Abstract It is well known that boundary integral equations are exact mathematical representations of the governing differential equations of a boundary value problem when the integrals are written over a closed-shape boundary representation (B-representation) of the domain, usually reffered to as a watertight B-representation. However, practical geometric design technics (namely, NURBS surfaces) often do not render a watertight B-representation. Non-watertight geometric models with small gaps and overlaps are often generated in the design stage of projects. Based on a proposed surface-independent discretization approach, the present study investigates how unsought gaps affect the response of boundary element models of linear elasticity problems. The developed surface-independent discretization is applied to discretize multiple-patches NURBS B-representation geometries. Linear triangular and quadrilateral elements are adopted to discretize the independent surfaces. Generalized discontinuous elements at the edges of the visible areas of the NURBS parametric spaces are detected by a Level Set function. An offset collocation strategy is adopted for the nodes at the edges of the visible part of the parametric spaces. Thus, singularities and near singularities due to collocation are avoided in the BEM equations. The influence of gaps in the convergence of the L2-norm of boundary displacement error is verified in a 3D example with an available analytical solution. A second example with available numerical solution is analyzed with a non-watertight BEM discretization for qualitative boundary field validation. Finally, a non-watertight B-representation geometry of a crane hook is analyzed. The obtained results have pointed out that, as long as the gaps (and overlaps) are small enough, BEM models built up from non-watertight geometries may produce valuable solutions for practical purposes. closedshape closed shape Brepresentation B (B-representation domain Brepresentation. representation. However namely, namely (namely surfaces Nonwatertight Non projects surfaceindependent surface approach problems multiplepatches multiple patches function Thus L2norm Lnorm L2 norm L D nonwatertight non validation Finally enough purposes

Abstract This work presents an extension of the displacement fitting technique for the assessment of stress intensity factors (SIFs) of three-dimensional linear elastic fracture problems using the dual Boundary Element Method. The developed framework accounts for higher-order terms of the asymptotic displacement solution near crack front. The number and location of points surrounding the crack front are properly defined in order to accurately evaluate the SIFs. Three-dimensional benchmarks demonstrate the efficiency of the proposed framework. Moreover, two different fracture criteria illustrate the influence of SIFs values with respect to the crack propagation angle and equivalent factors calculations. The proposed higher-order technique has demonstrated superior performance in comparison with the conventional displacement fitting technique.

Abstract A large number of references dealing with the geometric stiffness matrix of the DKT finite element exist in the literature, where nearly all of them adopt an inconsistent form. While such a matrix may be part of the element to treat nonlinear problems in general, it is of crucial importance for linearized buckling analysis. The present work seems to be the first to obtain an explicit expression for this matrix in a consistent way. Numerical results on linear buckling of plates assess the element performance either with the proposed explicit consistent matrix, or with the most commonly used inconsistent matrix.