The formability of aluminum sheet in incremental forming

In incremental forming, the sheet exhibits a unique pattern of the forming limit curve. In the present investigation, a forming tool containing a freely rotating ball was developed and used to characterize the formability of fully annealed Al 1050 sheet. Various strain paths were applied to the sheet by imposing different tool paths and the major and minor strains of deformed grids around cracks were measured. It was found that the formability of the sheet shows a distinct dependence on the strain path and appears as a straight line in the forming limit diagram. The most suitable forming limit curve for incremental forming was found to be the one that was obtained from a test in which straight paths, with an incremental increase of tool depth, were imposed using a square specimen with the fixed periphery.