A new model for low cycle fatigue of metal alloys under non-proportional loading

This paper proposes a new model for low cycle fatigue of metal alloys based on material sensibility to non-proportionality of loading. The model was examined by application to the prediction of the fatigue life in proportional and non-proportional low cycle fatigue tests for type BT1-0 titanium alloy. Tests were carried out in accordance with the plan of bifactorial experiment with three levels Mises’ strain: 0.7%, 0.9%, 1.1% and at three levels of non-proportion factor expressing the severity of non-proportional straining – 0, 0.5, 1. All the tests were carried out at room temperature. It was determined that additional hardening for non-proportional path tests is insignificant for BT1-0. Also proposed model was examined by tests for SNCM 630, Inconel 718, type 08X18H10T stainless steel, type BT9 titanium alloy. The model successfully correlated most of all fatigue data for all materials. The results showed that the model gave almost the same error both at proportional and non-proportional loading.