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Nguyen A.D.,Institute of General Mechanics | Stoffel M.,Institute of General Mechanics | Weichert D.,Institute of General Mechanics
Advanced Structured Materials | Year: 2011

A finite element model of non-local damage viscoplasticity for dynamic analysis of thin-walled shell structures is presented. To take void nucleation and growth into account, a non-local implicit gradient formulation is employed. The free energy function includes both a non-local damage variable on the mid-surface of shell structures and a local one in shell space. Local constitutive laws considering viscoplastic behavior, isotropic hardening and isotropic ductile damage leading to softening are used. The performance of the proposed approach is demonstrated through the numerical simulation of shock-wave loaded structures. © Springer-Verlag Berlin Heidelberg 2011. Source


Nguyen A.D.,Institute of General Mechanics | Stoffel M.,Institute of General Mechanics | Weichert D.,Institute of General Mechanics
European Journal of Mechanics, A/Solids | Year: 2010

Based on the static theory of strain-gradient viscoplasticity proposed by Anand et al. (2005), a one-dimensional dynamic analysis is derived for finite element computation of isotropic hardening materials. The kinetic energy is assumed to be composed of the conventional and internal kinetic energy. The internal energy is described phenomenologically in terms of the equivalent plastic strain in order to capture the heterogeneity of plastic flow. Herein the microscopic density is assumed to be related to the macroscopic one through a microscopic-inertia parameter. The macroscopic-force balance and microscopic-force balance including inertia effects are derived. The performance of the proposed formulation is illustrated through the numerical simulation of a one-dimensional dynamic problem. A parameter study to find the microscopic-inertia parameter is carried out. At last, suitable microscopic boundary conditions and dynamic effects are discussed through comparison with the conventional plasticity. © 2010 Elsevier Masson SAS. All rights reserved. Source


Nguyen A.D.,Institute of General Mechanics | Stoffel M.,Institute of General Mechanics | Weichert D.,Institute of General Mechanics
Computer Methods in Applied Mechanics and Engineering | Year: 2012

A finite element model of gradient-enhanced damage viscoplasticity for dynamic analysis of thin-walled shell structures is proposed. To take void nucleation and growth into account, the free-energy function is enhanced by introducing a non-local damage term, which is defined in terms of a new non-local variable and a local damage parameter. Local constitutive laws considering viscoplastic behavior, isotropic hardening and isotropic ductile damage leading to softening are used. The performance of the proposed model is demonstrated through numerical simulations of several examples including shock-wave loaded plates. © 2012 Elsevier B.V. Source

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