Crashworthiness Multi-Material Topology Optimization for Minimum Mass

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Authors
Hardman, Andrew
Keyword
optimization , crashworthiness , design , topology optimization , automotive design , multi-material design , multi-material topology optimization , computer aided engineering , CAE , FEA , Finite Element Analysis , Equivalent Static Load Method
Abstract
There is an increasing need for lightweight structures in the transportation industry, and within these lightweight structures crashworthiness and occupant safety is continually important to all stakeholders. Industry standard lightweighting tools such as topology optimization (TO) and emerging techniques like multi-material topology optimization (MMTO) are effective for designing lightweight structures subjected to linear loading, but they cannot consider dynamic crash loading. Crashworthiness is most effectively simulated using dynamic finite element analysis (FEA) techniques due to the geometric and material nonlinearities involved in a crash event. Dynamic simulations do not allow for the calculation of analytical sensitivity derivatives required for conventional gradient-based structural optimization strategies. Non-gradient based methodologies for crashworthiness optimization exist in the literature which optimize structures via direct use of dynamic responses, but they are prohibitively computationally expensive and require heuristic strategies for design evolution. The equivalent static load (ESL) method is used to generate linear static sub-problems which replicate the dynamic structural responses of crash simulations in the linear regime, such that they can be used in a relatively standard gradient-based TO problem. Resulting designs from the ESL problems are used as input for subsequent crash analyses to update the ESLs for additional sub-problems. The objective of this thesis is to develop a novel methodology for a MMTO design tool considering crashworthiness using a gradient-based optimization strategy. The dual loop optimization strategy using the ESL method is presented, along with a discussion of the tool’s operation flow and the material modelling and interpolation schemes. The new MMTO for crashworthiness methodology is demonstrated with three case studies. Comparisons between single and multi-material TO solutions are presented to show the benefit of MMTO when developing advanced designs. When applied to a Formula SAE chassis minimum-mass design problem with crashworthiness considerations, the MMTO tool developed in this work obtains a result with 30% better performance compared to the best design found with single-material TO.
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