Forming limit diagram for thin sheet metal at metal forming by movable media

The authors developed a combined numerical-experimental technique to obtain a Forming Limit Diagram of thin sheet metal for metal forming by movable media. The technique is based on deforming sheet samples until failure by pressure of polyurethane into a variety of elliptical dies. The required strain state is defined by the proportion of the elliptical die window. Through-thickness strain of the sample near a zone of failure or necking was measured, and major in-plane strains were obtained by finite-element simulation based on the familiar metal properties. Simplicity of measurements and absence of a grid on the surface of the sample are the advantages of the suggested technique. Points of the Forming Limit Diagram for the specific thin sheet stainless steel were obtained.