航空学报 > 2006, Vol. 27 Issue (6): 1107-1112

通用EIFS分布确定方法改进研究

杨谋存, 聂宏   

  1. 南京航空航天大学 能源与动力学院, 江苏 南京 210016
  • 收稿日期:2005-06-06 修回日期:2005-10-01 出版日期:2006-12-25 发布日期:2006-12-25

Advanced Method of Determining Generic Parameters of EIFS Distribution

YANG Mou-cun, NIE Hong   

  1. College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
  • Received:2005-06-06 Revised:2005-10-01 Online:2006-12-25 Published:2006-12-25

摘要: 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。

关键词: 原始疲劳质量(IFQ), 当量初始缺陷尺寸(EIFS), 极大似然估计(MLE), 裂纹形成时间(TTCI)

Abstract: 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.

Key words: Initial Fatigue Quality (IFQ), Equivalent Initial Flaw Size (EIFS), Maximum Likelihood Estimation (MLE), Time to Crack Initial (TTCI)

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