Molecular dynamics study of relationship between shear stress and velocity of dislocation for discrete dislocation dynamics
Nakatani Akihiro; Kitagawa Hiroshi; Nakatani Keiko
Abstract:Recently the discrete dislocation dynamics (DDD) methods have been applied to the problems of mesoscopic phenomena. In the DDD simulations, it is very important to know how a dislocation moves in the stress field. The relationship between the velocity of dislocation and external shear stress is often given artificially by referring to the experimental information or experience of researchers. Most of the relationships obtained are, however, qualitative and involve a lot of complex factors which depend on the experimental condition; temperature, grain boundary effect and so on. In this paper, the dynamic properties of edge dislocation whose Burgers' vector b is [111] /2 on 112 plane in bcc iron are studied by molecular dynamics (MD) using N body potential proposed by Finnis and Sinclair. Then, the relationship between the velocity v of dislocation and external shear stress t is investigated systematically. It is shown in our simulation that the relationship between v and t is linear in the low stress region and v becomes close to sound velocity asymptotically in the high stress region. These results agree with the experimental results qualitatively. An experimental expression of v - t relation for the DDD simulation is also proposed. Key Words:computational mechanics, molecular dynamics, discrete dislocation dynamics, dislocation shear stress