多轴变幅载荷下基于载荷支配模式的缺口件疲劳寿命预测方法

提出一种多轴变幅载荷下基于载荷支配模式的缺口件疲劳寿命预测方法。首先,通过循环计数方法确定多轴变幅载荷历程的计数循环(反复);其次,通过材料的循环应力应变关系和Neuber法推导出虚拟等效应变与真实等效应力之间的关系,并且分别将拉伸型和剪切型Shang-Wang多轴疲劳损伤参数替换虚拟等效应变幅来求解临界面上的真实等效应力幅;然后,通过真实等效应力幅和Neuber法则计算临界面上真实的拉压和剪切等效应变幅,并运用Manson-Coffin方程分别计算缺口部件的拉压和剪切疲劳寿命;最后,选择拉压和剪切疲劳损伤值中的较大值作为每个计数反复的疲劳损伤,并采用Miner法则进行疲劳损伤累积。缺口件多轴疲劳试验结果表明,采用基于载荷支配模式的缺口件疲劳寿命预测方法具有较高的预测准确度。

Notch Fatigue Life Prediction Methodology Based on the Load Control Modes under Multiaxial Variable Amplitude Loading

Based on the load control modes,a notch fatigue life prediction methodology for notched component is proposed under multiaxial variable amplitude loading.Firstly,the multiaxial cycle counting approach can be used to determine cycles and reversals in the loading history.Secondly,pseudo equivalent strain vs.real equivalent stress relationship can be determined using material cyclic stress-strain equation and Neuber rule,and axial strain-based and shear strain-based Shang-Wang multiaxial fatigue damage parameter can be used to replace the pseudo equivalent strain amplitude in order to calculate the real equivalent strain amplitude on the critical plane.Then,the real equivalent strain amplitude on the critical plane can be calculated using the real equivalent stress amplitude and the Neuber rule,and the Manson-Coffin equation can be used to calculate the tension-compression and shear fatigue life of the notched component.Finally,the larger one between the tension-compression fatigue damage and shear fatigue damage is selected as the determined fatigue damage in every counting cycle(reversal),and the determined fatigue damage in each counting cycle(reversal)is combined with Miner rule to accumulate the total fatigue damage.The results for multiaxial fatigue tests of notch component show that the fatigue life prediction method based on dominated load mode has high accuracy.