| Summary: | In this study, we proposed a new adjacent variable thickness hexagonal tube (AVTHT) and performed crushing analysis and crashworthiness optimization under multiple loadings. First, the finite element models were constructed and validated by experiments with four configurations of AVTHTs. Then, the numerical simulations under axial loading and multiple oblique loadings indicated that AVTHTs under various loading angles (0°, 10°, 20°, and 30°) and three patterns (<i>α</i>, <i>β</i>, and <i>θ</i>) exhibited different deformation modes, force-displacement characteristics, and crashworthiness indices. This suggested that we could change and determine the plate thickness configuration to make the AVTHTs exhibit the expected crushing performance under multiple loadings. Therefore, multi-objective optimization for minimizing maximum crushing force with multiple loadings (F<sub>maxw</sub>) and maximizing specific energy absorption with multiple loadings (SEA<sub>w</sub>) by changing the thickness configuration under multiple loadings was conducted. The results determined the thickness design domains and indicated that certain thickness ranges should be avoided, such as the ranges of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.55</mn><mo>≤</mo><mi>t</mi><mn mathvariant="italic">1</mn><mo>≤</mo><mn>1.6</mn></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.85</mn><mo>≤</mo><mi>t</mi><mn mathvariant="italic">1</mn><mo>≤</mo><mn>1.95</mn></mrow></semantics></math></inline-formula>, which was helpful for getting AVTHTs to achieve excellent crushing performance in railway vehicles. In the pareto results, increasing <i>t1</i> would not always increase the F<sub>maxw</sub> and SEA<sub>w</sub>. For example, when <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.75</mn><mo>≤</mo><mi>t</mi><mn mathvariant="italic">1</mn><mo>≤</mo><mn>1.8</mn></mrow></semantics></math></inline-formula>, increasing <i>t1</i> would lead to decline of F<sub>maxw</sub> and SEA<sub>w</sub>.
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