Influence of Pre-Forming on the Forming Limit Diagram of Aluminum and Steel Sheets

Tolazzi, Massimo; Merklein, Marion

doi:10.4028/www.scientific.net/kem.344.113

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…In [6] an increase of formability during plane strain loading after uniaxial pre-stretching is found for the Aluminum alloy AA5754. This already published increase of formability agrees with this investigation.…”

Section: Discussionmentioning

confidence: 84%

Influence of Different Pre-Stretching Modes on the Forming Limit Diagram of AA6014

Werber

Liewald

Nester

et al. 2012

KEM

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In order to evaluate the formability of sheet materials forming limit diagrams (FLD) are recorded which represent the values of major and minor strain when necking occurs. FLDs are recorded based on the assumption that exclusively linear strain paths occur. In real forming parts, however, particularly in those with complex shapes, predominantly non-linear strain paths occur which reduce the accuracy of the failure prediction according to a conventional FLD. For this reason forming limits after loading with non-linear strain paths have to be investigated. In this contribution a systematic analysis of the forming limits of a conventional AA6014 alloy after loading with non-linear strain paths is presented. This material is pre-stretched in uniaxial, plane strain and biaxial direction up to several levels before performing Nakajima experiments in order to determine FLDs. During the pre-stretching process as well as during the Nakajima experiment the strain distribution can be measured online very precisely with the optical deformation measurement systems GOM Aramis or VIALUX. The gained curves are compared to the FLD of the as-received material. The results prove a significant influence of the pre-stretching condition on the forming limits of the used aluminum alloy. For a low pre-stretching in uniaxial as well as in biaxial direction the FLDs show a slightly reduced formability while after higher pre-stretching levels the forming limit can be improved such as for biaxial loading after uniaxial pre-stretching. The formability after pre-stretching in plane strain direction was changed. Also, a shift of the FLD depending on the direction of pre-stretching can be observed.

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Section: Discussionmentioning

confidence: 84%

Influence of Different Pre-Stretching Modes on the Forming Limit Diagram of AA6014

Werber

Liewald

Nester

et al. 2012

KEM

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show abstract

“…Moreover, a pre-strain in uniaxial tension or plane strain tension leads to an increase of the formability. Tolazzi et al [4] proposed an experimental method for the determination of the FLD under non-linear strain paths in the Nakajima test.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Shear Stress State Under Non-Proportional Strain Paths Realized by Biaxial Stretching in the Marciniak Test

Suttner¹,

Merklein²

2015

Materials Today: Proceedings

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Complex parts with sharp corners are on the rise to satisfy increasing customer demands on the design. To realize these parts in single or multistage forming processes the information of the material behavior under linear and non-linear strain paths is essential. As Bauschinger already showed for the material behavior under cyclic loading, a reduction of the subsequent beginning of plastic yielding can be observed. Different research works studied the Bauschinger effect under cyclic proportional loading or nonproportional strain paths mostly with uniaxial pre-straining of the material. In this paper the material behavior under shearing after previous biaxial stretching in the Marciniak test is analyzed for the aluminum alloy AA5182 and the advanced high strength steel DP600. The Marciniak test is suited for biaxial pre-straining due to an almost almost equibiaxial strain state and a homogeneous strain distribution in-plane on the bottom of the specimen up to higher strains than in a biaxial tensile test. The subsequent shear test is realized with a modified shear test specimen according to the ASTM standard. Finally, the influence of biaxal pre-straining on the beginning of plastic yielding under shear condition, the hardening behavior and the maximum reachable shear strain is investigated for a better understanding of the material behavior under non-proportional loading paths.

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A comparative investigation on theoretical models for forming limit diagram prediction of automotive sheet metals

Pham

Mac

Kim

et al. 2021

Mechanics Based Design of Structures and Machines

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Influence of Pre-Forming on the Forming Limit Diagram of Aluminum and Steel Sheets

Cited by 5 publications

References 4 publications

Influence of Different Pre-Stretching Modes on the Forming Limit Diagram of AA6014

Influence of Different Pre-Stretching Modes on the Forming Limit Diagram of AA6014

Characterization of the Shear Stress State Under Non-Proportional Strain Paths Realized by Biaxial Stretching in the Marciniak Test

A comparative investigation on theoretical models for forming limit diagram prediction of automotive sheet metals

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