Browsing by Subject "microshear banding"

Now showing 1 - 1 of 1

Access status: Open Access ,
The thermodynamical theory of elasto-viscoplasticity accounting for microshear banding and induced anisotropy effects
(Wydawnictwa AGH, 2008) Perzyna, Piotr
The main objective of the present paper is the development of thermo-elasto-viscoplastic constitutive model of a material which takes into consideration induced anisotropy effects as well as observed contribution to strain rate effects generated by microshear banding. Physical foundations and experimental motivations for both induced anisotropy and microshear banding effects have been presented. The model is developed within the thermodynamic framework of the rate type covariance constitutive structure with a finite set of the internal state variables. A set of internal state variables consists of one scalar and two tensors, namely the equivalent inelastic deformation e/p the second order microdamage tensor [symbol] with the physical interpretation that ([formula]) defines the volume fraction porosity and the residual stress tensor (the backstress) alpha. The equivalent inelastic deformation [symbol] describes the dissipation effects generated by viscoplastic flow phenomena, the microdamage tensor [symbol] takes into account the anisotropic intrinsic microdamage mechanisms on internal dissipation and the back stress tensor alpha aims at the description of dissipation effects caused by the kinematic hardening. To describe suitably the influence of both induced anisotropy effects and the stress triaxiality observed experimentally the new kinetic equations for the microdamage tensor [symbol] and for the back stress tensor alpha are proposed. The relaxation time Tm is used as a regularization parameter. To describe the contribution to strain rate effects generated by microshear banding we propose to introduce certain scalar function which affects the relaxation time Tm in the viscoplastic flow rule. Fracture criterion based on the evolution of the anisotropic intrinsic microdamege is formulated. The fundamental features of the proposed constitutive theory have been carefully discussed. The purpose of the development of this theory is in future applications for the description of important problems in modem manufacturing processes, and particularly for meso-, micro-, and nano-mechanical issues. This description is needed for the investigation by using the numerical methods how to avoid unexpected plastic strain localization and localized fracture phenomena in new manufacturing technology.