一种考虑路径影响的剪切式多轴疲劳寿命模型

New Multiaxial Fatigue Life Prediction Model with Shear Form Based on the Strain Path

大量的试验证明,在相同等效应变条件下,多轴非比例加载下的疲劳寿命往往要远远低于多轴比例加载下的寿命。因此基于临界平面法,提出一种考虑加载路径影响的多轴疲劳剪切式寿命模型。该寿命模型以最大损伤平面为临界平面,并以临界平面上的正应变幅值,切应变幅值,平均静水应变以及一种加载路径影响因子作为主要损伤变量。其中,通过引入一种加载路径影响因子来考虑多轴非比例加载对多轴疲劳寿命的锐减程度影响。同时,借助平均静水应变这一损伤变量对多轴加载中的平均应变或应力影响进行修正。该模型不含任何材料参数,便于工程应用。根据已有4种材料的多轴疲劳试验数据对该新模型的有效性与适应范围进行了验证。

Many experimental data have demonstrated that the fatigue life under non-proportional loading, under the same equivalent strain, is far less than that under proportional loading. Therefore, based on the critical plane, a new multiaxial fatigue life prediction model as shear form based on the strain path is proposed. The maximum damage plane is defined as the critical plane and this model consists of four main damage parameters：normal and shear strain amplitudes on the critical plane, mean hydrostatic strain and a path-dependent factor. The path-dependent factor is presented to consider the influence of non-proportional loading. Meanwhile, the effect of the mean strain is corrected by the mean hydrostatic strain. It does not include any material constant which is very convenient for engineering design. Four kinds of materials are used to demonstrate the accuracy of the presented model.