不同应力比下Cu/WCp复合材料疲劳裂纹扩展行为及影响机制分析

通过粉末冶金工艺制备了一种高压电触头用Cu/WCp颗粒增强复合材料。研究了不同应力比下Cu/WCp颗粒增强复合材料的疲劳裂纹扩展行为,并结合裂纹闭合模型和两参数驱动力模型分析了应力比对Cu/WCp颗粒增强复合材料疲劳裂纹扩展速率的影响机制。研究结果表明:随着应力比R的增大裂纹扩展速率增大,尤其在近门槛值附近裂纹扩展速率差别最明显。裂纹闭合模型和两参数驱动力模型均可以较好地将不同应力比R下(da/d N-ΔK)关系曲线关联起来,且两参数驱动力模型的相关性更好。这说明导致不同应力比R下Cu/WCp颗粒增强复合材料疲劳裂纹扩展速率差异的原因主要是Kmax引起裂纹尖端单调损伤,其次是裂纹闭合效应。根据SEM断口分析发现高应力比的断面较低应力比的粗糙,低应力比时断口以基体撕裂为主而高应力比时以颗粒基体脱粘为主。

The Growth Behavior of Fatigue Crack and Mechanism Analysis of Cu/WCp Composites Under Different Stress Ratio

The high voltage electrical contact Cu/WCp particles reinforced composite material was prepared by powder metallurgy process.The growth behavior of fatigue crack was studied under different stress ratios.The influe-nce mechanism of stress ratio on growth rate of fatigue crack was studied by combining the crack closure model and the two parameter driving force model.Results showed that the crack growth rate increased with the increase of the stress ratio,especially in the near threshold region.The crack closure model and the two parameter driving force mo-del could effectively relate the (da/dN-ΔK)relationship curve under different stress ratios,and the correlation of the two parameters driving force model was better.It indicated that the reason for the difference of fatigue crack growth rate under different stress ratio was the crack tip monotonic damage caused by Kmax and the next was the degree of crack closure.Through the analysis of fracture surface morphology by SEM,the fracture could be found to be rough at high stress ratio.The fracture surface was dominated by the matrix tearing under low stress ratio and matrix particle debonding under high stress ratio.