ESPI system을 이용한 국부변형률이 저주기 피로수명에 미치는 영향에 관한 연구

초록

Low cycle fatigue cracks are mainly detected at discontinuous welded locations with high stresses under repeated cyclic static loads due to cargo loading and unloading. Theoretical and analytical methods have been used for evaluation of local stress and strain which have an effect on a prediction of fatigue life, but those have difficulties of considering stress concentration at notched location and complicated material behavior of welded joint or heat affected zone. Electronic speckle pattern interferometry(ESPI) system is nondestructive and non-contact measurement system which can measure the relatively accurate strain on large field such as welded zone and structural discontinuous location. In this study, local strain was measured on welded cruciform joint by ESPI system and then low cycle fatigue test was performed. Effect of local strain on low cycle fatigue life was examined by the value and distribution of measured local strain using ESPI system. Local strain and stress were calculated using Neuber’s rule. Moreover experimental fatigue life was compared with established design curves.