Stephan Wulfinghoff
Karlsruhe Institute of Technology
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Featured researches published by Stephan Wulfinghoff.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | 2012
Stephan Wulfinghoff; Thomas Böhlke
We propose a visco-plastic strain gradient plasticity theory for single crystals. The gradient enhancement is based on an equivalent plastic strain measure. Two physically equivalent variational settings for the problem are discussed: a direct formulation and an alternative version with an additional micromorphic-like field variable, which is coupled to the equivalent plastic strain by a Lagrange multiplier. The alternative formulation implies a significant reduction of nodal degrees of freedom. The local algorithm and element stiffness matrices of the finite-element discretization are discussed. Numerical examples illustrate the advantages of the alternative formulation in three-dimensional simulations of oligo-crystals. By means of the suggested formulation, complex boundary value problems of the proposed plastic strain gradient theory can be solved numerically very efficiently.
arXiv: Computational Physics | 2015
Eric Bayerschen; Markus Stricker; Stephan Wulfinghoff; D. Weygand; Thomas Böhlke
The gradient crystal plasticity framework of Wulfinghoff et al. (Wulfinghoff et al. 2013 Int. J. Plasticity 51, 33–46. (doi:10.1016/j.ijplas.2013.07.001)), incorporating an equivalent plastic strain γeq and grain boundary (GB) yielding, is extended with GB hardening. By comparison to averaged results from many discrete dislocation dynamics (DDD) simulations of an aluminium-type tricrystal under tensile loading, the new hardening parameter of the continuum model is calibrated. Although the GBs in the discrete simulations are impenetrable, an infinite GB yield strength, corresponding to microhard GB conditions, is not applicable in the continuum model. A combination of a finite GB yield strength with an isotropic bulk Voce hardening relation alone also fails to model the plastic strain profiles obtained by DDD. Instead, a finite GB yield strength in combination with GB hardening depending on the equivalent plastic strain at the GBs is shown to give a better agreement to DDD results. The differences in the plastic strain profiles obtained in DDD simulations by using different orientations of the central grain could not be captured. This indicates that the misorientation-dependent elastic interaction of dislocations reaching over the GBs should also be included in the continuum model.
International Journal of Plasticity | 2013
Stephan Wulfinghoff; Eric Bayerschen; Thomas Böhlke
Journal of The Mechanics and Physics of Solids | 2015
Stephan Wulfinghoff; Samuel Forest; Thomas Böhlke
International Journal of Plasticity | 2015
Stephan Wulfinghoff; Thomas Böhlke
Gamm-mitteilungen | 2013
Stephan Wulfinghoff; Thomas Böhlke
Acta Materialia | 2015
M. Ziemann; Ying Chen; Stephan Wulfinghoff; Christoph Kirchlechner; Nobumichi Tamura; Thomas Böhlke; Michael H. Walter; Patric A. Gruber
Pamm | 2013
Stephan Wulfinghoff; Eric Bayerschen; Thomas Böhlke
Pamm | 2014
Stephan Wulfinghoff; Eric Bayerschen; Thomas Böhlke
Pamm | 2014
Eric Bayerschen; Stephan Wulfinghoff; Thomas Böhlke