非一维应变冲击加载下高纯铜初始层裂行为

提出了一种锥形靶层裂实验新方法,开展非一维应变冲击条件下高纯铜初始层裂行为实验研究,讨论了锥形靶内部损伤分布特征及其与自由面速度典型特征之间的内禀关系.结果显示:1)初始层裂的锥形靶内部出现了连续损伤区,损伤区扩展方向与锥面平行,从锥底到锥顶呈现了不同的损伤状态,从微孔洞独立长大到局部聚集,最后形成宏观裂纹,这种损伤状态分布特征归因于锥形靶内部拉伸应力幅值和持续时间的空间演化;2)通过锥形靶横截面损伤度定量统计分析,揭示损伤演化早期的微孔洞成核与早期长大过程是随机的,而损伤演化后期的微孔洞聚集过程具有显著的局域化特征;3)不同位置处实测的自由面法向粒子速度剖面呈现出典型的层裂Pull-back信号,但是通过与内部损伤分布特征对比,揭示基于Pull-back速度获得高纯铜层裂强度本质是微孔洞成核阈值应力,Pull-back回跳速度斜率反映了损伤演化速率,Pull-back回跳幅值与损伤度引起的应力松弛密切相关.

Incipient spallation of high purity copper under non-one-dimensional strain shock waves

A new spallation experimental method by using conical target is proposed.Based on the analysis of wave propagation,the basic principle of spallation experiment of conical target is discussed.Then incipient spallation of high purity(HP)copper under non-one-dimensional strain shock wave is studied experimentally by using a gas gun setup.The damage distribution characteristics and micro-mechanism of conical HP copper target are analyzed.The intrinsic relationship between the characteristics of free surface velocity profiles and damage evolution is explored.The results indicate that 1)continuous damage zones including different damage states appear in the conical HP copper target with initial spallation from the bottom of cone to the top of cone along the direction parallel to the cone surface,which is attributed to the spatial evolution of the amplitude and duration time of tensile stress in the conical target;2)quantitative statistical analysis of damage inside conical HP copper target reveals that the nucleation and early growth of micro-voids are random,while the coalescence of micro-voids has significant localization characteristics;3)the normal free surface particle velocity profiles with typical pull-back spallation signals at different locations of conical HP copper target are measured by multi-channel photon Doppler velocimetry.Comparing with the damage distribution characteristics,it is revealed that the spallation strength based on pull-back velocity is independent of damage,and is the critical nucleation stress of micro-voids.But the slope and amplitude of pull-back rebound velocity depend on damage evolution process,which relates to the change of damage evolution rate and stress relaxation caused by damage degree respectively.