二、疲劳裂纹扩展的力学方程 远在本世纪三十年代中期,人们已认识到疲劳裂纹是工程设计中的一个严重问题。Deforest等为了确定疲劳裂纹出现后金属的剩余寿命,首次开展了一项探索裂纹扩展的研究工作。此后,人们对疲劳裂纹扩展过程进行了大量的试验与理论分析,建立一些半经验式和解析式力学方程,有的已应用于零件与结构的实际寿命的估算中。 1.早期的裂纹扩展公式 表3列出了一些早期的疲劳裂纹扩展的半经验公式。这些公式在一定试验条件下是 Second, the mechanical equation of fatigue crack growth Far in the mid-1930s, people have realized that fatigue crack is a serious problem in engineering design. For the first time, Deforest et al. Conducted a study to investigate crack propagation in order to determine the residual life of the metal after fatigue cracking. Since then, a great deal of experimental and theoretical analysis has been carried out on the fatigue crack growth process, and some semi-empirical and analytical mechanical equations have been established. Some of them have been used in the estimation of actual life of parts and structures. 1. Early crack propagation formulas Table 3 lists some of the early semi-empirical formulas for fatigue crack growth. These formulas are under certain experimental conditions