Elongated bumper bar with sections twisted rotationally about the axis of elongation and method of making the same

摘要

A bumper system for an automotive vehicle includes a rolled steel tube having a box or C-shaped cross section fixed to the forward ends of the side rails of the vehicle so as to extend transversely to the vehicle's longitudinal axis. The forward surface of the vehicle is formed by a plastic fascia which may have sloped surfaces for styling or aerodynamic reasons. The space between the forward end of the bumper bar and the fascia is filled with foam intended to absorb energy in an impact. To better match the sloped sections of the fascia, certain sections of the bumper bar are twisted about the longitudinal axis of the bar to create surfaces inclined relative to the vertical. The bars are formed by roll forming a steel web into an elongated member having generally vertical opposed faces. A section of the rolled member is heated above a metallurgical transition temperature. Then sections to be inclined are twisted about the longitudinal axis of the bumper bar in a die forming station and are then quenched to form a hardened steel member.