Journal of the Mechanics and Physics of Solids 50 (2002) 783–807 www.elsevier.com/locate/jmps A theoretical investigation of the inuence of dislocation sheets on evolution of yield surfaces in single-phase B.C.C. polycrystals Bart Peeters a ; ∗ , Surya R. Kalidindi b , Cristian Teodosiu c , Paul Van Houtte a , Etienne Aernoudt a a Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium b Department of Materials Engineering, Drexel University, Philadelphia, PA 19104, USA c LPMTM-CNRS, Universit e Paris Nord F-93430 Villetaneuse, France Received 18 January 2001; received in revised form 1 June 2001; accepted 1 June 2001 Abstract Accurate and reliable predictions of yield surfaces and their evolution with deformation re- quire a better physical representation of the important sources of anisotropy in the material. Until recently, the most physical approach employed in the current literature has been the use of polycrystalline deformation models, where it is assumed that crystallographic texture is the main contributor to the overall anisotropy. However, recent studies have revealed that the grain-scale mesostructural features (e.g. cell-block boundaries) may have a large impact on the anisotropic stress–strain behaviour, as evidenced during strain-path change tests (e.g. cross eect, Bauschinger eect). In previous papers, the authors formulated an extension of the Taylor-type crystal plasticity model by incorporating some details of the grain-scale mesostructural features. The main pur- pose of this paper is to study the evolution of yield surfaces in single-phase b.c.c. polycrystals during deformation and strain-path changes using this extended crystal plasticity model. It is demonstrated that the contribution of the grain-scale substructure in these metals on yield loci is comparable in magnitude to the eects caused by the dierences in texture. Furthermore, it is shown that the shape of yield loci cannot be predicted accurately by the traditional poly- crystalline deformation model with equal slip hardening. The trends predicted by the extended crystal plasticity model are in much better agreement with the experimental evidence reported in the literature than those represented in classical treatments by isotropic and kinematic hardening. ? 2002 Elsevier Science Ltd. All rights reserved. Keywords: Plastic anisotropy; A. Microstructure; Texture; Yield surfaces; Changing strain paths ∗ Corresponding author. Tel.: +32-16-32-17-80; fax: +32-16-32-19-90. E-mail address: bart.peeters@mtm.kuleuven.ac.be (B. Peeters). 0022-5096/02/$-see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII:S0022-5096(01)00094-1