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Investigation on Threshold Behavior of High Temperature Fatigue Crack Propagation and Its Mechanisms Using Macroscopic Experiments and Microscopic Molecular Dynamic Analyses

利用宏观实验和微观分子动力学分析研究高温疲劳裂纹扩展的阈值行为及其机制

基本信息

批准号：
09450050
负责人：
KUBO Shiro
金额：
$ 7.55万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

The present project investigated the near-threshold fatigue crack propagation behavior and mechanisms of the threshold For this purpose macroscopic high temperature fatigue crack propagation experiments were conducted. Effects of environment, loading frequency, temperature and loading history were examined. On the other hand microscopic molecular dynamic analyses on near-threshold fatigue crack propagation were made. The results obtained are summarized as follows.1.For SUS 304 stainless steel and Ni-base super alloy, high temperature fatigue crack propagation experiments were conducted in air and in vacuum. It was found that environment, loading frequency, and temperature had major influences on the near-threshold fatigue crack propagation rate da/dN and the threshold. The crack propagation resistance was lower that in air.2.For aged Cr-Mo-V steel, high temperature crack propagation behavior was investigated. The effect of aging on the crack propagation was small. The estimation of remaining life was made. The influences of many parameters on the life were identified.3.The simulations of the near-threshold fatigue crack propagation in iron were made using the molecular dynamics. A scheme was proposed which considered the decrease in the inter-atomic force due to oxidation of the new crack surface. It was found that near-threshold fatigue crack propagation behavior can be simulated by using the molecular dynamics. The effects of the orientation and grain boundary were examined. The crack propagation behavior contained in the linear elastic singular stress field was compared with that in the Hutchinson-Rice-Rosengren plastic singular field.

本课题研究了近门槛值疲劳裂纹扩展行为和门槛值机理，为此进行了宏观高温疲劳裂纹扩展实验。考察了环境、加载频率、温度和加载历史对材料性能的影响。另一方面，对近门槛疲劳裂纹扩展进行了微观分子动力学分析。1.对SUS304不锈钢和镍基高温合金在空气和真空中进行了高温疲劳裂纹扩展试验。结果表明，环境、加载频率和温度对近门槛疲劳裂纹扩展速率da/dN和门槛值有重要影响。裂纹扩展阻力低于空气中。2.对时效后的铬钼钒钢的高温裂纹扩展行为进行了研究。时效对裂纹扩展的影响不大。对其剩余寿命进行了估算。3.利用分子动力学方法对铁的近门槛疲劳裂纹扩展过程进行了模拟。提出了一种考虑新裂纹表面氧化引起的原子间作用力减小的方案。结果表明，用分子动力学方法可以模拟近门槛疲劳裂纹扩展行为。考察了取向和晶界的影响。比较了线弹性奇异应力场和Hutchinson-Rice-Rosengren塑性奇异场中的裂纹扩展行为。