通用EIFS分布确定方法改进研究

Advanced Method of Determining Generic Parameters of EIFS Distribution

基于概率断裂力学的基本假设和原理,提出一种改进的通用EIFS分布确定方法。新方法用小裂纹扩展曲线计算多种参考裂纹尺寸水平下的TTCI值,并对其进行极大似然估计。然后利用约束最小二乘法确定不同应力下的裂纹扩展参数和通用EIFS分布上限。在此基础上,根据分布参数的通用性条件确定通用EIFS分布参数。与改进前的方法相比,新方法充分利用分布函数和裂纹扩展提供的信息,提高参数估计的合理性和可靠性。对某零件的原始疲劳质量分析证明改进方法是可行的,便于工程应用。

According to the essential hypothesis and principle of probabilistic fracture mechanism, the advanced method of estimating generic parameters of EIFS distribution is presented. The new method calculates TTCI values at different reference-crack-sizes with growth curve of small crack and estimates TTCI distribution parameters with maximum likelihood estimation. Then, the generic upper limit of EIFS distribution and crack growth parameter under different stress levels are estimated with constrained least squares fitness. Based on these, the generic parameters of EIFS distribution are determined according to generality condition of EIFS distribution parameters. Compared to the old method, the new one makes adequately use of the information of crack growth and distribution function, which improves the rationality and reliability of estimated TTCI and EIFS distribution parameters. The IFQ analysis of a structure detail proves that the advanced method is feasible and convenient for application.