Electromagnetic forming of aluminium alloy sheet

Oliveira, D. A.; Worswick, Michael J.

doi:10.1051/jp4:20020709

Cited by 29 publications

(17 citation statements)

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“…In all the cases considered, the linearized perturbation criterion gives onset of necking strains that decrease from the quasistatic value (maximum force) monotonically with increasing loading rate. This result is in contradiction with experimental evidence from high strain rate free forming results that show formability equal to or greater than that under quasistatic conditions (see Hutchinson and Neale, 1977;Oliveira and Worswick, 2003;Hu and Daehn, 1996). The initial imperfection criterion is at this point the reasonable choice for ductility calculations of interest in this work.…”

Section: A5 Results and Discussioncontrasting

confidence: 74%

“…It is important to recall that all the results here depend on the imperfection parameter n, most significantly for strain paths with q > 0, a rather undesirable -but inevitable under adopted simplifying assumptions -feature of the FLD analysis. There is also some controversy about the magnitude and/or existence of a free forming EMF ductility increase over conventional techniques (see, for example, Oliveira and Worswick, 2003;Zhang and Ravi-Chandar, 2006;Oliveira et al, 2005). This issue should be investigated in the light of complete experimental evidence, especially since the material constitutive response is alloy-dependent (e.g.…”

Section: Resultsmentioning

confidence: 96%

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Theory of necking localization in unconstrained electromagnetic expansion of thin sheets

Thomas

Triantafyllidis

2007

International Journal of Solids and Structures

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Certain sheet metal alloys of industrial interest show a significant increase in ductility, over conventional forming methods, when high speed electromagnetic processes are used. The present work models the necking localization of a metal sheet during an electromagnetic process and examines the factors that influence this process. A Marciniak-Kuczynski ''weak band'' model is used to predict the onset of necking of a thin sheet under plane stress, an idealization of the local conditions in a thin sheet subjected to unconstrained electromagnetic loading. It is found that electromagnetic forming (EMF) increases ductility over quasistatic techniques due to the material's strain-rate sensitivity, with ductility increasing monotonically with applied strain rates. The electric current also increases onset of necking strains, but the details depend on thermal sensitivity and temperature-dependence of the strain-rate sensitivity exponent. Given the insensitivity of the results to actual strain profiles, this local type analysis provides a useful tool that can be used for ductility predictions involving EMF processes.

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Section: A5 Results and Discussioncontrasting

confidence: 74%

Section: Resultsmentioning

confidence: 96%

Theory of necking localization in unconstrained electromagnetic expansion of thin sheets

Thomas

Triantafyllidis

2007

International Journal of Solids and Structures

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“…Stuart Hydrodraw 625 solid film lubricant [31], which prevented pick-up on the die surfaces and was shown to provide a comparatively low coefficient of friction for hydroforming [1].…”

Section: Process Parameters Methods and Measurementsmentioning

confidence: 99%

Tube bending and hydroforming of aluminium alloy S-rails

Oliveira

Worswick

2009

Int J Mater Form

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“…Representative examples may be found in Imbert et al (2005a,b), Oliveira and Worswick (2003), Oliveira et al (2005), , where the onset of localization and failure in thin sheets formed with EMF is discussed. Hu and Daehn (1996), , , Ravi-Chandar (2006, 2008) present similar work with EMF tube and ring expansion.…”

Section: Introductionmentioning

confidence: 96%

Comparison of fully coupled modeling and experiments for electromagnetic forming processes in finitely strained solids

et al. 2010

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In fracture and fragmentation research the technique of electromagnetic forming, which uses electromagnetic (Lorentz) body forces to shape metallic parts, is finding significant use due to the high velocity, high strain rate loading it can impart without contact on workpieces. The same process is also becoming increasingly relevant for manufacturing processes in sheet metal forming, where this technique offers several advantages: speed, repeatability, nonSandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Companycontact loading, reduced springback and considerable ductility increase in several metals. Current modeling techniques for these coupled electromagnetic and thermomechanical processes are not based on coupled variational principles that can simultaneously account for electromagnetic and mechanical effects. Typically, separate solutions to the electromagnetic (Maxwell) and motion (Newton) equations are combined in staggered or lock-step methods, sequentially solving the mechanical and electromagnetic problems. To address this issue, Thomas and Triantafyllidis (J Mech Phys Solids 57:1391-1416, 2009) have recently introduced a fully coupled Lagrangian (reference configuration) variational principle, involving the magnetic field potential and the displacement field as independent variables. The corresponding Euler-Lagrange equations are Maxwell's and Newton's equations in the reference configuration under the eddy current approximation. This novel approach is used here to simulate free expansion experiments of AA6063-T6 aluminum tubes. A viscoplastic constitutive model, developed independently by the authors (Thomas et al. Acta Mater 55:2863-2873, 2007 for necking experiments in tubes of the same aluminum alloy, is used in the simulations. The measured electric currents and tube deformation-the latter obtained by Photon Doppler Velocimetry-show reasonably good agreement with the corresponding simulations, which are obtained using a variational integration numerical scheme that results in an efficient staggered solution algorithm. 123 68 J. D. Thomas et al.

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Electromagnetic forming of aluminium alloy sheet

Cited by 29 publications

References 0 publications

Theory of necking localization in unconstrained electromagnetic expansion of thin sheets

Theory of necking localization in unconstrained electromagnetic expansion of thin sheets

Tube bending and hydroforming of aluminium alloy S-rails

Comparison of fully coupled modeling and experiments for electromagnetic forming processes in finitely strained solids

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