Abstract

Thin-walled stiffened shell structures are very common as industrial products and their analyses by the finite element method can be difficult, in particular when the part is geometrically complex as found in the field of packaging. When the initial CAD definition is not available, reverse engineering is necessary, often based on the use of 3D scanners, in order to obtain a performing 3D geometrical model before considering finite element computations. The process of data capture to FEM can be time consuming and difficult for parts with several 3D stiffeners, depending on the strategies to reconstruct the part. This work focuses on the evaluation of three strategies applied to quite simple thin-walled parts using Geomagic and Abaqus software for the reconstruction and the simulation, respectively. Regarding FE simulations we focus on the computations of the first free frequency since this situation offers interesting comparison with experimental results. The criteria for the evaluation of the strategy are the times for scanning and processing of the data, the reconstruction, of the geometry for the FEM computations. We also study the influence of the strategies on the results of the simulations. These results depend on the type of element used and the present study reveals that for certain strategies the choice is restricted to the use of solid (mainly tetrahedron) elements, while another strategy allows the use of shell or solidshell elements. In this that case only one element through the thickness is used leading to very acceptable results for reduced calculation times but for a longer backward reconstruction time. The advantages and drawbacks of the 3D geometry reconstruction combined with FEM computational strategies are discussed.

Abstract

In this paper, a general and efficient approach to model thin-walled members and frames with complex geometries (including tapered segments and holes). The approach combines shell and GBT-based (beam) finite elements, using each of them where it is most efficient: (i) shell elements in the plastic and geometrically complex zones, and (ii) GBT elements in the prismatic and elastic zones. To illustrate the capabilities and potential of the proposed approach, a set of numerical examples are presented, concerning linear, bifurcation (linear stability) and first-order plastic zone analyses. The examples analysed involve (i) members with tapered segments, (ii) members with holes and (iii) tapered beam-column assemblies. For validation and comparison purposes, full shell finite element solutions are provided and it is demonstrated that the proposed approach yields very accurate solutions in all cases, while involving much less DOFs.