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Plastic irreversibility in cyclic loading with strain gradients

Wednesday (26.09.2018)
15:30 - 15:45 S1/01 - A4
Part of:

In microspecimens the dislocation microstructure evolution under fatigue loading is unusual: Bending experiments with single crystalline microbeams show the development of slip traces on the surfaces which are generated by dislocations leaving the specimen [1]. Under load, the dislocations are pushed in and over the neutral plane of the gradient and stabilized in a pile-up [2]. Upon unloading, the geometrically necessary dislocations disappear, but the dissolution path of the pile-up and the reason for associated permanent plastic deformation is less clear. By using Discrete Dislocation Dynamics simulations it is shown that the explanation for the formation of a slip trace during unloading and the almost dislocation free sample is an asymmetry between the backward and forward motion due to the mutual dislocation interaction [3]. Additionally, the imperfect geometry (e.g. taper) of the sample can introduce a bias due to the geometrically imposed change in length of dislocations during glide [3]. Based on this mechanism, the specimen can fail without storage of dislocations.

Dr.-Ing. Markus Stricker
École Polytechnique Fédérale de Lausanne EPFL
Additional Authors:
  • Dr. Daniel Weygand
    Karlsruhe Institute of Technology (KIT)
  • Prof. Dr. Peter Gumbsch
    Karlsruhe Institute of Technology (KIT)