Energy absorption mechanics for variable thickness thin-walled structures

This paper introduces axial functionally graded thickness (AFGT) and lateral functionally graded thickness (LFGT) to thin-walled square structures separately, and then investigates their crashworthiness theoretically, numerically, experimentally under axial crushing load. The quasi-static axial crush experiments and the corresponding finite element models are first conducted to analysis the deformation mode and crushing force for uniform thickness (UT), AFGT and LFGT square tube under the same mass. Then, theoretical models predicting the mean crushing forces of AFGT and LFGT square tubes are established. The results show that both theoretical solutions and numerical results for FGT tubes agree well with the experimental results. Energy absorption characteristics between FGT and UT square tubes with same mass are compared based on the validated numerical models, which shows that AFGT square tube can effectively reduce the initial peak force compared to UT square tube while LFGT square tube remarkably surpasses the UT square tube in specific energy absorption (SEA) under axial crushing. Furthermore, parametric studies are performed to investigate the effects of gradient thickness variation on the energy absorption characteristics of AFGT and LFGT square tubes. The results again demonstrate that both AFGT and LFGT square tubes can improve the crashworthiness of thin-walled square tubes.