Multi-fidelity crashworthiness optimization of a bus bumper system under frontal impact
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TECHNICAL PAPER
Multi‑fidelity crashworthiness optimization of a bus bumper system under frontal impact Erdem Acar1 · Burak Yilmaz1 · Mehmet A. Güler2 · Murat Altin3 Received: 21 May 2020 / Accepted: 13 August 2020 / Published online: 31 August 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract In this study, crashworthiness of a bus bumper system with a special honeycomb beam is optimized under impact loading using a multi-fidelity optimization approach. The crash performance of the bumper system is evaluated using two metrics: crush force efficiency (CFE) and specific energy absorption (SEA). An optimization with aggregated objectives is performed to seek for an optimum bumper design. Optimum values of the crashbox length, honeycomb wall angle and honeycomb wall thickness are obtained to maximize composite objective function that provides a compromise between these two metrics. Commercial finite element software LS-DYNA is used to compute CFE and SEA values. Multi-fidelity modeling is used to combine data of low-fidelity model at all training points with high-fidelity data at some randomly selected training points to obtain accurate response predictions in less computational time. It is found that multi-fidelity optimization can reduce the computational cost by 33% with only 2% smaller composite objective function value compared to the high-fidelity optimization alternative. Keywords Bumper system · Crashworthiness · Crush force efficiency · Energy absorption · Multi-fidelity optimization
1 Introduction Passenger safety is one of the most essential design elements in automotive industry (in particular, for busses and coaches) and gains more importance day by day. To protect driver and co-driver for a bus or coach in case of a collision, engineers study how to build crashworthy vehicles. Technical Editor: João Marciano Laredo dos Reis. * Erdem Acar [email protected] Burak Yilmaz [email protected] Mehmet A. Güler [email protected] Murat Altin [email protected] 1
Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
2
College of Engineering and Technology, American University of the Middle East, Egaila, Kuwait
3
Department of Automotive Engineering, Gazi University, Ankara, Turkey
Energy-absorbing elements are among the main structures used in vehicle design to achieve this goal. These structures absorb crash energy by transforming it into strain energy, while they deform. Due to huge occurrence ratio of frontal crashes among all, bumper systems are the most important and most studied energy-absorbing structures in vehicle design. Crashboxes are the main energy-absorbing components of the structure, while the bumper beam has more rigid structure to transmit crash energy to the crashboxes in various crash scenarios with a less energy-absorbing capability. Therefore, substantial number of studies is performed on crashboxes with various shapes, such as cylindrical straight tubes [1–3], square extrusions [4–6] an
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