Open Access

ARTICLE

Effect of Prestrain on Formability and Forming Limit Strains During Tube Hydroforming

by C. Nikhare¹, K. Narasimhan²

1 Department of Metallurgical Engineering & MaterialsScience, IIT BOMBAY, Powai, Mumbai 400 076, INDIA
2 Corresponding author. Email: nara@iitb.ac.in

Computers, Materials & Continua 2008, 7(3), 129-138. https://doi.org/10.3970/cmc.2008.007.129

Abstract

The tube hydroforming process is a relatively complex manufacturing process; the performance of this process depends on various factors and requires proper combination of part design, material selection and boundary conditions. In manufacturing of automotive parts, such as engine cradles, frames rails, sub-frames, cross members, and other parts from circular tubes, pre-bending and per-forming operations are often required prior to the subsequent tubular hydroforming process to fit the tubular blank in the complex die shape. Due to these pre-- hydroforming operations, some of the strains are already developed before going to the actual hydroforming process. Such developed strains before hydroforming process in the part is called as prestrain. In this paper the study of effect of prestrain on formability and forming limit strains during tube hydroforming is done by simulation by taking the material prestrain value. The forming limit strains of pre-strained tube during hydroforming are predicted. A series of tube bulge tests for tube hydroforming are simulated by a commercial finite element solver to predict the limit strains. Numerical simulation of forming limit strains in tube hydroforming with different internal pressure and different simulation set up with or without axial feeding are considered to develop wide range of strain paths in the present work. The effects of process conditions on the forming limit strains are detailed. In this paper the forming limit strains during tube hydroforming are simulated for prestrain and compared with zero prestrain. Prediction of limits strains is based on a novel thickness based necking criterion.

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