Eduardo Alberto de Souza Neto

Modelling of hydro-fracture flow in porous media

Purpose – The mechanical response of the skeleton of a porous medium is highly dependent on its seepage behaviour as pore pressure modifications affect the in situ stress field. The purpose of this paper is to describe how u‐p formulation is employed using an explicit time integration scheme where fully saturated and single‐phase partially saturated analyse are incorporated for 2D and 3D cases.Design/methodology/approach – Owing to their inherent simplicity, low‐order elements provide an excellent framework in which contact conditions coupled with crack propagation can be dealt with in an effective manner. For linear elements this implies single point integration which, however, can result in spurious zero‐energy modes which necessitates introduction of a stabilization technique to provide reliable results.Findings – The success of the modelling strategy ultimately depends on the inter‐dependence of different phenomena. The linking between the displacements components, network and pore pressures represent...

Yield surfaces of heterogeneous media with debonded inclusions

Purpose – The purpose of this paper is to present knowledge in estimating yield surfaces of heterogeneous media by use of homogenization, especially where the macroscopic behaviour is driven by weak interfaces between phase constituents. Design/methodology/approach – A computational homogenization procedure is used to determine the yield surface of a Representative Volume Element (RVE) that contains a fully debonded inclusion embedded within ideally plastic matrix, whereby the interface is modelled by a Coulomb type friction law. Findings – The macroscopic behaviour of the RVE is shown to coincide an RVE with a hole for expanding loads, whereas for compressive loads, it was shown to approach an RVE with a fully bonded inclusion. Originality/value – The present paper builds on Gurson’s work in estimating macroscopic yield surfaces of heterogeneous materials. The work is novel in the sense that there had been no previous publications discussing influence of weak interfaces on yield surfaces.

Advances in Computational Plasticity

Physiological and pathological aspects of soft biological tissues in terms of, e.g., aortic dissection, aneurysmatic and atherosclerotic rupture, tears in tendons and ligaments are of significant concern in medical science. The past few decades have witnessed noticeable advances in the fundamental understanding of the mechanics of soft biological tissues. Furthermore, computational biomechanics, with an ever-increasing number of publications, has now become a third pillar of investigation, next to theory and experiment. In the present chapter we provide a brief review of some constitutive frameworks and related computational models with the potential to predict the clinically relevant phenomena of rupture of soft biological tissues. Accordingly, Euler-Lagrange equations are presented in regard to a recently developed crack phase-field method (CPFM) for soft tissues. The theoretical framework is supplemented by some recently documented numerical results, with a focus on evolving failure surfaces that are predicted by a range of different failure criteria. A peel test of arterial tissue is analyzed using the crack phase-field approach. Subsequently, discontinuous models of tissue rupture are described, namely the cohesive zone model (CZM) and the extended finite element method (XFEM). Traction-separation laws used to determine the crack growth are described, together with the kinematic and numerical foundations. Simulation of a peel test of arterial tissue is then presented for both the CZM and the XFEM. Finally we provide a critical discussion and overview of some open problems and possible improvements of the computational modeling concepts for soft tissue rupture. Submitted as a Book chapter dedicated to Prof. D.R.J. Owen. O. Gültekin · G.A. Holzapfel (B) Institute of Biomechanics, Graz University of Technology, Stremayrgasse 16/II, 8010 Graz, Austria e-mail: holzapfel@tugraz.at G.A. Holzapfel Faculty of Engineering Science and Technology, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

Fully Coupled Three-Scale Finite Element Model for the Mechanical Response of a New Bio-Inspired Composite

This paper proposes a fully coupled three-scale finite element model for the mechanical description of an alumina/magnesium alloy/epoxy composite inspired in the mechanics and architecture of wood cellulose fibres. The constitutive response of the composite (the large scale continuum) is described by means of a representative volume element (RVE, corresponding to the intermediate scale) in which the fibre is represented as a periodic alternation of alumina and magnesium alloy fractions. Furthermore, at a lower scale the overall constitutive behavior of the alumina/magnesium alloy fibre is modelled as a single material defined by a large number of RVEs (the smallest material scale) at the Gauss point (intermediate) level. Numerical material tests show that the choice of the volume fraction of alumina based on those volume fractions of crystalline cellulose found in wood cells results in a maximisation of toughness in the present bio-inspired composite.Copyright