Z.L. Liu

Atomistic simulations of tension properties for bi-crystal copper with twist grain boundary

Molecular dynamics simulation using an EAM potential to explore the tension response for a nanowire with a twist grain boundary (GB) is presented in this paper. The relationship between the GB strength and the interface dislocation structure is discussed. For a low angle twist GB, partial dislocations nucleate from the screw dislocation at the GB before yielding and the interface yields at the point when the dislocation networks lose their stability. For a high angle twist GB, the interface yields at the point when the whole interface structure is disturbed and partial dislocations propagate into the grain after the yielding point. In addition, the study provides an insight into the understanding of the atomic mechanism for tension localization at the GB, which is obvious for the high angle twist GB, but indistinct for the low angle twist GB. The results presented may have obvious implications for the nanowire test.

Analytical and Numerical Investigations of Two Special Classes of Generalized Continuum Media

In this paper, the micromorphic theory and the second gradient theory are proposed-where the micromorphic model can be reduced to the second gradient model with the vanishing relative deformation between macrodeformation gradient and microdeformation. Analytical solutions for the simple shear problem in the case of a general small strain isotropic elasticity micromorphic model and the second gradient model are presented, respectively. Besides, uniaxial tension of a constrained layer with two different boundary conditions is also analytically solved. Finally, the micromorphic theory is implemented numerically within a two-dimensional plane strain finite element framework by developing two isoparametric elements.