Interaction of a transonic dislocation with subsonic dislocation and point defect clusters S.Q. Shi * , Hanchen Huang, C.H. Woo Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China Accepted 1 June 2001 Abstract The moving speeds of all observed dislocations in crystals are subsonic. There has been a view in the literature that the speed of subsonic dislocations can not be accelerated above the speed of sound because the energy required would be infinitely large. Recent molecular dynamics (MD) simulation had shown that it is possible to generate dislocations with an initial moving speed higher than the velocity of sound in solids. This raises a question: what will happen when a supersonic dislocation meets other defects along its moving path? This work reports the results of MD simulation on the interaction of a transonic dislocation with other subsonic dislocations as well as with point defect clusters. The results show that a vacancy cluster such as a void has an insignificant slow-down effect on the transonic dislocation, while a subsonic dislocation slows down the transonic dislocation to subsonic one. In some cases, the subsonic dis- location (or a subsonic part of a transonic dislocation) can overcome the traditional sound barrier. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Transonic dislocation; Molecular dynamics; Simulation; Mechanics 1. Introduction Recently, there is a renewed interest in high velocity dislocations [1–3]. A ‘‘relativistic’’ treat- ment of a moving screw dislocation was given 50 years ago by Frank [4] by means of a Lorentz transformation to the elastic shear wave equation, in which it was shown that the strain field of a high velocity dislocation contracts in the direction of motion and both the energy and stress become infinite as the velocity of the dislocation ðvÞ ap- proaches the transverse acoustic wave velocity ðc t Þ. Similar conclusions were also found for edge dis- locations. These solutions have led to a view that c t is the limiting speed for moving dislocations. It was recognized early that this type of treatments may not be appropriate for high velocity dis- locations because the linear elastic assumption is violated in these circumstances. Theoretical solu- tions for both transonic ðv > c t Þ and supersonic ðv > longitudinal wave velocity c l Þ motions of dis- locations were suggested [5–7], although the ex- perimental evidence is still missing up to today. Recent atomistic simulations [2] showed that the Computational Materials Science 23 (2002) 95–104 www.elsevier.com/locate/commatsci * Corresponding author. E-mail address: mmsqshi@polyu.edu.hk (S.Q. Shi). 0927-0256/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0927-0256(01)00227-0