Dislocation simulation of brittle-ductile transition in ferritic steels

Abstract

Two-dimensional discrete dislocation simulations of the crack-tip plasticity of a macrocrack-microcrack system representing the fracture behavior in ferritic steels are presented. The crack-tip plastic zones are represented as arrays of discrete dislocations emitted from crack-tip sources and equilibrated against the friction stress. The dislocation arrays modify the elastic field of the crack; the resulting field describes the elastoplastic crack field. The simulated crack system involves a microcrack in the plastic zone of the macrocrack (elastoplastic stress field). The effects of the crack-tip blunting of the macrocrack are included in the simulations; as dislocations are emitted, the microcrack is kept at a constant distance from the blunted tip of the macrocrack. The brittle-ductile transition (BDT) curve is obtained by simulating the fracture toughness at various temperatures. A consideration of the effects of blunting is found to be critical in predicting the sharp upturn of the BDT curve. The obtained results are compared with existing experimental data and are found to be in reasonable agreement.

Experimental and Discrete Dislocation Dynamics Approach to Initiation of Cleavage Fracture under Short Pulse Loads

“…Noronha (7)- (9) extensively investigated cleavage fracture from a microscopic crack existing on a crack line using a discrete dislocation dynamic model. In these studies, a two-dimensional coupling model in which a microscopic crack is located in the plastic zone ahead of a macroscopic crack is utilized.…”

Brittle–ductile transition in F82H and effects of irradiation

“…However, the variation of the dislocation mobility with temperature alone cannot explain the BDT behavior of microstructurally complex materials, like steels [5]. Recently, we introduced a discrete dislocation simulation model in which the effects of crack-tip blunting are incorporated by using elastic stress fields of blunted cracks [6]. Here, we extend our model to the case where …”

Brittle – ductile transition and scatter in fracture toughness of ferritic steels

“…However, the variation of dislocation mobility alone cannot explain the BDT behavior of microstructurally complex materials like steels [4]. Recently we introduced a discrete dislocation simulation model in which the effects of blunting are incorporated by using elastic stress fields of blunted cracks which captures the increase in fracture toughness around the transition temperature [5]. Here we analyse the model to study the observed scatter in the measured fracture toughness values around the ductile-brtittle transition temperature (DBTT).…”