Strain localization and fracture in isotropic damaging materials: a novel augmented-finite element strategy

CRACK PROPAGATION IN FINITE ELEMENTS AUGMENTED WITH EMBEDDED INTERPHASES

In the FE analysis of quasi-brittle materials, one of the main issues is how to correctly capture cracks propagation. In particular, under specific load intensity, strains progressively localize in narrow bands, leading to a global nonlinear softening response until collapse. A variety of FE models have been proposed, which may be separated in two main groups: discrete crack models and continuous models. Discrete crack models introduce a discontinuity along the inter-element boundaries or inside elements (intra-element discontinuity). Continuous models modify the constitutive relations of the local material to better describe its behaviour in presence of a fracture. In the framework of intr…

Strain localization and crack propagation in finite elements augmented with embedded interphases

Many engineering problems present the need to model discontinuities that arise when materials are outside their elastic limit. In quasi-brittle materials strains progressively localize in narrow bands, usually leaving elastic the surrounding bulk material. In the framework of FE models, considerable progresses have been done in order to correctly model strain localization and damage propagation; they could be mainly divided into two groups: discrete crack models and smeared crack models. In the ambit of discrete crack models, we propose a computational methodology which is based on the Augmented-Finite Element Method (A-FEM) [1]. Our formulation consists in the implementation of an intra-el…

Finite elements with embedded interphases for strain localization in quasi-brittle materials

The paper presents a continuous-discontinuous numerical strategy for sim- ulating localized failure in structures made of quasi-brittle materials using finite elements. The strategy is based on observing acting stresses scenarios, when a diffuse degradation is followed by high deformation bands localizing in certain regions of the structure. The numerical strategy should encom- pass both situations in accordance with the material’s constitutive model. This objective is achieved by introducing a thin layer into a finite element at a certain level of the deformation process. In this study, the thin layer is modeled for the first time by an interphase mechanical device whose consti- tutive beh…

Finite elements augmented with embedded interphases for application in quasi-brittle materials

Quasi-brittle materials mainly fail under shear or tensile stress state. When the stress limit is reached, fractures propagate and the stress-strain relation exhibits a softening branch until failure. In the framework of finite elements, discrete crack models and continuous smeared crack models have been implemented to best capture material’s response. In this ambit, we propose a strategy based on the Augmented Finite Element Method (A-FEM, [1]), which can be placed among the discrete crack models, since intra-element weak discontinuity is considered and modelled through a zero-thickness interphase model (IPH, [2, 3]). The original element is in practice divided in two elastic sub-elements …