A defect-mediated finite strain model enabling mesh-independent simulation of ductile damage

A defect-mediated mesh-independent Continuum Damage Mechanics model is proposed to simulate ductile damage under large deformation. The principal contribution of the present work lies in extending the underlying defect-mediated theory to the finite-strain regime and developing its corresponding numerical implementation. The model is geometrically characteristic in the sense that the crystalline defects are categorised according to their geometric contributions to macroscopic deformation. Hence geometrically characteristic field variables can be assigned to represent the collective behaviour of deviatoric defects (underlying plasticity also at large deformation) and volumetric defects (underlying damage). Then plasticity and damage are considered to be carried out by the “reactions” between these geometrically characteristic defects. In particular, mobile volumetric defects, such as point defects, are singled out to catalyse damage evolution, since void growth here is attributed to vacancy absorption, and thermodynamics simply offers an effective tool to formulate the directions of such defect reactions. It is shown that the numerical scheme associated with the proposed model mitigates the pathological mesh dependence commonly encountered in local damage formulations and yields mesh-independent macroscopic responses in the examples examined. Scale-consistent responses are also observed for geometrically similar structures discretised by proportionally scaled meshes and subjected to correspondingly scaled displacement loading. Several numerical examples of large-deformation ductile damage in structural components are presented to demonstrate the distinctive features of the proposed model.