Deformation Characteristics of Crashworthy Thin-Walled Steel Tubes Subjected to Bending

Abstract

The collapse behaviour and crashworthy characteristics of cantilever circular tubes subjected to bending are studied both theoretically and experimentally. Three different fixture devices were used and their effect on failure behaviour of the tube was investigated in detail. A theoretical method, proposed by Hodge, slightly modified, is used to analyse the elastic and elastoplastic phases of bending, while a rigid-perfectly plastic analysis is developed to describe the plastic bending phase. Agreement between experimental and theoretical results was found to be quite good.

Discrete element modelling of bendable tubes

“…After a certain threshold has been exceeded the structure becomes unstable and the tube locally flattens [25,6,30]. As previously stated this flattened cross-section offers less resistance to bending making the force deformation curve highly non-linear.…”

“…This approximation is sufficient for small forces and deformations (as was the case in the experiments of Lenaerts et al [24]). However, it has been shown that the bending behaviour of tubes is essentially non-linear [3,4,25,6]. …”

“…At this point a kink is formed and the cross-section locally completely flattens [25,6,30]. The tube then offers virtually no resistance to bending [4] and the tube buckles.…”

“…This flattening also occurs, to a lesser degree, further away from the hinge line. Elchalakani et al [6] improved the buckling model by Mamalis et al [25] and presented a closed-form solution for describing the buckling behaviour of circular tubes. They assumed a linear relation between the flattening and the distance from the hinge line.…”

“…Such behaviour is, however, not realistic. Mamalis et al [25], Elchalakani et al [6] and Poonaya et al [30] showed that flattening is plastic and increases with bending angle. Although the model is thus not suitable for large deformations it remains useful for smaller deformations.…”