Cruciform shape benefits for experimental and numerical evaluation of sheet metal formability

Leotoing, Lionel; Guines, Dominique; Zidane, Ibrahim; Ragneau, Eric

doi:10.1016/j.jmatprotec.2012.12.013

Cited by 64 publications

(36 citation statements)

References 13 publications

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“…For AA5086, the natural scattering due to multiple derivatives is certainly emphasized by plastic instabilities, like Portevin-Le Chatellier effects. For a given method to detect the onset of necking, the correlation between experimental results from the presented biaxial tensile test and from the conventional Marciniak test is very good [2].…”

Section: Methods To Detect the Onset Of Neckingmentioning

confidence: 79%

“…In the standard, the limit strains that can be imposed on the material are determined through interpolation, using a positiondependent method. Due to its simplicity, a critical ratio method was applied in previous author works [2,8] to determine forming limit points. Indeed, when necking occurs in a zone, a sharp change of strain is observed due to the onset of a plastic instability.…”

Section: Methods To Detect the Onset Of Neckingmentioning

confidence: 99%

“…Using a cross specimen to characterize and predict forming limit curves can be an interesting alternative to overcome the major drawbacks of the conventional methods [2]. The test is frictionless and one of the main advantages of this shape is that the strain path during the test and at the onset of necking can be directly controlled by the motion of four independent actuators, independently on the specimen geometry.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigations of the effect of strain path changes on forming limit curves using an in-plane biaxial tensile test

Leotoing

Guines

2015

International Journal of Mechanical Sciences

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International audienceOptimization of sheet metal forming processes requires a very good knowledge of material forming ability, more especially for aluminum alloys which generally exhibit a poor formability at ambient temperature. During the forming of industrial parts, very complex strain paths are usually observed and can affect the formability of the sheet. In this work, in order to investigate strain path effects on formability, an innovative one-step procedure is proposed to control the strain path changes with a single test, without unloading. The test is based on the use of a cruciform shape loaded with a planar biaxial tensile device. Strain path is controlled by the displacements in the two main directions of the cruciform specimen. For a given non-linear strain path type, experimental forming limit points are greatly influenced by the level of prestrain which can either improve or reduce formability. The same tendency is observed when using a predictive tool based on a finite element model of the same cruciform shape and a rather good correlation is observed between experimental and numerical results

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Section: Methods To Detect the Onset Of Neckingmentioning

confidence: 79%

Section: Methods To Detect the Onset Of Neckingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigations of the effect of strain path changes on forming limit curves using an in-plane biaxial tensile test

Leotoing

Guines

2015

International Journal of Mechanical Sciences

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“…stand-alone biaxial testing machines and link mechanism attachments for biaxial testing. Zidane et al [28] proposed a new cruciform design for formability tests and obtained the FLD of AA5086 at room temperature based on a servo-hydraulic biaxial test machine. Naka et al [29] used biaxial tensile tests and hot air blow heating with cruciform specimens to investigate the effects of strain rate and temperature on yield locus of AZ31.…”

Section: Introductionmentioning

confidence: 99%

Development of a New Biaxial Testing System for Generating Forming Limit Diagrams for Sheet Metals Under Hot Stamping Conditions

Shao

Lin

et al. 2016

Exp Mech

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Conventional experimental approaches used to generate forming limit diagrams (FLDs) for sheet metals at different linear strain paths are not applicable to hot stamping and cold die quenching processes because cooling occurs prior to deformation and consistent values of heating rate, cooling rate, deformation temperature and strain rate are not easy to obtain. A novel biaxial testing system for use in a Gleeble testing machine has been adopted to generate forming limits of sheet metals, including aluminium alloys, magnesium alloys and boron steel, under practical hot stamping conditions in which heating and cooling occur. For example, the soaking temperature is about 900°C and the deformation temperature range is 550-850°C for boron steel [1] and the soaking temperature is about 535°C and the deformation temperature range is 370-510°C for AA6082 [2]. Resistance heating and air cooling were introduced in this pioneering system and the thermal analysis of different heating and cooling strategies was investigated based on a type of cruciform specimen. FE models with a UAMP subroutine were used to predict temperature fields on a specimen in ABAQUS 6.12. Digital image correlation (DIC) system was used to record strain fields of a specimen by capturing images throughout the deformation history and its postprocessing software ARAMIS was used to determine forming limits according to ISO standards embedded in the software. Heating and cooling strategies were determined after the analysis. Preliminary results of forming limit curves at the designated temperatures are presented in order to verify the feasibility of this new method.

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“…A promising specimen shape (Fig. 1) following this requirement has been previously optimized by present authors [5,6]. The onset of necking is detected when the equivalent plastic strain increment ratio between two zones (necking and adjacent zone) reaches a critical value [5].…”

Section: The Cruciform Shapementioning

confidence: 97%

A Cruciform Shape to Study the Influence of Strain Paths on Forming Limit Curves

Leotoing

Guines

Zhang

et al. 2013

KEM

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Abstract.The optimization of sheet metal forming processes requires an accurate prediction of material behavior and forming abilities, especially for aluminum alloys which exhibit generally a low formability compared with typical mild steels. This study presents an original technique based on the use of a cruciform shape for experimental characterization and numerical prediction of forming limit curves (FLCs). By using a cruciform shape, the whole forming limit diagram is covered with a unique geometry thanks to the control of the displacements in the two main directions of the specimen. The test is frictionless and the influence of linear and non-linear strain paths can be easily studied since the strain path is controlled by the imposed displacements, independently on the specimen geometry. The influence of strain paths is first studied by introducing a linear prestrain (uniaxial, plane strain or equi-biaxial), in rolling direction. Afterwards non-linear prestrain paths are also tested.

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Cruciform shape benefits for experimental and numerical evaluation of sheet metal formability

Cited by 64 publications

References 13 publications

Investigations of the effect of strain path changes on forming limit curves using an in-plane biaxial tensile test

Investigations of the effect of strain path changes on forming limit curves using an in-plane biaxial tensile test

Development of a New Biaxial Testing System for Generating Forming Limit Diagrams for Sheet Metals Under Hot Stamping Conditions

A Cruciform Shape to Study the Influence of Strain Paths on Forming Limit Curves

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