The analytical method is used to study micro-plasticity indentation and the increment equation is worked out by analyzing the contacted nodes between rigid indenter with material. Then the experiment under various maximum loads (50mN, 100mN, 200mN, 300mN, 400mN, 500mN and650mN) at the constant loading speed 9.6841mN/s is carried out on MCT-W501 micro-indentation tester and the constitutive equation of AISI1045 steel is obtained by Taylor equation. The experimental result shows great indentation size effects, so the intrinsic material length is introduced to accurately simulate the micro-indentation plasticity changes. Based on ABAQUS analyzing software, the equation obtained by experiment is input to simulate the loading curve between indentation load and indentation depth considering the effect of strain gradient. The result shows that the square of hardness relative value has a linear decrease with the increase of indentation diagonal. Based on the result of simulation and calculation, the final constitutive equation is proposed and the data of modified equation is quite coordinate with experimental and calculated data with relative error less than 4.92% thus the constitutive equation is verified.
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