Showing papers on "Thermography published in 1995"

Energy flux to the ASDEX-Upgrade diverter plates determined by thermography and calorimetry

Abstract: A new thermography system with high time resolution was put into operation at ASDEX-Upgrade and is routinely used to determine the energy flux onto the lower diverter plates. The measurements allow the power deposition to be characterized during dynamic events such as ELMs and disruptions, as well as the asymmetry of the inboard/outboard power load. A power balance is set up even during single discharges and the losses are found to be fairly equal to the power input.

Apparatus for remote analysis of vehicle emissions using reflective thermography

Abstract: A system for remote analysis of vehicle emissions also determines whether each vehicle's engine and exhaust system are hot or cold by measuring infrared radiation reflected by the roadway beneath the vehicle. A source transmits a beam of radiation through at least a portion of the motor vehicle exhaust to a number of sensors. Each sensor generates a signal indicative of the absorption of the beam in a wavelength band indicative of a corresponding exhaust gas (e.g., CO, CO2, HC, NOx and H2 O). An infrared detector measures infrared radiation within a field of view including at least a portion of the roadway beneath each passing vehicle. A processor then computes the concentrations of each exhaust gas from the sensor signals, and determines whether the vehicle is hot or cold by measuring the intensity of infrared radiation detected by the infrared detector. Because cold vehicles can temporarily produce abnormally high pollution emissions, the processor can be programmed to separately identify hot vehicles having exhaust emissions that exceed air pollution limits. The system can also include a video camera and recorder to record the license plate and emissions data for each vehicle identified as failing to meet emissions limits.

Use of recovery-enhanced thermography to localize cutaneous perforators

Abstract: Recovery-enhanced thermography implies the scanning, after cooling, of the skin surface with ice water for several seconds Using this method, cutaneous perforators were clearly identified in constant distributions on the trunks of 12 healthy volunteers Clinically, preoperative recovery-enhanced th

Experimental analysis of surface flow on a delta wing by infrared thermography

Abstract: IR thermography has been employed for heat transfer measurements and surface flow visualizations on a 65-deg delta wing model.

Low-temperature Exotherm Measurement Using Infrared Thermography

Abstract: Infrared thermography was used successfully to measure the exotherm tempera- tures during freezing of well-watered and drought-stressed branches of jojoba ( Simmondsia chinensis (Link) Schneider). The exotherms were visualized easily as color changes on the monitor, while computer analysis software was used to plot the resulting temperature vs. time curves, suggesting that freezing sensitivity of jojoba is governed by supercooling. Each branch froze as a unit, and distinct initiation sites were absent. A second, previously tested method of differential thermal analysis was used simultaneously and confirmed the accuracy of the infrared technique. The actual freezing temperature for well-watered tissue was higher (-8C) than for tissue subjected to drought (-10C).

Design of a focal-plane array thermographic system for stress analysis

Abstract: A state-of-the-art thermographic system has been developed based on a 512×512 focal-plane array thermal imager. The system, dubbed FAST (for focal-plane array for synchronous thermography) is able to deliver high-resolution full-field thermoelastic stress scans in minutes rather than hours. The paper itemizes the hardware components together with their functions.

Issues associated with the use of infrared thermography for experimental testing of insulated systems

Abstract: Infrared scanning radiometers are used to generate temperature maps of building envelope components (windows, insulation), which may assist in evaluating their thermal performance. Accuracy of an IR scanner for laboratory-based surface temperature measurements was evaluated and details for achieving max accuracy identified. Minimum uncertainty in IR temperature measurement is {+-}0.5 C. Using an external reference emitter to scale the absolute value of IR scanner temperature measurements can improve the accuracy from 2 C to as low as 0.5 C for a 5 C span, which is comparable to accuracy of type T thermocouples. Operational procedures can easily increase errors; actual accuracy of an IR measurement will vary with test speciment geometry, temperature gradients, and scanner settings (emissivity, etc.). Future efforts for standard IR thermographic test procedures that should address standardization of various items are outlined. A database of temperature maps for a range of window systems is being created; representative data are presented for two insulated glazing units with different spacer systems.

