PhD Numerical scheme for modelling plastic slip on the micro scale


Department of Mechanical Engineering
Date off
31-05-2010
Reference number
V35.1023
The Department of Mechanical Engineering considers as the core of its activities design, realization and analysis of new products, processes and materials. Besides the basis of (solid and fluid) mechanics, materials, control and thermodynamics, parts of mathematics, physics, chemistry and computing science are important supporting tools. The field is explored by a combination of modeling using fundamental concepts and applied engineering and technology. Automotive Engineering Science and Micro- & Nano-Scale Engineering are important departmental themes. The Mechanical Engineering Department comprises about 1000 students and 250 staff members.
The section Numerical Methods in Engineering focuses on the development and implementation of computational methods for engineering applications in solid and fluid mechanics. The group has a strong reputation in the development of advanced numerical techniques, such as novel discretisation methods and robust solution algorithms for solving large systems.

For a wide range of crystalline solids, room temperature plastic deformation occurs as a consequence of the collective motion of dislocations gliding on specific slip planes. The mobility of dislocations is what gives rise to plastic flow at stress levels relatively low compared to the theoretical strength. In continuum plasticity, this slip is “smeared” out with the effect of individual dislocations ignored: such descriptions predict no size dependence of plastic deformation. The importance of size effects in Materials Engineering is increasing due to the development of new materials (e.g. Nanostructured alloys) and devices (e.g. MEMS) with characteristic length scales in the range 10nm to10µm. Existing continuum descriptions fail to predict a size-dependent response, and are thus unsuitable for application in these emerging fields.

Since the late 1980’s considerable activity has been directed at representing plastic flow in terms of the dynamics of large numbers of interacting dislocations, with the dislocations represented as line singularities in an elastic solid. This framework naturally accounts for both the stress enhancement due to organized dislocation structures and the stress relaxation arising from dislocation glide. Unfortunately, this discrete dislocation plasticity framework has been restricted to infinitesimal deformations; both the effect of lattice reorientation on dislocation glide and the effect of geometry changes on the momentum balance have been neglected.

Tasks
The main aim of the project is to develop the fundamental numerical methodologies for solving finite strain discrete dislocation plasticity problems. This is a numerically challenging task involving large-scale incompatible deformations. The outcome of the project has the potential to provide significant inputs to the development of new continuum crystal plasticity models and can be used to simulate plastic deformations on a microscopic scale in which the finite strain size effects play a key role, e.g. crack tip blunting.
Requirements
We are seeking a candidate interested in advanced finite element techniques. The candidate should be recently graduated from a MSc. program in mechanical engineering, civil engineering, applied mathematics or a related field, with;

  • Knowledge and experience in computational mechanics and/or mathematics;
  • Knowledge of material science, in particular metals;
  • Affinity for multidisciplinary research, engineering science;
  • Experience with finite element programming;
  • Capacity to write and communicate fluently in English.
Appointment and salary




We offer:
  • A challenging job at a dynamic and ambitious University
  • An appointment for four years
  • Biannual meeting with partners from the industry interested in the research topic.
  • Gross monthly salaries are in accordance with the Collective Labor Agreement of the Dutch Universities (CAO NU), increasing from Euro 2042 per month initially, to Euro 2612 in the fourth year.
  • An attractive package of fringe benefits (including excellent work facilities, child care and sport facilities)
Information






The project will be supervised by :