Multiple slip in continuum dislocation dynamics: dislocation reactison, cross slip and the formation of dislocation sources

• Applicant: Professor Dr.-Ing. Thomas Hochrainer
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257050271

The use of ever more miniaturized parts and devices and the increasing demand for high precision engineering recently brought the fundamentals of crystal plasticity again in the focus of applied science. Especially on small scales this revealed some shortcomings of classical continuum concepts of crystal plasticity. The current proposer was centrally involved in the development of the so-called continuum dislocation dynamics theory. This theory was originally developed in a higher dimensional configuration space, which contains the dislocation line-direction as independent variable. Yet there are recent systematic approaches how to derive theories without extra dimensions from the original approach. Although these theories are in principle applicable to general dislocation configurations, the actually worked out examples are as yet essentially restricted to single glide. Applications involving multiple slip were so far only modeled as a superposition of single glide.This project aims at incorporating effects of dislocation interactions during multiple slip into the continuum dislocation theory. We want to develop concepts how to consider dislocation reactions, cross slip and dislocation multiplication in the evolution of the density based description of the dislocation state. Emphasis is put on the interaction of dislocation belonging to different glide systems. As intermediate goals we identify (i) the modeling of dislocation (super) jogs and their effect on the dynamics, (ii) the modeling of dislocation reactions (Lomer lock, Hirth lock, collinear reaction) and their effect on the dynamics and (iii) the coupling of immobilized dislocation segments in reaction products or jogs on the multiplication of dislocations and the formation of dislocation sources. Closely related to the concepts needed for the collinear reaction discussed under point (ii) we also aim at incorporating cross slip into the current theory.The focus of the current project lies on the basics mathematical, that is essentially kinematical, description. We expect that this will already feature important geometric aspects of a dynamic theory. However, the actual physical dynamics, expressed in obstacle strengths, dissolving of dislocation reactions and the activation stress of dislocation sources will be tackled in the envisaged prolongation of the current project.

• DFG Programme: Research Grants