Material modeling of 6016-O and 6016-T4 aluminum alloy sheets and application to hole expansion forming simulation

Kuwabara, Toshihiko; Mori, Takahiro; Asano, Mineo; Hakoyama, Tomoyuki; Barlat, Frédéric

doi:10.1016/j.ijplas.2016.10.002

Cited by 151 publications

(42 citation statements)

References 62 publications

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“…The interface between the blank and the punch head was lubricated with Vaseline and 0.3 mm thick Teflon sheet, while no lubricant was applied to the interfaces between the blank and the upper/lower die. The periphery of the blank is clamped using a draw-bead (see detail in Figure 1) and the blank-holding force is approximately 800 kN [1]. …”

Section: Hole Expansion Testmentioning

confidence: 99%

“…The hole expansion test is commonly adopted to study the formability of metallic sheets, allowing the study of fracture occurrence in stretch-flanging areas [1]. The accurate prediction of thinning and localization of fracture by numerical simulation requires an accurate modelling of the plastic deformation behavior, namely the anisotropic yield function [2].…”

Section: Introductionmentioning

confidence: 99%

“…The accurate prediction of thinning and localization of fracture by numerical simulation requires an accurate modelling of the plastic deformation behavior, namely the anisotropic yield function [2]. However, some authors suggest that the friction model may also play a role because of its interaction with the material flow, since the strain distribution in the hole expansion test is not uniform [1]. Thus, despite the lubrication of the contact interfaces between the blank and the tools, friction can be an important factor in the finite element analysis, which is usually modeled by the Coulomb friction law.…”

Section: Introductionmentioning

confidence: 99%

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Study of the frictional contact conditions in the hole expansion test

Neto

Barros

Oliveira

et al. 2018

J. Phys.: Conf. Ser.

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Section: Hole Expansion Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Study of the frictional contact conditions in the hole expansion test

Neto

Barros

Oliveira

et al. 2018

J. Phys.: Conf. Ser.

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“…These values for the exponent should only be taken as guiding principles. It is visualized in [14] that the exponent can vary a lot for metallic materials. The utilized material model in [14] is Barlat 2000 [7, 8], equivalent to BBC05 [15].…”

Section: Introductionmentioning

confidence: 99%

BBC05 with non-integer exponent and ambiguities in Nakajima yield surface calibration

2020

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Reliable sheet metal forming simulations depend on accurate descriptions of real process conditions. These conditions include material behavior, lubrication systems, tool deformations, press dynamics, and more. Research on material models is the most mature area for describing these conditions in a reliable way. Several advanced and flexible models exists. This study focuses on two versions of yield criteria for sheet materials that are assumed to follow the plane stress assumption: the BBC05 model with integer exponent and the BBC05 model with non-integer exponent. The literature has previously described the BBC05 model with integer exponent. This paper elaborates on a modified version with non-integer exponent that offers more flexibility in the mathematical description. Furthermore, it outlines the implementation of this material model and similar yield criteria as user subroutines in finite element software. As mathematical flexibility increases, it enables more physically correct material approximations. However, it also becomes more challenging to calibrate because of ambiguities due to a larger number of mathematical variables. These ambiguities is demonstrated by using a Nakajima test without lubrication during inverse modeling of parameters for the BBC05 model. It shows that it is impossible to accurately identify the physically correct combination of friction coefficient and the yield surface exponent, k, using strain distributions and punch force. It is suggested to use two Nakajima tests in the inverse modeling process where friction can be neglected due to testing conforming to ISO12004-2. One test that corresponds to equi-biaxial strain of the sheet, and one that corresponds to plane strain in the transverse direction of the sheet. By utilizing these samples in the inverse modeling it is possible to separate friction from the exponent k. A non-integer value of k is found to yield the most reliable prediction of strains and forces in the simulations, thereby also demonstrating the need of flexible yield surface models such as BBC05 with non-integer exponent, YLD2000, Vegter and more advanced yield criteria.

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“…The choice of the yield locus exponent defines the geometry in the area between uniaxial and equi-biaxial stress as well as the area of shear stress. Considering this, an integration of additional material information in the associated flow rule Yld2000-2d can be done by an experimentally supported selection of the yield locus exponent m. Investigations by Kuwabara [18] and Merklein [19] have shown that the stress-state-dependent material behavior can be modelled by the use of a strain-dependent variation of the yield locus exponent.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Numerical Modelling Considering Plane Strain Material Characterization with an Elliptic Hydraulic Bulge Test

Lenzen¹,

Merklein²

2018

JMMP

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A precise characterization of material behavior is necessary to identify yield criteria or hardening laws for an accurate numerical design of sheet metal forming processes. Current models like Yld2000-2d or Hill'48 do not consider the plane strain state, though this condition is primary cause of failure in deep drawing. It is anticipated that an improved yield locus contour which considers the stress under plane strain conditions leads to better results in numerical simulations of a deep drawing process. Within this contribution, a new experimental setup to characterize both principal stress components under plane strain as additional input data for material modelling is presented. Therefore, hydraulic bulge tests are carried out with a novel elliptical die, which implements a plane strain condition. Moreover, the improvement of the material model is investigated exemplarily for the three sheet metal alloys DC06, DP600 and AA5182. The resulting material parameters are used to identify the yield locus for plane strain by varying the yield locus exponent of Yld2000-2d. The results prove that considering plane strain yield locus results in a better sheet thickness distribution in comparison to conventional modelling of the deep drawing process.

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Material modeling of 6016-O and 6016-T4 aluminum alloy sheets and application to hole expansion forming simulation

Cited by 151 publications

References 62 publications

Study of the frictional contact conditions in the hole expansion test

Study of the frictional contact conditions in the hole expansion test

BBC05 with non-integer exponent and ambiguities in Nakajima yield surface calibration

Improvement of Numerical Modelling Considering Plane Strain Material Characterization with an Elliptic Hydraulic Bulge Test

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