End flare of linear flow split profiles

Abstract

One approach to design load optimized structures is the use of bifurcations. Linear flow splitting is a continuous sheet-bulk metal forming process, whereby bifurcated profiles are manufactured without joining or external heat supply. By roll forming linear flow split profiles, a wide spectrum of profile geometries can be realized, e.g. multi-chamber-profiles. Those profiles often require high dimensional accuracy to ensure their functionality. During roll forming, process related residual stresses are induced, which are released when the profiles are cut to length. Thereby increased deformation at the profile ends occurs, also known as end flare. End flare of bifurcated profiles has not been investigated so far. The aim of this research is to investigate end flare after roll forming of linear flow split profiles. Therefore, end flare after roll forming of a conventional sheet metal and a linear flow split profile is compared. The effect of residual stresses induced by linear flow splitting as well as the effect of additional geometrical stiffness due to the bifurcations on the development of end flare are examined. It is found that the residual stresses induced by linear flow splitting have no significant effect on end flare. However, the geometrical bifurcation affects the roll forming process, leading to higher residual stresses in the flange, which significantly affect the magnitude and the direction of end flare.