Dynamical bending analysis and optimization design for functionally graded thickness (FGT) tube

As a relatively new component with a higher efficiency of material utilization, functionally graded thickness (FGT) structure with desired varying wall thickness has been becoming more and more attractive. In order to sufficiently understand the crashworthiness of FGT under lateral impact, firstly, the finite element (FE) models of thin-walled columns with uniform thickness (UT) and FGT under lateral loading are established and validated by experimental results. It is exhibited that the FE simulations are in good agreement with experimental tests. Then, the crashworthiness of UT tube and the corresponding FGT tube is compared, and the results reveal that the FGT tube can absorb more energy but generate larger force than UT tube under the same weight. Further, parametric analyses show the gradient exponent, wall thickness range, the tube diameter and yielding stress have significant effects on the crashworthiness of FGT tubes. Finally, a multiobjective particle swarm optimization (MOPSO) method is used to optimally seek for those design parameters, where surrogate modeling methods are adopted to formulate the specific energy absorption (SEA) and peak crushing force functions. The results yielded from the optimization demonstrate that the FGT tube is superior to its uniform thickness counterpart in overall crashing behavior under lateral impact. Therefore, FGT tubes are recommended as potential absorbers of crashing energy under lateral loading.