Crush box in an automotive passenger car has become an integral part of structural design performing various functions like optimizing energy absorption in high speed impacts, replaceable part during low speed impacts etc. Design of crush box for high speed impacts is very important as it is the first major energy absorbing component in the load path and its deformation significantly affects the overall vehicle crash behavior.
The present paper explains development of a hydro-formed crush box in the front end of a sports utility vehicle. Hydro-formed components have residual plastic strains and non - uniform thickness variation throughout their length which is difficult to measure from a physical test coupon. It is critical to add hydro-forming effects onto crash FE models as it significantly affects the deformation under high speed impact. But detailed forming simulations need mature design and material data which is not available during early phases of product development. Hence, leveraging CAE through front loading, a new method of mapping the residual effects of hydro-forming during early concept phase is proposed in the current study.
The crush box was tuned for optimum energy absorption through accordion crush and progressive deformation and was validated through a unique high speed physical test setup resembling impact loading during frontal crash. Results of the proposed mapping technique during early development phase showed good correlation with physical test and matched well with detailed forming processes evaluated during the matured design phase. The designed crush box was tested at full vehicle level for offset crash and good correlation was observed in terms of deformation and load carrying capacity.