Joining by Die-Less Hydroforming of Profiles with Oval Cross Section

Abstract:

Joining by die-less hydroforming is used to produce overlap joints by means of hydraulic expansion. Due to a difference in the elastic recovery of the two joining partners an interference pressure p remains at their contact area. Due to the possibility to produce multi-material joints without relying on heat, the process has great potential for joining parts in lightweight applications. Therefore, the process limits were extended so that profiles with non-rotationally symmetric cross-sections can be joined. For this purpose a new tool for profiles with oval cross-section was developed. The inner and the outer joining partner ware made of aluminum 6060 and aluminum 6082 respectively. The influence of the overlap length and different wall thicknesses of the outer joining partner were investigated by numerical simulations and validated by experiments. An upper limit in interference pressure was observed which was also found previously for profiles with circular cross sections. The fluid pressure limit is compared with the analytically calculated value for a configuration with circular tubes under equivalent conditions. The analytical model underestimated the pressure limit. In contrast to circular tubes, the strain distribution of profiles with oval cross sectional shapes is not uniform, which results in superposed bending stresses. Also a difference in stiffness of the inner and outer joining partner leads to a pressure depended contact area which is assumed constant in the analytical model.

• Periodical: Key Engineering Materials (Volume 767)
• Pages: 405-412
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.767.405
• Online since: April 2018
• Authors: Michael Müller, Soeren Gies*, A. Erman Tekkaya
• Keywords: Interference-Fit Joints, Joining by Die-Less Hydroforming, Profiles with Oval Cross-Sections, Tubes

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