A generic computational model for three-dimensional fracture and fragmentation problems of quasi-brittle materials

Abstract

Fracture and fragmentation in three dimensions are of great importance to understand the mechanical behaviour of quasi-brittle materials in failure stress states. In this paper, a generic computational model has been developed in an in-house C/C++ code using the combined finite-discrete element method, which is capable of modelling the entire three-dimensional fracturing process, including pre-peak hardening deformation, post-peak strain softening,

Numerical Model Study of Prototype Drop Tests on Cube and Cubipod® Concrete Armor Units Using the Combined Finite–Discrete Element Method

“…This work supports the contention that the risk of a major failure in situ and when handling and placing pieces is lower for Cubipod than for a conventional Cube of nearly the same size and made of the same concrete, for the same type of dynamic collision. The whole structural response of concrete armor units, which comprises multi-body interaction, rigid body motion, continuum deformation, fracture initiation and propagation, and post-fracturing interaction between discrete fracture surfaces and fragmented bodies, was accurately captured by three-dimensional numerical simulations in [14,30] and was repeated here to investigate drop test collisions.…”

“…Strain in the continuum domain will produce stresses in both the four-node and the six-node joint elements. In order to simulate the fracturing process clearly, the tetrahedral elements were allowed to separate according to a failure criterion applied to the joint elements [30]. The normal stress σ and the shear stress τ, corresponding to the normal displacement δ n and the shear displacement δ s between triangular surfaces N 1 N 2 N 3 and N 4 N 5 N 6 , respectively, were calculated according to the constitutive law presented in Figure 5.…”

“…Therefore, for normal stress σ, it means tensile strength f t , and, for shear stress τ, it means shear strength f s . A Mohr-Coulomb criterion with a tension cutoff was used to determine the shear strength on the basis of the normal stress acting perpendicular to the shear direction [14,30]. Fracture energy G f is a material property, which defines the energy needed for fracture surface to propagate per unit area, and it is the area under the graph (Figure 5).…”