Abstract
A crash box and a front side member are typical parts to absorb energy in frontal crash. A crash box couples a bumper beam on a front side member. Recently, an automotive crash box becomes to be needed to have characteristics of low impact force and high energy absorption in order to reduce the repairing cost and to achieve light-weight design. However, conventional crash boxes with collapse type have high impact force by buckling and low energy absorption due to local deformation by bending. Therefore, it is necessary a crash box to satisfy performance requirements for low speed crash. A front side member is a typical stiffness part to compose engine room, and is a main part to absorb energy in high speed frontal crash. A good front side member has crash characteristic that deformed front region absorbs much energy and rear part connected an engine and a transmission maintains the original shape.
In this paper, an integrated frontal energy absorber is developed to satisfy demands of low and high speed crashes simultaneously in spite of light and small part. The operation principal of new integrated energy absorber is double collapse of two tubes after expansion of a tube. Since tube expansion has uniform and low impact force and high energy absorption is able to be satisfied at low speed crash. As the velocity increases, a fixed tube and an outer tube are collapsed with shape of a double walled tube at the same time. A high strength and elongation steels like TWIP and stainless steel are suitable to be adopted and much crash energy can be absorbed since an outer tube is able to have plastic strain more than 40%. In order verify the newly energy absorber, a crash box was made of stainless steel 304 and crash tests performed with axial and inclined directions.
Keywords: energy absorber, tube expansion, double walled tube collapse, crash box, buckling