研究了最新ASME-VIII-2规范推荐的用于非比例载荷下循环计数的最大最小循环计数法。首先通过定义最大最小循环计数法在应力-应变迟滞回线上的循环路径，赋予了最大最小循环计数法合理的物理意义。然后结合von-Mises损伤准则和Miner线性损伤累积理论，编写了非比例加载下使用最大最小循环计数法进行疲劳循环计数的实用程序，并成功应用该程序实现了对某核电站振动小支管疲劳寿命的预测。对比了非比例载荷下最大最小循环计数法和传统雨流计数法的循环统计结果，表明非比例载荷下最大最小循环计数法统计的等效应力幅值约为雨流法的1.085倍，循环次数约为雨流法的1.478倍。

The max-min cycle counting method,which is recommended in the latest ASME-VIII-2 and used for cycle counting under non-proportional loading,is studied in this paper. By defining a new cycle path in the stress-strain hysteresis loop,the reasonable physical meaning of the max-min cycle counting method is given. Combining von-Mises failure criterion and Miner linear damage criterion,a Matlab program for fatigue life prediction is developed under nonproportional loading using the max-min cycle counting method.The program was successfully used to calculate the fatigue life of a small branch pipeline in a nuclear power plant.The cycle counting results obtained from the max-min cycle counting method and the conventional rain-flow method show that the equivalent stress amplitude of the maxmin cycle counting method is about 1.085 times larger than that of the rain-flow method and the number of cycles is about 1.478 times more than that of the rain-flow method under non-proportional loading.

O346.2