Showing papers on "Thermography published in 1988"

Theory and practice of radiation thermometry

Abstract: Partial table of contents: FUNDAMENTALS OF RADIOMETRIC TEMPERATURE MEASUREMENT. Physics of Thermal Radiation (D. DeWitt & F. Incropera). Thermal Radiative Properties of Materials (D. DeWitt & J. Richmond). RADIATION THERMOMETERS AND MEASUREMENT METHODS. Wide--Band Radiation Thermometers (R. Leftwich). Fast Radiation Thermometry (A. Cezairliyan, et al.). METHODS FOR CALIBRATION OF RADIATION THERMOMETERS. Calculation of Effective Emissivities of Cavity Sources of Thermal Radiation (R. Bedford). Detector--Based Traceability of Temperature Standards (A. Ono, et al.). APPLICATIONS OF RADIATION THERMOMETRY. Radiation Thermometry in the Steel Industry (F. Milhalow). The Application of Thermography for Building and Industrial Energy Management (P. Mill & G. McIntosh). Index.

Infrared thermography of the DIII-D divertor targets

Abstract: The power flow to the DIII‐D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8–12‐μm range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data (≂12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII‐D discharge are included.

Quantitative surface temperature measurement using two-color thermographic phosphors and video equipment

Abstract: A thermal imaging system provides quantitative temperature information and is particularly useful in hypersonic wind tunnel applications. An object to be measured is prepared by coating with a two-color, ultraviolet-activated, thermographic phosphor. The colors emitted by the phosphor are detected by a conventional color video camera. A phosphor emitting blue and green light with a ratio that varies depending on temperature is used so that the intensity of light in the blue and green wavelengths detected by the blue and green tubes in the video camera can be compared. Signals representing the intensity of blue and green light at points on the surface of a model in a hypersonic wind tunnel are used to calculate a ratio of blue to green light intensity which provides quantitative temperature information for the surface of the model.

Inspection of laminates and adhesive bonds by pulse-video thermography

Abstract: The use of thermography in NDT has been extended in recent years by the application of transient heat sources and the rapid scanning of the subsequent thermal fields by TV/video-compatible infrared imagers. Such a system is called pulse video thermography (PVT) and its use has been demonstrated in many practical cases. Limitations are however set by the nature of the thermal diffusion process, and their exact definition in practice is discussed from both theoretical and experimental points of view.

Quantitative Evaluation of Mental Work by Thermography

Abstract: Skin temperature has a close relationship to emotional state. The anther is proposing to define skin temperature of face as an index of mental stress. Skin temperature of face is remotely measured by thermography and digital image processing. From the result of experiments, it is proved that skin temperature of nose area is closely connected with the conditions of mental work. Under such intensive mental work load as repetitive calculation for a long time, nose temperature of the worker become lower than those under usual mental load. In this experiment, relation between skin temperature and heart rate variability is also studied. As an evaluation index of mental work, skin temperature is superior to heart rate variability in some cases. Mental stress of automobile driver, as a practical applicaton, is measured and effects of displaying graphic image are observed.

Infrared Radiation Model For Aircraft And Reentry Vehicle

Abstract: NIR.ATAM ( NATO InfraRed Air T.Arget Model ) is a computer model which predicts IR radiation of an aircraft in its natural surroundings. A special version of NIRATAM enables to treat a hypersonic reentry vehicle. The model takes into account the IR radiation emitted by aerodynamically and internally heated surface, hot engine parts and combustion gas and particles in the exhaust plume. The reflected radiation of the sky and terrain background and the sun on the aircraft surface is calculated. The atmospheric transmission and emission between target and observer and the radiation of a homogenous background in the scene is determined. The spectral response of a sensor is included. The development took place in collaboration with other NATO-countries. The code is of modular structure. One of the major modules (IRMA) , for the hot gas emission calculation, was developed at This paper describes the modules, the major features and shows some typical results. For the "Reentry-Version" the exhaust plume flew field model is replaced by an aerodynamic flow field model which determines the hypersonic flow around the body. A thermal model computes the aerodynamic heating and heat balance of the body by considering the convection , the thermal conduction and the radiative heat loss. A dynamic thermal map of the surface is computed for the course of reentry. The principal model components and steps for &terming the IR-signature are discussed and results for a typical reentry vehicle are presented in the paper. The code is applicable in the spectral range from 2 to 25 μm with 5cm ' spectral resolution. Radiation of gas can be predicted within the temperature range from 100 -- 3000° K . The results are presented as emission spectra and their cumulated integrals. Thermal images are provided in radiance and equivalent blackbody temperature values. The contributions of the different radiation sources are analysed.

