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Forming of Stringer Sheets with Solid Tools

Köhler, Stefan and Groche, Peter and Baron, Alexander and Schuchard, Maximilian (2016):
Forming of Stringer Sheets with Solid Tools.
In: Advanced Materials Research, Trans Tech Publications, Switzerland, pp. 3-10, 1140, ISSN 1662-8985, [Article]

Abstract

Stringer sheets are bifurcated parts that possess, compared to flat sheet metal parts, a higher stiffness due to their higher geometrical moment of inertia. Currently, the common way of forming spatially curved stringer sheets is hydroforming. This article shows the feasibility of forming stringer sheets by using solid tools with short process times, which is more relevant for the industrial application. A die-bending process with a slot in the punch for the stringer is investigated. Since buckling of the stringer is one of the occurring failure modes, depending on the stringer height, an analytical estimation of the critical stringer height is carried out while considering the bending angle, bending radius and sheet thickness. The subsequent numerical and experimental investigations show a good agreement with the analytical estimation. Finally, a stiffness test is carried out with stringer sheets of different stringer heights. The result of this test underlines the motivation of forming buckling-free stringer sheets with stringers as high as possible. The normalized stiffness increases with rising stringer height until buckling occurs. At this point the stiffness values begin to fall with growing stringer height.

Item Type: Article
Erschienen: 2016
Creators: Köhler, Stefan and Groche, Peter and Baron, Alexander and Schuchard, Maximilian
Title: Forming of Stringer Sheets with Solid Tools
Language: English
Abstract:

Stringer sheets are bifurcated parts that possess, compared to flat sheet metal parts, a higher stiffness due to their higher geometrical moment of inertia. Currently, the common way of forming spatially curved stringer sheets is hydroforming. This article shows the feasibility of forming stringer sheets by using solid tools with short process times, which is more relevant for the industrial application. A die-bending process with a slot in the punch for the stringer is investigated. Since buckling of the stringer is one of the occurring failure modes, depending on the stringer height, an analytical estimation of the critical stringer height is carried out while considering the bending angle, bending radius and sheet thickness. The subsequent numerical and experimental investigations show a good agreement with the analytical estimation. Finally, a stiffness test is carried out with stringer sheets of different stringer heights. The result of this test underlines the motivation of forming buckling-free stringer sheets with stringers as high as possible. The normalized stiffness increases with rising stringer height until buckling occurs. At this point the stiffness values begin to fall with growing stringer height.

Journal or Publication Title: Advanced Materials Research
Volume: 1140
Publisher: Trans Tech Publications, Switzerland
Uncontrolled Keywords: Bending, Stiffness, Stringer Sheet Forming
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institut für Produktionstechnik und Umformmaschinen (PtU)
Date Deposited: 01 Sep 2016 05:28
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