Abstract
Bursting in tube hydroforming is preceded by localized deformation, which is often called necking. The retardation of the initiation of necking is a means to enhance hydroformability. Since high strain gradients occur at necking sites, a decrease in local strain gradients is an effective way to retard the initiation of necking. In the current study, the expansion at potential necking sites was intentionally restricted in order to reduce the strain gradient at potential necking sites. From the strain distribution obtained from FEM, it is possible to determine strain concentrated zones, which are the potential necking sites. Prior to the hydroforming of a trailing arm, lead patch is attached to the tube where the strain concentration would occur. Due to the incompressibility of lead, the tube expansion is locally restricted, and the resultant strain extends to adjacent regions of the tube during hydroforming. After the first stage of hydroforming, the lead is removed from the tube, and the hydroforming continues to obtain the targeted shape without the local restriction. This method was successfully used to fabricate a complex shaped automotive trailing arm that had previously failed during traditional hydroforming processing.
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Recommended by Editor Jai Hak Park
Se-Ge-Ro Shin received his B.S. degree (2011) in Control and Measurement Engineering at Pukyong National Univeristy, Busan, Korea. Since 2012, he has been pursuing MSc studies in Mechanical Engineering at Pusan National Univeristy, Busan, Korea. His research interests are related to hydroforming process.
Young-Hoon Moon received his Ph.D degree in Metallurgical and Materials Engineering from Colorado School of Mines, Golden, USA. He is a professor in the School of Mechanical Engineering, Pusan National Univeristy, Busan, Korea. His research includes hydroforming, forging, rolling, laser forming, materials processing technology, and reliability analysis.
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Shin, S.G.R., Joo, B.D., Van Tyne, C.J. et al. Enhancing tube hydroformability by reducing the local strain gradient at potential necking sites. J MECH SCI TECHNOL 28, 4057–4062 (2014). https://doi.org/10.1007/s12206-014-0918-4
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DOI: https://doi.org/10.1007/s12206-014-0918-4