Lightweighting potential of an automotive roof reinforcement using aluminum alloys in place of high strength steels

Abstract

In recent years, weight reduction of vehicle parts has been a key priority for meeting the demand of reducing fuel consumption and environmental pollution while keeping passive safety needs. For that purpose, components made by hot stamped high strength steels are state of the art. On the other hand, the 6xxx and 7xxx aluminum alloy sheets are being studied due to their high specific strength and low density. However, extent of the lightweighting capacity of using aluminum alloys in comparison with steels in automotive parts is not fully known yet. In this work, in order to study the lightweighting aptitude of different aluminum alloys, a simplified real roof beam’s thicknesses were numerically optimized to reach the same flexural behaviour and energy absorption during a three point bending test. Besides AA7075-T6, AA6111-T6 and the AA6111-T4 high strength aluminum alloys, the often used DP 1000 and USIBOR 1500 high strength steels and a third generation FORTIFORM 1050 steel were included in the numerical study. The automotive roof reinforcements were manufactured in all six materials using the numerical optimal thicknesses, followed by their corresponding post forming heat treatment. Aiming experimental implementation, three point bending tests were carried out and the results were extrapolated with the use of numerical ones. As a result, the lightweighting potential of each material was worked out and ranked.