Papers by Keyword: Infrared Thermography (IRT)

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Authors: Li Huang, Zhuo Qiu Li, Xian Hui Song
Abstract: Based on the functional characteristics of carbon fiber reinforced concrete (CFRC), an improved infrared nondestructive testing method, to detect crack in CFRC by using infrared thermography, is presented in this paper. The principle is that when a CFRC specimen is applied a low voltage, crack existing in the specimen will result in non-homogeneous surface temperature distribution due to the electro-thermal effect of the material. Monitoring the temperature difference on the surface, the crack under the observed surface can be inspected by using infrared thermography. In theory, the mechanism causing the temperature difference comes down to an unsteady heat transfer problem with internal energy sources. In the case of the thermo-physical property of CFRC as given, the sensitivity of this method to the depth of the crack is analyzed by numerical computation.
Authors: He Hong Qin, Tao Wang, Wei Fan
Abstract: A novel air leak diagnosis and localization method for vessels is proposed. The tempreture field around the leak changes during air inflation and deflation.The changing phenomenon is acquired by thermal camera and the best detecting time is confirmed by temperature curves.Then a local gray-entropy difference algorithm is used to identify the leak area from infrared images captured during inflation and deflation. The gray information of local gray-entropy enhances the difference between leak area and non-leak area largely meanwhile the entropy information of local gray-entropy improves robustness performance.Experiments verify that the leak localization method is effective and sensitive.
Authors: Jeong Guk Kim, Sung Cheol Yoon, Sung Tae Kwon
Abstract: The tensile fracture behavior of polymer matrix composite materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, E-glass fiber reinforced epoxy matrix composites, which are applicable to bogie materials in railway vehicles to reduce weight, were used for this investigation. In order to explain stress-strain behavior of polymer matrix composite sample, the infrared thermography technique was employed. A high-speed infrared (IR) camera was used for in-situ monitoring of progressive damages of polymer matrix composite samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of polymer matrix composite materials during monotonic loadings.
Authors: Jeong Guk Kim
Abstract: Ceramic matrix composites (CMCs) have evolved as potential candidate materials for high-temperature structural applications due to lightweight, high-temperature strength and excellent corrosion and wear resistance. In this investigation, damage evolution and heat generation of CMCs during monotonic loadings were investigated using different types of nondestructive evaluation (NDE) techniques, such as acoustic emission (AE) and infrared (IR) thermography and microstructural characterization. IR camera was used for in-situ monitoring of temperature evolution, and the temperature changes during testing were measured. A significant temperature increase has been observed at the time of failure. Microstructural characterizations using scanning electron microscopy (SEM) were performed to investigate fracture behavior of CMC samples. In this investigation, the NDE technique and SEM characterization were employed to analyze damage evolution and progress of ceramic matrix composites during monotonic loading.
Authors: Jeong Guk Kim, Sung Tae Kwon, Sung Cheol Yoon
Abstract: The hot spot generation has been considered as the main degradation mechanism in railway brake disc. Therefore, the understanding of hot spots, also called hot judder, which is undesirable low frequency vibrations developed by non-uniform contact area between brake pad material and brake disc, is important for a better understanding of material design as well as enhancement of materials properties in railway brake disc. Also, infrared (IR) thermography is a powerful NDE technique for the characterization of thermal phenomenon in engineering components and/or systems including engineering materials. The high-speed IR camera provides the measurement of temperature change during brake operation as well as the images of temperature contour on the brake disc surface. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. Moreover, based on obtained thermographic images of hot spots, the hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed.
Authors: Jin Woo Kim, Dong Gi Lee, Jae Ki Sim, Jae Yeol Kim, Seung Hyun Choi
Abstract: Property of GFRP is naturally dependent on the property of matrix, but receives of temperature effects by external force. Therefore, determination of mechanical property by effect of temperature in GFRP is most crucial factor. In this paper, temperature distribution during crack propagation from temperature change under tensile test was proposed through IR thermography camera. Lock-in thermography method, which is one of technique in IR thermography camera to measure minute change in temperature, was utilized to monitor temperature distribution and change during crack propagation. Method to analyze temperature distribution during crack propagation under tensile test of GFRP via IR thermography camera was suggested. Anisotropy in fiber orientation showed longer fracture time and lower maximum temperature.
Authors: Lovre Krstulović-Opara, Endri Garafulić, Branko Klarin, Željko Domazet
Abstract: The article presents application of non destructive testing method based on the pulse heating infrared thermography used to detect material anomalies for the case of glass reinforced polymer structures. The goal of presented research, based on the thermal gradient approach, is to establish the procedure capable of filtering out anomalies from other thermal influences caused by thermal reflections of surrounding objects, geometry influences and heat flows for observed object.
Authors: T.J. Shelley, Chin Kian Liew
Abstract: This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm3 can be detected.
Authors: Justus Medgenberg, Thomas Ummenhofer
Abstract: The paper presents background information and experimental results regarding the assessment of fatigue damage in welded steel structures by thermographic investigations of thermomechanical coupling effects. The results confirm the high potential of specialized thermographic methods for the experimental characterization of all stages of fatigue damage in welded and un-welded components. The technique provides a new experimental mean to investigate early inhomogeneous fatigue damage as mesoplasticity and cracks in the weld toe. The method has been successfully applied during fatigue testing of welded components and allows detecting localized damage as early as 10% to 20% of the total fatigue lifetime of the tested specimens.
Authors: Su Young Kim, Doo Ik Lee, Keon Sik Kim, Dong Ok Kim, Young Kyoo Choi, Do Young Choi, Sabina Lim, Jae Dong Lee, Yun Hoo Lee
Abstract: Central poststroke pain can occur as a result of lesion or dysfunction of the brain from stroke, and may influence the autonomic nervous system to regulate the vasomotor activity which could result in the lowered skin temperature. In order to assess CPSP objectively, seventy patients with CPSP were evaluated as their pain with VAS pain score and the skin temperature of pain site by infrared thermography before and after pain treatment. And evaluated correlation between changes of temperature and VAS. The skin temperature of pain site was significantly lower than non-pain before treatment and improved after treatment(p<0.05), in accordance with significant improvement of VAS pain scores after treatment(p<0.05). And there was highly correlation between the changes of temperature and VAS(p<0.05). Therefore, it is suggested that the infrared thermography is very useful device for the evaluation of CPSP and its treatment.
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