基于纳米压痕实验拟合表面纳米化AZ91D镁合金弹塑性本构关系

Establish of Elastoplastic Constitutive Relation of AZ91D Mg Alloy Based on Nano-indentation Tests

为研究AZ91D镁合金的力学行为,采用纳米压痕技术,测得随深度连续变化的载荷-位移曲线;根据Olive算法,利用接触刚度连续测量(CSM)技术,分别得到AZ91D镁合金纳米层和基体的硬度和弹性模量。建立二维有限元模型,考虑Berkovich压头和样品之间存在摩擦,对Antunes提出的反分析法进行优化,通过正向分析(纳米压痕实验)和反向分析(数值模拟)的对比,得到特征应力、特征应变、应变强化因子,继而确定初始屈服应力,得到表面纳米化后AZ91D镁合金纳米层和基体的弹塑性幂函数本构关系。

The nano-indentation tests were taken to study the mechanical properties of AZ91D Mg alloy,the continuous variation curves of load-displacement were measured;according to the Olive algorithm,continuous stiffness technology were used to get hardness and modulus of nano layer and matrix of AZ91D Mg alloy.Two-dimensional finite element model was established,and the friction coefficient between sample and Berkovich indenter was considered.The inverse analysis method proposed by Antunes was optimized.The results of positive analysis（nano-indentation tests） and inverse analysis（numerical simulation） was compared,from which,the value of representative stress,representative strain,strain-hardening exponent and the value of initial yield stress were determined;the elastic-plastic constitutive model was established.