后悬架多轴疲劳寿命预测

Multiaxial Fatigue Life Prediction of Rear Suspension

以鹅卵石强化路面的道路载荷为边界条件,考虑材料弹塑性变形,对汽车后悬架进行瞬态动力学有限元分析,利用传统的应变寿命法计算得到后悬架单轴疲劳寿命.对应力—应变时间历程的二轴性分析表明:汽车后悬架局部危险区域承受多轴非比例载荷.基于多轴疲劳理论,考虑了材料的非比例强化的影响,分析了裂纹形式,选用基于临界面法的Bannantine模型和Wang-Brown模型预测了后悬架的多轴疲劳寿命,并与单轴疲劳寿命分析结果进行了比较.研究发现,在非比例循环载荷下,疲劳寿命将大大减少,按常规的单轴疲劳寿命估算方法,将给出偏于危险的预测.

Considering the elastoplastic deformation of material,a transient dynamic analysis for rear suspension is conducted under the boundary condition of cobblestone strengthen road loads.Crack initiation life of rear suspension is accounted by using traditional uniaxial strain life method.However,biaxial analysis of stress—strain time history indicates that the hazardous areas of rear suspension are subjected to a multiaxial non-proportional loading.Based on multiaxial fatigue theory,the material non-proportional appending hardening mechanism and crack type are considered.The multiaxial fatigue life is predicted by using Bannantine model and Wang-Brown model which are deduced with the critical plane method.Uniaxial fatigue life on the basis of the same material is also predicted for a comparison.It indicates that the life under the non-proportional loading is largely decreased and the result predicted by uniaxial fatigue theory is dangerous.