用塑性滞后能原理估算随机载荷下的疲劳寿命

 材料的疲劳损伤包括静力损伤和循环损伤,静力损伤为第一次静力加载引起的塑性应变能与静力韧性之比；循环损伤由循环塑性滞后能与疲劳韧性之比来计算,计算中计及了材料循环硬化（或软化）引起的屈服应力增大（或减小）的影响。为了简化计算,假设在循环加载时应力一应变曲线均按迟滞回线规律变化；不同应力变程下材料疲劳韧性可由对称循环的应力控制疲劳试验确定。本文提出了一种比较合理又便于工程应用的、用塑性滞后能原理估算随机载荷下疲劳寿命的新方法,初步的试验验证是令人满意的。

FATIGUE LIFE ESTIMATE UNDER RANDOM LOADING BASED ON PLASTIC HYSTERESIS ENERGY PRINCIPLE

There are static and cyclic damages in materials.The static damage is the ratio of plas- tic strain energy due to first applied static load to static toughness of material,and the cyclic damage can be obtained by calculating the ratio of cyclic plastic hysteresis energy to fatigue toughness of material.In calculating the cyclic damage,we have been concerned with influences of yield stress increment(or decrement)caused by cycle-dependent hardening(or softening)of material.In order to simplify the calculating,we assume that the stress-strain curves at cyclic loading all follow hysteresis loops and fatigue toughness of material under different stress ranges can be detennined by cyclic symmetry stress control fatigue tests.In this paper,we have advanced anew fatigue life estimating method under random loading.The new method is reasonable and convenient in engineering application. It is satisfactory in the preliminary experimental verification.