单晶镍纳米薄膜单向拉伸破坏的分子动力学模拟

Molecular dynamics simulation for failure process of monocrystalline nickel film under tensile stress

应用分子动力学方法模拟了单晶镍纳米薄膜受单向拉伸破坏的过程,得出纳米尺度单晶镍薄膜的应力—应变关系、能量演化曲线和镍薄膜构型的变化及微损伤的形成和扩展过程。模拟采用原子镶嵌势描述原子间作用,得到镍单晶薄膜的弹性模量,分析了拉伸过程中系统原子能量、应力变化和外荷载的关系。结果表明:纳米薄膜的自由表面影响拉伸过程中原子的运动和薄膜整体力学性能,纳米薄膜破坏的几何特征是原子空位的连接和晶胞缺陷的扩展;单晶的断裂接近脆性断裂,模拟得到纳米薄膜的断裂强度符合Griffith脆性断裂的能量平衡理论。

The failure process of monocrystalline nickel film under tensile stress was simulated with molecular dynamics method. The evolvement of atomic energy and arrangement of atoms in the model, the initiation and expansion of damage and the elastic modulus of monocrystalline nickel were obtained. Simulation results show that the free surfaces of single crystal take effect on the motion of atoms and mechanical properties of nano crystal. Atomic cavities and the growth of crack in crystal lead to the failure of nano film. The fracture of single crystal is similar to macro brittle rupture, and the fracture strength of the film can be explained well by Griffith's theory of rupture.