Damage regularisation with inertia gradients

A gradient enhanced model is formulated which simulates micro-structurally induced wave dispersion and is capable of achieving mesh objective results when modelling strain-softening materials. Length scale parameters are introduced to incorporate both micro-inertial effects and strain smoothing. The model is formulated such that all the gradient enhancement terms are contained within the kinetic energy functional, whilst all non-linear terms are linked to the strain energy functional. In addition, discretisation of the governing equations is performed in a manner such that only C0C0-continuity is required and is symmetric in the elastic range. Dispersion analysis is performed to show the correct format that a constitutive model must conform to in order that regularisation of strain-softening material models will occur. This dispersion analysis is then used to explore how the two length scales may influence the width of the zone in which strain localisation takes place. The efficacy of the model in simulating strain-softening behaviour in a mesh objective manner and the effects of wave dispersion on damage initiation and accumulation are demonstrated in numerical examples.

► Gradient elasticity modelling of both regularisation of strain softening and wave dispersion in a single framework.
► Gradient enhancements are incorporated into the kinetic energy functional.
► A symmetric, positive definite system of equations can be achieved in the elastic range.
► Only C0-continuity is required for the spatial discretisation, thus greatly facilitating finite element implementations..