材料残余应力对硬度测试影响程度的分析

测试了材料在残余应力下的硬度，分析了残余应力影响下的弹塑性本构关系，并进行了有限元计算，实验结果和计算结果吻合程度较高，说明有限元分析正确，在此基础上，定性定量地分析了残余应力对于硬度的影响，建立了硬度与残余应力之间关系的拟合函数公式。研究结果表明：残余拉应力对硬度影响明显，而残余压应力对硬度影响较小；载荷大小和残余拉、压应力程度影响压痕周围弹塑性变形从而产生隆起量或下沉量，引起压痕深度、接触面积的变化，影响硬度测量值。

Influence of Residual Stress on Indentation Hardness

The hardness was tested for the materials with residual stress. The elastic plastic constitutive relation affected by residual stress was analyzed and hardness was calculated by finite element method(FEM). The FEM calculated hardness agrees well with measured hardness from the hardness testing. So the FEM result is reliable. Based on the finite element simulation, the influence of residual stress on hardness was studied to establish the quadratic polynomial fitting expression to describe the relationship between hardness and residual stress. The result shows that hardness is seriously affected by tensile stress, and lightly affected by compression stress. The pile up or sink in emerged around indentation depends on both magnitude of load and degree of compression/tensile residual stress because of the different elastic plastic deformation, which affect the indentation depth and contact area and have an influence on the hardness testing values.