The Study Of Axial Folding Of Thin-Walled Columns And The Applications In Energy Absorbing Structueres Of Vehicle Impact

People's awareness of vehicle safety is strengthening as the number of vehicles and accidents increasing. Besides safe equipments widely used (safe belt, air bag), the energy absorbing structures are necessary to promise occupant safety. Frontal impact is the most frequent accident and thin-walled columns are the main energy absorbing structures.The thin-walled columns own qualities of light weight, high strength and three deformation modes as energy absorbing structures, which are axial folding, bending and torsion. Axial folding like an accordion in frontal impact showed perfect energy absorbing level. However, the theoretical mechanism of thin-walled columns'plastic deformation is very complicated and axial force with eccentricity in practical impact may exist. Therefore it is necessary to do some research on the plastic deformation and design parameters of thin-walled columns.First, the article introduced the basic theories of three modes, such as deformation mechanisms,energy absorbing principles, e.g. Then how to realize the axial folding by controlling the design parameters is studied. The effects of design parameters on the axial folding force were studied using VCS models and orthogonal experiments. And the way was exploited that enables the thin-walled column posses a certain energy absorbing ability, while the fluctuation of its folding force can be narrowed to make the deformation more stable. FE models were built to validate the concludes above.Second, the thin-walled columns loaded with eccentric axial force was studied by theoretical analyses and simulation. An eccentric axial force can regard as the combination of an axial force and a bending moment. The thin-walled columns with combined compression and bending may produce axial folding and bending. The conditions for axial folding were analyzed, and bending could be avoided by trigger design.At last, the model of frontal rigid barrier(FRB) was built using VCS on the basis of concludes above and impact simulation was completed. The crash box and rail were analyzed in detail as the main energy absorbing structures, which satisfied the requests of frontal impact. The result of VCS model is compared with the original experiments and target curves, and it was better than original experiments and approached to the target curves basically.