Papers by Keyword: Infrared Thermography (IRT)

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Authors: Jeong Guk Kim, Jong Duk Chung, Joon Hyun Lee, Yeon Uk Jeong, Yong Ki Hong, Won Kyung Kim, Jang Sik Pyun, Dae Sung Bae
Abstract: Nondestructive evaluation (NDE) techniques were used for the tensile damage characterization in ceramic matrix composites (CMCs). Ultrasonic testing (UT) and infrared (IR) thermography were employed to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UT C-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.
Authors: Qi Fang Zhu, Ze Ming Sun, Tong Da Ma, Pu Li, Zhi Gang Fan, Vladimir Platonovič Vavilov
Abstract: In this paper, the results of the first-stage research devoted to infrared thermographic detection of cracks in titanium alloys are presented. In application to the inspection of bottom-hole defects in 9.6 mm-thick Ti6Al4V titanium alloy samples, it has been found that a minimum detected defect should have diameter from one to two times greater than its depth. Images of phase are more noise-resistant and able to reveal deeper defects compared to images of amplitude. The test results obtained show that the Fourier analysis is a convenient data processing technique in active thermal NDT.
Authors: Hui Liu, Jun Yan Liu, Yang Wang, Hui Juan Li
Abstract: Lock-in thermography (LT), that is active infrared testing technology, mainly includes optical lock-in thermography (OLT) and ultrasound lock-in thermography (ULT). LT can be used to detect unbonds between honeycomb core and face sheet of sandwich structures. However, modulation frequency is an important influencing factor. In this paper, the principles of LT are represented, in experimental detections of simulated unbonds in honeycomb sandwich structures with Al-face sheet and CFRP-face sheet using OLT and ULT, detectability of OLT and ULT is compared and analyzed, effect of modulation frequency is researched and the optimal frequencies are obtained.
Authors: Jeong Guk Kim, Seung Koo Baek, Chang Young Lee, Sung Cheol Yoon
Abstract: The electrical units of diesel electric locomotives, which were used for over 30 years, were characterized for deterioration evaluation through insulation resistance measurement, degradation testing, and infrared thermography method. Especially, an infrared camera and thermocouples were employed for the evaluation. The thermocouples were attached on high-voltage cables connected to traction motors, for in-situ measurement of abnormal heating during test running. After test running, the thermographic images were obtained for the inspection of high-voltage cables using the infrared camera. The thermographic results were quantitatively analyzed, and compared with temperature changes during running. In this investigation, various analysis techniques for the safety characterization of diesel electric locomotives have been introduced, and the analysis results have been used to provide the deterioration or wear information in current locomotive systems.
Authors: Antonino Risitano, Carmelo Clienti, Giacomo Risitano
Abstract: In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest) to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported.
Authors: Won Tae Kim, Man Yong Choi, Jung Hak Park
Authors: Francois Maquin, Fabrice Pierron
Abstract: In order to fully understand the thermomechanical phenomena involved in high-cycle fatigue, a method for determining the dissipative thermal sources in a loaded metallic specimen from the spatio-temporal integration of the heat diffusion equation is proposed. Temperature fields obtained through a focal array infra-red camera are processed with this technique. After a refined analysis of the sensitivity of the method, preliminary tests have shown that it is possible to detect a burst of heat sources within the first couple of cycles for the specimen tested above a certain level of tensile stress. This behaviour is thought to be related to the microplasticity level.
Authors: Murat Selek, Ömer Sinan Şahin, Şirzat Kahramanlı
Abstract: In this study, the effects of hardness on temperature increase of ST 37 steel during fatigue loading were investigated. Steel specimens are made of ST 37 steel and subjected to heat treatment to obtain different hardness. The specimens were subjected to reverse bending fatigue loading and the specimens were observed by using a infrared (IR) camera during the test. The obtained thermal images were recorded by FLIR E45 IR camera and then transferred to the image processing program developed by using MATLAB. Thus after image processing, thermal values used to detect the temperature rise of the surface of the steel specimen under fatigue loading were obtained. During the fatigue, the material is subjected to strain energy input which result in plastic or/and elastic deformation. This event results in an increase of temperature within material. The energy conservation requires that the generated heat shows itself as heat transfer by conduction, convection and radiation and internal energy increase. Besides, if the material has undergone plastic deformation, an additional term which accounts this effect should be included within energy conservation equation. In order to observe the effect of plastic deformation upon temperature increase of material, the ability of plastic deformation has been changed through the change of hardness and the thermal variations during fatigue has been investigated.
Authors: Hong Qing Li, Yi Sheng Zhang, Liang Wang, Xiao Wei Tian, Chao Wang, Bin Zhu
Abstract: In order to meet the requirements of improving hot stamping process, the temperature distribution of high strength steel (HSS) sheets should be observed. However, the accurate measurement of temperature field in transfer where the temperature falls rapidly proves to be difficult due to the limitation of thermocouple. The infrared thermography could be used for accurate measurement of temperature field but the emissivity which is crucial to the accuracy and reliability of measurement results is not available. In this paper, a method to calibrate emissivity of HSS blank was developed for temperature measurement in hot stamping using infrared thermography. Experiments were performed on the emissivity calibration of the HSS Advanced 1500 in hot stamping. Emissivity dependence on temperature was investigated, so was the impact of little variation in emissivity on the temperature measurement. The validation tests were made and the results reveal that this calibration method of emissivity is accurate and feasible. This method is also appropriate for the calibration of emissivity in other temperature measurement situations.
Authors: N. Nunak, K. Roonprasang, T. Suesut, T. Nunak
Abstract: This paper proposes a method based on the spectra response of IR detectors mounted on thermographic camera for emissivity measurement at various target surface temperatures, while the reflected temperature istaken into account, and also studies on the effect of surface roughness on the emissivity value. The emissivity (ε8-14μm) of general engineering material such as iron, stainless steel, brass, copper and aluminum obtained in this paper are in agreement with other literatures. Finally, results found that the roughness and emissivity of equipment increases with increasing of the operating time.
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