Nondestructive Evaluation of Fiber Composite Laminates by Thermoelastic Emission

Abstract: During the rapid cyclic loading of a structure (≥ .5 Hz), the cyclic variation of surface temperature can be measured with infrared radiometry. The temperature variation is related to the reversible, adlabatic deformation of the material. Adiabatic thermography differs from disslpative thermography, where temperature variations are associated primarily with dissipated energy rather than stored energy. The radiometer system used in the present investigation is capable of resolving local stresses that reflect global stress distributions and macroscopic variations in material properties, including flaws and damage. The present paper emphasizes fundamental aspects of the technique for the nondestructive evaluation of fiber-reinforced composite laminates.

Weld Penetration Sensing And Control

Abstract: Penetration depth is a key variable, which needs to be controlled to ensure defect-free welds. One of the major problems involved with adaptive control penetration is the lack of suitable variables which can be viewed directly by the sensor. A proposed sensing technique is to relate the invisible variables, such as penetration depth and thickness of the welded steel plates, to visible variables of thermal images. The sensed infrared information was obtained through digital signal process of the thermal images associated with the high temperature of the molten metal pool and its vicinity during the welding process. Quantitative measurements were conducted to find a relationship between visible and invisible parameters. The thickness of plates being welded was varied and the corresponding changes in both penetration depth and surface temperature distributions were studied quantitatively. A least squares method was used to fit the obtained isotherms to an equation of an ellipse. The penetration depth and thickness of the materials being welded were found to be functions of the minor axes and the area of the ellipse for Gas Tungsten Arc Welding (GTAW). The experimental results can be used to achieve adaptive penetration depth control.

Thermal modeling for the estimation of energy losses from municipal heating networks using infrared thermography

Abstract: Analysis and simulation results are reported showing that there generally is a strong correlation between the thermal IR (infrared) contrast of a district heating line and its heat losses. A computer model based on the method of finite differences is described by which the temperature field and the heat flux around a buried heating line can be predicted. Algorithms are derived for the estimation of energy losses using thermal IR imagery as input data. The most promising algorithm is based on an integration of the surface temperature profile across the heating line. Under favorable conditions, it seems possible to estimate heat losses with an error (RMS) of 10 to 20% and a sensitivity of 10 to 20 W/m. The main limitations of the technique and the choice of favorable conditions for data acquisition are analyzed and discussed. >

Thermography For District Heating Network Applications: Operational Advantages And Limitations

Abstract: Detailed analysis of thermographic data for 440 km (250 miles) of district heating networks demonstrates that there is a strong connection between the condition of the heating culvert and the radiative surface temperature and surface temperature pattern. Provided the thermogram has a good geometric image it is possible to make an accurate determination of the position and extension of the damage of the culvert. However, to get this results one got to know what infrared system to use for a specific application, how to operate it, and during what weather conditions. In this paper is presented a project aiming at developing operational routines, and determining operational advantages and limitations for airborne and groundbased thermography for district heating applications. A comparison is made of the information content of thermograms from an airborne longwave infrared line-scanner, helicopterborne and groundbased mobile longvawe Thermovision. Thermal registration was performed repeatedly, for the same investigation area, during similar weather conditions. Evaluation of operational advantages and limitations for the different systems used was performed according to (a) an indicating method (qualitative), mainly pointing out areas with undefined damage of culverts, and (b) an analysis method (quantitative) , which gives temperature classified data for determing the condition of the network studied.

A Comparison of Steady State and Transient Thermography Techniques Using a Healing Tendon Model

Abstract: Steady state and transient thermal techniques were used to define the thermal signatures of surgically sectioned and sham-operated common calcanean tendons in four dogs. All limbs were imaged from the lateral side using an Inframetrics 525 system at - 1, 2, 4, 6, and 8 weeks after surgery. Individual video frames were used to compute absolute surface temperatures and rewarm curves for five predetermined 1 cm2 skin areas. Angiography was performed at each observation period to correlate changes in vascular morphology and thermal data. Thermal signatures and angiograms were similar in all animals before surgery. At 2 and 4 weeks after surgery, the absolute surface temperatures of the entire lateral crus area were elevated in three of four animals. During weeks 6 and 8, the surface temperatures, rewarm curves, and angiograms returned to presurgical values for the controls. Skin areas over the repaired tendons remained warmer and were shown to correlate with vascular proliferation by transient but not steady state techniques. Steady state and transient thermal imaging techniques can be used to detect vascular changes in the area around a healing tendon. However, our data indicate that transient thermal techniques are more suitable than steady state methods for localizing vascular disturbances in tissues. Thermographic imaging techniques may become a reliable noninvasive method to monitor wound healing processes if starting temperatures, cool down techniques, and time intervals for data collection are fully evaluated in future studies using transient thermal imaging protocols.

