Pseudo-bulk forming of thin-walled hollow components based on the self-consistency of internal pressure and shell deformation

Xiang, N. and Tian, Y.-L. and Shu, Y.-Q. and Zhang, H.-R. and Huang, T. and Wang, P.-Y. and Zhang, R. and Sun, W.-T. and Cheng, F.-Y. (2025) Pseudo-bulk forming of thin-walled hollow components based on the self-consistency of internal pressure and shell deformation. Materials and Design, 259: 114865. ISSN 0261-3069

Abstract

Instable metal flow easily occurs during the forming of thin-walled hollow components due to inappropriate control of forming load in conventional forming processes, thereby leading to forming failure. Accordingly, a Pseudo-Bulk Forming (PBF) method was proposed in this work, aiming at achieving the self-consistency of internal pressure and tubular blank’s deformation in a simple and stable way. In this process, Low-Melting-Point Alloy (LMPA) was solidified inside of tubular blank to constitute a composite rod and deformed simultaneously under compression. Then forming of thin-walled hollow component was converted to pseudo-bulk plastic deformation of a composite rod. PBF of a rectangular tube was taken as an example to study the loading conditions, stress state, and deformation behavior of tubular blank during this process experimentally and numerically. The results showed that PBF exhibited the advantages in preventing excessive thinning of shell thickness in hydroforming and inward buckling during roll-forming. The strong stability of LMPA’s plastic flow stress, which was caused by its low strain hardening behavior, could induce self-adaptive inner pressure on tubular blank, thereby resulting in the balanced metal flow in sidewall and corner regions. Besides, due to tangential friction generated by LMPA at LMPA/tubular blank interface and along metal flow direction, circumferential metal flow towards the corner region could be enhanced, and thereby leading to the conversion of stress states from tension-tension to tension–compression. The risk of fracture was then reduced and forming stability was improved in the case of forming structures with sharp corners.