Showing papers on "Thermography published in 1983"

Infrared thermography for sensing the arc welding process

Abstract: This paper was presented at the Annual AWS Convention, Philadelphia, Pa., Apr. 1983. The Authors present experimental results that could aid in the development of a closed-loop feedback system capable of correcting for perturbations that arise during automatic arc-welding. Specific weld faults were intentionally introduced into an arc-welding process, and the resulting surface isotherms were observed with a scanning infra-red camera for both stationary and moving arcs, Each fault produced a recognisably different distribution of the surface temperature. The results are presented and discussed in some detail, and it is concluded that infra-red thermography appears to be a suitable sensor for incorporation into a closed-loop feedback system for continuous process and quality controlled welding.

Processing Of Infrared Thermal Images For Aerodynamic Research

Abstract: Infrared thermography has been used, in wind tunnels, to study the transition from laminar to turbulent boundary layer. Different methods have been tested to increase legibility of infrared images, such as signal integration, histogram modifications, colour coding... Some examples of detection of the transition are given.

Introduction to correlation microwave thermography.

Abstract: Correlation microwave thermography, a new process based on a coherent detection of noise, is able to improve the localization of the thermal gradients in the tissues. We explain the principles of this method and describe the first system which has been built and tested. Several experiments point out that with this process better spatial resolution and flexibility can be expected.

Practical Thermal Measurement Techniques

Abstract: This paper presents fundamental principles for the utilization of infrared thermographyin quantitative studies. Step -by -step procedures are described for basic field measurementtechnique without the need for extensive ancillary equipment. Both temperature andemissivity measurements are discussed, and a graphical measurement technique is introduced.IntroductionThis paper has been written to aid new users of quantitative infrared thermography equip-ment in a few simple and yet highly effective techniques for performing thermal measure- ments. Serious manufacturers of IR imaging equipment provide formulae in their operatingmanuals that allow calculation of temperatures from thermal data acquired from theirimaging systems. Often these are confusing to the novice thermographer. Additionally,they are usually of such a complexity that they require use of a programmable calculatoror computer to solve them on a routine basis. It must be stressed, however, that theseprovide the MOST accurate way to make measurements with the thermal imaging system andshould always be used where critical measurements are to be carried out. However, for themajority of uses for plant maintenance or inspection, a simpler approach may be taken.TheoryLet us investigate the basic theory behind these measurements and then introduce waysto make these as "painless" as possible.All objects radiate infrared energy. Infrared energy is the same kind of energy asvisible light, only it has a different wavelength. It can be reflected, transmitted, andrefracted like light. Our eyes are not sensitive to it, so we must use electro- mechanicalsystems to sense it. For our purposes here, it is sufficient to know just a few thingsabout this infrared energy:

Inflammation of the lacrimal drainage system--assessment by thermography.

Abstract: Thermography is an investigative tool without side effects. To our knowledge thermography has not been evaluated in the assessment of lacrimal passage inflammation and obstruction. It can give an objective assessment of presence and degree of inflammation. An infrared scanning device was used to detect surface temperatures in 29 patients with known disorders of the lacrimal drainage passage. Thermal images were compared for bilateral symmetry and against the normal thermographic appearance of the face. Acute dacryocystitis and canaliculitis showed gross hyperthermia and asymmetry. Forty-two percent of patients with a picture of chronic dacryocystitis and 40% of patients with only tearing and no clinical evidence of inflammation showed temperature elevation on the side of involvement, whereas 58% and 60% of these respective groups showed symmetrical thermal patterns, suggesting no active inflammation. In a few cases there were discrepancies between clinical assessment and objective thermographic evaluation of the degree of inflammation. The implications of our results and possible applications of thermography are discussed.

