Abstract
This work falls within the scope of computer-aided optimal design, and aims to integrate the topology optimization procedures and recent additive manufacturing technologies (AM). The elimination of scaffold supports at the topology optimization stage has been recognized and pursued by many authors recently. The present paper focuses on implementing a novel and specific overhang constraint that is introduced inside the topology optimization problem formulation along with the regular volume constraint. The proposed procedure joins the design and manufacturing processes into a integrated workflow where any component can directly be manufactured with no requirement of any sacrificial support material right after the topology optimization process. The overhang constraint presented in this work is defined by the maximum allowable inclination angle, where the inclination of any member is computed by the Smallest Univalue Segment Assimilating Nucleus (SUSAN), an edge detection algorithm developed in the field of image analysis and processing. Numerical results on some benchmark examples, along with the numerical performances of the proposed method, are introduced to demonstrate the capacities of the presented approach.
Highlights
A topology optimization problem consists in the formulation of a lay-out problem, where the goal is to find the optimal distribution of material in a specific region, according to the applied loads, the possible support conditions, the volume of the structure to be constructed and possibly some additional design restrictions
Other recent approaches that recall shape and size optimization procedures for topology optimum design are the Moving Morphable Conponent (MMC) and the Moving Morphable Void (MMV) methods, introduced in Guo et al (2014) and Norato et al (2015), where the topology optimization problem can be solved based on explicit geometry description
In order to obtain a magnitude that describes the overhang situation of the structure, we will start from an edge detection algorithm that is typically used in image processing, but here the pixel intensity is substituted by the element material density
Summary
A topology optimization problem consists in the formulation of a lay-out problem, where the goal is to find the optimal distribution of material in a specific region, according to the applied loads, the possible support conditions, the volume of the structure to be constructed and possibly some additional design restrictions. The third level engagement considers the strategies involving a total integration of topology optimization and AM processes by introducing the overhang constraint into the design process, which enables a final result that can be directly manufactured and shows and acceptable compliance ratio with respect to the non-supported reference optimum structure. The approach proposed in this paper follows a different way and develops a novel global inequality constraint for the overhanging angle which is included explicitly in the topology optimization formulation problem This constraint can be added to the problem formulation as an additional inequality constraint along with the regular volume constraint for compliance minimization problems, and coupled with traditional mathematical programming optimization algorithms, like the Method of Moving Asymptotes (Svanberg 1987). Its extension to 3D problems is straightforward, as it can be checked in the work by Walter et al (2009a, 2009b)
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