Development of detective system of fatigue damage of metal matrix composite by X-ray diffraction at localized area

1）。研究了SiC颗粒增强铝合金的疲劳过程。对于细颗粒增强复合材料的情况下，裂纹萌生与基体滑移在颗粒丰富的区域。当裂纹撞击粒子时，它被减速。当裂纹变得比约150 μm长时，裂纹在裂纹扩展曲线中不显示大的不规则性。另一方面，对于粗颗粒增强复合材料的情况下，裂纹主要是由颗粒开裂循环载荷下发起。主裂纹与在主裂纹之前由颗粒断裂引发的子裂纹合并扩展。提出了一种新的金属基复合材料疲劳损伤X射线衍射检测系统。照射区域可聚焦在φ0.5mm以内。该系统可以测量缺口根部附近的应力分布。实验结果与有限元分析结果吻合较好。随着应力循环次数的增加，两个相的残余压应力均增加。另一方面，在最大施加应力下的相应力随着应力循环而减小，这是由于基体与颗粒之间的界面发生脱粘。疲劳损伤可以用相应力来评价。

1). Fatigue process in SiC particulate reinforced aluminum alloy was investigated. For the case of fine particle-reinforced composites, crack initiation was associated with matrix slip in a particle-rich region. The crack is decelerated when it hits the particle. When the crack becomes longer than about 150 μm, the crack does not show large irregularity in the crack growth curve. On the other hand, for the case of coarse particle-reinforced composites, cracks were mainly initiated by particle cracking under cyclic loading. A main crack propagated with coalescence with sub-cracks initiated from particle fracture ahead of a main crack.2). A new detective system of fatigue damage of metal matrix composite by X-ray diffraction was developed. The irradiated area could be focused within φ0.5mm. Stress distribution near the notch root could be measured by the system. The experimental data agreed well with the analytical value calculated by FEM.3). The compressive residual stress in both phases increased with stress cycles. On the other hand, phase stresses at the maximum applied stress decreased with stress cycles due to the debonding of the interface between the matrix and the particle. Fatigue damage could be evaluated by the phase stresses.