疲劳裂纹塑性闭合特性的数值分析方法  

THE CHARACTERIZATION OF PLASTICITY INDUCED FATIGUE CRACK CLOSURE BASED ON NUMERICAL ANALYSIS

作　　者：李亚智[1] 张自鹏[1] 何静[1] 

机构地区：[1]西北工业大学航空学院航空结构工程系,西安710072

出　　处：《固体力学学报》2009年第4期383-388,共6页Chinese Journal of Solid Mechanics

基　　金：黄玉珊先生基金部分资助

摘　　要：塑性诱导裂纹闭合是导致裂纹闭合发生的主要机理之一.利用弹塑性有限元法模拟含中心裂纹矩形板试件的疲劳裂纹扩展,并确定疲劳裂纹张开、闭合应力水平.通过计算,考察应力比R、裂纹长度、最大应力强度因子Kmax等对疲劳裂纹张开闭合应力的影响规律.论文阐述了所采用的裂纹扩展模拟方法及确定裂纹张开和闭合应力的原理.采用了等K加载方式,即在裂纹扩展中裂尖应力强度因子的最大值Kmax保持不变(给定R比,最大应力σmax随裂纹长度变化).分析了两种Kmax水平下R比分别为0.3,0,-0.5和-1.0共8种载荷工况.结果表明,对各个载荷工况,用瞬时最大应力σmax正则化的裂纹张开、闭合应力水平σop/σmax和σcl/σmax与裂纹长度无关.等K循环加载比等幅循环加载更有利于分析影响裂纹闭合水平的因素和闭合效应对疲劳裂纹扩展的影响规律,为建立基于裂纹闭合效应的疲劳裂纹扩展规律模型提供了一种新的思路.The crack closure in fatigue crack growth has always attracted great attention of many people. One of the major reasons for the phenomenon of metallic materials is the plasticity induced crack closure （PICC）. In this paper the fatigue crack growth was simulated by elastic-plastic finite element method and crack opening/closure levels （σop and σd） was estimated. The calculations focused on the effects of the maximum stress intensity, load ratio and crack length on the crack opening/closure levels. The scheme for implementing the calculation and searching the crack opening/closing stress levels was depicted in detail. The special attention was paid to the ＂constant-K＂ loading where the cyclic loadings was applied by keeping the maximum stress intensity factors Kmax invariable at given load ratios,such that the maximum stress σmax varies with the crack length. Two Kmax levels with four load ratios （R=0.3,0,-0.5 and -1） for each were considered. The results indicated that σop and σd , normalized by a are independent of the crack length. The constant-K loading makes more sense than the constant amplitude cyclic loading in distinguishing the effects of load level and crack length on the PICC and offers a new idea to characterize crack growth behavior.

关 键 词：疲劳裂纹扩展 裂纹闭合 弹塑性有限元 等K加载 

分 类 号：O346.1[理学—固体力学]