과대 하중작용 시 균열성장 지연 거동에 대한 파괴역학적 정리

초록

In order to clarify the effect of overload on crack growth behaviors, fatigue tests for overload were carried out for round plain specimens of SM45C steel. In the experiment, typical semi-elliptical crack shape was found and further crack growth behaviors were tested. Using three types of single overload fatigue tests, Crack growth retardation phenomenon were examined. The growth rate of surface crack(da/dN) during retardation period was analyzed in terms of △K and △Keff. On the growth rate of surface crack analyzed by △K, the dependence of overload stress levels appears. However, on the growth rate by △Keff obtained by Willenborg analysis, there is a non-liner relationship between da/dN and △Keff with narrow scatter band.

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