A new singular boundary element for crack problems: Application to bolted joints

The present paper is concerned with the effective numerical implementation of the two-dimensional Dual Boundary Element Method to analyse the mixed-mode crack growth in bolted joints. All the boundaries are discretized with discontinuous quadratic boundary elements and the crack-tip is modeled by singular elements that exactly represent the strain field singularity 1/. The Stress Identity Factors can be computed very accurately from the crack opening displacement at collocation points extremely close to the crack tip. Furthermore, the analysis of two-dimensional elastic contact problems is developed, with an iterative procedure. The contact equations are written explicitly with both transactions and displacements retained as unknowns. The computed results show that the proposed approach for Stress Intensity Factors evaluation is simple, produces very accurate solutions and has little dependence on the size of the elements near the crack tip. The algorithm is applied to several two-dimensional examples and the results obtained are in very good agreement with analytical solutions and experimental results carried out at the AEROSPATIALE Research Centre.