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Conference Object Citation - Scopus: 166The Increased Forming Limits of Incremental Sheet Forming Processes(Trans Tech Publications Ltd, 2007) Allwood,J.M.; Shouler,D.R.; Tekkaya,A.E.Incremental sheet forming is known to give higher forming limits than conventional sheet forming processes, but investigation of this effect has been impeded by the computational cost of process models which include detailed predictions of through thickness behaviour. Here, a simplified process is used to gain insight into the mechanics of a broad class of incremental forming processes. The simplified process is described and shown to give increases in forming limits compared to a conventional process with the same geometry. A model of the process is set up with a commercial finite element package, validated, and used to trace the history of a 'pin' inserted perpendicularly into the workpiece. The history of the deformation of the 'pin' demonstrates significant through thickness shear occurring in the direction parallel to tool motion. This insight is used to modify an existing analysis used to predict forming limit curves. The analysis shows that for a sheet with uniform proportional loading, the forming limit is increased when through thickness shear is present, and this is proposed as an explanation for the increased forming limits of incremental sheet forming processes.Conference Object Prediction of plastic instability and forming limits in sheet metal forming(2011) Şanay,B.; Kaftanoglu,B.In this study, FLD's are predicted by simulating Nakazima test using a finite element software. Strain propagation instability criterion is used to evaluate the limit strains from the finite element simulations. SAE 1006, material is used in this study and 7 different specimen geometries are analyzed. Furthermore, FLD's are also predicted by theoretical approaches namely; Keeler's model, maximum load instability criterion, Swift-Hill model and Storen-Rice model. At the end of the study, the calculated FLD's are compared with the experimental results. © 2011 IBF (RWTH Aachen) & IUL (TU Dortmund).
