Under the leadership of Danish Technological Institute, Dept. of Energy Technology the initiative was taken in 1991 to coordinate a project to explain and produce documented material for the interpretation of thermograms and to develop practical guidelines for thermographic inspection in electrical plants. Representatives include insurance companies, electricity utility companies, thermography contractors, industrial companies, and suppliers of electrical components and materials from 20 different firms. The project report describes the causes for thermally related defects in electric plants, statistical adaption of already detected defects, defect sources of electric thermography and practical tests charting excess temperature as a function of the current at different typical defects. The guidelines describe how a thermographic examination of larger electrical plants should be carried out in practice. This includes the agreement between customer and thermography contractor, report elaboration, and how different defects are interpreted. This paper describes the project's main contents and its expected effect on industry and insurance companies.

Justifying the costs of starting and maintaining an in-house IR thermography program is essential in ensuring continued funding and sponsorship. Cost benefit studies, whether brief and general, or strictly formalized, tend to focus on costs associated with projected equipment failure and production downtime. While these numbers can be quite dramatic, their validity rests on acceptance of the predicted failure which is inevitably the subject of some conjecture.

The ALL-RED Project was developed to evaluate the use of IR thermography in three specific new areas: condenser air-in leakage; condenser tube leaks; and boiler casing leaks. These areas have plagued the utility industry by causing unscheduled downtime, increasing maintenance costs, and creating performance difficulties. Developing techniques that include: establishing specific methods of detection for each application; preparing guidelines for a program structure, technical approach, and cost benefit; as well as organizing a training program, will further enhance the use of this versatile technology and help utilities reduce down time and maintenance costs through condition monitoring using advanced IR Thermography techniques.

Detection of problems in high-voltage power lines is difficult with ground-based equipment because IR sensor units are subject to error caused by background thermal patterns such as clouds and tall trees. Travel is often slow due to soft sandy soil, moist areas, gullies, and creeks. Such difficulties were eliminated by the use of an airborne Probe Eye Scanner/Normal Color Video System (PESNVS) in an exploratory test. The equipment was mounted in a Piper Twin Comanche and was flown over power lines in east Florida. For ground verification, the PESNVS was mounted in a 4-wheeled vehicle and operated in field surveys under the high tension power lines where three anomalies had been detected aerially. Faulty components (operating above normal temperature) of the same high tension transmission lines were confirmed by the ground surveys.

The purpose of this paper is to explain and discuss the necessary steps for preparing a written practice for qualification and certifications as Level I, II, and III in the Thermal/Infrared Inspection Method. This paper will also discuss the requirements of this practice to meet the latest guidelines of ASNT-TC-1A, 1992 Edition.

Japanese living houses mainly consist of wooden elements in high-temperature and moist conditions. To modify the hot and humid environment, a conventional old house was partially rebuilt and repaired. Especially in the winter season, a diagnostic thermographic test was used to find deteriorated and leaking parts of interior and exterior walls. Macroscopic deteriorated parts were checked again in detail. The deteriorated element was then removed. During the reconstruction process, a new solar heat and air conditioning system using a silica-gel adsorber and underground water was installed to cool and warm up the living room. Thermography tests of this remodeled house show that room temperature is always constant and mild to human beings, especially in the winter. Temperature and heat flow distribution of flowing air in the living room was measured using thermal net and wire methods. Leaking thermal streak flow of the gap was locally visualized by the IR radiometer and a highly sensitive video camera. It was verified that IR thermography is a useful measuring instrument to check thermal defects of a house.

An IR scanner and a nuclear moisture meter were used to survey a ballasted roof suffering chronic leaks. Infrared surveys, conducted with the ballast in place, uncovered five small wet areas. The thermal anomalies were faint and may have been missed during a routine IR roof moisture survey. Nuclear readings were taken on a 1.5-m (5-ft) grid. HIgh nuclear readings were obtained at the one grid point that fell within one of the five wet areas detected during the IR survey. The other four wet areas were missed. However, the nuclear meter found an additional nine small wet areas that the IR scanner missed. All but one of these areas contained wet urethane insulation directly below the membrane. In three other areas of the roof, nuclear readings were higher than those over the rest of the roof. Core samples verified that the perlite insulation at the base of the roof was wet in these areas, two of which were small but one was 12 X 12 m (40 X 40 ft) when squared off. This `deep' moisture was not detected thermographically. On this roof IR and nuclear surveys both provided valuable information but each missed a portion of the problem. When used in combination, their strengths were complementary.

