(1. 中国工程物理研究院 总体工程研究所,绵阳 621999;
2. 中国科学院 材料力学行为和设计重点实验室 中国科学技术大学近代力学系,合肥 230027)
摘 要: 利用MTS、中应变材料试验机和分离式霍普金森拉杆获得TC11钛合金在应变率1×10-3~1×103 s-1范围内的应力-应变曲线,利用金相显微镜和扫描电子显微镜观察材料组织和断口形貌,基于修正的Johnson-Cook本构模型进行不同应变率下拉伸力学行为的有限元数值模拟。结果表明:TC11的初始屈服行为表现出明显的应变率强化特性,在中应变率范围内呈现出应变率不太敏感向应变率敏感的转折现象,材料的应变硬化率随着应变率的提高而逐渐降低。TC11的α晶和片层α+β束被拉长,呈现韧性断裂机制。修正Johnson-Cook模型计及应变率对初始屈服应力和应变硬化行为的不同影响,数值计算曲线与试验曲线吻合较好,能够较好地应用于TC11应变率相关力学行为的数值仿真。
关键字: 钛合金; 应变率; 本构模型
(1. Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621999, China;
2. CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China)
Abstract:The MTS809 machine, moderate strain-rate testing setup and the split hopkinson bar system were adopted to conduct uni-axial tension tests of TC11 at strain rates ranging from 1×10-3 s-1 to 1×103 s-1. The observation of microstructure and the fracture morphology was carried out via the optical microscope and SEM. A modified Johnson-Cook model was proposed to predict the mechanical behavior. Experimental results indicate that there is a positive strain-rate sensitivity with respect to the initial yield behavior. However, the transition of rate dependent sensitivity is presented at the moderate-rate loading conditions. The α grains and α+β colonies are stretched along the tension direction and break in a manner of ductile fracture. The modified Johnson-Cook constitutive model incorporates the different strain rate effects on the yield stress and strain hardening behavior. Excellent agreement between the experimental data and model predication indicates that such model is suitable for the rate-dependent numerical simulation of titanium alloy TC11.
Key words: titanium alloy; strain rate; constitutive model