Numerical Investigations on Thermal Forming Limit Testing with Local Inductive Heating for Hot Forming of AA7075

Reuther, Franz; Lieber, Thomas; Heidrich, Jürgen; Kräusel, Verena

doi:10.3390/ma14081882

Cited by 7 publications

(3 citation statements)

References 36 publications

(39 reference statements)

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“…Some works, for instance [11], enhanced hot gas bulge test by modifying the ellipticity of the die as in [9] to obtain different strain paths and succeeded in determining the right side of the FLD of Magnesium alloy AZ31B sheets at 400°C. Apart from punch-based tests and bulge tests, another recent study [12] investigated in-plane test concepts for FLD determination of AA7075 alloy in between 200 and 400 °C.…”

Section: High Temperature Flds and Characterization Methodsmentioning

confidence: 99%

Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy

Teeuwen

Baru

Tilly

et al. 2022

IOP Conf. Ser.: Mater. Sci. Eng.

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In order to meet the continuously increasing environmental concerns, automotive lightweight concepts of replacing steels with high strength aluminium alloys are one promising solution. Therefore, complex automotive structural components manufactured with new processes like rapid gas-based hot sheet metal forming can become a key factor from a forming technology point of view. A product and process development phase, which is mainly assisted by numerical simulations, mandates knowledge of the material forming limits under the process conditions. The aim of this work is to determine the FLD of a 6xxx precipitation-hardening aluminium alloy within the solution heat treatment temperature range under gas-based hot forming process conditions. For this purpose, a hydraulic double-layered bulge test, as introduced by Banabic, is used as the basis and a high-temperature test setup as well as a characterization methodology are established. FE simulations are utilized to optimize the specimen geometries aiming at specific strain paths. Experiments are conducted with the optimized specimen geometries and the high-temperature FLD is extracted. The FLD is further used in simulations for process parameter identification for failure-free gas-based hot forming of a laboratory scale benchmark component. Experimental validations showed the reliability of the methodology and the determined FLD for failure prediction in the novel forming process.

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Section: High Temperature Flds and Characterization Methodsmentioning

confidence: 99%

Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy

Teeuwen

Baru

Tilly

et al. 2022

IOP Conf. Ser.: Mater. Sci. Eng.

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show abstract

“…They also detected a low increase of the yield strength whereas the maximum flow stress decreased for rising strain rates. For the aluminum alloy AA7075, Reuther et al [9] determined a negative strain rate dependency in W-temper condition as well. In case of the uniform elongation, no clear trend is visible.…”

Section: Achievements and Trends In Materials Formingmentioning

confidence: 99%

Numerical and Experimental Investigations on the Mechanical Properties of Milled Specimens from an AA7020 Tube

Reblitz

Reuther

Trân

et al. 2022

KEM

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The reduction of weight is crucial in the automotive sector to reach a lower energy consumption and an increased range, especially for electrically powered vehicles. In this regard, body-in-white parts offer a high potential for the application of lightweight construction. The required weight savings can be achieved by implementing parts with a high strength-to-weight ratio. A promising approach is the combination of lightweight materials and lightweight design, which can be realized by tubular components made of high strength aluminum. Due to their structural stiffness and high crashworthiness, those structures are often used as safety-relevant car body components. However, the material characterization of tube profiles is a major challenge, which in turn impedes an accurate numerical simulation and precise process design. In contrast to flat semi-finished parts, various effects of the production process and the geometry, regarding the stress state under load, must be taken into account. For this purpose, adapted testing methods considering the geometrical and mechanical properties of the tubular parts have to be investigated, in order to generate an accurate material model and process design. Within this research work, tubular components made out of AA7020 in W-temper condition were used to analyze the mechanical properties. In this regard, several tensile specimens are milled from a tube, so they also have a curvature profile. The experimental tensile tests have been performed at different strain rates by using an universal testing machine from type Gleeble 3500. To ensure a proper measurement of the mechanical properties, the clamping jaws of the testing machine are adjusted to the curved samples. The investigated material parameters are subsequently transferred to an FE-Model with curved specimen to enable an accurate prediction of the forming behavior. In addition, an FE model of a flat tensile specimen was also created for comparison, in order to gain a profound knowledge regarding the influence of the geometric and mechanical properties of tubular components.

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“…However, the Nakajima test requires the use of expensive equipment and is considered a time-and resource-consuming methodology; moreover, friction is a common issue in this test since it affects the accuracy of the crack location. In addition, the implementation of the Nakajima test at elevated temperatures can be challenging, especially when it comes to capturing the strain data [10,11].…”

Section: Introductionmentioning

confidence: 99%

Development of the Forming Limit Diagram for AA6016-T4 at Room Temperature Using Uniaxial Tension of Notched Samples and a Biaxial Test

2023

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Within the framework of the formability limit assessment in sheet metal forming, testing of notched tensile samples coupled with digital image correlation (DIC) has been analysed as an alternative to overcome the implications of Nakajima testing in relation to times of test preparation, cost of the equipment, presence of friction, and amount of material required for the test. Additionally, the complications of the Nakajima testing at elevated temperatures need to also be considered. In this work, specific notched sample geometries have been investigated to accurately identify the forming limits of Aluminium alloy AA6016 in T4 condition. Once the notched geometry had been defined, experimental tensile testing of the samples coupled with DIC technology allowed us to identify the formability limits of interest. Finally, a comparison at room temperature with the conventional Nakajima testing was performed experimentally. Two different methodologies for strain limit evaluation in notched samples have been investigated in the present analysis. The first one is called a position-dependent method and is based on the inverse best-fit parabola of the “bell-shaped curve”, which is used in the conventional Nakajima test. The second approach referred to a time-dependent method and is based on the strain rate evaluation at the necking zone. This strain-rate-dependent method, which works in combination with DIC measurements, was found to be more accurate to determine the necking limits than the previous one; in addition, it also provides more accurate information for the safe zone of forming.

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Numerical Investigations on Thermal Forming Limit Testing with Local Inductive Heating for Hot Forming of AA7075

Cited by 7 publications

References 36 publications

Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy

Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy

Numerical and Experimental Investigations on the Mechanical Properties of Milled Specimens from an AA7020 Tube

Development of the Forming Limit Diagram for AA6016-T4 at Room Temperature Using Uniaxial Tension of Notched Samples and a Biaxial Test

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