a b s t r a c tA new technique for modeling cracks in quasi-brittle materials based on the use of interface solid finite elements is presented. This strategy named mesh fragmentation technique consists in introducing sets of standard low-order solid finite elements with a high aspect ratio in between regular (or bulk) elements of the mesh to fill the very thin gaps left by the mesh fragmentation procedure. The conception of this strategy is supported by the fact that, as the aspect ratio of a standard low-order solid finite element increases, the element strains also increase, approaching the same kinematics as the Continuum Strong Discontinuity Approach. As a consequence, the analyses can be performed integrally in the context of the continuum mechanics, and complex crack patterns can be simulated without the need of tracking algorithms. A tension damage constitutive relation between stresses and strains is proposed to describe crack formation and propagation. This constitutive model is integrated using an implicit-explicit integration scheme to avoid convergence drawbacks, commonly found in problems involving discontinuities. 2D and 3D numerical analyses are performed to show the applicability of the presented technique. Relevant aspects such as the influence of the thickness of the interface elements and mesh objectivity are investigated. The results show that the technique is able to predict satisfactorily the behavior of structural members involving different crack patterns, including multiple cracks, without significant mesh dependency provided that unstructured meshes are used.

No abstract

No abstract

No abstract

The study of drying process in soils has received an increased attention in the last few years. This is very complex phenomenon that generally leads to the formation and propagation of desiccation cracks in the soil mass. In recent engineering applications, high aspect ratio elements have proved to be well suited to tackle this type of problem using finite elements. However, the modeling of interfaces between materials with orthotropic properties that generally exist in this type of problem using standard (isotropic) constitutive model is very complex and challenging in terms of the mesh generation, leading to very fine meshes that are intensive CPU demanding. A novel orthotropic interface mechanical model based on damage mechanics and capable of dealing with interfaces between materials in which the strength depends on the direction of analysis is proposed in this paper. The complete mathematical formulation is presented together with the algorithm suggested for its numerical implementation. Some simple yet challenging synthetic benchmarks are analyzed to explore the model capabilities. Laboratory tests using different textures at the contact surface between materials were conducted to evaluate the strengths of the interface in different directions. These experiments were then used to validate the proposed model. Finally, the approach is applied to simulate an actual desiccation test involving an orthotropic contact surface. In all the application cases the performance of the model was very satisfactory.

No abstract

The modelling of fracture formation and propagation in geo-materials is a subject of interest in several problems and applications. In this work, finite elements with high aspect ratio are used to study the hydraulic fracture process in the context of conventional continuum constitutive (stress-strain) relationships based on the damage theory. The deformable porous material is solved in a coupled manner by considering a fully hydro-mechanical approach. The adopted approach is explained and validated against analytical and numerical solutions.

No abstract