激光冲击强化TC4钛合金强化层弹塑性本构参数反演分析  

Reverse Analysis of Elasto-plastic Constitutive Parameters of Strengthening Layer for Laser Shock Processing TC4 Titanium Alloys

作　　者：王淑娜 伏培林 李嘉伟 张旭[1] 阚前华[1] WANG Shu-na;FU Pei-lin;LI Jia-wei;ZHANG Xu;KAN Qian-hua(Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province,School of Mechanics and Aerospace Engineering,Southwest Jiaotong University,Chengdu 611756,China)

机构地区：[1]西南交通大学力学与航空航天学院应用力学与结构安全四川省重点试验室,成都611756

出　　处：《表面技术》2023年第10期411-421,共11页Surface Technology

基　　金：国家自然科学基金(12072295,12192214,11872321)。

摘　　要：目的 获取TC4钛合金激光冲击强化层的弹塑性本构模型参数,结合纳米压痕试验和有限元模拟技术,进行激光冲击强化TC4钛合金的材料参数反演计算。方法 首先,在TC4钛合金试样侧面沿强化层深度方向进行纳米压痕测试,获得距表面不同距离处的载荷-压入深度曲线。进而,基于幂律应变硬化模型,通过无量纲方程和有限元模拟反演得到激光冲击强化TC4钛合金梯度强化层的弹塑性参数。最后,将反演获得的弹塑性本构模型材料参数用于有限元模拟,将模拟结果与试验结果进行对比,验证参数反演结果的合理性。结果 强化层表面的弹性模量和纳米硬度较母材分别提高了11%和30%,强化层内的应变硬化指数和屈服强度沿深度方向分别递增和递减。模拟的载荷-压入深度曲线与试验曲线吻合较好,最大压入载荷、弹性模量和纳米硬度的模拟误差分别小于1%、7%和3%,证实了参数反演结果的合理性。结论 通过无量纲方程反演算法得到的强化层本构参数有较强的可信度。激光冲击强化可有效提升TC4钛合金的表面力学性能,强化层的本构参数呈梯度分布,表面的抗塑性变形能力大幅提升。Laser shock processing(LSP) can form a strengthening layer with a gradient structure on the surface of parts,and thus improves the fatigue life.It is of great significance to obtain the elasto-plastic parameters of TC4 titanium alloy after LSP for the fatigue life prediction.However,there are few reports on the determination of elasto-plastic parameters of LSP TC4titanium alloy.The reverse algorithm combining the nano-indentation experiments with finite element simulation is an effective method to obtain the constitutive parameters of the thin strengthening layer.Therefore,employing the nano-indentation experiments and finite element simulation,the reverse analysis of the LSP TC4 titanium alloy was conducted to determine the elasto-plastic parameters.First,the nano-indentation experiments of the LSP TC4 titanium alloy specimen were carried out based on the Nano indenter G200 nano-indentation experimental apparatus with the Berkovich diamond indenter,and the indentation depth of 1 000 nm was set by the displacement-controlled method.Then the nano-indentation experiments were carried out on a single side of specimen along the depth direction of the strengthening layer,and the corresponding load-displacement curves at different distances from the surface were obtained.Subsequently,the distributions of elastic modulus and nano-hardness along the depth direction of the strengthening layer were obtained after using the Oliver-Pharr method to determine the unloading stiffness and the reduced modulus from the unloading curves.Then,following the power-law strain hardening assumption,the yield stress and strain hardening index of the surface strengthening layer were determined by numerically solvingthe dimensionless equations of the representative stress,the ratio of plastic work to total work,and the ratio of residual depth to pressing depth,respectively.Therefore,the elasto-plastic parameters of the surface strengthening layer of LSP TC4 titanium alloy were obtained.Finally,the elasto-plastic parameters obtained by the r

关 键 词：TC4钛合金 激光冲击强化 纳米压痕 无量纲分析 反演分析 有限元模拟 

分 类 号：TG146.23[一般工业技术—材料科学与工程]