基于能量法的多轴疲劳寿命预测方法

Multiaxial fatigue life prediction is significant for ensuring the structural security and economic feasibility of engineering components, in which the critical and first step is to choose a suitable fatigue damage parameter. In this respect, the Smith-Watson-Topper (SWT) parameter is widely used for fatigue analysis of tensile-type failure. Unfortunately, since this parameter assumes that fatigue damage is totally driven by the tensile components on the critical plane, it potentially leads to un-conservative prediction results for fatigue life, especially under non-proportional loading conditions. To overcome this deficiency, the Glinka parameter and the Chen-Xu-Huang (CXH) parameter are developed. However, the Glinka parameter is merely applicable for the fatigue behaviors dominated by shear failure as its critical plane is defined as the plane with the maximum shear strain, and the CXH parameter frequently produces conservative prediction results. In order to improve the applicability of the SWT parameter for various materials and loading paths, two new energy-based parameters, which can be regarded as two modified SWT parameters, are proposed in this paper. These new parameters can not only reflect the mean stress effect, but also consider the influences of normal and shear components on fatigue life. Furthermore, through combining these parameters and the critical approach, a unified model for multiaxial fatigue life prediction is developed. The proposed model takes the two new energy parameters acting on the critical plane as the fatigue damage parameters to distinguish different failure modes. The proposed model, the SWT model, the Glinka model and the CXH model are used to evaluate the fatigue life of six kinds of materials under various loading paths. The results show that the proposed model has better prediction accuracy and application stability no matter the dominant failure modes of materials are known or not.