Infrared thermography of negative DC and negatively enhanced AC point-to-plane corona discharge in air

Abstract: Corona discharge for point-to-plane gaps in air was investigated with emphasis given to thermographic analysis of the air gap using an infrared scanning system. Corona discharge was generated under two conditions: using negative voltage on the point and a grounded plane, and using 60 Hz AC voltage on the point and positive DC voltage on the plane (negative enhancement of AC corona). Changes in the infrared images of the air gap were observed as the corona discharge current increased. These images showed the region of the gap with the elevated apparent temperature indicating a source of infrared radiation in the gap. The relationship between the pattern in the air gap and corona discharge current was studied. It was observed that the intensity of the infrared signal generated in the gap increased with the discharge current. Temperature distribution on the anode surface was measured. In the case of the negatively enhanced AC corona, fluctuation of the region with elevated apparent temperature was observed. >

Infrared Thermography Development For Composite Material Evaluation

Abstract: The increasing use of fibre reinforced composite materials in structural components, mainly in the aircraft industry has induced manufacturers to acquire appropriate non destructive testing means. Then the necessity to manufacture with larger production rate and tighter quality control requires inspection techniques having higher speed and finer resolution with more accuracy and intelligence than the conventionnal one's used today, namely ultrasonics and X - radiography. A large assessment program has been carried out in order to demonstrate the applicability and reliability of infrared thermography as a method for the inspection of composite and bonded materials.The technique has been developed for an industrial utilization and to specify the systems required for its application. The developments undertaken and the results we have obtained in the final stage of the program are presented.© (1988) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Characterization Of Boundary Layer Conditions In Wind Tunnel Tests Through Ir Thermography Imaging

Abstract: A computerized infrared (IR) imaging system is evaluated as a diagnostic tool for aerodynamic research by performing experimental tests in a subsonic wind tunnel. In particular, the IR technique is used to characterize the behaviour of the boundary layer on two wing models, having different cross-sections, by measuring the temperature distribution over their heated surfaces. The results show that IR thermography is capable of immediately yielding accurate information on the location and extent of the transition between laminar and turbulent flow and on the region of separation, for the whole boundary layer over the surface of a model wing.

Reconstruction techniques for the inspection of composite materials using thermal images

Abstract: A novel approach for the inspection of composite materials is presented, which utilises image processing techniques for the characterisation of flaws in composites. The technique is based on transient thermography coupled to the processing of infrared images obtained by exciting a composite specimen by a thermal pulse. The authors focus on the reconstruction algorithms developed for subsurface defect location, and overview the associated image processing techniques, as well as the experimental set-up for testing composites and generating thermal images. >

New modes of data handling in computerized thermography

Abstract: The use of thermography and its acceptance as a diagnostic tool are currently limited by the subjective visual interpretation of thermograms. Although computerized thermography handles imaging data digitally, little has been done to use this digital information beyond the display of temperature contour maps. Several computer utilities have been developed to facilitate objective assessment of thermograms. These include facile enclosures of thermological features, statistical assessment of the temperature distribution in the enclosed domains and the use of temperature-gradient profiles. Such tools enable clinicians to justify clinical management decisions objectively, and facilitates the creation of databases with inputs from different medical centers. >

Time-Resolved IR Video Imaging with Synchronized Scanned Laser Heating

Abstract: Recent advances in the speed and sensitivity of cooled HgCdTe detectors have made it possible to construct an infrared video camera with a single detector by using mirror scanning techniques. The commercial availability of this kind of camera has led to interesting techniques for active thermography measurements. For example, they have been used with flash lamps for imaging defects in materials [1], and with a scanned IR source for measuring thermal diffusivities [2,3]. With an infrared camera, vast amounts of thermal information from an entire area can be gathered in parallel. This method has obvious advantages in imaging as compared to the more traditional methods of acoustic detection, optical beam deflection or focused (unscanned) IR detection, each of which require a slow scan of the sample to obtain an image. The traditional methods, however, due to the continuous nature of their detectors, can gather fast temporal thermal information by using modulated heat sources [4]. The intrinsic bandwidth of detection is only limited by that of the detectors. The infrared video camera, due to its fixed rate of 50 or 60 fields per second, cannot catch fast thermal phenomena in the millisecond range when used with a fixed area source (flash lamp) or a scanned (unsynchronized) IR source. The method described here combines some of the advantages of both methods by using a focused and scanned optical laser beam, synchronized with the vertical scan of the video camera. It is capable of observing thermal phenomena on a sub-millisecond time scale and also can acquire data on an entire vertically scanned line at the video field rate.

