An efficient constitutive model for room-temperature,low-rate plasticity of annealed Mg AZ31B sheet |
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Authors: | M. Li X.Y. Lou J.H. Kim R.H. Wagoner |
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Affiliation: | 1. Simulia Central Region, 1440 Innovation Place, W. Lafayette, IN 47906-1000, USA;2. School of Materials Science & Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Room 288, Atlanta, GA 30332, USA;3. Department of Materials Science and Engineering, The Ohio State University, 477 Watts Hall, 2041 College Road, Columbus, OH, 43210, USA |
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Abstract: | Metals and alloys with hexagonal close packed (HCP) crystal structures can undergo twinning in addition to dislocation slip when loaded mechanically. The complexity of the plastic response and the limited extent of twinning are impediments to their room-temperature formability and thus their widespread adoption. In order to exploit the unusual deformation characteristics of twinning sheet materials in designing novel forming operations, a practical plane stress material model for finite element implementation was sought. Such a model, TWINLAW, has been constructed based on three phenomenological deformation modes for Mg AZ31B: S (slip), T (twinning), and U (untwinning). The modes correspond to three testing regimes: initial in-plane tension (from the annealed state), initial in-plane compression, and in-plane tension following compression, respectively. A von Mises yield surface with initial non-zero back stress was employed to account for plastic yielding asymmetry, with evolution according to a novel isotropic and nonlinear kinematic hardening model. Texture and its evolution were represented throughout deformation using a weighted discrete probability density function of c-axis orientations. The orientation of c-axes evolves with twinning or untwinning using explicit rules incorporated in the model. |
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Keywords: | Magnesium alloy Constitutive modeling Texture Slip Twinning |
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