Design optimisation of tapered thin-walled square tubes

This paper presents a crashworthiness optimum design of the tapered thin-walled tubes with square cross sections. In this study, three design variables that fully describe the tapered thin-walled square beam's geometry are optimised to maximise the beam's energy absorption capability during crashes. The specific energy absorption (SEA) and the ratio between the average and maximum crushing forces (Favg/Fmax), which is also referred to as the 'crush force efficiency', are considered as objective functions separately. During the optimisation, the objective of SEA and Favg/Fmax are formulated using the response surface method as function of the design variables. Optimal designs are decided based on the developed RS models for each design objective, and the results show that the optimised design variable values are same for both design objectives. Therefore, in such crashworthiness design of tapered square tubes, either SEA or Favg/Fmax can be considered as the design objective. After obtaining the optimal design, the sensitivity of the design variables on the tapered square beam's crash performance are analysed. Analyses involved in this paper are undertaken using finite element models and, the finite element solver LS-DYNA and the computer program MATLAB are used to perform all the analyses and the optimisation.