耐久性分析相对小裂纹扩展速率公式的参数确定方法

结构细节相对小裂纹扩展速率公式是采用概率断裂力学方法进行结构耐久性分析的关键。针对目前需进行多个应力水平下的成组疲劳试验以确定相对小裂纹扩展速率公式适用范围和参数的问题，首先，通过将应力强度因子修正系数展开为多项式，基于材料稳定裂纹扩展段的裂纹扩展速率公式得到了耐久性分析的相对小裂纹扩展速率公式。然后，以受远场均匀拉伸载荷作用的中心圆孔板为对象，分别基于应力强度因子近似解和FRANC3D软件进行裂纹扩展分析，得到相对小裂纹尺寸范围及对应裂纹扩展参数的确定方法。最后，进行了3种试件在等幅交变应力下的耐久性试验，验证了该方法的正确性。 

Parameter determination method of relative small crack growth rate formula in durability analysis

Relative small crack growth rate formula of structural details is the key to durability analysis using probabilistic fracture mechanics method. In order to determine the applicable range and parameters of the formula, it is necessary to carry out group fatigue tests under multiple stress levels, which is too complex. To solve this problem, in this paper, first, the stress intensity factor correction coefficient is expanded to a polynomial, and the relative small crack growth rate formula for durability analysis is obtained based on the crack growth rate formula of material stable crack growth section. Then, various crack growth of the central hole plate subjected to far-field uniform tensile load is analyzed based on the approximate solution of stress intensity factor and FRANC3D software, and a method is obtained to determine the relative small crack size range and the corresponding crack growth parameters. Finally, the correctness of the method is verified by durability tests of three specimens under constant amplitude alternating stress.