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Abstract :
[en] Maximum size constraints in topology optimization increase the complexity of the designs. It introduces extra channels and cavities that hinder the manufacturability of the component. In this work the show some contributions to improve the manufacturability of designs that include a maximum size control in topology optimization.
References of the abstract :
The combination of topology optimization and additive manufacturing has brought a recent break-through in engineering. Topology optimization aims at generating innovative concepts with high performance to weight ratio, but the optimized designs are often difficult to fabricate as-it-is using classical fabrication processes. In the AERO+ research project [1], we focus on metal additive manufacturing processes, and particularly on Electron Beam Melting (EBM) and Selective Layer Manufacturing (SLM) processes. Among others, the maximum size of structural elements has been reported as a manufacturing limitation for theses processes mainly due to overheating problems. The maximum size constraint in topology optimization is based on restricting the amount of material within the neighborhood of each point in the design domain [2], leaving out the control over the void phase. This could lead to designs with ultra small-scale hollows as pointed in [3]. Therefore, the geometrical control over both phases is mandatory and, to the best of our knowledge, Lazarov and Wang [3] present the only work dealing with that restriction. In their work, maximum size constraints are developed with morphological operators and the minimum void size is controlled by geometric constraints [4].
The current work presents a new method to control the length scale of the void phase in a problem already including a maximum size control. This is done by adding an extra constraint in each design point which relies on the maximum size formulation [2]. This aims at moving away the solid elements rather than imposing a maximum size. In order to avoid the computational overburden on the optimizer, the p-mean function is used to aggregate the local constraints. The method is intended to be validated on 3D design domains of the compliance minimization problem. Up to now, results obtained with MATLAB for 2D design domains in the context of linear elasticity problems as the compliance minimization, the heat transfer problem and the compliant mechanism, show encouraging perspectives with optimized designs better adapted to the additive manufacturing technologies.
REFERENCES
1. AERO+ Feasibility Study of Additive Manufacturing for Aerospace Applications. Project funded by the Pole of Competitiveness SKYWIN in the framework of the Plan Marshal of the Walloon Region of Belgium.
2. Guest J. Imposing maximum length scale in topology optimization. Structural and Multidisciplinary Optimization. 37:463-473, 2009.
3. Lazarov BS, Wang F. Maximum length scale in density-based topology optimization. Computer Methods in Applied Mechanics and Engineering. 318:826-844, 2017.
4. Zhou M, Lazarov BS, Wang F, Signmund O. Minimum length scale in topology optimization by geometric constraints. Computer Methods in Applied Mechanics and Engineering, 293:266-282, 2015.
