A Micromorphic Damage-Plasticity Model to Counteract Mesh Dependence in Finite Element Simulations Involving Material Softening

摘要

A gradient-extended damage-plasticity material model is presented which belongs to the class of micromophic media as proposed by Forest (J Eng Mech 135:117-131, 2009) [17]. A 'two-surface' formulation is utilized in which damage and plasticity are treated as independent but strongly coupled dissipative phenomena. To this end, separate yield and damage criteria as well as loading/unloading conditions are introduced. The model is thermodynamically consistent and accounts for both nonlinear kinematic and isotropic hardening as well as damage hardening. Various theoretical and numerical aspects of the formulation are discussed. Emphasis is also put on a procedure to enforce stress constraints at the local integration point level which provides, for instance, the basis for a straightforward integration of 3D gradient-extended material models into beam or shell elements or for their usage in 2D plane stress computations. A structural example problem illustrates the merits of the model and its ability to deliver mesh-independent results in coupled damage-plasticity finite element simulations.