The use of indoor thermography for inspection of building of modern steel construction gives rise to several questions about the consequences of constructional mistakes and poor craftsmanship. In this paper is presented the result from a case study of a newly constructed tennis court building, with a modern steel construction. The main purpose of this study is to investigate the consequences of unsuitable choice of construction related to function and to different climate conditions, constructional mistakes and poor craftsmanship.

The results of a combined aerial and ground-based structural heat loss survey are presented. The aerial imagery was collected by a thermal IR line scanner. Enhanced quantitative analysis of the imagery gives the roof heat flow and insulation level. The ground images were collected by a video van and converted to still frames stored on a video disk. A computer based presentation system retrieves the images and other information indexed by street address for screening and dissemination to owners. We conclude that the combined aerial and ground survey effectively discriminates between well insulated and poorly insulated structures, and that such a survey is a cost-effective alternative to site audits.

Thermographic NDT based on the transient temperature distribution under the Joule effect heating by an electric current was discussed. Two different types of inspection methods, the singular method and the insulation method, were examined. The singular method based on the heat concentration at the crack tip was successfully applied to the identification of the through- thickness and surface cracks embedded in steel plates. The resolution of the crack identification by the singular method was examined by the current intensity factor and the thermal diffusion length. The insulation method based on the temperature turbulence appears on the sample surface due to the thermal insulation of the defect was tested for the identification of the delaminated defect in CFRP. Two methods of the Joule effect heating, the direct current application and the induction heating, were successfully applied for the thermographic NDT of the delaminated defects in CFRP samples. The thermographic NDT developed in this study was found to be applicable to nondestructive flaw- and defect- inspection both in metallic and composite materials.

We describe pulse-echo thermal wave imaging and present images of defects in fiber- reinforced polymers and ceramics. In addition we will show thermal images of propagating cracks in polymers.

Experimental and analytical methods were used to study heating techniques for IR thermography inspection of superplastic formed/diffusion bonded (SPF/DB) structural components. Various thermal loads were investigated to determine the parameters required for highest flaw detection sensitivity. Finite element analysis was used to determine optical heating techniques. According to the analysis, short burst, high intensity heating on the inspection side of the part is required for the highest flaw detection sensitivity. The analytical results were verified using an IR camera and heat lamps to detect unbonds in four-sheet SPF/DB panels. Good quantitative agreement between the analysis and laboratory experiments was obtained.

The marine industry is now facing the problems that were faced by the aircraft industry 20 to 25 years ago: glass-fiber-composite structures do not lend themselves to traditional methods of interrogation. Both the material response and the failure modes of composites are different from traditional materials. Infrared thermographic techniques were investigated for application to composite hull structures and found to be very effective in locating and identifying damage to both solid laminate and sandwich panel construction. The thermographic techniques have been applied to cruising as well as racing yachts with good results. Indicated damage has matched well with the damage discovered during repair operations. More recently, the thermographic techniques have been applied to much thicker solid laminate hull construction used in a new U.S. Navy mine hunter, the MHC-51, U.S.S. Osprey. Thermographic investigations were performed on large test panels used to evaluate different material systems for this vessel and on the vessel itself to provide a baseline thermal characterization. Later this year, shock trials will be performed on the U.S.S. Osprey. Additional thermographic studies are planned following the shock trials.

Fiberglass is a combination of glass fiber reinforcing material and plastic resin. The advantages far outweigh the disadvantages that are commonly found in commercial structures. Fiberglass does not suffer from dry rot or worms as found with wood; from rust, a common problem with steel; or from electrolysis, common problems with both steel and aluminum. However, compared to steel, fiberglass has low fatigue and buckling strengths. This can cause delaminations where stress concentrations are located. Many other factors contribute to delaminations that are invisible to the eye. For this reason an IR thermographic procedure was developed to detect these delaminations and other flaws in fiberglass structures. Due to the confidentiality of this project, neither the name of client or the location of this fiberglass structure will be reviled in this paper.

The use of microwaves as a heating source in time-resolved IR radiometry provides the ability to heat surface and subsurface microwave-absorbing regions of a specimen directly. This can improve the contrast and spatial resolution of such regions and enhance their detectibility when compared with conventional laser or flashlamp sources. The experiments reported here use microwave heating with IR detection. Results on plexiglass-water-Teflon test specimens with absorbers at different depths in the sample are described by a 1D analytical model. Measurements using microwave and optical heating on epoxy-coated steel pipes are compared and demonstrate the ability of microwave heating to detect subsurface water voids very efficiently. Other applications of the method to microwave imaging, field mapping and imaging of defects in composite materials are discussed.

