基于能量法的多轴疲劳寿命预测方法

Fatigue Life Prediction under Multiaxial Loading Using Energy-based Models

多轴疲劳寿命预测对于确保工程构件的安全性及经济性具有重要意义,其中损伤参量的选取对于预测结果的精度具有关键影响作用.Smith-Watson-Topper(SWT)能量参数是目前常用的损伤参量,但由于仅考虑了拉伸应变能对材料损伤的贡献,因此其常做出偏于危险的预测结果.针对此问题,Glinka及Chen-Xu-Huang(CXH)能量参数被相继提出.然而试验验证表明:Glinka参数通常仅适用于以剪切型失效为主要失效模式的材料,CXH参数则易给出过于保守的预测结果.为提高SWT参数对各种材料与加载路径的适用性,论文在评估Glinka及CXH参数的基础上,提出了两个修正的SWT能量参数,并建立起了一个统一的多轴疲劳寿命预测模型.针对不同的疲劳失效形式,所提出的能量参数不仅可考虑平均应力效应,且可同时包括临界面上不同加载方向对材料损伤的影响.通过六种材料的多轴疲劳试验数据对新模型、SWT模型、Glinka模型及CXH模型进行了验证,结果显示新模型比其他三种模型具有更好的寿命预测精度及稳定性.

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.