关于多轴疲劳寿命临界面法影响因素的分析与计算

本文以拉-扭非比例加载下的薄壁圆管试件为研究对象,以最大法向应变的最大剪应变平面为临界面,并对此临界面上的应变状态进行了分析。采用统一型疲劳寿命预测模型,以正火45钢为例,研究了非比例加载时相位差对疲劳寿命的影响,进而对不同正应变幅和应变幅值比加载下的危险相位差的变化规律进行了计算分析。结果发现:应变幅值比对疲劳寿命最短时的危险相位差的影响呈先上升后下降的趋势;并给出了不同应变幅值比时危险相位差的计算通式,式中的系数可通过材料力学性能与单轴疲劳参数计算得到。最后给出了15种材料的系数供实际应用时参考。

Analysis and calculation on the influencing factors of the multiaxial fatigue life based on the critical plane approach

The tension-torsion thin walled tube specimens are investigated under non-proportional loading.The plane that has the maximum normal strain and shear strain is considered as the critical plane and its strain state is analyzed.The unified prediction model is used to calculate the fatigue life.Taking 45 steel as an example,the influence of the phase difference on fatigue life is studied.The change rule of the dangerous phase difference in different positive strain amplitudes and strain amplitude ratios is analyzed.The results obtained indicate that the dangerous phase difference raise first and then descend as the strain amplitude ratios increase.A general formula to calculate dangerous phase difference is presented,which coefficients can be obtained with material mechanics performance and uniaxial fatigue parameters.Finally,the coefficients for 15 kinds of common materials are given for reference of engineering practice.