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以工业纯铝L2为研究对象就微压痕试验过程中保压阶段的尺度效应进行研究。研究发现微压痕试验过程中有保压台阶的瞬间形成,即在达到最大载荷后的保压段,虽然载荷不变,但压入深度却在增加,保压平台的出现和保压时间的关联性不大。随后通过采用带内禀长度微塑性本构方程的有限元模拟,并引入折合材料内禀长度,将模拟结果与相同保压时间、不同载荷压痕试验过程中的尺度效应进行对比分析,并解释了微纳米压痕试验保压平台的反常规律,获得反映材料尺度效应的内禀长度为5.09μm,以及反映微纳米压痕保压阶段尺度效应的材料折合内禀长度为4.90μm,研究表明:保压平台的产生来源于保压阶段应变梯度的减小,相当于几何必需位错密度降低到保压前的96.27%,这种保压平台的形成机理和微纳米压痕试验过程中的几何尺度效应与载荷尺度效应有关。
The industrial pure aluminum L2 was used as the research object to study the scale effect of the pressure-holding stage during the micro-indentation test. It is found that there is an instantaneous moment during the micro-indentation test to maintain the pressure-relief step, that is, the pressure-holding step after the maximum load is reached. Although the load remains constant, the indentation depth increases while the occurrence of the pressure- Little relevance. Then by using the finite element method with intrinsic length of micro-plastic constitutive equation and introducing the intrinsic length of the equivalent material, the simulation results are compared with the scale effect during the same indentation test and different load indentation tests, and the explanation is made The anomalous law of pressure-holding platform of micro-nanoindentation test, the intrinsic length of 5.09μm, which reflects the scale effect of material, and the equivalent intrinsic length of material which reflects the scale effect of micro-nano indentation and pressure-holding stage are 4.90μm. The results show that: The generation of the pressure-holding platform comes from the decrease of the strain gradient during the dwell phase, corresponding to 96.27% of the geometric necessary dislocation density reduced to the pre-dwell level. The formation mechanism of this dwell platform and the geometry of the micro-nanoindentation test Scale effect and load scale effect.