The feasibility of nondestructive testing (NDT) by IR stimulated thermography of satellite structures during their assembly has been evaluated. After a comprehensive bibliography has been collected and analyzed, a comparison between calculated theoretical signals and experimental thermograms obtained on composite samples has been achieved, leading to good results and confirming the limits of the method. Then, a mock-up representative of the satellite structure complexity has been designed and manufactured. An original heating system has been developed, while a fast acquisition system has been adapted to several conventional IR cameras. The feasibility was demonstrated through a large number of trials during which several parameters such as heater and camera locations, level of illumination, camera wavelength range, etc., were systematically changed. By using conventional image processing, and more specific data processing techniques, the threshold of defect detection has been decreased and the analysis of thermal images sequences has been facilitated. The identification of all environmental conditions interfering with this NDT method is underway; it will lead to effective instructions for the NDT of satellite structures by IR stimulated thermography.

The thrust structure at the aft end of the Atlas space launch vehicle is a composite sandwich comprised of aluminum honeycomb core with fiberglass/phenolic face sheets. The surface area of this structure is approximately 600 ft². In 1992, General Dynamics Space Systems Division (GDSS) began using thermographic nondestructive testing (TNDT) for quality verification of these complex composite parts. TNDT has been used on these parts during manufacture and assembly, and on the launch pad at Cape Canaveral. The NDT technique used on these parts since their design in 1957 was `coin tap.' Compared to this method, TNDT provides a greatly improved inspection in less time and at a lower cost. A heat gun with a diffuser attachment is used to heat the inspection area while the area is monitored thermographically. TNDT is a rapid, remote, non-contact, highly portable, real-time scanning technique that can provide a well-documented video record of subsurface structural details including facesheet disbonds and skin delaminations. A specification and test procedure has been written, equipment has been procured, and personnel have been trained and certified. TNDT is a production test method at GDSS.

This paper will discuss the process and rationale involved with dynamic, phase-locked, IR imaging using the TIP Workstation as a platform. This technique can be applied to most rotating structures including tires, wheels, gears and propellers. Actual IR and visual images of tires will be presented.

This paper contains experimental results obtained by applying both one-side and two-side diffusivity measurement procedure for Russian-made cutting tools. Experimental set included CO₂ laser with energy up to 12 J in 4 ms pulse and diffusivity measurement device TAU- 1. In two-side test the correlation coefficient between wear resistance and obtained value of diffusivity was estimated to be K equals -0.61. In one-side test the ratio of signals at 6 and 9 ms after flash was accepted as wear resistance criterion. The corresponding correlation coefficient was K equals 0.59. Some results obtained with Swedish-made tools of unknown composition are also discussed.

Railroad track failure, attributed to moisture trails and erosion voids in the rock ballast and subsoils that support the tracks, slowly deteriorate the railbed to a critical point in which iron rail shift occur. All railroad lines experience failures on a regular basis, but the recent Flood of '93, that inundated thousands of square miles of land and hundreds of miles of railroad tracks in the midwestern United States, brought a new impetus to quickly locate and repair these hidden subsurface defect areas. This paper illustrates a new technology combination of nondestructive remote sensing, computer-enhanced IR thermography and ground penetrating radar, that was used to detect buried moisture trails and erosion voids of railroad track beds. This technology combination is described in theory and by discussion of a case study based upon a successful project, conducted immediately following the flood, for Burlington Northern Railroad.

This paper discusses the design of a nondestructive method for in situ detection of moistened areas in buildings and the evaluation of the water content in porous materials by thermographic analysis. The use of heat transfer model to interpret data allows to improve the measurement accuracy taking into account the actual boundary conditions. The relative increase of computation time is balanced by the additional advantage to optimize the testing procedure of different objects simulating the heat transfer. Experimental results on bricks used in building for restoration activities, are discussed. The water content measured in different hygrometric conditions is compared with known values. A correction on the absorptivity coefficient dependent on water content is introduced.

Nondestructive testing by IR thermography with heat injection has found numerous applications in the industry. However this technique is not always reliable for the inspection of nonplanar objects. The goal of the method presented here is to determine the shape of objects present in the field of view from the corresponding single early recorded IR digital image, in order to first correct distortions due to inspected object shape and second to detect potential subsurface defects.

