LOCAL-EFFECTS IN ENGINEERING WITH MACRO-ELEMENTS

The presented strategy for coupling the Finite Element Method and the Boundary Element Method is based on a hybrid formulation for the trial and test functions. The usual variational formulation of the problem for the whole domain Omega is extended by a coupling equation, using a second bilinear form for the BE substructures. This offers the possib ility to construct a two grid method with different discretization par ameters for the FE- and the BE-substructures. The properties of the co upling operator like symmetry and positive definiteness are guaranteed only on the continuous level. An essential feature of the proposed me thod is the realization of these properties also on the discrete appro ximation level with an a priori defined accuracy. This is carried out in an adaptive scheme by expanding the Poincare-Steklov operator on th e BE-substructures in a Neumann series and defining error indicators f or the construction of the discrete coupling operator. The proposed FE /BE-technique handles in particular stress concentration problems very efficiently, providing a locally high resolution of the investigated stress field. (C) 1998 Elsevier Science S.A.