This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.
Finite element models often include multiple parts that are challenging or time consuming to weave into an integrated, sound, numerically valid model. The parts may require different mesh densities, or may not line up in a way that is convenient to achieve an integral mesh. And quite often, the model is an assembly of separate models, possibly created by different analysts. The task of connecting the different parts together and ensuring there are no unwanted “cracks” in the model is a challenge, especially in large assembly models with tens or hundreds of parts.
Glued contact is a technique used by structural analysts to meet this challenge. “Glue” is a term used to describe setting up a model so that parts act as though they are bonded together. Glued contact (aka tied contact) uses multi-point constraints to tie parts together. Glued contact can be used to model fastened connections (bolts, rivets, shear pins, etc.) or actual bonded connections. Glued contact is fast and easy to setup because mesh congruency is not required.
This paper will present several recent advancements in glued contact which enable the structural analyst to more efficiently and accurately build these large assembly models. The segment-to-segment glued contact method in MSC Nastran will be presented. This method allows cross-sections of beams and shell edge faces to be available for gluing, making it much easier to assemble an idealized “stick & panel” loads model. This method also allows the structural analyst to add joint flexibility to glued connections, achieving more accurate stiffness representation and load distribution in the assembly model. An aircraft wing assembly model will be used to demonstrate the effects of flexible glued contact on normal modes and load distribution.
When adding joint flexibility to a glued connection, the analyst can specify stiffness values in the tangential and normal directions. This paper will use a simple airframe splice joint example to demonstrate how to convert fastened joint stiffness values into glued contact stiffness values. The resulting load distribution inside the glued joint will be compared with results from a model using discrete fastener representations.
|Date||5th June 2018|