中文摘要：

提出一种多轴随机载荷下的疲劳寿命预测方法。该法首先基于yonMises等效应变和等效应力概念、符号修正公式以及传统的单轴雨流计数法，提出一种多轴随机载荷下的循环计数方法。此法主要针对多轴随机载荷下vonMises等效应变和等效应力历程中的符号丢失问题，建议采用一种符号公式来加以修正，以便于结合单轴雨流计数法对修正后的yonMises等效应变历程进行较为精准地循环计数，从而不仅有利后续疲劳损伤的正确估算，还可使单轴循环计数法能有效地应用于多轴载荷一时间历程。然后分析yonMises等效应变循环内的应变状态，并定义该循环内的临界平面和构造损伤参量的基本参数。最后，将提出的计数方法结合几种常见的临界面多轴疲劳损伤模型以及线性损伤定律，对随机拉一扭加载下的Enl5R钢薄壁管疲劳试件进行寿命预测验证，预测结果与试验结果吻合较好。

英文摘要：

According to the concept of critical plane, a fatigue life prediction method is presented under random muhiaxial loading. Firstly, a muhiaxial cycle counting method is proposed based on the yon Mises equivalent strain and equivalent stress concept, sign correctional formula and traditional uniaxial rainflow cycle counting method. This method mainly aimed at solving the problem of ＇sign lost＇ in von Mises equivalent strain and equivalent stress history under multiaxial random loading, suggesting adopt a sign formula correct it, then cycle count the yon Mises equivalent strain history with a traditional uniaxial cycle counting method, which can not only be convenient for evaluating the damage of succeeding procedure, but make the uniaxial cycle counting method successfully apply in multiaxial load-time history. After that, the normal and shear strains are analyzed for cycle-counted equivalent strain cycles, and the critical plane as well as fatigue damage parameters are also defined for these cycles. Finally, combining several familiar multiaxial fatigue damage models, Miner＇s linear rule together with uniaxial fatigue data of EnlSR steel, predicting its fatigue life under random axial-torsional loading, and the results show that the life predictions agree well with experimental results.