Ti-6Al-4V在高应变率下的动态剪切特性及失效机理

采用基于霍普金森压杆的新型加载技术对Ti-6Al-4V材料的动态剪切特性及失效机理进行了测试研究。获得了Ti-6Al-4V材料在超过104 s-1应变率下的剪应力-剪应变曲线及失效参数。研究发现，材料的流动应力存在明显的应变率强化效应；随着应变率的增加，材料的失效应力逐渐增大，而失效应变逐渐减小。采用ABAQUS/Explicit对加载过程进行了数值模拟。结果显示，剪切区材料基本处于平面剪切状态，应力应变场分布较为均匀，计算得到的剪应力-剪应变曲线与实验结果吻合较好。经断口分析可知，随着应变率的升高，Ti-6Al-4V的失效机理存在由韧窝、拉伸韧窝至台阶及河流花样的演化过程，材料的失效模式主要表现为韧性断裂。

Dynamic shear behavior and failure mechanism of Ti-6Al-4V at high strain rates

Dynamic shear properties and failure mechanism of Ti-6Al-4V were studied at strain rates in excess of 104 s-1, with a new loading method based on the split Hopkinson pressure bar (SHPB) technique. The shear stress-shear strain curves and failure parameters of Ti-6Al-4V were acquired in a wide range of high shear strain rates. It is found that the flow stress of the material shows an obvious strain rate hardening effect. With the increase of strain rates, the failure stress of the material increases gradually, while the failure strain decreases. The loading process was modeled by ABAQUS/Explicit software. The results show that the shear zone material is substantially in the state of plane shear. The tested stress-strain curves have good agreement with the simulated results. The fracture surface examination shows that with the increase of strain rate, the failure of Ti-6Al-4V is closely related to the different behaviors of dimples, and it indicates an evolution process from dimples and tensile dimples to steps and river patterns. The fracture analyses show that the failure mode of the material is mainly ductile fracture.