Real-time welding process control using infrared sensing

Abstract: The thermal distribution changes associated with gas tungsten are welding process were studied to identify and correct for weld joint offsets for butt joints These changes were experimentally measured using infrared thermography In the weld offset conditions the slope of the temperature distributions were found to be altered dramatically Not only did offset produce asymmetric temperature distributions but a steep increase in gradients was also observed These changes were then used to detect and correct initial errors in the position of the torch during the welding of straight and curved contours of perfectly fitted butt joints and joints with gap

Microwave excitation for thermographic NDE: An experimental study and some theoretical evaluations

Abstract: The theme of microwave heating for thermographic nondestructive evaluation has been addressed experimentally. Slabs and sandwiches, made of Kevlar or fiberglass, containing artificial defects were heated by means of cavity applicators fed by 2.45 GHz high microwave power (600-1,700 W). The results, compared with that obtained using X-ray, ultrasound, and infrared excited thermography, showed the effectiveness of this technique. Some simple theoretical modelling has been also developed.

Differential thermography applied to structural integrity assessment

Abstract: A dual-function for differential-thermographic devices is discussed. It is shown that differential thermographic cameras can be used for rapid inspection of structures as well as for stress analysis. Reviews of forced diffusion thermography (FDT), thermoelastic stress analysis (TSA), and differential thermographic cameras are offered. A new stress intensity measurement technique using TSA data in the vicinity of cracks is described in more detail.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Infrared thermography and Fourier transform infrared spectroscopic study of CO oxidation over a catalyst washcoat supported on a metal substrate

Abstract: Spatiotemporal oscillations on a Rh/SiO{sub 2} washcoat catalyst supported on an Al disk are studied using infrared thermography to visualize the temperature patterns. The dynamics of the temperature pattern oscillations were analyzed with the empirical eigenfunction method. During self-sustained and forced oscillations, these patterns are characterized by a pulsating oscillation with one hot spot near the reactor inlet. Proper vibration of the O{sub 2} and CO flow rates when the reaction is near transitions between steady states or in an oscillatory regime decreases the ignition/extinction temperature, increases the time average temperature and CO conversion, and dramatically suppresses the self-sustained oscillations. In situ Fourier transform infrared spectroscopic results indicate that feed vibrations prevent the formation and propagation of high CO coverage on the catalyst surface.

Shape reconstruction from a single thermal image

Abstract: One of the problems associated with nondestructive testing by infrared thermography with heat injection is related to the inspection of nonplanar objects. A method is proposed to determine the shape of an object present in the field of view from the corresponding single, early-recorded thermal image. Such shape reconstruction enables the correction of thermal image distortions due to object shape.

Characterization of CFRP with Lockin Thermography

Abstract: Thermal waves are suited for non-contacting inspection of near-surface areas of solids [1]. The reason for this depth limitation is the strong attenuation of this modulated thermal diffusion process. The resulting depth range is frequency dependent, hence it has been pointed out very early that thermal waves allow for depth profiling by variation of modulation frequency [2, 3].

Detection method for flaw of material by infrared thermography

Abstract: PROBLEM TO BE SOLVED: To obtain a detection method in which the state of the surface of a material is protected from a disturbance and in which the reproducibility of an image can be held by a method wherein an object to be tested is brought into close contact with an electronic cooling and heating plate so as to be heated and cooled, a part between an infrared camera and the object to be tested is held in a vacuum state by a vacuum chamber and the flaw of the material is detected on the basis of a thermal image obtained by the camera. SOLUTION: As the heating and cooling medium of an object 1 to be tested, an electronic cooling and heating plate 2 which makes use of the Peltier effect by a thermal semiconductor is used, and a thermal image is measured through the vacuum chamber 3. In the plate 2, a current is made to flow to an N-P direction out of a P-N pair in a pi-shaped series circuit in which the thermal semiconductor composed of two kinds of a P-type element and an N-type element is bonded to a metal electrode, heat is absorbed at the upper part of a pi- shape, and heat is generated at its lower part. Then, the heat is pumped to the lower part from the upper part, and a heating operation and a cooling operation are performed. The object 1 to be tested is brought into close contact with the surface of the plate 2 so as to be heated and cooled, it is assembled to the chamber 3, a part between a camera 7 and the object 1 to be tested is held in a vacuum state, and it is possible to prevent a disturbance due to the open air. COPYRIGHT: (C)1997,JPO

