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Research Papers: JOINING

Analytical Model to Determine the Strength of Form-Fit Connection Joined by Die-Less Hydroforming

[+] Author and Article Information
Christian Weddeling

Institute of Forming Technology and
Lightweight Construction,
TU Dortmund University,
Baroper Strasse 303,
Dortmund 44227, Germany
e-mail: Christian.Weddeling@iul.tu-dortmund.de

Soeren Gies

Institute of Forming Technology and
Lightweight Construction,
TU Dortmund University,
Baroper Strasse 303,
Dortmund 44227, Germany
e-mail: Soeren.Gies@iul.tu-dortmund.de

Nooman Ben Khalifa

Institute of Forming Technology and
Lightweight Construction,
TU Dortmund University,
Baroper Strasse 303,
Dortmund 44227, Germany
e-mail: Nooman.Ben_Khalifa@iul.tu-dortmund.de

A. Erman Tekkaya

Institute of Forming Technology and
Lightweight Construction,
TU Dortmund University,
Baroper Strasse 303,
Dortmund 44227, Germany
e-mail: Erman.Tekkaya@iul.tu-dortmund.de

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received November 28, 2014; final manuscript received June 10, 2015; published online September 4, 2015. Assoc. Editor: Yannis Korkolis.

J. Manuf. Sci. Eng 137(5), 051014 (Sep 04, 2015) (10 pages) Paper No: MANU-14-1639; doi: 10.1115/1.4030878 History: Received November 28, 2014

Modern lightweight concept structures are increasingly composed of several dissimilar materials. Due to the different material properties of the joining partners, conventional and widely used joining techniques often reach their technological limits when applied in the manufacturing of such multimaterial structures. This leads to an increasing demand for appropriate joining technologies, like joining by die-less hydroforming (DHF) for connecting tubular workpieces. The present work introduces an analytical model to determine the achievable strength of form-fit connections. This approach, taking into account the material parameters as well as the groove and tube geometry, is based on a membrane analysis assuming constant wall thicknesses. Besides a fundamental understanding of the load transfer mechanism, this analytic approach allows a reliable joining zone design. To validate the model, experimental investigations using aluminum specimens are performed. A mean deviation between the calculated and the measured joint strength of about 19% was found. This denotes a good suitability of the analytical approach for the design process of the joining zone.

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References

Figures

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Fig. 3

(a) Parameters and assumptions of the analytical prediction of the forming pressure pi developed by Gies et al. [12] and (b) determination of the current forming height h∧

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Fig. 2

Process sequence of DHF [8]

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Fig. 1

Industrial examples: (a) bundle heat exchanger, (b) camshaft, and (c) lightweight frame structure of the Collaborative Research Center SFB TR10

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Fig. 4

Analytically determined forming pressures compared to experimental results [12]

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Fig. 5

(a) Assumed inward bending in the groove center during pull-out and (b) geometrical assumptions

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Fig. 7

Calculation of the angle α [8] and the radius Rr1

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Fig. 6

Prediction of meridional stress increase Δσϕ due to a change in curvature

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Fig. 8

Determination of the principle radius R2

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Fig. 12

Measurement of the groove filling [8]

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Fig. 13

Comparison of analytically predicted (Eq. (47)) and experimentally determined specific joint strength

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Fig. 9

Specimens used for the experimental validation [8]

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Fig. 10

Experimental setup used for the DHF joining experiments [8]

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Fig. 11

Typical pull-out curve of a form-fit connection featuring a groove width of 12 mm and a groove depth of 2 mm joined by DHF

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