Thin-walled tubes are widely used in vehicle structures.Axial folding of thin-walled tubes is proved to have advantages in energy absorption.The traditional design of thin-walled tubes is with uniform wall thickness.Advancement of manufacturing methods has now made variable tube wall thickness available,which is termed as functionally graded thickness (FGT).This paper documents a study on energy absorption of thin-walled tubes with thickness varying along circumferential direction.First,finite element models of thin-walled square tubes with thickness continuously varying along the circumferential direction are set up.Then static simulations of axial crushing with different section configurations are conducted for analyzing the energy absorbing performance and mass efficiency.The results show that,if the wall thickness near the corner areas of the tube is thicker than that near the mid-point areas of the side walls,the average crushing force and the energy absorption are greater than that with uniform thickness.This is due to that the deformation mechanisms are different in the two areas.Variable wall thickness along the circumferential direction can also affect the folding wave length,which is another mechanism for energy absorption improvement.This preliminary study has demonstrated that thin-walled tubes with FGT along the circumferential direction have potential to achieve lightweighting with comparable crash energy absorption in vehicle safety design.