Polarization-sensitive thermal imaging sensor

Abstract: Conventional methods in robot vision use the intensity of light reflected or emitted by objects in order to perform object recognition. However, information contained in the polarization of the light can often aid in the determining of surface properties such as roughness, index of refraction, and spatial orientation. Imaging of such surface properties would facilitate image segmentation and classification of objects in military target recognition, environmental monitoring, oceanography, forestry, agriculture, and automated assembly. Physics Innovations Inc. is developing a thermal imaging technique where, in each image pixel, three Stokes parameters are sensed simultaneously and at video frequencies. The Stokes parameters are intensity I, percent of polarization P, and angle of the plane of polarization (phi) . Although infrared, thermal intensity images of terrestrial scenes have low contrast, images of P and (phi) are expected to have high contrast. In this paper the Physics Innovations sensor is described. We also discuss our evolution of the performance of a prototype sensor. Images of I, P, and (phi) from the prototype sensor demonstrate that, for common man-made objects with smooth surfaces, surface orientation can be derived. Surface orientations can be measured in the same image frame as temperature distribution. From our results using the prototype sensor, we conclude that three-dimensional information, in addition to thermal information, can be derived from polarization-sensitive, thermal imaging.

Infrared thermographic evaluation of marine composite structures

Abstract: Glass fiber composite materials have been used for many years in the construction of pleasure, cruising, and racing marine vessels. These vessels have demonstrated excellent performance characteristics and have been reliable in service. Even so, as with all material systems, they are subject to damage from accident, neglect, and abuse. Traditional nondestructive inspection approaches are not always fully effective for examining composite marine structures. Infrared imaging offers a particularly attractive approach for the inspection of composite material structures. Glass fiber composites frequently possess a combination of thermal properties that make them good candidates for infrared thermographic evaluation while other nondestructive evaluation approaches provide limited success. Infrared thermography combines the advantages of being nondestructive with the capability of rapidly inspecting wide surface areas.

An optimized experimental method for measuring thermal conductivity of thin, boron‐doped diamond films

Abstract: A novel experimental method has been developed and applied to measure the thermal conductivity of a thin (5.6 μm thick) boron‐doped diamond film produced by a hot filament CVD process. Thermal fields were created by Joule heating in a 3‐mm‐diam, free‐standing diamond diaphragm; infrared imaging thermography was used to quantify these fields. Parameter estimation was applied to determine the thermal conductivity of the film using more than 100 temperatures in each property determination. The experimental design chosen was selected on the basis of an analysis which maximized the sensitivity for the determination of thermal conductivity while minimizing the uncertainty in the estimation of this property. Parameters such as characteristic length, film resistivity, and thickness were chosen from the model to reduce convective effects, obtain the desired temperature rise, and minimize the uncertainty in the estimation of the thermal conductivity. Preliminary results for the thermal conductivity were obtained us...

Potential applications of ocular thermography

Abstract: Thermography is an investigative technique which allows rapid color-coded display of the temperature across a wide surface by means of infrared detection. We describe an ocular thermographic study of a normal population and present case studies describing the application of this technique for patients with ocular disease. We found that 95% of the normal population have an interocular temperature difference (temperature of center of right cornea minus temperature of center of left cornea) of 0.60 degrees or less. There appears to be a greater difference in temperature between the limbus and the center of the cornea in patients with dry eyes. This technique has potential for evaluating tear film disorders and inflammatory conditions, for monitoring the progress of such conditions, and for evaluating the efficacy of various treatments.

