted volume average of temperature P = kB ∫w(r) T(r) dV where k is Boltzmann's constant, B is the bandwidth, T(r) is the temperature at the position r and w(r) is the weighting function. The weighting function depends on the structure and dielectric properties of the tissues being viewed, the measurement frequency and the characteristics of the antenna. The Glasgow developed microwave thermography system operates at a central frequency of 3.2 GHz, chosen to give the optimum compromise between the depth from which radiation may be received, which decreases with increasing frequency, and the lateral spatial resolution which increases with increasing frequency. A Dicke configuration radiometer receiver and a cylindrical low-impedance waveguide antenna, which operates in contact with the skin surface, are used. The output from the radiometer is calibrated to degrees Celsius to give a "microwave temperature" of the tissues being viewed. The tissue temperature distribution, T(r), reflects the vascular and metabolic state of the tissue. Diseases which affect these physiological functions will result in changes in the tissue temperature and hence in the measured microwave temperature. It is not possible, however, to solve the indirect problem of retrieval of the temperature distribution in the tissue from a single frequency measurement of microwave temperature. It is therefore necessary to model the temperature distribution in the tissue and, from this, solve the direct problem of calculation of the microwave temperature. Measured microwave temperatures may then be compared with those modelled to indicate the physiological state of the tissue. Pennes (1948) The temperature distribution in the tissue may be determined by solution of the steady-state heat transfer equation KV2T +Wbcb(Ta -T) + Q = 0 where K is the thermal conductivity of the tissue, Wb is the perfusion rate of blood through the tissue, cb is the specific heat capacity of the blood, Ta is the arterial blood temperature and Q is the rate of metabolic heat generation in the tissue. The boundary condition of heat loss at the skin surface is governed by the equation K dT/dn= h(T-Te ) where Te is the ambient temperature and h is the heat transfer coefficient due to the combined effects of heat loss by radiation, convection and evaporation. The microwave temperature may be calculated from the modelled temperature distribution and use of plane wave theory to determine the weighting function, with an increased power attenuation constant to account for the response of the antenna. The modelling of the tissue is simplified by the fact that both the tissue thermal conductivity and the microwave dielectric properties of the tissue depend primarily on the water content of the tissue. This thermal and electromagnetic modelling has been carried out to determine the expected microwave temperature profiles across the female breast. Microwave and infra-red temperature measurements were made on a group of young, normal women and a group of older, post-menopausal women with breast disease. In general the younger women will have higher water content breast tissue than that of the older women due to the higher proportion of glandular and connective tissue and the smaller proportion of low water content fat tissue.

11 citations


01 Jan 1989
TL;DR: Information obtained from the literature, responses to a Federal Register notice of this assessment, PHS agencies and medical specialty groups failed to support claims of efficacy of thermography as a useful diagnostic modality for non-breast indications, suggesting that thermography lacks sensitivity, specificity, or predictive value.
Abstract: Thermography is the measurement of self-emanating infrared radiation revealing temperature variations at the body surface. The two commonly employed methods demonstrating such changes are telethermographic infrared detector/imagers and heat-sensitive cholesterolic liquid crystal systems. Both methods sense body temperature and demonstrate areas of differing heat emission by producing brightly colored patterns. Each color represents a specific temperature level. Interpretation of color patterns in dermatomes or other anatomic distributions are proposed as an aid in diagnosing and evaluating a vast array of diseases. Information obtained from the literature, responses to a Federal Register notice of this assessment, PHS agencies and medical specialty groups failed to support claims of efficacy of thermography as a useful diagnostic modality for non-breast indications. Rather, it suggested that thermography lacks sensitivity, specificity, or predictive value. Unassailable data are lacking to indicate that thermography provides a useful guide to monitor the effect of treatment of any disease entity. The evidence suggests that thermography may only confirm the presence of a temperature difference, that other procedures are needed to reach a specific diagnosis, and that thermography may add little to what physicians already know based on history, physical examination, and other studies.

Proceedings ArticleDOI
21 Mar 1989
TL;DR: In this paper, a numerical approximation was used to determine the ability of a thermographic imaging camera to detect defects in a panel of graphite epoxy composite while excitation is provided by a specific, commercially available high-energy pulsed xenon flash lamp capable of repetitive pulses of 600 J each.
Abstract: A numerical approximation was used to determine the ability of a thermographic imaging camera to detect defects in a panel of graphite epoxy composite while excitation is provided by a specific, commercially available high-energy pulsed xenon flash lamp capable of repetitive pulses of 600 J each. A three-dimensional mathematical model was developed, which simulated the composite panel. The panel consisted of eight plies and included implanted circular defects. Defects modeled included delaminations, overlaps, and teflon inserts. During the first second of the simulation, six heat pulses of 0.2 msec duration were applied to the front surface of the sample. Temperature variations appear on the rear surface of the sample due to the presence of defects inside the panel, which cause the heat to diffuse through the sample at modified rates. A minimum temperature difference of 0.18 °F (0.1 °C) was detectable by the thermal imaging camera. The purpose of this study was to determine whether the purchase of a xenon flash lamp system was warranted for thermographic nondestructive testing (NDT) on graphite epoxy laminates.

