4 April 1997 Application of infrared thermography to fracture mechanics
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We have studied the possibility of applying infrared thermography to the problems of fracture mechanics. First of all we have shown that the stress intensity factor, K, can be analyzed by measuring the distribution of the elastic component of the sum of the principal stress around the crack tip by an infrared stress measuring device, SPATE- 8000. Next, the increase of temperature produced by the plastic deformation at the crack tip has been measured by a thermal video system (TVS). It has been found that the distribution of the temperature increase (Delta) Tp in the plastic zone is proportional to 1/r where r is the distance from the crack tip. Then a method of measuring the J-integral by the TVS has been proposed. Finally, we have developed an experimental and computational hybrid measuring system for the purpose of nondestructive detection of cracks embedded in the structural members. The system consists of TVS and an engineering work station (EWS), by which image processing of the thermal image can be carried out by the developed expert system. It has been shown that fatigue cracks in the steel specimens and delaminated defects in the honeycomb sandwich structures can be detected fairly well through the developed system.
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Nagahisa Ogasawara, Nagahisa Ogasawara, Masaki Shiratori, Masaki Shiratori, } "Application of infrared thermography to fracture mechanics", Proc. SPIE 3056, Thermosense XIX: An International Conference on Thermal Sensing and Imaging Diagnostic Applications, (4 April 1997); doi: 10.1117/12.271644; https://doi.org/10.1117/12.271644

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