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.

Resource Abstract

Lightweight design has initiated a trend towards more complex materials such as fiber compounds, porous metals or ceramics and hybrid materials such as metal-metal laminates. At the component level, lightweight design increasingly leads to complex shapes resulting from bionic optimization which can only be produced by 3D printing, casting or injection molding. Their mechanical properties may be sensitive to defects such as porosity which are inherent in these production methods.

As a consequence, there is an increased need for micromechanics simulations to determine the effective mechanical properties of complex materials and to assess the mechanical strength of components with optimized shapes and internal defects. Classical FEM simulations may not always be well suited to address these problems because they require the generation of geometry conforming meshes which must be fine enough to capture all relevant geometric details on the one hand, but coarse enough to keep the computational effort at a practical level on the other hand. Furthermore, the mesh cells must conform to certain shape criteria in order to assure the numerical stability of the simulation.

Recently, mesh-less and immersed-boundary finite element methods have been used to overcome the meshing problem. Such methods do not require the generation of a boundary-conforming mesh and are suited for the simulation of arbitrarily complex domains. This approach is implemented in the Structural Mechanics Simulation module of VGSTUDIO MAX by Volume Graphics and works directly on CT scans which accurately represent internal discontinuities as well as complex material structures and outer shapes.

In order to validate this simulation approach, a comparison between experimental and simulated results of tensile tests was conducted for two types of additively manufactured AlSi10Mg components, a tension rod and a bionically optimized aeronautic structural bracket, showing a good correlation between the predicted and measured tensile strengths and the locations of the first crack occurrences. The approach was also validated against a classical FEM simulation for a solid cube and a cubic lattice made from Ti6Al4V, with the results of the two methods being in good agreement.

The simulation approach presented here can be used to determine the effective mechanical properties of new materials with inherently complex internal structures. For manufactured components, it can be used in both R&D and quality assurance to determine the influence of defects or shape deviations on the mechanical stability. This can be done by simulating the internal stress distributions for both a CAD model of the ideal component and CT scans of prototypes or manufactured parts and comparing their respective hotspots. In such comparisons, the tolerancing criterion for the actual components is that defects or shape deviations must not lead to local stress peaks which are significantly higher than those found in the ideal component.