Simultaneous optimization of multi-part structure topologies and connection points

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Abstract

Given the growing number of environmental and societal concerns we confront today, the idea of sustainability has gained importance. At the same time, new strategies for improving the performance of structures and systems have been developed due to developments in engineering and computational design. This research aims to generate a sustainable design using topology optimization by focusing on design for disassembly. One advantage of design for disassembly is that when a product can be disassembled, the parts can be reused, repaired, recycled, and remanufacture. This facilitates other aspects of product sustainability, such as the product's life cycle and end-of-life. A structure is divided into two parts and attached by a connection point, this connection point is called the connector. Due to sustainability, the connection method needs to be a non-destructive method, which in this case is the bolts. Next to the connector, two voids are required to insert, tighten and remove the bolts. Therefore, in this research, a structure is optimized using topology optimization and simultaneously optimizing the position of cut lines and connectors. The approach taken uses level set functions to model the cut of the structure, as well as the connectors and the voids. Then, they are converted into a density field using a smoothed Heaviside function. A Solid Isotropic Material with Penalization (SIMP) motivated method is used to join all the different density fields into an equation for the interpolated elasticity modulus. The optimization aims to minimize compliance with volume and no-overlap constraints. The non-overlap constraint is applied to the connectors.
The structure and the position of the cut line and the connectors are optimized using the Method of Moving Asymptotes (MMA) method. A gradient based sensitivity analysis is used in the MMA. Afterwards, the influence of the cut line, the connector and the voids are observed individually. After optimizing the parts individually, the full optimization was performed, where the structure, the cut lines and the connectors with the voids were optimized. Furthermore, a parameter study was done to observe their influence on the final layout. The optimizer's behaviour was observed by looking at the optimization results and the parameter study. For example, how the optimizer tends to stack some connectors together to create a member of the structure or the influence of the voids.

With the approach presented, the main idea of optimizing a structure using topology optimization and simultaneously dividing it and optimizing the connector's position is obtained. However, the optimization has some limitations, as some assumptions and design considerations are not accurate, further research is needed to get accurate results.