Influence of contact conditions and strain path on stretching of steel and Al-alloy sheet metals

Abstract

Biaxial tension – stretching of sheet metals is one of characteristic stress-strainschemes, which in the course of sheet metal forming by deep drawing may exist in particular work piece zones or may dominate completely (Erichsen’s test). In such forming conditions, tribological conditions of tool and sheet metal contact are extremely important. In addition to fracture depth, which is a main investigation indicator, the paper also presents more complex parameters for estimation of contact conditions influence – fracture force and realized strains distribution, as well as relations in forming limit diagram. Furthermore, it shows that in the multistage forming conditions, i.e. at modification of so called strain paths, contact conditions have a considerable influence on the degree of realized limit strains. Steel and Al-alloys sheet metals were used in the experiment. In addition to the analysis from the formability aspect, the specified methodology can be used with great success for the estimation of technological qualities of lubricants for deep drawing.