残余应力影响下的圆锥压入问题

Conical Indentation Under Residual Stress

利用有限元分析了材料在压痕过程中各变量,并计算了硬度HRC值,与在硬度试验中所测HRC值吻合,证实了有限元分析的正确性;在此基础上,分析了试件具有残余应力时的压入响应问题,研究了残余应力对圆锥压入响应的影响,探讨了压痕法测试残余应力所存在的问题。研究结果表明:残余拉、压应力以不同程度影响压入响应,压应力使圆锥压头处出现隆起量,而拉应力使其出现下沉量,该表现用于直观法预测残余应力;拉应力使压痕处塑性区域增加,压应力使塑性区域减少,在压痕法测量残余应力时,由于塑性区域事先的未知性而影响应变测试位置的确定,从而影响测量残余应力的准确性。

The finite element method is used to study indentation parameters under load, and calculate hardness. The calculated values agree well with the measurements, indicating effectiveness and reliability of the finite element analysis. Based on numerical simulation of a cone indenter, we analyze the indentation response of materials with varying residual stress, and the effect of residual stress on the indentation response. The problem arising from indentation for measuring residual stress is studied for the plastic region around indentation. The result shows that the residual stress affects indentation response in different degrees. Pile-up appears around the cone indenter due to compression stress, and sink-in appears due to tensile stress. These can be used to determine the residual stress by direct observation. Plastic region is clearly widened with tensile stress and narrowed with compression stress. The position for strain becomes uncertain in the indentation test due to unknown plastic region, which can affect the measuring results of residual stress.