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Study on the mechanism of cumulative fatigue damage of advanced engineering materials under service loadings

先进工程材料服役载荷下累积疲劳损伤机理研究

基本信息

批准号：
06452149
负责人：
JONO Masahiro
金额：
$ 4.35万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452149/
关键词：
Advanced Engineering Material Ceramics Metal Matrix Composites Service Loading Fatigue Strength Fatigue Crack Growth Direct Observation Image Processing

项目摘要

In this project, fatigue crack initiation and propagation behavior undre constant and variable amplitude loadings were investigated on advanced engineering materials such as titanium alloys, powder metallurgy (P/M) aluminum alloys, metal matrix composites (MMC) and ceramics.Crack opening behavior of titanium alloys under variable amplitude loadings was found to depend on the microstructure of materials, which resulted in the different crack growth rates against the identical stress intensity factor depending on the materials. Acceleration of crack growth by load reduction was observed for the small fatigue cracks, while retardation was found for conventional long fatigue cracks on the titanium alloys as well as high strength structural steels.As to the SiC reinforced aluminum matrix composites, i.e.SiC particle reinforced P/M composite and SiC whisker reinforced casting composite, fatigue crack initiation and growth mechanisms were found to be defferent depending on the geometry of SiC and production processes. A fatigue crack initiated in the vicinity of SiC particle in the P/M composite and a single or a few cracks propagated until fracture. On the other hands, in the casting composite, fatigue cracks easily initiated at the whisker/matrix interfaces or at the sites where SiC whisker was pulled out and some microcracks were found to coalesce to form a main crack. Furthermore, SiC reinforcement irrespective of particle or whisker was found to be benefit for fatigue characteristics of MMC due to the increase of fatigue crack growth resistance.Through the direct observation of fatigue crack growth behavior under a single overload on a 3% silicon iron, it was found that the retardation behavior was closely correlated with deflected or branched cracks.Finally, crack growth acceleration under repeated two step loadings was found on a sintered silicon nitride, to the contrary of the retardation behavior usually observed on the metallic materials.

本项目研究了钛合金、粉末冶金（P/M）铝合金、金属基复合材料（MMC）和陶瓷等先进工程材料在恒幅和变幅载荷下的疲劳裂纹萌生和扩展行为。发现钛合金在变幅载荷下的裂纹张开行为取决于材料的微观结构，从而导致不同的裂纹扩展。根据材料的不同，针对相同应力强度因子的速率。对于小疲劳裂纹，观察到载荷减少会加速裂纹扩展，而对于钛合金和高强度结构钢上的常规长疲劳裂纹，则发现了延迟裂纹扩展。对于 SiC 增强铝基复合材料，即 SiC 颗粒增强 P/M 复合材料和 SiC 晶须增强铸造复合材料，发现疲劳裂纹的萌生和扩展机制为根据 SiC 的几何形状和生产工艺而有所不同。疲劳裂纹在粉末冶金复合材料中SiC颗粒附近萌生，单个或多个裂纹扩展直至断裂。另一方面，在铸造复合材料中，疲劳裂纹很容易在晶须/基体界面或SiC晶须被拉出的位置处产生，并且发现一些微裂纹合并形成主裂纹。此外，由于增加了疲劳裂纹扩展抗力，SiC 增强材料无论颗粒或晶须都对 MMC 的疲劳特性有益。通过直接观察 3% 硅铁单次过载下的疲劳裂纹扩展行为，发现延迟行为与偏转或分支裂纹密切相关。最后，发现重复两步加载下的裂纹扩展加速。烧结氮化硅，与通常在金属材料上观察到的延迟行为相反。