Proceedings ArticleDOI
09 Jan 1989
TL;DR: In this paper, the application of infrared thermography in the measurement of heat transfer in two distinctly different short duration hypersonic facilities is discussed; they demonstrate the advantage of the infrared technique in providing twodimensional heat transfer maps as opposed to the zero-dimensional measurements enabled by discrete point gauges.
Abstract: Some results and conclusions from the application of infrared thermography in the measurement of heat transfer in two distinctly different short duration hypersonic facilities are presented. First results from a blowdown tunnel are discussed; they demonstrate the advantage of the infrared technique in providing twodimensional heat transfer maps as opposed to the zero-dimensional measurements enabled by discrete point gauges. The spatial resolution characteristics of the infrared scanning radiometer are sufficient to sense localized hot spots that may be quantified by concentrating the field of view onto the area of interest. In intermittent facilities, the technique is shown to provide qualitative information on the location of hot spots or, in a single-line scan mode, a heat transfer distribution along one direction. In the latter case, the presence of hot dust in the flowfield may pose problems in arriving at quantitative results.

Book ChapterDOI
01 Jan 1989
TL;DR: In this paper, a thermographic technique is used to detect disbonds in a laminated structure, where heat is applied to a structure, and the subsequent temperature profiles are detected with an infrared (IR) imager.
Abstract: The detection of disbonds in a laminated structure is the focus of many nondestructive techniques.One of the promising techniques is thermography, where heat is applied to a structure, and the subsequent temperature profiles are detected with an infrared (IR) imager.If there is an even application of heat, an elevated temperature profile will appear, as a result of the reduction in heat flow from the surface layer to subsurface layers.Two advantages of the thermographic technique over more conventional ultrasonic techniques are that it can be easily made noncontacting and that large areas can be inspected in a short period of time.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the possibility of using infrared thermography as seedling vitality test before planting and found that the field performance conformed to the IR measurements of the seedlings.
Abstract: The possibility of using infrared thermography as seedling vitality test before planting was investigated. The temperature of seedlings of Scots pine and Norway spruce was determined in the laboratory before planting using the AGA Thermovision System. It was found that the field performance conformed to the IR measurements of the seedlings. The “cold”; (high‐transpiring) seedlings performed better than the “warm”; (low‐transpiring) ones. Some of the measurement problems discussed concern illumination and the interpretation of the thermo‐grams because of the small size of conifer needles. The IR measurements might be a tool in a future system for grading seedlings.

Proceedings ArticleDOI
18 Sep 1989
TL;DR: In this paper, a method has been developed which applies liquid-crystal thermography to the measurement of surface heat flux short-duration hypersonic facilities, which has been successfully applied over a wide range of model scales and test times.
Abstract: A method has been developed which applies liquid-crystal thermography to the measurement of surface heat flux short-duration hypersonic facilities. Flat-plate thermographs are compared with Eckert's prediction of surface heat flux to provide a calibration which replaces the liquid-crystal static color calibration. This allows measurements of high surface heat flux, avoiding sources of error associated with the large temperature gradient through the liquid-crystal layer and its response time. In conjunction with this, a multi-substrate model construction has been used, which allows measurement of surface heat flux on complex configurations. The technique has been successfully applied over a wide range of model scales and test times. >

Proceedings ArticleDOI
09 Jan 1989
TL;DR: In this article, the authors present results of proof-of-concept experiments for a nonintrusive diagnostic technique capable of rapid measurement of convective heat transfer distributions over broad surface areas with high spatial resolution.
Abstract: This paper presents results of proof -ofconcept experiments for a nonintrusive diagnostic technique capable of rapid measurement of convective heat transfer distributions over broad surface areas with high spatial resolution. This technique requires special, yet not difficult, preparation of the surface of interest, which results in minimal surface instrumentation. IR thermography. based on video camera technology, is used to obtain surface temperature distributions. These distributions plus surface substrate temperatures obtained by a few thermocouples are all that is required to infer accurate, highly resolved distributions of local heat transfer coefficient behavior. Optical access windows are required in the wall of the flow passage for this technique. I R thermography temperature calibration techniques and preparation of the surface of interest are discussed, along with the influence of contaminating background I R radiation. Comparisons of heat transfer coefficient behavior measured by this technique with those by conventional techniques are presented to illustrate this technique's capabilities for convective heat transfer resulting from an air jet impinging on a heated plate.

