The Analysis of Mechanically Fastened Repairs and Lap Joints

Abstract

A new Dual Boundary Element formulation is presented, which allows for the analysis of mechanically fastened repairs and lap joints. The method requires only the boundaries of the problem to be discretized and the fasteners location is simply defined by a set of internal points.The technique enables the evaluation of fastener forces, sheet stresses and the stress intensity factors which are important parameters for a Damage Tolerance assessment.Examples of applications to repair designs and to a lap joint are presented to demonstrate the robustness of the new formulation that is proposed in this paper. NOMENCLATURE a = crack length b, bj, bf" = fastener forces D , = total number of fasteners in the m-th patch E = Young's modulus G = shear modulus h, h , = thickness K , , K , , Kn. KO = stress intensity factors L = crack tip element length M = total number of patches p = fastener pitch R =total fastener force tj, tj'-= boundary tractions uj, u!= = boundary displacements K = material constant v = Poisson's coefficient oij, aim = sheet and patch stresses obr = fastener hole bearing stress ow = sheet gross stress 4 = fastener diameter ' & Uij, S, , , Dijl =fundamental solutions r, Gm, r -oundaries @, Qrn = fastener shear flexibility coefficient s1, OPm = domains A@', Aul D b I b -crack opening displacements

A Probabilistic Approach in Fuselage Damage Analysis via Boundary Element Method

“…Studies on tolerance to probabilistic damage are based on manufacturing components [27] and the dispersion of fatigue life from the distribution of initial defects [28]. Other works relate damage tolerance through computational methods, using XFEM [29,30], BEM [31], and DBEM [32].…”

Boundary element analysis of cracked panels with mechanically fastened repair patches

“…can be evaluated numerically using the a logarithmic weighted Gaussian integration formula. Two more options for modelling fastener forces were also studied by Salgado [4]. The displacements of a point x9 at the boundary of the mth patch of thickness h m are given, for the case of zero body forces on the patch, by…”

“…for the bending problem. H m , G m are the well-known boundary element influence matrices for both plane stress [4] and plate-bending [11] problems, and D m is a matrix determined by the displacement fundamental solution.…”

“…Young et al [3] presented a BEM formulation for analysing repair patches using Green's function with a crack. Salgado and Aliabadi [4] presented the dual boundary element method (DBEM) for analysing repair patches. Their method is a boundary-only formulation and allows for automatic crack growth analysis (see reference [5] for a review).…”

Boundary element analysis of stiffened panels with repair patches

“…The stiffeners can be attached to the sheets with rivets. BEM formulation for two-dimensional riveted panels with cracks can be found in [52], while applications to riveted repairs in [54] and [70]. Widagdoo and Aliabadi in [75] analyzed the effect of different materials for composite riveted patches.…”