Showing papers on "Thermography published in 1985"

The Non-Destructive Evaluation Of Composites And Other Materials By Thermal Pulse Video Thermography

Abstract: The detection of sub-surface defects and structures, by thermal pulse video compatible thermal imagers, ie beginning to complement the slower methods of ultrasonic scanning and in some applications to surpass them In principal a short pulse of radiation is emitted from a xenon flash tube and is absorbed by the surface of the material under inspection This energy diffuses as heat through the material and sub-surface features are revealed as variations in surface temperature, either on the far face or near face, by a scanning infra-red camera The promise of thermal pulse thermography lies in its ability to inspect materials for defects and quality with great speed and without physical contact Other methods of applying heat are currently being investigated

Method of and apparatus for thermographic identification of parts

Abstract: A method and apparatus for the non-destructive identification of coated and uncoated metal parts employing infrared thermography. The apparatus comprises a means for directing infrared radiation onto the surface of a part; a means for scanning the part surface for reflected infrared radiation; a means for capturing the reflected radiation and converting it into a signal representative of variations in radiation reflected from the surface of the part; means for etching an identifying code into the surface of the part; and means for displaying the signal as a video image. The method comprises altering the surface reflective characteristics of a part to produce an identifying code, irradiating the part with infrared radiation of a specific wavelength and detecting differences in the amount and intensity of radiation reflected from the part.

Test Of Jet Engine Turbine Blades By Thermography

Abstract: Two applications of thermography for testing and development of turbomachinery components are described: (1) Fabrication defects in the cooling system of internally cooled turbine blades are detected by transient heating of the blade and measurement of its surface temperature distribution by an infrared imaging system. Defects like blocking, narrowing, widening, and mispositioning of cooling channels can clearly be identified by the disturbance of the transient surface temperature distribution of the blade. (2) To improve the cooling configuration of turbine blades, the cooling effectiveness over the total blade surface must be determined under test conditions similar to those in the turbomachine. The infrared measurement of blade surface temperature distributions in a hot air cascade and the method to correct the infrared intensities for radiation reflected at the measuring surface are illustrated in an example.

The Thermal and Spatial Resolution of a Broad-Band Correlation Radiometer with Application to Medical Microwave Thermography (Short Paper)

Abstract: The improved spatial and thermal resolution of a broad-band microwave correlation radiometer is discussed. Theoretical upper and lower bounds of the combined spatial and thermal resolution in a dense transmission medium are presented along with data obtained for two thermal sources in air. The application of broad-band correlation techniques to medical microwave thermography is novel, and the results indicate that electronic scanning of tissue should be possible.

Imaging of hydrocarbon vapours and gases by infrared thermography

Abstract: The use of an infrared imaging technique for the visualisation of hydrocarbon gases and vapours has been demonstrated. The theoretical background of the method is discussed, as are some general instrumentation requirements. Laboratory investigations of the approach have been carried out with commercial infrared thermography equipment to examine sensitivity to different hydrocarbons. The studies have also clarified the requirements of and the potential for an instrument development programme. The potential of image processing techniques for the improvement of instrument sensitivity and image quality has also been examined.

Analysis and Application of Thermography in Medical Diagnosis

Abstract: Thermography is the term used to describe the technique of mapping skin temperature patterns and the interpretation of that information to assess physiologic status. The temperature map is typically obtained with a scanning infrared radiometer; a CRT typically provides a visual image of the map. Temperature levels may be displayed by various shades of grey or by colors representing discrete temperature levels. Photographs of the displayed image provide a record of the temperature patterns. Liquid crystals applied directly to the skin or encapsulated in sheets of plastic have also been used to portray skin temperature. Skin temperature maps have been used in a wide range of medical applications. These applications include, but are not limited to, breast cancer detection, assessment of peripheral vascular disease, soft tissue trauma, infection, rheumatology, detection of thyroid cancer, viability of skin flaps, monitoring densitized tissues, diagnosis of occlusive disease of the carotid artery, and diagnosis and treatment-monitoring in headache. Applications will be treated in detail later in this chapter.

