Fully automatic modelling of mixed-mode crack propagation using scaled boundary finite element method

Mixed-mode fracture of concrete is encountered frequently in design of concrete structures. To accurately analyzed and design a concrete structure, it is essential to understand the failure mechanisms of concrete under mixed-mode types of loading. A model, which was originally proposed for mode I failure of concrete, is extended to characterized mixed-mode crack propagation. Crack initiation angles, final failure path, and crack instability of concrete specimens/structures are discussed. A series of mixed-mode notched beam tests were performed to verify the proposed model. The theoretical predictions were found to be in good agreement with the experimental results.

Mixed-mode fracture of concrete

An interactive approach to local remeshing around a propagating crack

Bridging crack model for fracture of spruce

Modeling of crack propagation via an automatic adaptive mesh refinement based on modified superconvergent patch recovery technique

This paper attempts to answer two commonly raised questions during the preparation of a finite element mesh, for the linear elastic fracture analysis of cracked structure: how to set up the finite element mesh around the crack tip, and what level of accuracy is to be expected from such a modelling.



Two test problems, with known analytical expressions for their stress intensity factors, are analysed by the finite element method using the isoparametric quadratic singular element. The modified parameters were the order of integration, aspect ratio, number of elements surrounding the crack tip, use of transition elements, the singular element length over the total crack length, the symmetry of the mesh around the crack tip. Based on these analyses, a data base is created and various plots produced. The results are interpreted, the accuracy evaluated and recommendations drawn.



Contrary to previous reports, it is found that the computed stress intensity factor (SIF) remains within engineering accuracy (10 per cent) throughout a large range of l/a (singular element length over crack length) for problems with a uniform non-singular stress distribution ahead of the crack tip (i.e. double edge notch), and l/a should be less than 0·1 for problems with a non-singular stress gradient (i.e three-point bend). Also, it is found that the best results are achieved by using at least four singular elements around the crack tip, with their internal angles around 45 degrees, and a reduced (2 × 2) numerical integration.

David Schwemmer

Papers

Numerical evaluation of the quarter‐point crack tip element