The mechanics of incremental sheet forming

Theory of single point incremental forming

https://home.kpn.nl/i.w.c.emmens/pdf/36.pdf

An overview of stabilizing deformation mechanisms in incremental sheet forming

This paper presents synthetically the most recent models for description of the anisotropic plastic behavior. The first section gives an overview of the classical models. Further, the discussion is focused on the anisotropic formulations developed on the basis of the theories of linear transformations and tensor representations, respectively. Those models are applied to different types of materials: body centered, faced centered and hexagonal-close packed metals. A brief review of the experimental methods used for characterizing and modeling the anisotropic plastic behavior of metallic sheets and tubes under biaxial loading is presented together with the models and methods developed for predicting and establishing the limit strains. The capabilities of some commercial programs specially designed for the computation of forming limit curves (FLC) are also analyzed.

/pdf/advances-in-anisotropy-and-formability-110f64hopf.pdf

Advances in anisotropy and formability

https://www.tpbin.com/Uploads/Subjects/5dad275d-23af-4a2f-bb98-b443c70fe2e6.pdf

A new approach for failure criterion for sheet metals

Generalised forming limit diagrams showing increased forming limits with non-planar stress states

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.

D.R. Shouler

Papers

Generalised forming limit diagrams showing increased forming limits with non-planar stress states

The Increased Forming Limits of Incremental Sheet Forming Processes

Design and use of a novel sample design for formability testing in pure shear

Paddle Forming: A Novel Class of Sheet Metal Forming Processes

A novel sample design for formability testing in pure shear