Infrared thermographic temperature measurement during laser heat treatment

Abstract: A commercial infrared thermography system has been used to monitor workpiece surface temperatures during laser heat treatment. A simple optical filtering technique was used to increase the upper temperature limit of the thermography system. Experimental results are presented which demonstrate an accuracy of ±10%. The filtering technique is applicable to most commercial infrared thermographic systems.

Vehicular view field monitoring system

Abstract: PURPOSE:To facilitate the monitoring of the view field for night running by photographing a 2-D image of a view field outside a car to accentuate thermal images of subjects by diciding on the temperature thereof according to the reference temperature CONSTITUTION:An infared visicon camera 1 is carried on a car to project a 2-D image on a display section 2 by a thermography in a front view field A temperature sensor S1 for measuring the atmospheric temperature, a temperature sensor S2 for measuring the surface temperature of a body and a temperature sensor S3 for measuring the road surface temperature are mounted on the car The detection temperatures of the temperature sensors S1, S2 and S3 are read into an image processing section 3 and thermal images of various subjects in the picture are projected on a display section accentuating by kinds by diciding on the temperature of various subjects necessary for monitoring other cars, pedestrians, road surfaces and the like

Thermographic diagnosis of arthritis in peripheral joints

Abstract: The measurement of absolute temperatures on the surface of the human body using quantitative thermography allows this technique to be used in rheumatology, for the diagnosis and monitoring the course of inflammatory diseases of the locomotor system. The patient is exposed to a room temperature of 18 degrees C and the skin temperature measured over the joint for a defined area (region of interest). Inflamed joints show distinctly higher absolute temperatures than normal ones within the observation time of 40 minutes. Moreover, the skin over healthy joints cools faster and to a greater extent than skin over inflamed joints, whose temperatures remain the same or even rise minimally in more acute cases. Using two measurements, the determination of the absolute temperatures (static thermography), and the changes in these temperatures within a definite time interval (dynamic thermography) it is thus possible to establish a diagnosis of arthritis in the regions of the peripheral joints with the help of standardised nomograms with an accuracy of more than 90%, and to follow the course of the disease more exactly.

Radiometric Calibration And Image Processing Of Landsat Tm Data To Improve Assessment Of Thermal Signatures

Abstract: Absolute radiometric analysis of Landsat Thematic Mapper (TM) thermal infrared image data requires processing to remove atmospheric effects and knowledge of target material type in order to obtain kinetic surface temperatures. Results are presented in which a modified version of the LOWTRAN-5A atmospheric propagation model is used to remove atmospheric effects. Target emissivities are estimated by using shorter wavelength bands of the TM sensor to outline general land cover classes, and assigning an emissivity to the land cover type. By combining atmospheric effects, emissivity, and internal radiometric calibration data, surface temperature images have been generated. These images include corrections for internal sensor calibration, emissivity, upwelled radiance, and atmospheric transmission. These techniques have been implemented using parallel processing methods on an image display system resulting in relatively high image throughput rates. Using the higher resolution short wavelength data in processing the thermal infrared data has an additional advantage in that it gives the appearance of improving the resolution of the thermal infrared data. These displays clearly aid the assessment of thermal signatures.

Microprocessor Based Radiation Sources And Radiometers For Testing Thermal Imaging Systems

