A comparative study on the forming limits of an aluminum sheet-metal in negative incremental forming

The paper presents a comparison of the forming limits of an aluminum sheet-metal tested by forming two categories of the parts: (1) the parts whose slope varies along depth and (2) the parts having fixed slope along depth. In order to design the former kind of the parts/surfaces, the curve-segments of various geometrical functions were selected as generatrices, and the mathematical formulation was carried out to predict the formability parameters – forming angle limit and thinning limit – of the sheet-metal. The formability parameters from these parts were acquired by forming them until they were fractured, and the results obtained showed that the formability of the sheet-metal depends upon the slope distribution along an axi-symmetric part to be formed. A collection of the latter category of the parts/surfaces was created with a variety of slopes, and the maximum slope/wall angle that the sheet-metal can endure without fracturing was determined. It has been concluded that the formability of the sheet-metal depends upon the slope distribution along the part utilized in the test, and the former category of the parts exhibit higher forming limits than the latter one.