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 free ly rotating ball was developed and used to characterize the formability of fully annealed Al 1050 sheer. Various strain paths were applied to the shee t by imposing different tool paths and the major and minor strains of defor med 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 fr om a test in which straight paths, with an incremental increase of tool dep th, were imposed using a square specimen with the fixed periphery. (C) 2001 Elsevier Science B.V. All rights reserved.