Although infrared thermography is a well developed technology, its applications to nondestructive testing (NDT) are only now beginning to approach maturity. The efforts of many to have infrared thermography recognized by the NDT community, as a powerful and reliable tool for the inspection of materials, structures, and assemblies, has been inhibited by the absence of recognized standards for the method. The unavailability of standard test methods, standard practices, and even a standard terminology, has undoubtedly been responsible, to some extent, for the fact that neither the American national standard for the qualification and certification of NDT personnel, nor the comparable ISO standard, include infrared thermography among the recognized NDT methods.

The Air Combat Maneuvering Instrumentation (ACMI) is a telemetry system employed by the joint armed services for scoring weapon accuracy during Red Flag and Top Gun simulated air combat. Thermal imaging was employed as the basis of a repair process. A series of IR photograms, collected during circuit warm-up, is employed to characterize the temperature of every part of the circuit board in question. After sampling the warm-up transients of known good cards, the system has a clear indication if a given component is functioning correctly. The Neural Radiant Energy Detection System is now employed as the basis for repaid for the ACMI. During the repair process, out-of-thermal-tolerance components are replaced, resulting in a high reliability repair process. As a result, the ACMI is out of emergency repair status for the first time in 10 years. The approach offers a significant improvement over traditional electronic fault diagnosis where, in many instances, a faulty component cannot be isolated from the response of an electronic circuit card, particularly in cases of shorts and feedback loops.

This paper concerns thermal analysis of the IC package board. To analyze fundamental mechanisms of fluid flow and heat of the IC board array, the IR radiometer is used to visualize radiation temperature pattern of the IC package surface through a transparent plastic wall. Considering transmission rate of the plastic wall, the measured radiation temperature was transformed into the real temperature as function of the emissivity of the IC surface. Isotherm of the radiation temperature distribution of the front and back side surface of the IC board shows the existence of thermal wake pattern caused by surrounding air flow. Steady state and transient 2D temperature distribution of the IC package, heat transfer rate of the front and back side of the IC board and cooling enhancement effects were measured and analyzed systematically.

The use of thermography within the lamp manufacturing industry can improve the quality of many types of lamps ranging from normal incandescent lamps to highly specialized lamps for sports arenas, airports or small lamps for cars. There is a strong demand for more light for the same energy input. Specialized lamps for all possible purposes are developed. But it also forces the lamp manufacturers to utilize the available materials to their extremes. The exact control of the temperatures inside or on the lamp shell has therefore become increasingly necessary as temperatures in lamps can be rather extreme. In plasma lamps for example, the plasma can have a temperature of 6000 C, the bulb around 700 C and the electrodes inside the bulb can have temperatures in excess of 2000 C. Thermographic methods have shown their applicability for a large number of measurement cases. Some of these methods and measurement cases are described. As these applications put very special demands on the measurement equipment, these demands are explained in more detail.

The aim of the study was to test the effect of skin creams and their components in windy (3 m/s) and cold (-15 degree(s)C) conditions on face temperature and heat flux. The tests were carried out in a climatic chamber with 18 persons sitting in front of the opening of the wind tunnel, the wind directed against the face. Skin temperatures were measured from 4 points on both sides of the face with thermistors and the heat fluxes were measured using heat flux sensors on both cheeks. Also the ambient temperature and wind were registered. In addition to these measurements an IR thermal scanner was also used to measure the spatial and temporal distribution of temperature variation on the face during the exposure. The results were continuously recorded on VHS-video tape. Using still pictures from recorded material the area temperature of the cheek was measured, which described the mean temperature of the cheek. Test periods were 30 minutes and the same test subjects were not used until 48 h after the previous cold exposure. The test persons were young (20 - 30 years) healthy male persons. The total number of tests was 38.

In general, measurement error, including a precision error and a bias error, is defined as the difference between the true and measured values. Moreover, measurement error is also necessarily included in the temperature measurement using IR radiometer; however error estimation for IR radiometer has not been investigated yet. In the present study we discussed several primary factors on a measurement error and estimate a qualitative error pertaining to IR radiometer using the uncertainty analysis method based on ANSI/ASME PTC 19.1 - 1985. Detailed clarification of measurement error is important to develop a practical temperature measurement using IR radiometer. It was newly revealed from the uncertainty analysis utilized here that the measurement using IR radiometer is available in obtaining several radiative quantities. In addition, from a series of thermal visualization using IR radiometer, the relation between friction energy and a surface temperature is clarified to tribology behavior of the surface.

