Limiting Drawing Ratio and Formability Behaviour of Dual Phase Steels—Experimental Analysis and Finite Element Modelling

Three different dual-phase steels are selected (DP500, DP600 and DP780) to study and analyze the effect of microstructure on formability behaviour for this kind of materials, which are nowadays commonly used in sheet metal forming. This class of advanced high strength steels have a microstructure predominantly composed by a soft ferritic matrix, which ensures good formability, combined with hard martensite particles that give the material its strength. Moreover, the mechanical behaviour of dual-phase steels can be affected by the volume fraction of martensite present in the material matrix, thus providing different levels of formability. This paper presents a formability study and a limiting drawing ratio identification of dual-phase steel sheets, with different amounts of martensite, using a deep drawing test. Experiments and finite element simulations have been performed to analyze and compare the obtained results for this kind of advanced high strength steels. Different experimental tests have been performed with different loading conditions, such as tensile test, biaxial bulge test and Swift test in which formability can be dependent on mechanical properties of material and loading conditions. It is shown that selected materials have a decreasing formability with higher content of martensite, independently from the loading conditions or different material characteristics (e.g. different evolution of anisotropy with rolling direction).