A Comparison of the Response of HSLA and Dual Phase Sheet Steel in Dynamic Crush

Continuing pressure to reduce mass and cost of vehicles is driving the development of new high strength steel products with improved combinations of strength and formability. Galvanized, cold rolled dual phase steel products are new alternatives to conventional high strength low alloy (HSLA) steel for strength limited applications in vehicles. These steels have higher tensile strengths than HSLA products with nearly equivalent formability.

This paper compares the performance of HSLA and dual phase sheet steel products in a series of drop tower tests. Samples were prepared by stamping the steel sheets into typical rail-type parts using a production-intent die process. The parts were sectioned, and subsequently fabricated into hat-shaped assemblies that were then dynamically crushed by a drop weight. The experiments were designed such that the entire energy input by the drop weight was absorbed by the samples.

Results discussed in the paper include comparisons of the forces and total displacements measured during the tests. The results are presented as direct comparisons of energy absorption among the materials, as well as through correlation with mechanical properties. The results lead to the conclusion that dual phase steel absorbs approximately 10% more energy per unit mass than HSLA steel with similar yield strength and formability, and that energy absorption scales with the tensile strength of the sheet product.