Journal ArticleDOI
Yoshiyasu Ito1, Masahiro Saito1, Hideo Kashiwaya1, Masayuki Oishi1, Kaneko Tadashi1 
TL;DR: In this article, the thermal properties of zirconia stabilized with 8wt% of yttria was studied by the laser flash method. But the results indicated that the thermography method as a new technique was useful for nondestructive testing to detect the interfacial cracks of coated materials.
Abstract: The thermal properties of plasma sprayed coating of zirconia stabilized with 8wt% of yttria was studied by the laser flash method. The experimental results were used for the thermal conduction analysis of stabilized zirconia coated materials with a penny-shape crack at interface using the finite element method. The analysis was conducted to find nondestructively the interfacial crack from the surface temperature distribution of coating. It was verified that the interfacial cracks become less detectable with increasing coating thickness and with decreasing crack size. It was also confirmed by the experiment using infrared thermography that fairly good agreement between the measured and real crack size was obtained for the crack diameter not less than 3mm. The results indicated that the thermography method as a new technique was useful for nondestructive testing to detect the interfacial cracks of coated materials.

Journal ArticleDOI
TL;DR: A high degree of reproducibility was observed, but no increase in heat was found over selected rheumatoid joints in a evaluation of a new portable, light-weight, infrared thermometer for the measurement of the skin temperature over joints.
Abstract: A study is reported of the evaluation of a new portable, light-weight, infrared thermometer, for the measurement of the skin temperature over joints. A high degree of reproducibility was observed, but no increase in heat was found over selected rheumatoid joints. The instrument wilt prove useful in detecting temperature changes in disease states where the changes are considerable, and where the ambient temperature can be strictly controlled.

Proceedings ArticleDOI
18 Sep 1989
TL;DR: In this article, the authors describe special applications of infrared imaging for the measurement of the surface temperature distribution on models exposed to a hypersonic flow field, which demonstrate the advantages and limitations of this measurement technique.
Abstract: The authors describe special applications of infrared imaging for the measurement of the surface temperature distribution on models exposed to a hypersonic flow field. A number of infrared images are shown, which demonstrate the advantages and limitations of this measurement technique. In connection with image processing of an IBM computer the infrared thermovision proves to be a powerful tool for obtaining a quick survey of the surface temperature distribution on wind-tunnel models. Due to the high framing rate of the camera system used, it is possible to calculate the time-dependent heat flux from the flow to the model surface from the recorded temperature data. All the examples are taken from experiments carried out with different kinds of models at the H2K blowdown facility in Cologne. >

Book ChapterDOI
01 Jan 1989
TL;DR: In this paper, the authors used infrared thermography to examine the mechanical response of concrete and rock specimens subjected to given static unconfined compressions and to a superimposed vibratory excitation.
Abstract: Infrared thermography has been used as a nondestructive and noncontact technique to examine the mechanical response of concrete and rock specimens subjected to given static unconfined compressions and to a superimposed vibratory excitation. The parameter investigated in this paper is the heat generation due to energy dissipation by the material which has been excited beyond its stable reversible limit. This useful technique allows accurate illustration of the onset of unstable crack propagation and/or flaw coalescence when increasing irreversible microcracking is generated by vibratory loading.

Journal Article
TL;DR: In this article, the use of commercially available infrared (IR) scanning system for measurement of convective heat rates is described, and preliminary measurements are performed on a flat plate located within the test section of a low-density continuous flow facility.
Abstract: The use of commercially available infrared (IR) scanning system for measurement of convective heat rates is described. Preliminary measurements are performed on a flat plate located within the test section of a low-density continuous-flow facility. Flow conditions are characterized by a Mach number of 20.2 and a Reynolds number of 2280. Convective heat rates as low as 0.5 kW/m are measured at the model wall. Basic system, data reduction, and result comparisons are briefly presented. The data accuracy is discussed and limitation of IR scanning system is pointed out for large optical incident angles of the scanning camera axis over the investigated surface.

Book ChapterDOI
TL;DR: In this paper, ground-penetrating radar and infrared thermography are used to determine the location of delaminations and debonded sections of pavement, and the infrared scanner will detect temperature differences between the two areas.
Abstract: New technologies have enabled the pavement engineer to develop a better picture of the pavement structure. Two of these new technologies are ground-penetrating radar and infrared thermography. Each of these techniques allows the pavement engineer to nondestructively evaluate subsurface defects within and under the pavement. Infrared thermography is now widely used to determine the location of delaminations within the pavement. In the case of delaminations or debonded sections of pavement, the thin delaminated area will heat faster than the adjacent thicker section, and the infrared scanner will detect temperature differences between the two areas. This process is widely used to inspect bridge decks. It is used to determine the extent of deterioration beneath asphalt overlays on the deck and this save the costs of removal of the asphalt and any waterproofing membrane. Ground-penetrating radar can be used to determine a number of characteristics useful to the pavement engineer in developing a rehabilitation scheme. Radar is used to determine the condition of joints in concrete pavement, to locate and size voids beneath the pavement, to determine the thickness of pavement, and to determine the composition of pavement structure. Case histories are presented to discuss each of these technologies and their applications. These technologies are presently being written to ASTM standards for particular applications, including determination of delamination using infrared thermography and determination of pavement layer thickness using ground-penetrating radar. Limitations in the use of techniques are also discussed.