Abstract: In the last few years, the sensitivity of Forward looking infrared (FLIR) devices has increased considerably. The requirements on the testing stations in production and in the field have changed accordingly. The heart of the test station is the infrared source, usually a "differential blackbody". In order to make much more accurate measurements, the source must be such that: 1. Its temperature and emissivity profiles are as uniform as possible. 2. The differential temperature is as stable as possible in the short term (hours) and long term (months). 3. The recalibration procedures are as simple as possible, reliable and traceable to an international standard. 4. The differential temperature is measured and displayed with high resolution (of the order of 0.001C). CI has recently developed a new differential blackbody source, based on very stable electronics, and microprocessor based technology, in an effort to meet the modern requirements for this type of instrumentation. The microprocessor is especially useful to automatically take into account systematic temperature gradients between the probe used to control the temperature and the emitter surface, or the emissivity differences between the emitter and reference plate, if needed. CI has also developed new radiometric calibration and uniformity test techniques, which use a particular version of its telescopic radiometers. These radiometers can measure temperature differences of the order of millidegrees near room temperature, and are also based on a special microprocessor programme which translates the detector signal to a temperature reading. This paper will describe some of the common problems encountered in the differential blackbodies, and to some extent, the work recently performed at CI to solve them. A radiometric technique to measure the temperature uniformity and stability will also be described.

Computerised infra-red thermography in medicine and physiology

Abstract: The use of computerized infra-red thermography is discussed in relation to the measurement of human skin surface temperat.ure. Numerical analysis of digitized thermograms enables quantitative descriptions of thermal patterns to be made which are now adding muc.h to our understanding of the mechanisms involved in physiological thermal processes. Examples are given of the way that such analysIs IS also becoming increasingly useful in clinical diagnosis and assessment.

Aerial Thermography And Spot Radiometer Applications For Detecting Thermal Anomalies Of Office Buildings

Abstract: Aerial thermography and spot radiometer techniques were used for the assessment of roofs and heat loss through building envelopes of office buildings. The inspections were part of the diagnostic programs developed by the National Bureau of Standards (NBS) for the General Services Administration (GSA) to evaluate the thermal integrity of new and existing office buildings. The infrared inspections by aerial thermography and the spot radiometer measurements were performed by outside contractors; all other tests in the program were performed by NBS. This paper presents the analysis and results reported by the contractors, and discusses the capabilities and limitations of equipment, and make recommendations for aerial thermography and spot radiometer inspections on office buildings. Also included are comparisons of R-values determined from spot radiometer and heat flow meter measurements, and discussions of the results in conjunction with the ground-based infrared survey and other techniques that were utilized. Specification formats for procurement of contractor services are suggested for further development.

Automatic Welding: Infrared Sensors for Process Control

Abstract: A feasibility study was performed to determine if infrared thermography could be used to detect perturbations in the arc welding process which result in defects. Data were gathered using an infrared camera with a resolution of.2C which was trained on the molten metal pool during welding. Several defects were then intentionally induced and the resulting thermal images were preserved on film. These images revealed that different types of weld defects induce different characteristic changes in the thermal image by detectably altering the temperature field around the weld. These perturbations in the temperature field can be used to identify and locate defects such as arc misalignment, plate gap, puddle impurities etc. Macrostructural examinations permitted investigations into the relationships between weld puddle penetration depth and the temperature field. Using computer aided processing of these thermal images, it is expected that the welding process can be controlled to a higher degree than is presently possible.

Thermographic Studies Of Catalytic Reactions

Abstract: Infrared thermography has been used to study spatial temperature distributions on heterogeneous catalytic surfaces under ordinary reaction conditions. Thermograms of supported catalyst wafers, gauzes, and foils, obtained under steady-state and oscillatory conditions, showed the presence of marked thermal variations on the surface of the catalysts. In the case of supported catalysts, large temperature variations were observed under steady-state conditions, and thermograms show that hot spots with high activity seem to dominate the process. In such a case, conventional calculations of specific reaction rate and turnover numbers with the implicit assumption of spatial uniformity would be in error. Thermographic observation has shown that spatial variations of the rate of reaction on catalytic surfaces seem to be greater than was previously suspected, and the implications, both practical and theoretical, may be far reaching. This work was the first to use thermal imaging techniques in the study of spatial phenomena on catalytic surfaces under steady-state and dynamic conditions. The technique yields valuable information and is potentially a useful and inexpensive addition to the array of tools available to researchers for the understanding of catalytic processes. Thermography may be useful in the testing and screening of catalysts, and appears to be the only generally useful method for obtaining spatial information on catalytic surfaces under ordinary reaction conditions.

