Abstract
The present work demonstrates that the pencil glide mechanism is a physically reliable and a computationally efficient model to simulate the nonlinear behaviour of b.c.c. single and polycrystals. For that purpose, the pencil glide extension of Schmid’s criterion used by Gilormini [1] is incorporated in a single crystal model and in a homogenized polycrystal model accounting for large elastoviscoplastic deformations. The response of the pencil glide model in terms of stress-strain curves and lattice rotation is compared to the prediction based on the consideration of all ({110}〈111〉+{112}〈111〉) slip systems. In the case of α-iron single crystals both approaches are shown to accurately reproduce recent experimental results [2, 3]. The comparison is extended to α-iron polycrystals behaviour under tension, compression, rolling and simple shear loading conditions. The evolution of crystallographic textures obtained either based on pencil glide or using the 24 slip systems is analyzed and compared to classical experimental results from the literature. Limitations of the approach, especially in the case of simple shear textures, are also pointed out. The pencil glide approach can be viewed as a reduced order model enhancing computational efficiency of crystal plasticity simulations involving many slip mechanisms.
Highlights
Many crystals with b.c.c. structure exhibit a specific plastic behaviour at low temperature characterized by the difficulty of identifying the slip planes along which dislocations are gliding, whereas the slip direction is clearly defined
The homogenization β-model at large deformations has been used to predict the crystallographic textures of b.c.c. metals when accounting for 24 slip systems or when introducing the pencil glide mechanism instead
The effect was first analyzed in the case of single crystal behaviour including a detailed comparison with recent experimental results for α-iron
Summary
Many crystals with b.c.c. (body centered cubic) structure exhibit a specific plastic behaviour at low temperature characterized by the difficulty of identifying the slip planes along which dislocations are gliding, whereas the slip direction (given by the Burgers vector) is clearly defined. Hill [9], Mecking [10, 11], Kocks [12], van Houtte [13] and Arminjon [14, 15] have proposed several classes of polycrystal models allowing for non homogeneous stress and strain values between the various orientation classes of grains These models essentially lead to deformation textures in good agreement with measured ones. Depending on specific weighting parameters present in these models, they can account for the whole span of the solution domain between the lower and upper bounds Another class of non-homogeneous models which make use of the Eshelby theory to estimate the local tress and strain is the viscoplastic self-consistent scheme (VPSC) [16, 17]. The distribution of orientations, the pole figures and the ODF (Orientation Distribution Functions) maps are obtained by means of the ATEX software (http://www.atex-software.eu/)
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