基于最大切应变幅和修正SWT参数的多轴疲劳寿命预测模型

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The most components of engineering structures are usually subjected to a complex loading. It is unable to meet the requirements of engineering precision if a uniaxial fatigue model is used under multi-axial loading. The calculation of fatigue life prediction under mulfiaxial loading causes people＇s attention more and more. A new multiaxial fatigue life prediction model is proposed based on the critical plane criteria. The model integrates the respective advantages of Fatemi-Socie（FS） model and Smith-Watson-Topper（SWT） parameter. The damage parameter in this model takes the sum of the maximum shear strain amplitude and the modified SWT parameter on the maximum shear strain amplitude plain. It can consider the effects of additional cyclic hardening due to non-proportional loading and mean stress on the multi-axial fatigue life of material. The proposed model can be applied to proportional and non-proportional loading. The model is evaluated by the multiaxial fatigue test data of pure titanium, BT9 titanium alloy, 304 stainless steel, $45C steel and 1045HR steel. The multi-axial fatigue life prediction results of these materials under proportional and non-proportional loading are almost within a factor of two scatter band of the test result. The result shows that the new multi-axial fatigue life model has high prediction accuracy.工程中的大多构件承受着复杂的载荷形式，将单轴疲劳模型应用到多轴载荷情况已不能满足工程精度的要求，多轴载荷下的疲劳寿命计算日益引起人们的重视。基于临界平面的思想，结合Fatemi-Socie（FS）模型和Smith-Watson-Topper（SWT）参数各自的优点，提出一种新的多轴疲劳寿命预测模型。该模型以最大切应变幅与最大切应变幅平面上修正SWT参数的和作为多轴疲劳损伤控制参量，此参量可以同时考虑非比例附加循环硬化和平均应力对材料多轴疲劳寿命的影响，能同时适用于比例和非比例加载下的多轴疲劳问题。采用纯钛Ti、BT9钛合金、304不锈钢、S45C钢和1045HR钢5种材料多轴疲劳试验数据对提出的模型进行评估和验证，对几种材料比例和非比例加载下的多轴疲劳寿命预测结果大都分布在试验结果的2倍分散带之内，结果表明提出的多轴疲劳寿命模型具有较高的预测精度。