Phenomenological aspects of infrared imaging in aeronautical research

Abstract: The various factors leading to obtaining a thermography of an aerodynamic body of interest using an infrared imaging camera are scrutinized. Included is a description of how the various heat transfer mechanisms determine the final surface temperature that may be time dependent even for steady state flows. Some constraining factors of the camera are also discussed. Finally, a method is outlined showing how the infrared imaging of aerodynamic configurations may ultimately evolve as a computational fluid dynamics code validation tool.

Method and device for corrosion diagnosis

Abstract: PURPOSE:To diagnose the state and degree of internal corrosion by measuring the external surface temperature of an object. CONSTITUTION:The temperature output signal of the external surface temperature distribution of the object 1 to be measured from a thermography device 7 and ambient temperature from a temperature sensor 8 are inputted to a microcomputer 9 to correct the ambient temperature, which is displayed 10 as color patterns by temperature ranks. At this time, a thin part 4 is displayed as a hot spot 11 and a part where there are corrosion products 3 is displayed as a cold spot 12. Consequently, a tank, a piping, etc., whose internal corrosion states can not be inspected directly with the naked eye are diagnosed from outside the tube walls and the object of measurement can be diagnosed on site while used.

Hostile High Energy Visible Laser Environment Provitang Destruction Of Optical Signal. In Imaging Systems

Abstract: In this paper will be described the analytical expressions which will provide the damage thresholds of infrared and visible imaging systems when subjected to high power continuous wave and repetitive pulsed laser devices The primary optical components that comprise a system are generally optical substrates that have vapor deposited reflective metal films or are diamond turned metallic substrates to maximize reflectivity Additionally, one will find optical thin films used to enhance reflectivity and transmission through the optical train For those systems that are designed for the infrared, the materials that have the best reflectivity at 106 pm 106 p,m, etc are very highly absorbing in the visible portion of the spectrum This enhanced absorption in the visible portion of the spectrum provides for very low damage thresholds when subjected to visible continuous wave and repetitive pulsed lasers Thereare, of course, visible optical systems which are very sensitive to the visible portion of the spectrum, ie, the eyes of a human being Equations are provided for one and three dimensional analysis of temperature gradients in the optical thin films and slip and melt thresholds for metallic substrates Further, equations are provided for both the semi-infinite plate boundary condition and for those substrates that have a thickness less than required for semi-infinite plate boundary using the Reverse Thermal Wavemodel Pictures of in band and out of band damage are provided and curves are plotted for the various coatings on commonly used substrate materials

Bibliography Of The Application Of Infrared Thermography To Electronic And Microelectronic Circuits

Abstract: Monitoring and Analyzing the Dynamic Junction Temperature Distribution of RF Power Transistors by Using RM-50 Infrared Micro-Imager

The Application Of Infrared Thermography In Fire And Explosion Investigation

Abstract: Infrared thermography has been used in medically related litigation for several years. In past years its use has increased in areas of non-medical litigation. The use of infrared thermography in non-medical legal matters usually revolves around complex technical issues connected with loss or life or loss of property. Losses involving fire and explosion often deal with heat transfer phenomenon readily observed and recorded by infrared scanners. Infrared thermography is a powerful visual media that simplifies the presentation of physical phenomenon to lay people who often decide as judge or jury the outcome of a court action involving a loss. Several examples of infrared thermography utilized in fire and explosion investigation are presented. Examples of infrared thermography usage in fire origin investigation, explosion investigation, equipment failures and potential equipment failures are presented.

Infrared remote sensing system

Abstract: PURPOSE:To make the actual condition of non-steady thermal motion and the structure of an object body of measurement as a medium clear by measuring the heat balance of the surface of the object to be measured by a grand truth system, and analyzing the non-steady thermal motion of a model to be measured by a simulator. CONSTITUTION:The grand truth system 1 measures temperature such as outside air and in-room air temperature, temperature, in a wall, and external wall and in-wall temperature. Further, the radiant heat of the sun to the wall surface is measured by a radiation sensor 4b, etc. Then a simulation system 2 analyzes the non-steady thermal motion with various data obtained by thermography and grand truth. A dynamic analysis is taken by a differentiation equation prescribing the non-steady thermal motion of the object and under various conditions prescribing its phenomenon to make the actual structure which causes the phenomenon clear.

Defect Detection and Quantification in Laminated Composites by EATF (Passive) Thermography

Abstract: For over twenty years [1–3, for example] thermography has been under development as a nondestructive evaluation (NDE) technique for composite materials. Several techniques are in use in laboratory, manufacturing quality control, and field inspection applications. The purpose of this paper is to present the capabilities of the externally applied thermal field (EATF) [4] (also called passive [5]) thermographic NDE method, to discuss the applications for which it seems best suited, to describe its limitations, and to highlight directions of further development.