Evolution of Continuum from Elastic Deformation to Flow

TL;DR

This paper develops an evolution theory describing the transition of continuum deformation from elastic to flow, integrating elastic, plastic, and flow behaviors through explicit formulations based on polar and Chen decompositions.

Contribution

It introduces a unified formulation for deformation evolution from elastic to flow, clarifying strain definitions and the intrinsic relation among deformation parameters.

Findings

Plastic deformation as irreversible local rotation

Path-dependent feature of classical plasticity expressed via Chen strain

Flow motion can be described within the same formulation system

Abstract

Traditionally, the deformation of continuum is divided into elastic, plastic, and flow. For a large deformation with cracking, they are combined together. So, for complicated deformation, a formulation to express the evolution of deformation from elastic to flow will help to understand the intrinsic relation among the related parameters which relate the deformation with a stress field. To this purpose, Eringen polar decomposition and Trusedell polar decomposition are formulated by explicit formulation of displacement field, based on Chen additive decomposition of deformation gradient. Then the strain introduced by the multiplicative decomposition and the strain introduced by the additive decomposition are formulated explicitly with displacement gradient. This formulation clears the intrinsic contents of strains defined by taking the Eringen polar decomposition and Trusedell polar decomposition. After that, it shows that the plastic deformation can be expressed as the irreversible local average rotation. For initial isotropic simple elastic material, the path-dependent feature of classical plasticity theory is naturally expressed in Chen strain definition. It is founded that for initially isotropic material the motion equations require a non-symmetric stress for dynamic deformation and a symmetric stress for static deformation. This controversy between dynamic deformation and static deformation can be used to explain the cracking or buckling of solid continuum. Finally, the research shows that the flow motion of continuum can be expressed by the same formulation system. So, it forms an evolution theory from elastic deformation to flow of continuum.