一、疲劳裂纹扩展速率前面介绍了线弹性断裂力学和弹塑性断裂力学的断裂判据和材料断裂韧度的测试方法。但上述判据只适于一次加载断裂的情况,工程上很多构件承受重复变动载荷,在重复应力作用下,在原始裂纹α_0《α_σ时,经过一定循环周次,裂纹会慢慢扩展,由α_0长大到临界尺寸α_σ,最后发生脆断。因此,裂纹从一定的初始尺寸扩展到临界尺寸,需 First, the fatigue crack growth rate In front of the introduction of the elastic fracture mechanics and elastoplastic fracture mechanics fracture criteria and material fracture toughness test methods. However, the above criteria are only suitable for the case of one-time loading fracture. Many components of the project are subjected to repeated variable loads. Under repeated stress, when the initial crack α_0 ”α_σ, after a certain number of cycles, the crack will slowly expand, by α_0 Grow up to the critical dimension α_σ, and finally the brittle fracture occurs. Therefore, the crack propagates from a certain initial size to a critical dimension.