Infrared Thermography Techniques for EMI/EMC Measurements

Abstract: The measurement o f s u r f a c e c u r r e n t s i n ­ duced by i n c i d e n t e l e c t r o m a g n e t i c r a d i a t i o n can be a d i f f i c u l t and t ime-consuming t a s k . This measurement in fo rm a t io n i s very u se fu l in many EMC r e l a t e d f a c t o r s and c o n s i d e r a t i o n s such as s h i e l d i n g , an tenna and p e n e t r a t i o n po­ s i t i o n i n g , and hot s p o t i s o l a t i o n . I n f r a r e d the rm ograph ic t e c h n iq u e s have been dev i sed t o d e t e c t I R h e a t in g due t o RF s u r f a c e c u r r e n t d i s t r i b u t i o n s on m e t a l l i c and n o n m e t a l l i c s t r u c t u r e s . An overview of t h e t e c h n iq u e s un­ der development t o a s s i s t th e EMI/EMC r e ­ s e a r c h e r and e n g in e e r i s p r e s e n te d .

Zoom Lenses For The Thermal Infrared

Abstract: The paper is intended to familiarise optical designers with mechanically and optically compensated zoom lenses which operate in the thermal infrared waveband and especially the 8-13 micrometer waveband. Apart from illustrating various infrared zoom lenses a description and performance analysis is given for two final designs.

Incorporating Geometric And Radiative Effects Into Infrared Scanning Computer Analysis

Abstract: A NASA program, the SILTS experiment (Shuttle Infrared Leeside Temperature Sensing) will utilize an infrared scanning system mounted at the tip of the vertical stabilizer to remotely measure the surface temperature of the leeside of the Space Shuttle during entry from orbit. Scans of the fuselage and one wing will be made alternately. The experiment will correlate real full scale data to ground-based information. In order to quantitatively assess the temperature profile of the surface, an algorithm is required which incorporates the Space Shuttle shape, location of specific materials on the surface, and the measurement geometry between the camera and the surface. This paper will discuss the algorithm.

Present Results and Trends in Microwave Thermography

Abstract: We summarize the data obtained on Microwave Thermography, an application of Radiometry devoted to the reception of thermal noise leading to information about the temperature in living tissues We describe the processes experimented until now and explain their domain of application in biomedical engineering Experiments on animals and clinical evaluations are at present being continued Research is also carried out in the laboratory in order to improve the characteristics of this technique : elaboration of algorithms for thermal Pattern Recognition (or interpretation of the radiometric data), achievement of a multiprobe scanning microwave thermograph, and the study of the possibilities offered by Correlation microwave Thermography

Infrared Imaging Techniques For Flaw Detection In Composite Materials

Abstract: With the development of the new super strength lightweight composite materials, flaw and void detection in the various layers have become of major importance. Special infrared imaging techniques have been developed to show these voids. Included in these nondestructive methods are active steady state, active pulsed, and fast recording with slow playback of infrared images. Emissivity correction techniques have also been considered. Considerable time can be saved by using an imaging system since the size and shape of a defect or void is known at a glance. With video recording, documentation is achieved and further analysis is also possible without tieing up the part. Growth or changes of marginal flaws or voids can be traced during the manufacturing process, noting if they increase to the point of nonacceptance. An 8-13μ infrared scanner compatible with a video recorder and a line integrator proved most effective. Colorizing the image also made the flaw visualization easier.

Radiometer input circuit requirements for microwave thermography

Abstract: Radiometer system performance requirements and problems relevant to the technique of medical microwave thermography are briefly reviewed. The Dicke-type radiometer input circuit normally used for this application is analysed to determine the factors limiting measurement performance. It is shown that input circuit losses combined with aerial to body impedance mismatch can cause significant measurement errors.

Use Of Infrared Imagery In Continuous Flow Wind Tunnels

Abstract: Thermal mapping with infrared imagery is a very useful test technique in continuous flow wind tunnels. Convective-heating patterns over large areas of a model can be obtained through remote sensing of the surface temperature. A system has been developed at AEDC which uses a commercially available infrared scanning camera to produce these heat-transfer maps. In addition to the camera, the system includes video monitors, an analog tape recording, an analog-to-digital converter, a digitizer control, and two minicomputers. This paper will describe the individual components, data reduction techniques, and typical applications. *

Thermography-applications to the manufacture and nondestructive characterization of composites

