An experimental and theoretical study of a forming limit curve in incremental forming of sheet metal using spherical roller

In the present article, an incremental sheet metal bulging test by a rolling ball is proposed in order to determine industrially the forming limit curve of the incremental forming of sheet metal. Performing the incremental bulging test using a ball roller, it is found that the strain paths are approximately linear and that the strain ratio is approximately equal to the passage ratio defined in the text. It is shown that the forming limit curves for hard aluminum, annealed aluminum, brass and stainless steel sheets can be expressed as epsilon1 + beta (g)epsilon2= Eps and that the forming limit curves are considerably larger than those based on the usual bulge tests. Comparison is also made between the experimental forming limit curves for the incremental forming and theoretical forming limit curves based on diffused necking and localized necking theories.