Evaluation of nonlocal approaches for modelling fracture near nonconvex boundaries

TL;DR

This study evaluates various nonlocal damage models with different boundary averaging procedures for fracture simulation near nonconvex boundaries, calibrated against mesoscale analyses, and compares their performance in 2D bending tests.

Contribution

It introduces and compares multiple nonlocal averaging procedures for fracture modelling near complex boundaries, calibrated with mesoscale analysis results.

Findings

Nonlocal models can accurately predict fracture near nonconvex boundaries.

Different averaging procedures vary in effectiveness depending on boundary type.

Elastoplasticity combined with nonlocal damage offers an alternative modeling approach.

Abstract

Integral-type nonlocal damage models describe the fracture process zones by regular strain profiles insensitive to the size of finite elements, which is achieved by incorporating weighted spatial averages of certain state variables into the stress-strain equations. However, there is no consensus yet how the influence of boundaries should be taken into account by the averaging procedures. In the present study, nonlocal damage models with different averaging procedures are applied to the modelling of fracture in specimens with various boundary types. Firstly, the nonlocal models are calibrated by fitting load-displacement curves and dissipated energy profiles for direct tension to the results of mesoscale analyses performed using a discrete model. These analyses are set up so that the results are independent of boundaries. Then, the models are applied to two-dimensional simulations of three-point bending tests with a sharp notch, a V-type notch, and a smooth boundary without a notch. The performance of the nonlocal approaches in modelling of fracture near nonconvex boundaries is evaluated by comparison of load-displacement curves and dissipated energy profiles along the beam ligament with the results of meso-scale simulations. As an alternative approach, elastoplasticity combined with nonlocal or over-nonlocal damage is also included in the comparative study.