连续球压痕试验检测金属材料应变硬化指数方法的修正

Correction of Detecting Method for Strain Hardening Exponent of Metallic Materials by Continuous Spherical Indentation Test

采用连续球压痕试验获取金属材料压入载荷-深度曲线,将该曲线计算转化为表征应力-应变数据并拟合即可得到应变硬化指数n;通过采用材料塑性拓展指数确定材料完全塑性变形区间,采用迭代算法对塑性约束因子进行修正以及考虑压痕堆积效应获得真实接触深度对连续球压痕试验测定n值方法进行修正。采用修正方法得到6061铝合金、6063铝合金、45钢、ST钢、AIF1合金、X52钢、X60钢、SK3钢等8种材料的n值,并与单轴拉伸试验结果进行对比。结果表明:未修正方法得到的n值与拉伸试验结果的相对误差均在10%以上,采用3种方法修正后相对误差减小,除X60钢的相对误差为8.6%外,其他均在5%以下。

Indentation load-depth curves of metallic materials were obtained by continuous spherical indentation tests. The curves were transformed into the representative stress-strain data by calculation, and then the data was fitted to obtain the strain hardening exponent n. The detecting method for n values by continuous spherical indentation tests was corrected by using the material plastic expansion index to determine the complete plastic deformation interval of the material, using the iterative algorithm to correct the plastic constraint factor, and considering the indentation accumulation effect to obtain the true contact depth. The correction method was used to calculate n values of eight materials including 6061 aluminum alloy, 6063 aluminum alloy, 45 steel, ST steel, AIF1 alloy, X52 steel, X60 steel and SK3 steel, and the obtained n values were compared with those by uniaxial tensile tests. The results show that the relative errors between the n values obtained by the uncorrected method and the tensile tests were more than 10%. After correction by the three methods, the relative errors were reduced;all were reduced to less than 5% except the relative error of X60 steel, that was 8.6%.