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Development of evaluation technique for fatigue strength in discontinuously reinforced composites

非连续增强复合材料疲劳强度评价技术的发展

基本信息

批准号：
10650083
负责人：
AKINIWA Yoshiaki
金额：
$ 2.05万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

1. For the case of fine particle-reinforced composites, crack initiation was associated with matrix slip in a particle-rich region. On the other hand, for the case of coarse particle-reinforced composites, cracks were mainly initiated by particle cracking under cyclic loading.2. For the case of fine particle-reinforced composites, the crack is decelerated when it hits the particle. When the crack becomes longer than about 150μm, the crack does not show large irregularity in the crack growth curve. For the case of coarse particle-reinforced composites, main crack propagated with coalescence with sub-cracks initiated from particle fracture ahead of a main crack.3. When compared at the same stress intensity range, crack propagation rate, da/dN, decreases with increasing volume fraction of SiC particle. SiC particles act as a resistance of crack propagation. For the case of a coarse particle composite, da/dN is lower than that of a fine particle composite for lower stress intensity range region. The crack closure increases with particle volume fraction, when compared at the same Kmax. Increase of the crack closure at threshold with volume fraction is mainly caused by the roughness of fracture surface.4. The fatigue strength of notched components increases with increasing volume fraction of SiC particle. The prediction method based on a resistance-curve was proposed.5. Model of fatigue crack interacting with the secondary phase and grain boundary was proposed to evaluate the fatigue limit of smooth specimen on the basis of plasticity induced crack closure model.

1. 对于细颗粒增强复合材料，裂纹萌生与颗粒丰富区域中的基体滑移相关。另一方面，对于粗颗粒增强复合材料，裂纹主要是由循环加载下颗粒开裂引发的。2．对于细颗粒增强复合材料的情况，当裂纹撞击颗粒时，裂纹会减速。当裂纹变得长于约150μm时，裂纹在裂纹扩展曲线中不表现出大的不规则性。对于粗颗粒增强复合材料的情况，主裂纹随着与主裂纹之前的颗粒断裂引发的子裂纹的合并而扩展。3．在相同应力强度范围下比较，裂纹扩展速率da/dN随着SiC颗粒体积分数的增加而减小。 SiC颗粒起到裂纹扩展的阻力作用。对于粗颗粒复合材料的情况，对于较低应力强度范围区域，da/dN 低于细颗粒复合材料的情况。与相同 Kmax 相比，裂纹闭合随着颗粒体积分数的增加而增加。阈值裂纹闭合随体积分数的增加主要是由断裂表面的粗糙度引起的。 4．缺口部件的疲劳强度随着SiC颗粒体积分数的增加而增加。提出了基于电阻曲线的预测方法； 5．在塑性诱导裂纹闭合模型的基础上，提出了疲劳裂纹与第二相和晶界相互作用的模型，以评估光滑试件的疲劳极限。