IDENTIFYING GLOBAL/LOCAL INTERFACE BOUNDARIES USING AN OBJECTIVE SEARCH METHOD

One of the key components in computational mechanics procedures using global/local methods is the specification of the global/local interface. Global/local interfaces are usually specified by visually examining some measure of response such as colour-coded contour plots of stresses or strain energy. However, when both global and local domains are modelled in three dimensions, such a specification is not as obvious, and it lacks objectivity and uniqueness. An Objective Search Method (OSM)is presented to specify the global/ local interface in three dimensions in a precise, repeatable and automated manner. The OSM performs the search incrementally in all directions in three dimensions radiating from a location of interest until certain generalized guidelines are satisfied and the global/local interface is identified. The OSM is suited to problems where localized phenomena exist but where their domains are not known a priori. The generalized guidelines for the OSM require the identification of nodes lying on the external surfaces of the model. As an important component of the OSM, a unique method to identify surface nodes has been developed and is also presented. Finally, the uniqueness, sensitivity and versatility of the OSM is illustrated using two example problems and the computational effort involved with the OSM is discussed in the context of a third example problem