Lightweight design of electric bus roof structure using multi-material topology optimisation

Youngsuk Jung, Sunghoon Lim, Jongmin Kim, Seungjae Min

Research output: Contribution to journalArticle


This paper presents a multi-material topology optimisation (MMTO) process for the lightweight design of an electric bus roof structure including the self-weight. The usage of electric buses is increasing owing to environmental issues. However, it is challenging to design a lightweight structure, because the heavy battery pack mounted on the roof increases the deformation and reduces the safety. In a design including the self-weight, the appropriate distribution of multiple materials improves the performance more than that of a single material. The MMTO method has been applied to identify the optimal distribution of multiple materials. However, in the real-engineering problem, only a simple objective function such as compliance and a single constraint function such as the volume of material have been considered, whereas the mass reduction is the most important factor. In this paper, an MMTO process is proposed for the lightweight design of the bus roof structure to consider multiple displacement constraints including the self-weight. To control the complexity of the distribution of multiple materials for improving the manufacturability, the welding surface function is proposed. An optimisation process was constructed that can handle the complex finite-element model and multiple load cases, and it was validated according to the well-known compliance minimisation problem. Mass reduction was achieved via the lightweight optimisation, and the interfacial area between the different materials was reduced by employing the welding surface function.

Original languageEnglish
Pages (from-to)1273-1285
Number of pages13
JournalStructural and Multidisciplinary Optimization
Issue number3
StatePublished - 2020 Mar 1


  • Electric bus
  • Lightweight design
  • Multi-material topology optimisation
  • Self-weight loading

Fingerprint Dive into the research topics of 'Lightweight design of electric bus roof structure using multi-material topology optimisation'. Together they form a unique fingerprint.

  • Cite this