基于分子动力学的多晶石墨烯拉伸力学性能的应变率相关性

Effects of tensile strain rate on mechanical properties of polycrystalline graphene based on molecular dynamics

应变率是材料力学性能和变形机制的重要影响因素.利用维诺图理论,创建了不同晶粒尺寸的多晶石墨烯模型;利用分子动力学(MD)法,研究了不同拉伸应变率下多晶石墨烯的弹性模量、拉伸强度、极限应变等与拉伸应变率之间的关系.结果表明,多晶石墨烯的拉伸强度随拉伸应变率的增大而呈线性增大的趋势.对同一应变率而言,拉伸强度随晶粒尺寸的增大而增大,但对拉伸应变率的敏感度呈减小趋势.随拉伸应变率的增大,弹性模量呈增大趋势,但其受影响程度取决于应变率与阈值的关系.随着拉伸应变率的增大,极限应变呈增大趋势.对同一应变率而言,随晶粒尺寸的减小,极限应变呈增大趋势.研究结果对明确拉伸应变率与多晶石墨烯拉伸力学性能之间的相关性具有一定的参考价值和意义.

Strain rate is an important influence factor on the mechanical properties and deformation mechanism of materials. In the present paper, the polycrystalline graphene model of different grain size is built up using the theory of Voronoi diagram. Moreover, based on molecular dynamics （MD） numerical simulation, the effects of tensile strain rate on Youngrs elastic modulus, ultimate stress and ultimate strain are analyzed. The results indicate that, with the increase of tensile strain rate, tensile strength shows an increase trend. For the same strain rate, tensile strength increases with the increase of grain size, but the strain rate sensitivity shows a decrease trend. Elastic modulus increases with the increase of strain rate. However, the influence extent of strain rate on elastic modulus depends on the relationship between the strain rate and the threshold value. With the increase of tensile strain rate, ultimate strain shows an increase trend. For the same strain rate, tensile strength increases with the decrease of grain size. The research results can offer reference about the correlation between tensile strain rate and the tensile mechanical properties of polycrystalline graphene,