Material Stress Inspection By Digital Thermographic Image Processing

Abstract: Within the elastic range, a body subjected to tensile or compressive stresses experiences a reversible conversion between mechanical and thermal form of energy. If adiabatic conditions are maintained, the relationship between reversible temperature change and the corresponding change in the sum of the principal stresses is linear and independent of loading frequency. The inspection of the thermoelastic effect on spot weldings using infrared-based systems can give significant data for non destructively evaluation of welding defects. A specimen was first modeled by Finite Element Technique and then tested on an MTS unit monitored by an infrared camera. A digital image processing computer facility was used to compare sequences of images to investigate the dynamic behaviour of the temperature differences. Theo-retical and experimental results are compared.

Computer-Aided Tomographic Thermography

Abstract: The use of thermography as a medical diagnostic tool has been described in Chap. 25. In contrast to x-ray and ultrasound-imaging techniques, which detect structural differences, thermography is sensitive to functional parameters, such as circulation and metabolic rate, thus providing information not obtainable with other methods.

Evaluation Of Photovoltaic Panels With Ir Thermography

Abstract: Electronic infrared thermography allows fast and non-destructive measurements of temperature distributions of encapsulated solar cells on a panel under various operating conditions. Differences in the performance of the individual cells can be visualized and so called "hot spots" in the panel (due to partial shadowing, etc.) can be analyzed. IR image analysis was also used to determine the IR emissivity of different types of solar cells. This is one of the important criteria for the evaluation of the electrical-thermal behaviour of a cell for photo-voltaic or combined photovoltaic thermal applications. We designed a portable IR measuring system having both on-line and off-line interfacing possibilities with a minicomputer for image processing and analysis. During field measurements, the composite video signal of the IRT system is recorded on a video cassette. For analysis, the thermal images can be visualized on a TV moni-tor and, at the same time, they are digitized and transferred onto a PDP-11 computer for processing. A suit-able software package was developed to obtain different types of thermograms such as simple line profiles, 3-dimensional relief images and isothermal maps.

Test Of Jet Engine Turbine Blades By Thermography

Abstract: Two applications of thermography for testing and development of turbomachinery components are described: (1) Fabrication defects in the cooling system of internally cooled turbine blades are detected by transient heating of the blade and measuring its surface temperature distribution by an infrared imaging system. Defects like blocking, narrowing, widening and mispositioning of cooling channels can clearly be identified by the disturbance of the transient surface temperature distribution of the blade. (2) To improve the cooling configuration of turbine blades the cooling effectiveness over the total blade surface must be determined under test conditions similar to those in the turbomachine. The infrared measurement of blade surface temperature distributions in an hot air cascade and the method, to correct the infrared intensities for radiation reflected at the measuring surface, are illustrated in an example.

Measurement Of The MTF Of Thermal And Other Video Systems

Abstract: Some of the techniques which can be used for measuring the MTF of video imaging systems are described, including a recently developed scanning microphotometer based on a linear CCD array. The relative merits of the different techniques are discussed.

A water surface as a thermal reference object for thermography

Abstract: The work reported indicates that a continuously stirred water bath forms an adequate reference target for the calibration of thermographs. Targets of various sizes can be produced easily and are useful for testing the performances of these instruments.

A Topical View of the Value of Infrared Thermography in Breast Cancer

Abstract: Infrared thermography (IRT) is still not well-known or as much used as it deserves, because its purpose is generally misunderstood. It is a method of functional investigation, and does not give anatomical static images but yields unique data on the dynamic behavior of breast cancers.

Applications Of Real-Time Thermography For Nondestructive Testing Of Composites

Abstract: Recent improvements in thermal imaging systems having video recording and digital processing capabilities have resulted in renewed interest in thermography as a viable nondestructive evaluation technique. Examples of the use of real-time thermography for monitoring plastics manufacturing processes and structural integrity of fiber reinforced composites are presented. Newly developed passive thermographic and vibrothermographic techniques for characterization of composite materials are discussed.