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1、400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A.Tel: (724) 776-4841 Fax: (724) 776-5760 SAE TECHNICAL PAPER SERIES 2000-01-3429 Predicting Truck Tire Problems with the Thermal Image Inspection Station (TIIS) in the Lab and in the Field Douglas Miller National Automotive Center, U. S. Army Ta
2、nk-automotive and Armaments Command Ray Schandelmeier and Ferdinand Zegel Radian Inc. Truck and Bus Meeting and Exposition Portland, Oregon December 4-6, 2000 The appearance of this ISSN code at the bottom of this page indicates SAEs consent that copies of the paper may be made for personal or inter
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9、re abstracted and indexed in the Global Mobility Database 2000-01-3429 Predicting Truck Tire Problems with the Thermal Image Inspection Station (TIIS) in the Lab and in the Field Douglas Miller National Automotive Center, U. S. Army Tank-automotive and Armaments Command Ray Schandelmeier and Ferdina
10、nd Zegel Radian Inc. Copyright 2000 Society of Automotive Engineers, Inc. ABSTRACT Radian Inc, working in partnership with the U. S. Army National Automotive Center, has been designing and developing a Thermal Imaging Inspection Station (TIIS) for assessing and diagnosing the condition of truck tire
11、s and other components of vehicles in a real-time operational environment. Recently, multiple failures of M939 truck tires (14.00R20, Load Range J, manufactured by both Michelin and Goodyear) have been reported, and the U. S. Army Tank-Automotive and Armaments Command (TACOM) contracted with Radian
12、to participate in a tire-testing program, using the TIIS at the TACOM tire-testing lab and in field tests, in hopes of determining the cause of these failures. Tires that failed on the tire dynamometer demonstrated similar problems to tires that failed in field operations. Thermal images recorded in
13、 the lab and in the field under similar conditions were highly comparable. The similarities indicate that the tire dynamometer can probably do a credible job of simulating operational conditions in the field and that the TIIS is very promising as a diagnostic and predictive tool. Further enhancement
14、s of the TIIS and extended tire-testing programs are already underway. INTRODUCTION The United States Army National Automotive Center (NAC) working in partnership with Radian, Inc. of Alexandria, VA initiated a program to determine the feasibility of utilizing commercially available thermal imaging
15、cameras, automated personal computers, and customized digital analytical software to assess and determine the condition of truck tires and other components of vehicles in a real-time operational environment. The system that Radian has designed and is developing is called the Thermal Imaging Inspecti
16、on Station (TIIS). Early tests using the first configuration of the TIIS to detect flaws and predict impending failure in brakes, bearings, and tires were showing promise. During the period when tests of tires were being conducted at the Tank-Automotive and Armaments Command (TACOM) Team Truck tire-
17、testing facilities, two accidentsone of them fatalwere reported as having been caused by the failure of a tire on a 5-ton military wrecker truck. Team Truck maintains facilities for testing samples of new tires procured for trucks, HMMWVs, and other vehicles used by the military and for examining an
18、y tires suspected of having flaws. In a typical test of new tires, they use a tire dynamometer to test a tire during 48 hours of continuous use under various speeds and load weights. When a particular type, or a particular lot of tires is suspected of having flaws, the sample tire is subjected to a
19、similar continuous-use test until it fails. Tires are also examined by x-ray, to discover defects or weaknesses, but the procedure must be performed before the tire is subjected to testing on the tire dynamometer and/or after the tire has failed: it cannot be used during. After a suspect tire has fa
20、iled on the tire dynamometer, and has been x-rayed, it is dissected for further examination. Aware that the NAC-Radian project had been testing a radial tire for the HMMWVwhich is similar in construction to the type of tire that had failedand indeed that the project had already established a thermal
21、 signature for a new, high-quality HMMWV tire, Team Truck perceived a timely opportunity. In cooperation with NAC, they asked Radian to use the model TIIS to participate in their own tests of a tire from each of the vehicles involved in the two accidents. They hoped that the new tool might help them
22、 determine whether the failures might be due to some defect or weakness in the tire. They also hoped it might prove an effective tool for a more extensive evaluation of tires during tests on the dynamometer. Naturally, from a limited sample of only two tires and without precise control data on a new
23、 tire of the same make and model, no definitive conclusions could be drawn. However, the data from the tests gave strong indications that with refinements to the system and the development of sound testing protocols, the TIIS would likely fulfill its promise as a diagnostic tool and has led to furth
24、er cooperative programs and to the evolution of the system. Recently, multiple failures of M939 truck tires have been reported. In an effort to determine the cause of these failures, Radian was contracted by the U.S. Army Tank- Automotive and Armaments Command in Warren, Michigan to use their therma
25、l physics expertise and the TIIS they are developing to participate in a tire-testing program. Discoveries and revelations during lab tests and during interaction with personnel in the units that have experienced problems, in the units that have provided the used tires for the tests, with the compan
26、ies who produce the tires, and with analysts who use other modes of examining or testing tires have opened a floodgate of questions about the failure of these tires and have led to an extended testing program and several refinements in experimental protocol. In an effort to gain further insight into
27、 the performance of the tires while they are in use, as well as to compare data from the lab with data from the field, field tests were conducted at Yuma Proving Ground (YPG) in Arizona and during YPGs Mountain Brake Test near Towne Pass, CA. It is the comparison of failures of tires sent to the lab
28、 from the field and failures experienced during lab testing and the comparison of thermal images from the tire- testing lab and from the field that is the subject of this paper. METHODS THERMAL-IMAGE INSPECTION STATION (TIIS) In general, the Radian Thermal Imaging Inspection Station (TIIS) comprises
