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. (c) 2006 Elsevier B.V. All rights reserved.