Simulating time-dependent quasi-brittle failures based on a multilinear releasing mechanism of viscous force (VF) fields

Abstract

The time-dependent progressive failures in heterogeneous brittle materials are modeled by considering the temporal stress redistribution mechanism due to local breakages. The influence of local breakages lies in two kinds of stress redistributions: (1) Internal forces in the breaking element are assumed to release infinitely fast when compared with external loadings, and the corresponding viscoelastic deformation of the specimen happens in a finite speed. This deformation delay is implemented by introducing a VF field all over the specimen. (2) Then the gradual release of VF fields stored previously follows, resulting in the viscous recovery of the entire specimen, which is approximated as a multilinear process. The main characteristic of the present algorithm is its linearity, i.e. no nonlinear iterations are included. Numerical results of uniaxial tensile/compressive, anchor bolt pull-out and Brazilian tests show that the proposed model is capable of overcoming the over-brittle issue in existing lattice models and capturing the strain rate sensitivity, which agree well with experimental observations.