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A Method for Measuring In-Plane Forming Limit Curves Using 2D Digital Image Correlation
Journal Article
05-16-03-0019
ISSN: 1946-3979, e-ISSN: 1946-3987
Sector:
Topic:
Citation:
Agha, A. and Abu-Farha, F., "A Method for Measuring In-Plane Forming Limit Curves Using 2D Digital Image Correlation," SAE Int. J. Mater. Manf. 16(3):281-291, 2023, https://doi.org/10.4271/05-16-03-0019.
Language:
English
Abstract:
With the introduction of advanced lightweight materials with complex
microstructures and behaviors, more focus is put on the accurate determination
of their forming limits, and that can only be possible through experiments as
the conventional theoretical models for the forming limit curve (FLC) prediction
fail to perform. Despite that, CAE engineers, designers, and toolmakers still
rely heavily on theoretical models due to the steep costs associated with
formability testing, including mechanical setup, a large number of tests, and
the cost of a stereo digital image correlation (DIC) system. The international
standard ISO 12004-2:2021 recommends using a stereo DIC system for formability
testing since two-dimensional (2D) DIC systems are considered incapable of
producing reliable strains due to errors associated with out-of-plane motion and
deformation. This work challenges that notion and proposes a simple strain
compensation method for the determination of FLCs using a low-cost single-camera
(2D) DIC system. In this study, formability tests are performed on an
automotive-grade 6xxx series aluminum alloy using the Marciniak in-plane FLC
testing method. The tests are performed on a custom setup that enables
simultaneous optical strain measurements using a stereo DIC as well as a 2D DIC
system. The results show how 2D DIC FLC points match those obtained by stereo
DIC using two popular FLC approaches: ISO 12004-2 section-based spatial method
and a time-dependent linear best fit (LBF) method.