Optimized AHSS Structures for Vehicle Side Impact

Advanced high strength steels (AHSS) have been widely accepted as a material of choice in the automotive industry to balance overall vehicle weight and stringent vehicle crash test performance targets. Combined with efficient use of geometry and load paths through shape and topology optimization, AHSS has enabled vehicle manufacturers to obtain the highest possible ratings in safety evaluations by the Insurance Institute for Highway Safety (IIHS) and the National Highway Traffic Safety Administration (NHTSA). In this study, vehicle CAE side impact models were used to evaluate three side impact crash test conditions (IIHS side impact, NHTSA LINCAP and FMVSS 214 side pole) and the IIHS roof strength test condition and to identify several key components affecting the side impact test performance. HyperStudy (R) optimization software and LS-DYNA (R) nonlinear finite element software were utilized for shape and gauge optimization. Simplified bending crush simulation models were developed and a cross-section optimization was performed for bending crush performance. The optimized cross-sections were then applied to rocker reinforcement, B-pillar reinforcement, front seat cross-member, roof rail and door-beams to reduce the B-pillar and door-beam deformations during side impact crash tests. Finally, a material and gauge optimization was conducted on side structures using dual phase (DP) steels with 590 to 980 MPa minimum tensile strength. Mass savings was achieved without compromising the side impact crash test performance when AHSS and optimized cross-sections of the structural components were applied.