双频载荷等效计数法

本文提出双频载荷等效计数的两种方法:其一,首先对载荷进行雨流计数,利用应力-应变(ε-σ)滞回环,使雨流计数前、后的双频载荷具有一一对应关系,从而推导出叠加在大载荷基础上的小载荷的等效循环计数公式。其二,将大载荷的雨流计数结果转化为脉动载荷,再将小载荷叠加上去,使转换后的载荷与原载荷有其对应区间,然后,依据等级载荷累加原理得出双频载荷等效计数公式。最后根据等效应力公式和疲劳累积线性损伤公式得到双频载荷疲劳寿命估算公式。

Methods for Uounting Equivalently the Dual-Frequency Load

The methods for counting equivalently the dual- frequency load are prop-osed. The first is using stress- strain hysteresis to the rain- flow counting forthe load, thus enabling the two dual- frequency loads before and after rainflowcounting to be corresponding with each and every. So a cyclic counting formu-la can be derived, equivalent to the low load which is superimposed on highload. The second is converting the rain- flow counting for high load into imp-ulse load and then superimposing the low load onto it, thus having a corres-pondent interval between the original and converted loads. So a formula isobtained for counting equivalently the dual- frequency load on the principle ofiterative addition of graded loads. An estimation of fatigue limit is formulatedfor dual- frequency load, based on the calculations of stress equivalent tofatigue and of linear cumulative damage.