Abstract: The increasing use of composite materials in military and commercial aircraft requires the development of improved quality control and nondestructive inspection techniques to assure their structural integrity and reliability. Infrared thermography is particularly useful for rapid scanning and detection of manufacturing inhomogeneities and inservice damage states in composites. The relationship between the surface thermal patterns and the interior damage is governed by the type of damage, thermal conductivity of the material and the distance between the surface and the damaged region. Applications of real-time thermography as a quality control technique for processing fiber reinforced composites, and as a nondestructive technique for monitoring growth and development of defects in composite laminates and rotor blades during low-frequency, high amplitude fatigue tests will be discussed. Applications of high frequency vibrothermography for characterizing composite structures will also be presented. This latter technique involves the use of high-frequency, low amplitude ultrasonic excitation of a sample.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Infrared Thermal Imaging Of Refinery Equipment

Abstract: Abnormal temperature increases in refinery process equipment are usually indicative of a condition that will eventually result in serious operational problems or equipment failure. Infrared instruments are available that provide both thermal imaging and temperature measurement capabilities. Several examples of the application of infrared thermal imaging in refineries are described. The examples are chosen to show the capabilities of the infrared instruments, the diversity of application, and the techniques required to obtain meaningful information.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of thermography in the prevention of pressure sores

Abstract: Localised changes in the temperature of the skin are a valuable guide to the condition of tissue subjected to ischaemia. Thermography has significant advantages in the detection of these temperature abnormalities, but environmental and other factors may influence thermographic results. Accessories to enhance thermographic researching and interpretation are suggested. Three clinical applications of thermography are discussed.

Microwave Interaction with Thin Multiple Conductive Coatings.

Abstract: : This report presents the analytic solution for the surface temperatures of the first layer of a system of N layers being exposed to microwave radiation This provides for a correlation between surface temperatures is to be measured via infrared thermography (Author)

Temperature Measurements On Semi-Permanent Mold Surfaces Using Infrared Thermography

Abstract: Die surface temperature and internal die thermal balance are critical to the quality of semi-permanent mold die castings. Measurements of the surface temperature are currently made using either hand-held contact temperature probes or optical pyrometers. Neither measurement technique provides a thermal map of the entire die surface. This paper discusses the use of infrared thermography for die surface temperature measurement. Using infrared thermographic techniques, scans were made over the surface of an experimental 302 CID semi-permanent mold cylinder head die during several casting cycles. The results obtained were in reasonable agreement with the temperature measurements made using optical pyrometers and the contact probes. In addition, using gray-level conversion the IR technique provided a measure of the temperature gradient over the surface of the die. Such thermal mapping has not been practical using optical or contact temperature probes.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Thermographic Detection of Polymer/Metal Adhesion Failures

Abstract: Thermography is based on the remote mapping of surface temperature distributions. When heat is appropriately applied to a sample, subsurface flaws can become projected onto the surface temperature profile due to differences between their thermal transfer properties and those of the bulk. Although not widely exploited in this area in the past, thermography can be an effective nondestructive means of monitoring polymer/metal bond continuity. This work examines the nature of thermographic detection techniques as they relate specifically to polymer/metal adhesion studies. The physical phenomena involved are reviewed, and a basic heat transfer model is presented as a prototype for quantitative analysis of thermographic data. Fundamentals of instrumentation and experimental techniques are outlined, and one specific experimental system is detailed. The application of thermography to polymer/metal adhesion studies is demonstrated by specific examples, and much of the previous pertinent work reported in the literature is referenced.

Using thermography to correct wet streaks. Third in a series on infrared thermography

Abstract: Utilisation de la thermographie pour corriger les inegalites du profil transversal d'humidite du papier

Applications of aerial thermography for residential energy analysis

Abstract: The effectiveness of aerial infrared thermography as a procedure for residential energy analysis is investigated. Factors affecting the accuracy and utility of this technique are identified and analyzed, including the effects of local microclimate and different thermostat set points. Guidelines are presented concerning the recommended use of aerial thermography as a procedure for assessing the thermal performance of residences.

