Numerical modelling of rock materials with polygonal finite elements

This article presents some preliminary results on numerical modeling of rock ma-terials with polygonal finite elements. A method to describe the rock microstructure based onVoronoi diagrams, representing the rock grain texture, is sketched. In this method, the mineralsconstituting the rock are represented as Voronoi cells which themselves are polygonal finite ele-ments. A three-point bending problem under plane stress linear elasticity condition is solved inorder to compare the performance of polygonal elements to ordinary finite elements. Moreover,it is demonstrated by solving the stress state in uni-axial compression that the heterogeneitydescribed with the present method results in short-range tensile stresses which could initiatemode-I cracks.

Voronoi Polygonal Hybrid Finite Elements with Boundary Integrals for Plane Isotropic Elastic Problems

Polygonal finite elements with high level of geometric isotropy provide greater flexibility in mesh generation and material science involving topology change in material phase. In this study, a hybrid finite element model based on polygonal mesh is constructed by centroidal Voronoi tessellation for two-dimensional isotropic elastic problems and then is formulated with element boundary integrals only. For the present [Formula: see text]-sided polygonal finite element, two independent fields are introduced: (i) displacement and stress fields inside the element; (ii) frame displacement field along the element boundary. The interior fields are approximated by fundamental solutions so that they exactly satisfy the governing equations to convert element domain integral in the two-field functional into element boundary integrals to reduce integration dimension. While the frame displacement field is approximated by the conventional shape functions to satisfy the conformity requirement between adjacent elements. The two independent fields are coupled by the weak functional to form the stiffness equation. This hybrid formulation enables the construction of [Formula: see text]-sided polygons and extends the potential applications of finite elements to convex polygons of arbitrary order. Finally, five examples including patch tests in square domain, thick cylinder under internal pressure, beam bending and composite with clustered holes are provided to illustrate convergence, accuracy and capability of the present Voronoi polygonal finite elements.