Steel Market Development Institute, Great Designs in Steel 2013

Bumper Group Technology Presentation, Presented by

Presentation Title: Next Generation of Roll Formed Bumper Beams: How geometric optimization and processing ingenuity will allow steel to compete on mass with aluminum bumper cross sections

Abstract:

Shape recently completed development on the MonoLeg bumper beam, Figure 1 below, which can level the playing field against Aluminum bumper beams, saving 5-10% mass from current state of the art roll formed AHSS beams.

Figure 1

Shape is committed to helpingOEMs achieve theirmass reduction targets by optimizing its cross section geometries and utilizing the highest AHSS material grades in the world. Focused on taking full advantage mechanical characteristics of martensitic steel grades, Shape has developed a bumper beam cross section called the MonoLeg. This beam section was designed for high torsion strength. This enables it to perform equivalently with extruded aluminum beams during impacts to the IIHS bumper barrier, which often imparts a torsion load. Shape’s MonoLeg bumper beam accomplishes this by doublings the J-value (torsion constant) of a typical roll formed B section bumper. This, combined with thehigher mechanical properties of AHSS, puts the MonoLeg on par with aluminum window pane sections of similar mass, see table 1 below.

Laser welding and section forming methods implemented for the manufacture of the section were new to Shape and requireda disciplined approach to process development.Beams made from 1300, 1500 and 1700 MPa martensitic steels validatedthesection design through static and dynamic testing. Mass competitiveness with Aluminum has been demonstrated on several case studies for various OEMs. Given the wide range of bumper design attributes and performance criterion, there are a wide range of comparisons that can be made, in general our internal studies have shown that compared to an equivalent mass Aluminum beam, the JG value for the MonoLeg is 90% of Al, and the bending characteristics sYS * Zexceeds Aluminum by up to 10%, resulting in nearly equivalent back of beam strokes during IIHS bumper barrier impact. See IIHS Bumper Barrier impact results below for the Aluminum beam and MonoLeg beam highlighted in Table 1 above.

Figure 2

Tom Johnson

616.850.3649

Joe Matecki

616.850.3799

Brian Oxley

616.844.3476