It is necessary to obtain a surface radiation temperature that does not include reflection energy, because the influence of reflection energy on measured images of a surface radiation temperature is comparatively large on a metal surface. In general, there are two ways to eliminate reflection energy and to specify a true temperature. One typical method is the analytical method which obtains a true surface temperature after measuring a true emissivity using IR radiometer. Another is based on the bicolored method applying pseudo gray-body approximation, in which a true surface temperature can be acquired after eliminating emissivity on a surface with the aid of radiation energy possessing various detection wavelengths. The surface temperature measurement using bicolored radiometer combined with pseudo gray-body approximation has not been discussed yet. Therefore, in the present study, we will propose and investigate the bicolored temperature measurement based on a power law description of energy for various detection wavelengths. And then its applicability and accuracy on temperature measurement will also be estimated as follows.

An IR imaging technique has been developed to map 2D electric field distributions near an emitter or a scattering body. This technique is applied to design a highly directive microwave aperture antenna. The antenna is made from circular waveguides. The antenna is fed with a circularly symmetric coaxial TM₀₁ mode. From symmetry, the TM₀₁ mode does not radiate in the bore-sight direction from an open-ended circular waveguide; however, the dominant circular TE₁₁ mode does have a directive main beam radiation pattern.

A new (lambda) T relation of blackbody for optimizing the efficiency of production of radiation was derived by use of Gauss-laguerre method. We have given the experimental investigation of the new relation of blackbody relation and discussed its application.

We are developing dual-band IR (DBIR) imaging and detection techniques to inspect airframes and concrete bridge decks for hidden corrosion damage. Using selective DBIR image ratios, we enhanced surface temperature contrast and removed surface emissivity noise associated with clutter. Our surface temperature maps depicted defect sites, which heat and cool at different rates than their surroundings. Our emissivity-ratio maps tagged and removed the masking effects of surface clutter. For airframe inspections, we used time-resolved DBIR temperature, emissivity-ratio and composite thermal inertia maps to locate corrosion-thinning effects within a flash-heated Boeing 737 airframe. Emissivity-ratio maps tagged and removed clutter sites from uneven paint, dirt and surface markers. Temperature and thermal inertia maps characterized defect sites, types, sizes, thicknesses, thermal properties and material-loss effects from airframe corrosion. For concrete inspections, we mapped DBIR temperature and emissivity-ratio patterns to better interpret surrogate delamination sites within naturally- heated, concrete slabs and removed the clutter mask from sand pile-up, grease stains, rocks and other surface objects.

This paper will detail the successful uses of IR cameras within New York's weatherization program, examine and evaluate the reasons thermography has not reached the level of use of other technologies, and present New York's strategy to see thermography's full potential realized within the State.

The results of our work on the development of emissivity models and IR filters for applications in multi-wavelength imaging pyrometry are presented. Techniques such as Fourier transform IR spectroscopy have been deployed to determine the emissivity of Si and SiO₂/Si in the temperature range of 331 to 1235 K. These measurements have been obtained for n-Si, p-Si and SiO₂/Si in the oxide thickness range of 60 to 500 nm. These results coupled with calculations of emissivity from first principles lead us to model the wavelength dependence of emissivity. Preliminary measurements of emissivity of HgCdTe are reported.

Analytical and experimental methods were used to study a series of test specimens consisting of plasma sprayed layers of NiCrA1Y I Zr02ofvarious compositions. The coatings were seeded with artificial defects and were sprayed on steel disks. Two types of defects were used: flat bottomed holes drilled in the steel substrate and patches of room temperature vulcanizing silicone within the coatings. Defect sizes ranged from 0. 1 to 10 mm and were at depths below the coating surface from 0.6 to 3.6 mm. The method of time resolved infrared radiometry was used with two different heat sources, an acetylene torch and a high intensity lamp, to inspect the coatings. The torch allowed excellent sensitivity at depths of less than 2 mm and the lamp revealed flaws through the full coating thickness. Two analytical models were developed to study heat flow in the test specimens: a finite element model and an electrical analog model. Results from the two models were compared to check consistency and the finite element model results were compared with experimental results. The finite element code was chosen for further development due to its greater flexibility and ease of use. This paper was presented at the Thermosense XV conference.