Hopkinson压杆反射拉伸下PMMA动态破坏现象实验研究

利用Hopkinson压杆系统对PMMA变截面柱锥试样进行冲击加载，研究材料动态拉伸断裂特性和破坏机理。由于PMMA的拉压强度差别不大，采用圆柱状试件难以产生反射拉伸破坏，因此，将试样设计为圆柱锥状，实验时，将试样的圆柱端粘贴于输入杆上。实验结果表明，在一定的撞击速度下，由于应力波的汇聚作用，在试样锥段产生了反射拉伸破坏；当撞击速度较高时，在产生反射拉伸破坏的同时，试件中还产生了银纹区，随着打击速度的提高，银纹区域增大。同时根据断口的SEM观察，研究了材料的破坏机制。

Experimental Investigation on the Dynamic Failure Phenomena of PMMA Under the Loading of Hopkinson Pressure bar

The dynamic fracture and fracture mechanism of PMMA is experimentally studied through Hopkinson Pressure Bar System. The cylinder-cone specimen of PMMA is impacted by the input bar which is impacted by projectile at different velocity. Due to the convergence of the stress wave, the dynamic fracture of the specimen occurs after the stress wave reflects from the free end. The experiments show that when the impact velocity is not high, the dynamic tension fracture appears in the specimen. When the impact velocity is high enough, the dynamic fracture occurs , the craze zone comes into being simultaneously and the dimension of the craze zone increases with an increase of the impact velocity. Failure mechanism of the PMMA is investigated according to SEM.