Low-cycle fatigue behavior of stainless-steel elbows having local wall thinning

Abstract

Elbow pipes present a complex stress field during deformation. The stress field becomes more complicated due to the wall thinning. Thus, predicting their failure behavior is difficult. In previous studies, low-cycle fatigue tests were performed on carbon steel elbow pipes, and a revised universal slope method was proposed to predict their fatigue lives. However, the accuracy of predictions has not been verified on materials other than carbon steel. Therefore, in this study, low-cycle fatigue tests and a finite-element analysis were performed on carbon steel (STPT410) and stainless steel (SUS304) elbows. The low-cycle fatigue life of SUS304 elbows was observed to be three to four times longer than that of STPT410 elbows. Analysis of results revealed that the fatigue life predicted by the revised universal slope method shows a tendency similar to the experimental results, and the fatigue life of SUS304 can be predicted with high accuracy as well as STPT410.

Keywords

• elbow
• low-cycle fatigue
• multi-axial stress
• carbon steel
• stainless steel
• revised universal slope method