cross section crash boxes

(a) (b) (c) (d)
Figure 3.7. Simulations of the deformation mode of circular tubes with circumferential
imperfections; a/t ratios a) 5%, b)10%, c)50% and d)100% (Source: Galip
and Liman 2004).
The static and dynamic crushing behavior of thin walled circular stainless steel,
mild steel and Al alloy tubes were investigated (Hsu and Jones 2004). Energy efficiency
factor was defined as total elastic and plastic strain energy absorbed by a structural
member divided by the energy absorbed in the same volume of material up to the failure
in tension for evaluating the crashworthiness level of structure. It was reported that
stainless steel circular tubes absorbed the highest energy among the tested tubes (Figure
3.8). However, calculated energy efficiency factor of stainless steel circular tube was
found the lowest for both the quasi-static and impact loading. The critical specimen
length for the transition from the efficient progressive buckling to the catastrophic
global bending for quasi-static loading was found to be similar for three tubes. The
critical tube length of the transition was shown to increase with increasing impact
velocity.
The crushing behavior of circular CR 1018 steel tubes with groove patterns was
studied experimentally and numerically,(Mamalis, et al. 2003c). Model and simulations
showed similar deformation modes (Figure 3.9(a) and (b)). The initial peak load value
of grooved tube was found to be lower than that of non-grooved tube (Figure 3.9(c)).
The number of grooves was found not to affect the peak load values in both experiments
and simulations, while the number of load peaks and the values of mean load decreased
with increasing number of grooves (Figure 3.9 (d)).
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