用比值法计算材料及其机件的疲劳损伤

提出了在非对称循环加载下描述材料弹塑性材料行为的损伤演变速率方程式与各个历程与不同损伤量DCi相对应的寿命NCi估算式。其方法是采用以塑性应变幅同弹性应变幅之比值ΔEp／Δεe作为应力应变参量，以常用的材料常数作为材料参数。而且，还提出了与常用材料常数、平均应力与平均应变、加载临界历程长短有着函数关系的综合性材料常数的新概念。此外，以汽车的某一零件为例，计算了它的疲劳损伤。其计算结果与Landgraf方程式计算结果一致，且计算精度较高。这对避免过多而重复的疲劳试验，对方便工程应用，对节约人力、时间和资金有着实际意义。

Fatigue Damage Calculated by the Ratio-Method to Materials and Its Machine Part

Several new calculating equations on the damage-evolving rate are suggested for describing the elastic-plastic behavior of some materials under un-symmetric cyclic loading. And the estimating formulas are given of the life relative to varied damage value D oi at each loading history. The method is to adopt the ratio of plastic strain range to elastic strain range as the stress-strain parameter, using the staple material constants as the material parameters in damage calculating expression. And it gives out a new concept of the compositive material constant, that has a functional relation with the staple material constants, average stress,average strain and critical loading time. In addition, it calculates fatigue damage as example for a part of car, its calculating results are accordant with the Landgraf's equation, and calculating precision is more rigorous, so could avoid unnecessary fatigue tests and will be of practical significance to stint times, manpower and capitals, and to provide convenience for engineering applications.