The Application Of Infrared-Sensors In Medicine

Abstract: Infrared-sensors are used in medicine to detect the temperature of the skin. The temperature distribution over the human skin surface gives insight into many physiological problems concerned with thermoregulation and metabolism. Skin temperature patterns in dermatologic, vascular, locomotor and malignant diseases can provide valuable information for clinical diagnosis and therapeutic assessment. Skin temperature can be measured accurately by several means. Infrared thermography can register overall skin temperature and its distribution comprehensively. This noninvasive, no-touch technique is the measurement of skin surface temperature by the emission of heat energy in the infrared portion of the spectrum, with the human skin being an excellent black body radiator. The physical conditions of the skin and the environment are important when determining skin temperature with infrared-sensors. The thermal imaging system has to produce a high quality thermal picture of the skin within a short observation time. The processing of thermographic images by computer methods offers the promise of improving and enhancing the utility of thermography as an clinical and research instrument.

Design Analysis Of Rotating Machinery Using Infrared Thermography

Abstract: The analysis of vibratory and acoustical signals from rotating machinery has been used successfully for several decades to determine the adequacy of rotating machine design or operation. Certain vibration or acoustical signals are characteristic of machines encountering problems or near failure. Likewise the thermal signature from a rotating machine may have significant diagnostic value. Friction, damping and material deformations are typical sources of thermal energy easily detected by thermal measurements. Thermocouple thermography has been used to determine rotating machine temperatures. However, point measurements are difficult to obtain because of signal coupling problems with the rotating machine. In the past temperatures could only be obtained by stopping the machine and quickly taking temperature measurements hoping that the temperature information would not dissipate by transient affects. Infrared thermography has solved some of these problems by offering a noncontact thermal measurement along with a display of. temperature fields which facilitates the location of hot spots. Several examples of rotating machinery are reviewed such as couplings, power transmission belts, gears and rotors. The significance of the temperature distribution on the power transmission component is discussed. Infrared thermography appears to be a useful tool in diagnosing problems in rotating machinery.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Trends in quantitative aerial thermography

Abstract: Recent improvements in aerial thermographic techniques, particularly in achievable spatial resolution and noise equivalent temperature variation, have enabled the use of thermography in a more objective fashion. Interpretation of the information contained in thermograms has also been improved through the use of certain techniques accounting for roof material type (emissivity), background effects, and atmospheric variables. With current methods, roof surface temperature from aerial imagery can be measured to within 1.8/sup 0/F (1.0/sup 0/C) of the actual temperature. These advances in thermogram analysis have opened the door for potential direct measurement of rooftop heat-loss levels from thermogram data. Ultimately, it is felt that this type of information would make it feasible to direct intensive energy-conservation efforts toward a smaller population, where the need and cost benefits will be the greatest.

Temporal variations of temperature of the breast by cholesteric liquid crystal contact plate thermography.

Abstract: Thermography of the breast is considered by some to be a risk marker for the presence of abnormalities of the breast. Circadian variations in the temperature of the skin of normal and cancerous breasts have been documented. A temporal study was undertaken to verify whether or not thermograms obtained at different hours of the day are sufficiently similar to be clinically useful. Eleven healthy women underwent four serial thermographic evaluations each at three to four hour intervals. Significant differences were observed between the early morning results and subsequent evaluations. Reproducible thermograms were obtained for all studies done from 12 noon onward. This is a possible indication that the timing of thermographic examinations has to be standardized to ensure that reliable comparisons are being made.

Development Of Economic Techniques For Residential Thermography

Abstract: Infrared thermography has proven to be a valuable tool in the detection of heat loss in both commercial and residential buildings. The field of residential thermography has needed a simple method with which to report the deficiencies found during an infrared scan. Two major obstacles hindering the cost effectiveness of residential thermography have been 1) the ability to quickly transport some high resolution imaging system equipment from job site to job site without having to totally dismount the instruments at each area, and 2) the lack of a standard form with which to report the findings of the survey to the customer. Since the industry has yet to provide us with either, we believed it necessary to develop our own. Through trial and error, we have come up with a system that makes interior residential thermography a profitable venture at a price the homeowner can afford. Insulation voids, or defects can be instantly spotted with the use of a thermal imaging system under the proper conditions. A special hand-held device was developed that enables the thermographer to carry the equipment from house to house without the need to dismantle and set up at each stop. All the necessary components are attached for a total weight of about 40 pounds. The findings are then conveyed to a form we have developed. The form is simple enough that the client without special training in thermography can understand. The client is then able to locate the problems and take corrective measures or give it to a con-tractor to do the work.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.