摘要随着陆地资源的日渐减少，海洋资源的开发与利用便成为世界各国所关注的焦点。人类对海洋的探索与开发，离不开深海载人潜器的帮助，作为深海科学考察的重要工具，深海载人潜器在海洋环境研究、海底资源勘探、海洋生物多样性研究方面起着至关重要的作用。但在实际工作过程中，潜水器的耐压壳体不仅将受到下潜、上浮的循环载荷作用，当处于一定深度是还将受到持续载荷。所以，载人潜器的耐压壳体结构疲劳还存在这保载-疲劳问题。Ti-6Al-4V钛合金作为深海载人潜器耐压壳结构的主流使用材料，对钛合金材料进行保载-疲劳裂纹扩展速率的研究有着重要的工程应用意义。95177

因此，本文主要内容有对Ti-6Al-4V钛合金以及裂纹扩展速率研究的发展史进行了综述；对Ti-6Al-4V钛合金进行保载时间为60s和120s情况下保载-疲劳裂纹扩展速率试验；基于已有的钛合金保载-疲劳裂纹扩展速率的预报模型对Ti-6Al-4V钛合金进行保载时间为60s和120s进行了预报，并对预报结果和试验结果进行了对比，验证了预报模型的精度；对保载时间不同情况下的保载-疲劳裂纹扩展速率进行了对比分析。

毕业论文关键词：Ti-6Al-4V钛合金；保载-疲劳；裂纹扩展；预报模型

Abstract With the declining of the land resources, the development and utilization of marine resources has become the focus of the world。 Without the help of deep sea manned submersible，human cannot take the exploration and development of the ocean。 As an important tool for deep sea scientific investigation, deep sea manned submersible plays a vital role in marine environment research, submarine Resources exploration  and  marine   biopersity  research。   Because   of  the  complexity     and

variability of the marine environment, submersible is subjected to periodic fluctuating loads during its service。 Therefore, the fatigue failure is one of the  main failure models of the marine structure during service。 However, in the actual work process, submersible pressure hull structure is subjected to the dwell load when ping to the work depth except cycle load when pe and come-up。 As the main material of the submersible pressure hull structure, it is important to study the method of predicting the dwell-fatigue crack growth rate of the Ti-6Al-4V titanium alloy。

Therefore, the main purpose of this paper are as follows: Study the history of crack growth rate of the titanium alloy; Carry out the dwell-fatigue crack growth rate test ;Compare the between test result and the predicted dwell-fatigue result; Then the applicability of the modified model for predicting the dwell-fatigue crack growth rate is validated and effects of different hold times on the dwell-fatigue crack growth rate are compared。

Keywords: Ti-6Al-4V titanium alloy; dwell-fatigue; crack growth rate: predicted model

目录

第一章绪论 1

1。1课题研究的背景与意义 1

1。2国内外研究历史及进展 3

1。2。1国内外Ti-6Al-4V钛合金发展 3

1。2。2国内外钛合金在实际工程应用的发展与研究 4

1。3疲劳裂纹扩展理论进展 8

第二章裂纹扩展速率基础理论 11

2。1疲劳裂纹扩展速率的表达式 11

2。2疲劳裂纹扩展曲线 12

2。3小裂纹效应 14

2。4裂纹扩展速率模型