A large deformation atomistic study examining crystal orientation effects on the stress - strain relationship

A large deformation atomistic study examining crystal orientation eects on the stress±strain relationship M.F. Horstemeyer *, M.I. Baskes, A. Godfrey, D.A. Hughes Center for Materials and Engineering Sciences, Sandia National Laboratories, Livermore, CA 94551-0969, USA Recieved in ®nal revised form 21 June 2000 Abstract We performed large deformation molecular dynamics calculations using the embedded atom method in order to examine yield and plastic ¯ow of single crystal nickel. A parametric study using an analysis of variance technique was used to eciently determine the in¯uence of the deformation path, temperature, size scale, strain rate, and crystal lattice orientation with respect to yield and the plastic energy. The analysis of variance study revealed that orientation had a primary in¯uence on the volume averaged shear stress, demonstrating the continued importance of slip within the crystal lattice for small sized metals and high applied strain rates. Consequently, other orientations were examined with a focus on averaged shear stress, axial stresses, and stress distributions. Results are presented for crystals oriented for single, double, quadruple, and octal slip, as well as a pseudopolycrystal. One last interesting point is that orientation eects on the stress-strain curves could be only approximately normalized by application of the Schmid factor. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: B. Finite strain; Molecular dynamics; Crystal orientation; A. Dislocations; A. Constitutive behavior 1. Introduction The stress state of a metal single crystal is dependent upon the crystallographic orientation, deformation path, temperature, applied strain rate, and size of specimen if it is at or below the micron range). Extensive experimental studies have shown that yield and plastic ¯ow exhibit a strong dependence on all of these parameters. For example, from the initial experiments of Ludwig and Scheu 1925), many researchers have shown that ductile metals experience a higher work hardening rate, International Journal of Plasticity 18 2002) 203±229 www.elsevier.com/locate/ijplas 0749-6419/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0749-641900)00076-0 *Corresponding author. Fax: +1-510-294-3410. E-mail address: [email protected] M.F. Horstemeyer).

A large deformation atomistic study examining crystal orientation effects on the stress - strain relationship

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crystallographic deformation

stress strain relationship

molecular dynamics

crystal orientation