不同应变率下Q345钢材力学性能试验研究

Experimental study on dynamic mechanical behavior of Q345 steel under different strain rates

利用INSTRON拉伸试验机和Zwick/Roell HTM5020型高速拉伸试验机对Q345钢材进行准静态和高速拉伸试验.采用ANSYS中的LS-DYNA模块对不同加载速率下的拉伸试验进行仿真模拟,通过试验与仿真相结合的方式获得了钢材的真实应力应变曲线.仿真结果显示,Q345钢的真实应力应变关系在低应变率和高应变率下可分别近似用Ludwik模型和Voce模型描述.通过采用Hollomon准则和Voce准则的线性组合模型(H/V-R模型)对试验数据进行拟合,验证了H/V-R模型能比较准确地反映Q345钢的应变率效应,但和试验数据仍稍有偏差.为得到更优的经验型本构模型,将Wagoner的应变率准则引入H/V-R本构模型,进一步优化得到了可准确反映Q345应变率效应的H/V-R2经验型本构模型.

Quasi-static and dynamic tensile tests of Q345 steel were performed with INSTRON and Zwick/Roell HTM5020 testing machine. Simulations of these tensile tests under different strain rates were developed using LS-DYNA of ANSYS. And their true stress-strain relationships after necking were obtained through a hybrid experimental-numerical method. The simulation results show that the true stress-strain relationship of Q345 steel can be approximately described with Ludwik model at quasi-static strain rates and with Voce model at higher strain rates. The linear combination of Hollomon and Voce （H/V-R） model is adopted to fit the experimental data. The results show that the H/V-R model can predict the strain rate effects of Q345 steel although there is still a little deviation between the experimental and fitting results. To establish a better constitutive model, the Wagoner rate law is introduced into the H/V-R model. Then an empirical constitutive model H/V-R2 which can reflect the strain rate effect of Q345 steel accurately is finally obtained by further improvement.