29、 a thermal imaging camera, a tripod, a first-surface mirror, two Black Bodies used as calibration devices, a computer system, an electronic data recording device, a tape recorder and color monitor connected to the system for real-time monitoring and recording, and special software. Evolution of the
30、TIIS equipment Of the original components the first iteration of the TIISonly the camera, the tape recorder and monitor; the 300 Black Body, and such items as the tripod and cables remain. The original computer was not rugged enough for the environmental conditions of lab and field testing, nor for
31、transporting the TIIS to testing sites. The faster processor speed and the increased memory and storage capacity of the new computer, which is built for rugged use, have speeded data collection and analyzation considerably. A second Black Body has been added, for calibrating the data recorded with t
32、he new software (described below), and we have exchanged the Zip drive for a CD-RW drive for data recording. A first-surface mirror has been added to the lab equipment to capture thermal data from the tread and opposite sidewall. Evolution of the TIIS Software For early tests, Radian developed a sof
33、tware program called TireSoft. The software captured thermal images from the camera in gray scale, which corresponded from black to white with the radiant energy emanating from the target source. The gray scale was then translated into a 256-color spectrum. The Black Body was placed near the target,
34、 within the view of the camera, and then calibrated to a precise temperature that could be used as an exact reference temperature for calibrating the images taken by the camera during tests. It was known that there is a certain loss of energy (temperature) between the target and the camera (which ha
35、s to be placed at a distance from the tire on the dynamometer or from any target, to accommodate the focal range of the lens), but because the Black Body and target were on approximately the same plane, equidistant from the camera, the minimal temperature differential was not a factor. The software
36、provided the high and low temperatures in any given image and calculated the mean temperature and standard deviation within the zone but, in order for it to do so, each image had to be calibrated independently, in comparison with the temperature of the Black Body when the image was opened in the sof
37、tware. This was speedily accomplished, but only after the image had been recorded and “recalled”. Thus, although the image was displayed on the monitor in real time, and showed “trends” in thermal pattern as the tests progressed, calibrated images and data analyses were not available until afterward
38、s. And, the even larger difficulty with the software arose when one tried to circumscribe the target, or energy source, as an “area of interest”. Because the camera records a rectanglethat is, because it cannot record oddly shaped areasit is impossible to record an image that does not include extran
39、eous thermal data. With the tire dynamometer, for example, a sidewall view of the tire necessarily includes parts of the wall beyond the machinery as well as the arm of the tire mount, part of the surface drum, the hub, and other such parts. Thus, the relatively stable temperatures of the extraneous
40、 elements captured along with the data on the rotating tire are irrelevant to the image and have to be excluded from calculations. It was not difficult to circumscribe an “area of interest” of an image, but it was extremely difficult to do so in precisely the same dimensions each time a particular i
41、mage, or a new image, was opened. Thus, it was impossible to get exact, repeatable, quantifiable data that would statistically substantiate the results that had been observed on the computer screen as the images were being recorded. This difficulty led to a search for an adaptable software program t
42、hat could address these limitations. The new TIIS software is called ThermoSoft. To address the first limitationafter-the-fact data analysesthe new operating program of the TIIS calibrates the data directly from the camera. Therefore, the pixel-by-pixel data is immediately available, in near real ti
43、me, as the images are being recorded. And, it is available as energy intensity (gray scale), color, and temperature in both Celsius and Fahrenheit. However, because the new software is calibrated directly from the camerathus reading the temperature as the energy reaches the camera rather than as it
44、leaves the sourcethe drop in temperature between the source and the camera now became a factor. We recorded images with the Black Body set to various temperatures in each of the four temperature ranges that the camera records and determined that the temperature dropped by a percentage rather than by
45、 a specific number of degrees. Thus, we needed two Black Bodies, set near each limit of the temperature range being recorded, to plot a curve and determine the drop in temperature between the camera and the source. To address the second software limitationproscribing the “area of interest” consisten
46、tly and repeatably ThermaSoft allows the operator to proscribe an area and save it as a template that can be placed on an image and used each time the image is opened. The data for the area of interest can be analyzed both visually and statistically. The same template can be used for viewing the ima
47、ges during testing; it can be used for each image in a test, and from test to test, without making any changes in the basic image data being recorded; and it can be fused with any particular image and saved as a separate file. Templates can be created before a test is run, or during a test, if inves
48、tigators want to observe a particular area during testing. Or they can be created after the data have been recorded, if investigators want to examine and analyze a particular area in tests theyve already run. Any number of templates can be created and applied to the images. Current Configuration of
49、the TIIS Individual components of the TIIS are described below. Thermal imager The camera is a Cincinnati Electronics IRRIS-160 ST Indium-Antimonide Focal-Plane-Array (FPA) system. It is a calibrated system with an internal Black Body that provides a reference temperature point for each pixel of the image. It is cooled by a Sterling cycle micro-cooler in order to keep the FPA at liquid- nitrogen temperature 77 K. It is equipped with a 50- mm KRS-5 lens. The camera can be set for four temperature ranges (values in Centigrade): 1. 40 to 45 2. 20 to 80 3. 30 to