结构系统疲劳失效相关性的宏细观分析与可靠性建模

Fatigue failures of structure systems can be regarded as a process in which micro-damage of the component or structural detail is gradually accumulated from micro, meso to macro scale and finally induces the catastrophe. As the necessary information for system-level probabilistic analysis of the structure, the failure-dependence mechanism is always complex because of the multi-physics characteristics of the damage evolution process. By means of the macro-meso-scale sequential method, relationships between fatigue lives of components and macro-meso-scale random variables are built to illustrate the statistical correlation mechanism of fatigue lives of components for reliability modeling of typical structure systems. The specific route is as follows. Firstly, fatigue fracture process of the component is divided into three stages, namely crack initiation, short crack growth and long crack growth. Corresponding stage-life models are built according to different physical characteristics at the macro-scale and the meso-scale respectively. Secondly, all stage-life models are linked and decoupled based on macro-meso-scale information transmission, so as to the total-life expression and probability distribution function are obtained successively. Finally, the quantitative index of fatigue failure time-varying dependence is derived by which the system-level reliability model can be built. Owing to the two-scale probability analysis method, a new idea is proposed to study fatigue failure dependence of structure systems. By introducing microstructure parameters, a new path for precise modeling of system-level structural fatigue reliability is put forward.

结构系统的疲劳失效是元件或结构细节的微损伤从微观、细观到宏观跨尺度累积而诱发灾变的过程。作为系统级概率分析的必需信息，元件之间的失效相关机理因损伤演化过程在各尺度上的多物理性而具有复杂形式。本项目在结构系统疲劳可靠性分析中采用宏细观双尺度串行法，建立元件疲劳寿命与宏细观综合随机变量群之间的关系，阐明元件疲劳寿命的统计相关机理，实现典型结构系统疲劳可靠性建模。具体技术路线是：将元件疲劳断裂过程分为裂纹萌生、短裂纹扩展和长裂纹扩展三大阶段，先后在细观、宏观尺度上按不同物理机制分段建模，再根据双尺度随机变量群的信息传递关系对阶段寿命模型进行跨尺度串接与解耦，得到元件总寿命方程以及寿命分布函数，由此导出疲劳失效时变相关性量化指标和系统可靠性模型。双尺度概率分析方法的选用，为结构系统疲劳失效相关性研究提出了新思路；材料细观结构参数的引入，为结构系统疲劳可靠性的精细化建模开辟了新途径。

结构系统疲劳失效是元件或结构细节的微损伤从微观、细观到宏观跨尺度累积而诱发灾变的过程。该项目在结构系统疲劳可靠性分析中采用宏细观双尺度串行法，建立元件疲劳寿命与宏细观综合随机变量群之间的关系，阐明元件疲劳寿命的统计相关机理，实现典型结构系统疲劳可靠性建模。主要成果包括：根据晶粒尺寸分布函数建立多晶体金属二维微结构有限元模型；借助Schmid因子建立细观主应力与分解切应力之间的关系，导出分解切应力变程的概率分布；基于Tanaka-Mura微裂纹形核机制分析裂纹形核寿命的细观相关性，建立结构表面疲劳裂纹形核寿命的细观概率模型；基于广义发生函数法，实现可修系统疲劳寿命概率建模；分析结构系统各单元疲劳失效内在的统计相关机理，利用Copula函数建立串联、并联结构系统的疲劳可靠性模型。双尺度串行法的选用，为结构系统疲劳失效相关性分析提出新思路；材料细观参数的引入，为结构系统疲劳可靠性的精细化建模开辟新途径。