一、变动载荷和变动应力在工程实践中,结构和另部件受到的载荷不可能是完全静止的,绝大部分的载荷是随时间而变化的。我们把大小、方向或大小和方向随时间而变化的载荷叫做变动载荷。(有的文献称它为疲劳载荷,有的则称它为交变载荷,我们认为只有把等幅变动载荷称为交变载荷才更为妥当些)在变动载荷作用下结构和另部件内部就受到变动应力(也可称为疲劳应力)。变动载荷按其随时间的变化规律,可以分为确定的和随机的两类。所谓确定的变动载荷是指载荷随时 First, the change in load and stress In engineering practice, the load on the structure and the other components can not be completely static, the vast majority of load changes over time. We refer to the size, direction or size and direction of the load changes over time called the variable load. (Some literatures call it fatigue load, while others call it alternating load. We think it is more appropriate to call the dynamic load with alternating amplitude only.) Under the action of fluctuating load, Subject to variable stress (also known as fatigue stress). Changes in load according to its variation over time, can be divided into two categories of certain and random. The so-called change in load is defined as load at any time