Fatigue damage in diameter-enlargement part formed by cyclic bending and axial compressive Load

摘要

We proposed a new cold processing method to partially enlarge the diameter of a shaft with a combination of a cyclic bending load and an axial compressive load that is lower than the yield stress of sample material. We call this cold processing method a diameter-enlargement working method, and call this processed part a diameter-enlargement part. Key features of the processing method are chiefly as follows: the diameter enlargement deformation progresses easily under a low axial compressive load at room temperature; the processed part has little temperature increase, although the processing causes large plastic deformation. We have tested the influence of the processing conditions and the mechanical properties of the sample materials in terms of diameter enlargement deformation behavior. However, little is known about the fatigue damage condition in a diameter-enlargement part. Therefore, we carried out processing experiments to clarify crack generation conditions, and simulated working processing using finite element method in order to investigate behaviors of stress and strain during the processing. Furthermore, we evaluated low cycle fatigue damage in the processed part by using the Manson-Coffin expression. This paper clarified the mechanism of crack generation during the processing and evaluates the fatigue strength of the processed part.