Cost and Weight Optimization of Hybrid Parts Using a Multi-material Topology Optimization Approach

Abstract

Topology optimization is widely used in the industry with the objective to minimize the weight of structures or to maximize their stiffness. Typically, there is no special focus on the costs of the resulting part, as there is a direct correlation between material costs and weight.

When looking at hybrid designs, combining a lightweight material with high costs and a material with lower costs but worse specific properties, this simplified view on costs is no longer sufficient. The correlation between costs and weight of the part is no longer met, as the material costs highly depend on which material is primarily used. The optimization problem, therefore, extends to a multi-objective problem with the competing aims ‘minimization of weight’ and ‘reduction of costs’. Additionally, a more complex manufacturing process has a major share in the overall costs of the part.

The presented approach uses an extended cost calculation model to estimate the manufacturing costs of the hybrid component based on its geometrical properties. The epsilon-constraint-method is used to transform the costs objective function into an additional constraint. To be able to satisfy this new cost constraint, a group of fuzzy rules, which influence the usage of each material and therefore the costs, were added to the step size controller used by the topology optimization approach. By varying the costs constraint, different Pareto-optimal solutions can be found.