冲击波作用下铝的准弹性卸载行为

根据一维应变冲击波的基本关系,将Cochran等定义的有效剪切模量与准弹性卸载过程的纵波和体波声速关联起来,并藉此研究了冲击波作用下铝的准弹性卸载特性.利用VISAR高压声速测量技术获得了LY12铝在20～100 GPa压力下沿着准弹性卸载过程的有效剪切模量,结果表明LY12铝的有效剪切模量随卸载应力的下降而迅速下降.采用与卸载应力成线性关系的方程对有效剪切模量进行了近似描述,该方程的斜率随初始冲击压力的增加而增加,体现了准弹性卸载行为的压力相关性.将有效剪切模量结果与准静态实验结果进行了比较,由此分析了冲击波作用下准弹性卸载过程的可能物理机制.应用有效剪切模量方程对6061铝合金的准弹性行为进行了模拟,计算结果与实验结果符合很好.

QUASI-ELASTIC RELEASE BEHAVIOR IN SHOCK-LOADED ALUMINUM

Based on the intrinsic relations under uniaxial strain conditions, the effective shear modulus defined by Cochran and Guinan was correlated to the longitudinal and bulk sound velocities, and used to study the quasi-elastic behavior of LY12 Al. Unloading wave profile measurements using VISAR technique were performed on LY12 Al over the shock stress ranging from 20 to 100 GPa from which sound velocities and the effective shear modulus along the quasielastic release path were evaluated. Results show that the effective shear modulus decreases rapidly with the release stress and can be approximated by a linear function of release stress. The slopes of the linear function increase with the initial shock-loading stress which is implied that the quasi-elastic behaviors are depended on the shock-loading stress. By using the linear function of effective shear modulus, the performed numerical simulations well reproduce the release wave traces of the Al-alloys reported in the literature. The effective shear modulus in the present study is compared with that obtained from quasi-static experiments and the possible micromechanisms of quasi-elastic release behavior in shock-loaded materials are also discussed.