This paper deals with the crash energy absorption and the local buckling characteristics of the
expansion tube during the tube expanding processes. In order to improve energy absorption capacity
of expansion tubes, local buckling characteristics of an expansion tube must be considered. The local
buckling load and the absorbed energy during the expanding process were calculated for various
types of tubes and punch shapes with finite element analysis. The energy absorption capacity of the
expansion tube is influenced by the tube and the punch shape. The material properties of tubes are
also important parameter for energy absorption. During the expanding process, local buckling occurs
in some cases, which causes significant decreasing the absorbed energy of the expansion tube.
Therefore, it is important to predict the local buckling load accurately to improve the energy
absorption capacity of the expansion tube. Local buckling takes place relatively easily at the large
punch angle and expansion ratio. Local buckling load is also influenced by both the tube radius and
the thickness. In prediction of the local buckling load, modified Plantema equation was used for
strain hardening and strain rate hardening. The modified Plantema equation shows a good agreement
with the numerical result.