Delay-active damage versus non-local enhancement for anisotropic damage dynamics computations with alternated loading

Abstract

International audienceAnisotropic damage thermodynamics framework allows to model the concrete-like mate- rials behavior and in particular their dissymmetric tension/compression response. To deal with dynamics applications such as impact, it is furthermore necessary to take into account the strain rate effect observed experimentally. This is done in the present work by means of anisotropic visco-damage, by introducing a material strain rate effect in the cases of posi- tive hydrostatic stresses only. The proposed delay-damage law assumes no viscous effect in compression as the consideration of inertia effects proves sufficient to model the apparent material strength increase. High-rate dynamics applications imply to deal with wave prop- agation and reflection which can generate alternated loading in the impacted structure. In order to do so, the key concept of active damage is defined and introduced within both the damage criterion and the delay-damage evolution law. At the structural level, strain localization often leads to spurious mesh dependency. Three-dimensional Finite Element computations of dynamic tensile tests by spalling are presented, with visco-damage and either without or with non-local enhancement. Delay- damage, as introduced, regularizes the solution in fast dynamics. The location of the macro-crack initiated is found influenced by non-local regularization. The strain rate range in which each enhancement, delay-damage or non-local enhancement, has a regularizing effect is studied

A microstructurally-based internal length for strain localization problems in dynamics

“…Most of the time, this delay effect in the material behavior is incorporated through phenomenological models (Desmorat et al, 2010;Sluys and De Borst, 1992;Wang et al, 1996;Glema et al, 2000;Graff et al, 2004;Pedersen et al, 2008). Those different models permit a regularization of the strain localization problem.…”

A fixed directions damage model for composite materials dedicated to hyperbaric type IV hydrogen storage vessel – Part I: Model formulation and identification

“…The order of this characteristic time is much smaller than the viscous characteristic time mentioned in the previous paragraph. However, a dependence on the strain rate is introduced [33]. The introduction of a regularized damage variable is a possible way to avoid convergence problems.…”

On structural computations until fracture based on an anisotropic and unilateral damage theory

“…The calculation of softening models such as those defined in ''The case of softening damage'' section over a domain goes through a critical point where a loss of ellipticity, i.e., a loss of uniqueness of the solution (Needleman, 1988;Peerlings et al, 1998;Pijaudier-Cabot and Benallal, 1993) occurs and leads to pathological mesh dependencies (Desmorat et al, 2010;Ladeve`ze et al, 2000). Several remedies exist for damage models, including nonlocal formulations (Desmorat et al, 2010; The delay-effect method First, in order to have a damage variable with an order of magnitude of 1, let us rewrite eqs.…”

“…Peerlings et al, 1998;Pijaudier-Cabot and Benallal, 1993;Voyiadjis et al, 2004) and delay-effect approaches(Desmorat et al, 2010;Kerfriden et al, 2009;Ladeve`ze et al, 2000). The latter was chosen for our work because it is a local method, which is easy to implement in FE codes such as Abaqus/Standard.…”