Forming Limit Curves of Electrically Conductive Layers Printed on Sheet Metal Surfaces

Abstract

Forming limit diagrams are a useful tool to anticipate the formability of sheets for various sheet metal forming processes. The objective of this paper is to propose a method for calculating forming limit diagrams for conductive and nonconductive printed layers on sheet metal surfaces. These printed layers can be used to manufacture printed electronics like strain gages or temperature sensors. In this paper the forming limits of these printed layers are determined in notched tensile tests by evaluating the crack pattern on the surface of the printed specimens. The crack pattern is digitized with a reflected light microscope. Additionally, the major and minor strains of the printed specimens are measured with an optical deformation analysis system. The forming limit diagrams for the investigated printed layers are subsequently calculated by synchronizing the crack pattern with the measured major and minor strains on the specimens’ surfaces. The results achieved by this method are tested for reproducibility.