Effect of forming strategies on strain paths and local strain evolution in incremental sheet forming using digital image correlation
Raphaël LE FRANC, Ahmad AL KHATIB, Jean-François COULON, Jean-Benoît LE CAM, Gwenaël PICAUT
Abstract. Incremental sheet forming (ISF) is widely used for prototyping and small-batch production due to its flexibility and cost efficiency, particularly in the aeronautics and aerospace industries. Unlike traditional stamping, ISF uses a single hemispherical tool mounted on a robot or Computer Numerical Control (CNC) machine, which induces complex strain paths and higher formability. This necessitates a deeper understanding of deformation mechanisms to accurately define forming limits of this process. The aim of this paper is to study the strain path and local strain evolution in the ISF of AA2024-O aluminium alloy sheets and to investigate the influence of forming strategy on these strains. To achieve this, a novel method is employed by combining the wing stars test with the Digital Image Correlation (DIC) technique. The wing stars test, commonly used to characterize the Forming Limit Curve at Fracture (FLCF), is used to create a two-wing star (TWS) shape, inducing strain paths between equibiaxial strain and plane strain. DIC is utilized to capture surface strain on the sheet during the forming process, enhancing our understanding of deformation mechanisms. Strain paths and local strain evolution in different zones of the sheet during the tool’s pass are captured for three forming strategies. These strategies involve a cycle of four upward and downward tool passes, each with a fixed ΔZ per pass. The results demonstrate differences in strain paths in the zones near the wall of the TWS for the three strategies. Additionally, strain patterns for each strain component are identified in each zone of the TWS shape after the tool pass. The aim of this work is to understand the deformation mechanisms of the two-wingstar (TWS) geometry in order to reliably extract and control the evolution of deformation paths. This will enable the implementation of this test as a characterization method for incremental forming within industrial context.
Keywords
Incremental Sheet Forming, Digital Image Correlation, Strain Evolution, Strain Path, Forming Limit Curves at Fracture
Published online 5/7/2025, 10 pages
Copyright © 2025 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Raphaël LE FRANC, Ahmad AL KHATIB, Jean-François COULON, Jean-Benoît LE CAM, Gwenaël PICAUT, Effect of forming strategies on strain paths and local strain evolution in incremental sheet forming using digital image correlation, Materials Research Proceedings, Vol. 54, pp 1211-1220, 2025
DOI: https://doi.org/10.21741/9781644903599-132
The article was published as article 132 of the book Material Forming
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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