Quasicontinuum simulation of fracture at the atomic scale
We study the problem of atomic scale fracture using the recently developed quasicontinuum method in which there is a systematic thinning of the atomic-level degrees of freedom in regions where they are not needed. Fracture is considered in two distinct settings. First, a study is made of cracks in single crystals, and second, we consider a crack advancing towards a grain boundary (GB) in its path. In the investigation of single crystal fracture, we evaluate the competition between simple cleavage and crack-tip dislocation emission. In addition, we examine the ability of analytic models to correctly predict fracture behaviour, and find that the existing analytical treatments are too restrictive in their treatment of nonlinearity near the crack tip. In the study of GB-crack interactions, we have found a number of interesting deformation mechanisms which attend the advance of the crack. These include the migration of the GB, the emission of dislocations from the GB, and deflection of the crack front along the GB itself. In each case, these mechanisms are rationalized on the basis of continuum mechanics arguments.
© 2004 IOP Publishing Ltd Received 23 March 1998, accepted for publication 14 June 1998, Print publication: Issue 5 (September 1998) We are grateful to C Briant, A Carlsson, R Clifton, B Freund, J R Rice, D Rodney, J Schiotz, and V B Shenoy for discussions, to S W Sloan for use of his Delaunay triangulation code and to M Daw and S Foiles for the use of their Dynamo code. We are also grateful to AFOSR who supported this work under grant No F49620-95-I-0264 and the NSF through grants CMS-9414648 and the Brown MRSEC DMR-9632524, the DOE through grant DE-FG02-95ER14561. RM thanks the NSERC for its support.