Nondestructive evaluation of weld defects by infrared thermography

Abstract: In order to clarify the applicability of infrared thermography to the nondestructive evaluation of weld defects, an infrared measurement was conducted on the welds with various artificial defects. Two heating methods, a moving gas flame and a Joule effect by electric current flow, were used for the fast and large area inspection with readily interpretable images of defects. Finite element analysis was also used for the theoretical analyses of beat conduction and electric current flow, together with the development of imaging technique for the evaluation of the shape and size of defects. As the results of infrared measurements and theoretical analyses, the selection of heating method and the acquisition of infrared images were important for the clear image and precise measurement of weld defects. As for the clear images, the Joule effect heating was useful for the detection of open-to-the-surface defects, while the moving gas flame heating was available to the inner defect parallel to the surface. It was also clarified that the types of defects were identified by the distribution of high and low temperature regions. In the measurement of defect size, defect edges were evaluated by the positions with maximum temperature gradient in the moving gas flame heating,more » and with minimum second derivative of temperature in the Joule effect heating. The effective images for the precise measurement of defect size were obtained from the ones immediately after current flow in the Joule effect heating, and just before the arrival of gas flame beneath the defect.« less

Thermal sensing and imaging of the dry-sliding contact surface using IR thermomicroscope

Abstract: A new experimental technique using an infrared (IR) thermography combined with IR transmitting materials is proposed for the visualization of the contact surface temperature of two solids. A dry sliding contact between a pin and a disk is investigated. IR transmitting solids such as sapphire, alumina ceramics and silicon are employed for the disk material. The temperature distribution on the contact surface is measured by the IR thermography through the IR transmitting disk. It is found that the temperature rise on the contact surface as well as the contact area is accurately analyzed from the obtained thermal images. The influence of contact pressure and sliding velocity on the contact surface temperature is discussed. Further, the dynamic process of wear of bearing steel against sapphire is investigated under dry sliding contact by the new type IRCCD thermography. Transient temperature distribution around the frictional heat spot was computed by the FEM analyses in order to estimate the magnitude of flush temperature from the experimental result in the dry sliding contact. All the results show that the proposed technique is useful for examining the successive process of the tribological phenomena.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using infrared thermography for the creation of a window surface temperature database to validate computer heat transfer models

Abstract: IR thermography is well suited for resolving small differences in the thermal performance of highly insulating window systems. Infrared thermographic measurements made in conjunction with reference emitter techniques in a controlled and characterized laboratory setting can have an absolute accuracy of {plus_minus}0.5{degree}C. Quantitative infrared thermography requires that a number of sources of error related to measurement accuracy and test environmental conditions be quantified and minimized to the extent possible. Laboratory-based infrared thermography can be used to generate window surface temperature profile databases which can be used to direct the development of 2-D and 3-D finite element and finite difference method fenestration heat transfer simulation codes, identify their strengths and weaknesses, set research priorities, and validate finished modeling tools. Development of such a database is under way at Lawrence Berkeley Laboratory, and will be made available for public use.

Transient thermal nondestructive testing (NDT) of defects in aluminum panels

Abstract: This paper describes results of the inspection of aluminum specimens by transient infrared thermography. The inspected specimens contain various defects: internal and external corrosion, delaminations and water between two sheets. The accent is made on comparison between scanning IR radiometer and FPA camera, verification of theoretical data by experiment, discrimination between different defects and simple inversion method for corrosion data.

Novel applications of thermal imaging in the steel industry

Abstract: Near infrared (NIR) thermal imaging using Si CCD cameras is a cost-effective technique for generating thermographs of hot objects having temperatures above 350 degree(s)C. The relatively low cost and the favorable performance of the technique makes it the preferred thermal imaging technology for solving many measurement problems in the steel industry. In recent years, a number of systems have been developed by BHP Research and installed within BHP's steelworks to fulfill various measurement tasks. This paper provides an overview of the technique together with a description of several industrial applications that BHP Research has developed.

Microwave-source time-resolved infrared radiometry for monitoring of curing and deposition processes

Abstract: Thermal wave methods employing optical heating sources have been used successfully in the past to determine layer thicknesses or thermal diffusivities. However, monitoring of curing or deposition processes can be difficult with such techniques due to changes in the sample surface properties such as optical absorption during processing. The method introduced in this paper, microwave-source time-resolved infrared radiometry (TRIR) in conjunction with intentionally embedded carbon or metal fibers allows the determination of surface layer thickness and thermal diffusivity almost independently of the surface properties of the layer. This suggests the use of fibers as embedded sensors in applications where layer thickness or thermal properties need to be controlled during processing.