基于应变率阶跃测试的晶体铜压入应变率敏感性研究

纳米压入测试可以原位获取材料的诸多力学性能,包括弹性模量,硬度,屈服应力,应变率敏感指数等。本文利用应变率阶跃测试技术对多晶铜试样的应变率敏感性进行测试分析,硬度-位移曲线表明压头下方所存在的变形梯度对各阶跃应变率下的硬度值存在明显影响;采用基于晶体细观机制的塑性应变梯度理论对压入变形梯度效应予以修正,比较了修正与未修正数据所得的应变率敏感指数,在有效剔除压入变形梯度影响的基础上,应变率阶跃测试可实现单次压入下材料应变率敏感性的测试表征。

Research on the strain rate sensitivity of crystal copper indentation based on strain-rate-step tests

Some mechanical properties of materials,such as elastic modulus,hardness,yield strength,and strain rate sensitivity,can be in-situ obtained by nano-indentation tests.In this work,indentation strain-rate-step tests are carried out to examine the strain rate sensitivity of polycrystalline copper samples.Hardness-indentation depth curves show that the deformation gradient underneath indenter has significant influence on the hardness values at each step of strain rate.The plastic strain gradient theory based on crystal mesoscopic mechanism is adopted to modify the indentation deformation gradient effect.The strain rate sensitivity index obtained from the modified and unmodified experimental data are compared.It is shown that strain-rate-step tests can be used to characterize the strain rate sensitivity of materials under a single indentation test on the basis of effectively removing the influence of indentation deformation gradient.