Behavior of Initiation and Propagation of Fatigue Cracks around Microholes

J. Ocean Eng. Technol. 1987;1(2):74-82.

미소원공주위의 피로크랙발생전파 거동에 관한 연구

송삼홍,오환석

고려대학교 기계공학과,고려대학교 기계공학과

Keywords: micro hole, fatigue crack initiation, micro crack, interference effect, micro hole tip, fatigue crack propagation, stress field

핵심용어: 미소원공, 피로크랙발생, 미시크랙, 간섭효과, 미소원공선단, 피로크랙전파, 응력장

Abstract

This study has been made to investigate into the behavior of fatigue limit, of fatigue crack initiation, and of fatigue crack propagation under the condition of rotating bending stress; specifically on the independency of stress field as well as the crack behavior of surface micro hole defect, which is made artificially through the specimen. The results obtained can be summarized as followa; 1) For the single micro hole defect, initiation of fatigue crack is occurred at both tips of microhole defect simultaneosly along the slip which are produced in the range of maximum principal stress arround micro hole defect independent of the size of micro hole defect. 2) For the neighbored deuble micro hole defects with equal size, in the range ($frac{L}{r}$)ratio $gtrsim$ 3 defined as the size of micro hole defect(2r) to the distance between the centers of micro hole defects (2L), the crack behavior of the micro hole defects is same as single one. However, for the range of $frac{L}{r}$<3, the interference effect becomes significant as the ratio approaches to 1.