Graph Based Algorithms to Enhance Mid-Surface Design Fidelity of Finite Element Models of Extrusion Profiles

Abstract

Extruded profile structures are widely used as efficient and lightweight crash energy absorbers in vehicle structures throughout the automotive industry. For the development and evaluation of new concepts and designs, finite element simulations are used to decrease costs and shorten development periods. In order to get good accordance between physical responses of extrusion profiles and their finite element representations under crash loads, a certain degree of modeling detail is needed. These details can be radii and material accumulations which are usually provided in volumetric CAD (Computer Aided Design) models. Leaving out these details in the profile cross section geometry can lead to differences in the buckling wavelength of walls and therefore in the deformation behavior.However, CAD designers are usually not incorporated into every design iteration of the CAE (computer aided engineering) departments and therefore these details might be missed out when design changes are rapidly imposed on a finite element shell mesh level. Furthermore, structural optimization methods applied to improve the profile’s mechanical behavior might not even allow for CAD designers to be involved. In this work two efficient yet simple to configure graph based algorithms to automatically apply rounded corners and to consider material accumulations at intersection points of walls of the profile are provided. These algorithms work with a graph based representation of the profile’s cross section geometry in order to perform geometric calculations. To describe the profile’s geometry the graph syntax of the optimization method “Graph and Heuristic based Topology Optimization” is used. Based on the graph a three-dimensional finite element representation of the profile is generated by an extrusion along a defined spline. This finite element model is the basis for further mesh modifications and conclusively for the simulation itself. The algorithms have proven their ability to increase the quality of the finite element representation of extrusion profiles and therefore increase the accordance between physical tests and simulation results in terms of geometry and result accuracy.KeywordsExtrusion profilesDesign process automationFinite element modellingCrash simulationMathematical graphs