文档介绍：哈尔滨工程大学本科生毕业论文
基于裂纹扩展的结构疲劳寿命分析
院(系)名称: 船舶工程学院
专业名称: 船舶与海洋工程
学生姓名:
指导教师:
2011年6月
摘要
疲劳破坏是船舶结构的主要失效形式之一。大量断裂事故的分析表明,疲劳断裂与结构中存在的裂纹有关。实际上,结构在刚开始投入使用时就已经存在裂纹。考虑到裂纹的扩展过程,本文采用基于Paris裂纹扩展模型的线弹性断裂力学理论,利用有限元软件ANSYS建立结构裂纹模型,对不同裂纹状态下的应力强度因子进行计算,从而预测结构疲劳寿命。本文主要包括以下几点内容:
,建立结构裂纹模型。
,计算不同类型裂纹的应力强度因子,并与理论值比较。
,得到不同裂纹长度下的应力强度因子,采用Paris裂纹扩展理论进行结构寿命的计算,并与试验值和S-N曲线值进行对比。
,应力水平,材料属性等影响结构裂纹扩展寿命的一些因素进行分析研究。
关键词: 疲劳;裂纹扩展;应力强度因子;有限元
ABSTRACT
Fatigue damage is one of the main factors to influence the safety of the structure. It could be found that fatigue fracture has direct relationship with cracks in structures from the analysis of a large number of fracture accidents. in fact, the crack has been existing before the es into work, aiming at the crack propagation life, stress intensity of three-dimensional crack model under different length of cracks is calculated by using the finite element software ANSYS,which is based on the crack propagation life of Paris crack propagation model of linear-elastic fracture mechanics theory. then the fatigue life of structure can be predicted. the following contents will be illustrated in this paper :
1. The program of three-dimensional crack model which is based on APDL language piled..
2. Stress intensity factor is solved using 1/4 displacement method, pared with the theoretical value.
3. Based on the results which are analysed under different crack levels by the software, structure life is calculated, pared with the value of the tests and the results of S-N curve.
4. The factors such as the initial crack size, stress level, material properties which affect the crack propagati
on life are discussed.
Key words: Fatigue;crack propagation;stress intensity factor;the finite element
目录
第一章绪论 1
研究目的和意义 1
断裂力学研究现状 2
结构裂纹扩展寿命研究现状 2
裂纹尖端应力强度因子研究 3
有限元方法及ANSYS简介 4
本论文的研究内容 6
第二章疲劳寿命计算方法 7
疲劳破坏机理 7
疲劳的定义 7
裂纹形式划分 7
疲劳破坏的过程 9