基于应力等效关系的汽车零部件疲劳寿命预测模型

Model for Fatigue Life Prediction on Auto Parts Based on Stress Equivalence Relation

对于预测多级应力加载下的汽车零部件疲劳寿命,已有的相关非线性模型通常需要依赖大量的试验数据,或者较难选取合适的基准值,使得疲劳可靠性理论在汽车领域的应用存在一定局限性。针对此问题,基于材料疲劳寿命特性曲线,通过分析两级应力之间疲劳损伤转化过程,建立了一种考虑相邻载荷作用的等效转化关系,推导了两级、三级及更高应力等级情况下相邻应力之间的疲劳累积损伤等效公式和剩余疲劳寿命的表达式,进而提出了一种基于应力等效关系的疲劳寿命预测模型。该模型的计算过程仅需不低于两级应力的材料疲劳寿命试验结果。采用二级、三级、四级及五级应力加载试验数据,分别计算并对比了Miner模型、Manson模型、Subramanyan模型、Hashin模型及新模型的相对误差平均值和最大值,进一步汇总了两级至五级应力下各模型疲劳累积损伤与疲劳累积寿命的预测结果、各模型预测疲劳损伤与试验疲劳损伤之差的分布。结果表明,基于相邻载荷作用等效转化的新模型在疲劳寿命的整体预测结果优于Miner模型、Manson模型、Subramanyan模型及Hashin模型,可更为准确地应用于材料多级应力下的疲劳寿命/损伤预测。

For predicting the fatigue life of auto parts under multi-stage stress loading,the existing nonlinear models usually need to rely on a large number of test data,or it is difficult to select a suitable reference value,which makes the application of fatigue reliability theory in automotive field has certain limitation.Due to this issue,a fatigue damage transformation process between two stage stresses is analyzed based on the fatigue life characteristic curve of material.Then a relationship considering equivalent transformation of adjacent loads is established.The equivalent formula of fatigue cumulative damage and the expression of residual fatigue life between adjacent stresses under two-,three-,and higher-stage stress are derived.Then a fatigue life prediction model based on stress equivalence relation is proposed.The calculation process of proposed model requires only the fatigue life test result of the material with no less than two sage stresses.Existing two-,three-,four-,and five-stage stress loading test data are used for verification.The average and maximum relative errors of Miner model,Manson model,Subramanyan model,Hashin model,and the proposed model are calculated and compared respectively.Furthermore,the predicted result of fatigue cumulative damage and fatigue cumulative life,and the distribution of difference between fatigue cumulative damage and test cumulative damage predicted by each model are summarized under two-to five-stage stress.The result indicates that the proposed model based on equivalent transformation of adjacent loads has better overall fatigue life prediction result than Miner model,Manson model,Subramanyan model,and Hashin model.That can be more accurately applied to the fatigue life/damage prediction under multi-stage stress.