Theoretical analysis of functionally graded thickness tubes under dynamic external inversion loading

The effect of strain rate on dynamic external inversion loading of Functionally Graded Thickness (FGT) tubes are studied analytically and their results are compared with Finite Element (FE) results. Based on the deformation theory and using rigid-perfectly plastic (R-PP) material idealization, a theoretical solution for dynamic inversion crushing load is derived by dividing the contact region of circular sections into three different sections. Comparing analytical and FE results indicates that prediction of crashworthiness loading for different thickness distribution of FGT tubes are satisfactory. Also, it is found that the concave distribution of thickness for FGT tubes improves the energy absorption more efficient than other geometries.