200 / 2019-08-25 00:01:15

Molecular dynamics simulations on shock response and spalling behaviors of semi-coherent {111} Cu-Al multilayers

metallic multilayer; shock response; spalling behavior; molecular dynamics simulation

计算力学新方法，新理论 > 微纳米尺度理论与计算

Shock response and spalling behaviors of semi-coherent {111} Cu-Al multilayer are investigated by molecular dynamics simulations. Firstly, the influences of interfaces on shock wave propagation are studied. The simulations show that reflection-unloading happens when the shock wave propagates from Cu to Al and reflection-loading occurs when the shock wave propagates from Al to Cu. Strong discontinuities of stress components at the interfaces are revealed as well, the discontinuities are correlated to mismatches of Hugoniot curves and elastic-plastic properties of the two materials adjacent to the interfaces. Secondly, shock induced dislocation activities are studied. It is found that slip transmissions of lattice dislocations across the interfaces are direction-dependent. A lattice dislocation can transmit more smoothly across an interface from Cu to Al than from Al to Cu. This direction-dependent feature is attributed to different contributions of the coherent stress at distinct interfaces. In addition, spalling fracture of Cu-Al multilayers after stress wave reflection at the free surface is studied. It is observed that ductile damage only nucleates in Al phase near the interfaces while the Cu layers are free of damage. Due to complex reflection and transmission of the stress waves at the interfaces, the profile of the free surface velocity histories of the multilayer target is quite different from that of the single-crystalline counterpart. The simulations reveal an interesting phenomenon that an incipient damage zone is re-healed in latter stages due to complex stress wave interactions. Moreover, analysis on thermal dissipation in the spalling damage zones is also provided in this paper.