Abstract
Thermal conductivity of the surface layer of engineering materials changes apparently at the early stage of degradation because of many micro-cracks. A new method to evaluate and diagnose the degree of degradation of materials from the change of thermal conductivity is proposed. It is theoretically discussed that the existence of the micro-crack layer influences on temperature responses measured by a thermophysical handy tester. By definition of a thermal degradation parameter, the deteriorative stage of materials can be evaluated. In order to verify this theory, fatigue tests using metallic materials are conduced, and comparative studies between before and after fatigue test are made. A correlation between the existence of micro-crack and the decrease of thermal conductivity can be obtained by them. As a result, it is ascertained that the thermal degradation parameter can be easily estimated from the temperature response curve obtained by the tester.
