On the use of the shear punch experiments in determining mechanical properties of various dual phase steels

Dual phase steels are being extensively considered as a structural material for automobiles because of the favourable combination of strength and formability. Crashworthiness of these new steels is an area of great importance. High strain rate testing is one approach to measure the ability of materials to absorb energy in a crash situation. The objective of this paper is to examine the effect of the deformation rate on the mechanical properties of dual-phase and multi-phase steels. Shear-punch experiments are conducted both at quasi-static and dynamic rates for this purpose. The ease of preparation of shear punch specimens compared to the tension specimen makes this approach attractive in evaluating key mechanical properties, such as ultimate tensile strength (UTS) and ductility limits, of automotive materials mostly in sheet forms. A qualitative correlation between the quasi-static shear punch and tension experiments results is made, and parallels of this correlation are considered for the dynamic rates of deformation. A servo hydraulic MTS machine is used for performing the quasi-static experiments, with a special fixture for the shear tests, while the high rate experiments are conducted using the shear version of the Split Hopkinson Pressure Bars (SHPB) setup. Dual phase steels DP600/300 and DP600/400 are tested as well as alternate microstructure dual phase steels with different fractions of martensite obtained by changing the intercritical annealing temperature and water quenching.