Estimation of Low Cycle Fatigue Life of Elbow Pipes Considering the Multi Axial Stress Effect

Abstract

The stress states of elbow pipes are complex and different from those of straight pipes. Manson's universal slope method cannot predict the lowcycle fatigue lives of elbow pipes under combined cyclic bending and internal pressure. In this work, fatigue tests and finite element analysis showed that the multiaxial stress factor (i.e., ratio of axial stress to hoop stress) is quite high at elbows. This paper proposes a revised Manson's universal slope method that considers the multiaxial stress factor to predict the lowcycle fatigue lives of elbows under combined cyclic bending and internal pressure with considerably high accuracy.