Lightweight B Pillars

Safety in the passenger compartment

B pillar test stamping with NanoSteel NXG™ 1200 B pillar test stamping with NanoSteel NXG™ 1200

Challenge

The occupant safety cage is one of the most important areas of the vehicle body structure design. B pillars are a core element, providing support that connects the roof structure and the floor rocker between the driver & passenger seats. In the event of a rollover or side impact crash, the B pillar is designed to both distribute and dissipate energy around the passengers.

Designing B pillars that are high performance, lightweight and affordable is a fundamental engineering challenge. Today, body structure designers have a few typical options:

They may select a hot stamped steel to deliver the highest available strength. However, hot stamping involves expensive capital equipment and most lack the ability to use a galvanic corrosion protection coating, potentially impacting durability. In addition, designing the B pillar to deform in a predictable manner during a crash event can involve the additional complexity of a tailor-welded blank containing material that will not harden during the quenching process to contribute a weak point in the structure.

Another approach to B pillar design includes conventionally stamped components with added steel reinforcements to strengthen certain areas; this avoids new hot stamping investment but adds weight and welds. Body structure engineers can alternatively use tailor-welded or tailor-rolled blanks to change grade or add thickness where needed. These tactics have their own drawbacks including the potential for increased weight from increased steel thickness. 

NanoSteel Approach

NanoSteel’s AHSS offers a novel solution to engineer’s B pillar challenges by providing the ability to use existing stamping infrastructure to create advanced high-strength lightweight parts. The strain hardening feature of the material means that body structure engineers can use the introduction of geometric features to increase both yield and tensile properties. In areas where lower strength and higher energy absorption are needed, geometric features can be kept simple to retain properties closest to the annealed material state. In areas that demand very high strength, additional geometric features such as beads and sharp corner radii can increase local stiffness and modify strain distributions thereby increasing strength properties without adding mass. With NanoSteel’s AHSS, reinforcement welding and mixed material solutions are unnecessary.

NanoSteel’s AHSS is currently in validation testing with several OEM and Tier 1 suppliers to evaluate optimal design and manufacturing approaches for this key body structure component.

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