3D study of plastic flow localization at a void-sheet

The notions of plastic flow localization are outlined in the paper. It is shown that each type of localized plasticity pattern corresponds to a definite stage of deformation hardening. In the course of plastic flow development, a changeover in the types of localization patterns occurs. The types of localization patterns are limited in number: four pattern types are all that can be expected. A correspondence was set up between the emergent localization pattern and the respective flow stage. It is found that the localization patterns are manifestations of the autowave nature of plastic flow localization process, with each pattern type corresponding to a definite mode of autowave. In the course of plastic flow development, the following modes of autowaves will form in the following sequence: switching autowave → phase autowave → stationary dissipative structure → collapse of the autowave. Of particular interest are the phase autowave and the respective pattern observed. Propagation velocity, dispersion, and grain size dependence of wavelength were determined experimentally for the phase autowave. An elastic-plastic strain invariant was also introduced to relate the elastic and plastic properties of the deforming medium. It is found that the autowave characteristics follow directly from this invariant.

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Effects of Crystallographic Texture on Plastic Flow Localization

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.340-341.211 ◽

2007 ◽

Vol 340-341 ◽

pp. 211-216

Author(s):

Mitsutoshi Kuroda

Keyword(s):

Shear Band ◽

Plane Strain ◽

Plastic Flow ◽

Texture Component ◽

Three Dimensional ◽

Cube Texture ◽

Shear Band Formation ◽

Flow Localization ◽

Band Formation ◽

Plastic Flow Localization

In this study, effects of typical texture components observed in rolled aluminum alloy sheets (i.e. Copper, Brass, S, Cube and Goss texture components) on plastic flow localization are studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain is characterized in terms of an elastic-viscoplastic continuum slip constitutive relation. First, forming limits of thin sheet set by sheet necking are predicted using a Marciniak–Kuczynski (M–K-) type approach. It is shown that only the Cube texture component yields forming limits higher than that for a random texture in the biaxial stretch range. Next, three-dimensional shear band analyses are performed, using a three-dimensional version of M–K-type model, but the overall deformation mode is restricted to a plane strain state. From this simple model analysis, two important quantities regarding shear band formation are obtained: i.e. the critical strain at the onset of shear banding and the corresponding orientation of shear band. It is concluded that the Cube texture component is said to be a shear band free texture, while some texture components exhibit significantly low resistance to shear band formation. Finally, shear band developments in plane strain pure bending of sheet specimens with the typical textures are studied.

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