Journal Article
TL;DR: In this article, the theoretical basis and practical procedures for use of thermography in detection of pavement distress are described, along with some recent applications on airport taxiways, bridge decks, and parking garage slabs.
Abstract: This paper describes the theoretical basis and practical procedures for use of thermography in detection of pavement distress. It also illustrates the field use of thermography with some recent applications on airport taxiways, bridge decks, and parking garage slabs. It provides an overview of a staged research process under way by the authors to integrate nondestructive pavement testing using infrared thermography with evaluation models that form the basis for an integrated pavement testing, management information system.

Journal Article
TL;DR: A patient suffering from cervical disc herniation was tested for presence of nerve irritation using infrared telethermography and the thermal findings and asymmetries observed followed a dermatomal pattern of hypothermia and decreased thermal emission.

Proceedings ArticleDOI
18 Sep 1989
TL;DR: In this article, the boundary-layer transition from the laminar to the turbulent regime and the onset of the separation were detected by surface thermography of the airfoil performed with an infrared imaging system.
Abstract: A study of boundary-layer flow regimes on a NACA 0012 airfoil from zero angle of attack up to separation is presented. The boundary-layer transition from the laminar to the turbulent regime and the onset of the separation were detected by surface thermography of the airfoil performed with an infrared imaging system. The findings were compared with observations of aluminum-foil tufts visible with the infrared imaging system. This arrangement allows the infrared imaging system to assume the dual role of flow regime detection through surface thermography and flow visualization through the observation of the aluminum-foil tufts. Ultimately, the temperature history on an uncontaminated surface will provide an interpretation of the state of boundary-layer flow. Separation studies performed on the NACA 0012 airfoil showed that aluminum foil tufts can be observed with infrared imaging systems. >

Book ChapterDOI
01 Jan 1989
TL;DR: In this paper, a real-time video-thermographic camera was used to detect near-surface delaminations in composite materials by monitoring the infrared radiation emitted from the surface of the sample.
Abstract: Vibrothermography is a technique that combines mechanical, vibrational excitation with real-time video thermography to detect defects in advanced composite materials. Basically, a mechanical oscillatory load is applied to the material. Mechanical energy is dissipated as thermal energy throughout the material, but preferentially in regions surrounding delaminations. The resulting temperature distribution is detected by monitoring the infrared radiation emitted from the surface of the specimen with a real-time video-thermographic camera. Regions that have near-surface delaminations are easily detected by the temperature-gradient pattern that is established.


Proceedings ArticleDOI
Matthew Fairlie1, Warren Fraser1, Bahram Farahbakhsh1, R. Lamb1, Otto Meijer1 
21 Mar 1989
TL;DR: In this article, the process information from the mill control computer is used to automatically select emissivity factors from a lookup table and a second technique for adjusting emissivities factors, using reference point temperatures measured by a separate sensor will also be described.
Abstract: In this paper we report our experience using infrared imaging systems to monitor temperature variations in aluminum strip during hot rolling. Because of the low emissivity of aluminum surfaces infrared cameras are sensitive not only to temperature variations in the strip, but also to changes in surface characteristics caused by changes in alloy and surface roughness. In the system described in this paper, process information from the mill control computer is used to automatically select emissivity factors from a lookup table. A second technique for adjusting emissivity factors, using reference point temperatures measured by a separate sensor will also be described. Results from tests, comparing temperatures measured by infrared imaging systems with contact temperature probes indicate good agreement between the two techniques at later stages in the hot rolling process, when surface emissivity is uniform. Factors affecting the installation of a thermal imaging system on a production line, in particular the location of the camera and integration with other temperature measurement systems, are also discussed.

Book ChapterDOI
01 Jan 1989
TL;DR: Based on the measurement of the electromagnetic thermal noise generated by living tissues, microwave radiometry is a starting point for a non invasive thermometric process in a depth of the subcutaneous tissues of up to several centimeters as discussed by the authors.
Abstract: Based on the measurement of the electromagnetic thermal noise generated by living tissues, microwave radiometry is a starting point for a non invasive thermometric process in a depth of the subcutaneous tissues of up to several centimeters.