载荷形式对疲劳寿命预测方法的影响

EFFECT OF THE METHODS OF ESTIMATING FATIGUE LIFE IN THE DIFFERENTIAL TYPES OF LOADING

用力学分析方法解析了多种载荷条件下试件断面上各点应力分布规律，并根据这个分布规律由现有的大量旋转弯曲疲劳寿命实验数据推算同样材料的其他载荷形式下的疲劳寿命。同时，在旋转弯曲载荷条件下，通过建立试件表面应力应变与名义应力应变关系式，如果得出在单向拉压圆形试件名义应力与旋转弯曲圆形试件表面应力相等时，通过试件断面上的应力梯度值和材料的静拉伸强度值，可以简便地预测出材料任何尺寸大小、一定应力水平下的疲劳寿命；也可以由已知载荷形式下的疲劳寿命数据预测其他载荷形式下的疲劳寿命。预测结果与实验结果基本吻合。

An attempt was made to predicte fatigue life from rotating bending to push pull by using the stress gradient relation on the section of specimens for carbon steels. Because there are stresses gradients under bending and no these gradients under a push pull loading. Knowing the diference of the she gradient on the section of specimen under hath types of laoding, the fatigUe life may ie also predicted based on the mechanics method for the same shape of specimen and the material under these types of laoding. Therefor, the fatigue life can be estimated from the very much fatigue data under rotating bending to fatigUe life under an other types of loading for the same material. In this paper, it can be proposed that a simple method of calculation the fatigue ide for carbon steels under differential types of loading by the mechanics analysis. However, they must be used the relationships between the constants in the empirical 'equations of the peteing the fatigue life and the ultimate tensile strength of materials. It can also be calculated stress-strain curves for each other type of loading by the relationship among the stresses gradients on the sections of specimens. The results of prediction have shown to be in good agreement.