Mechanism of Springback Influence on Stiffness of Automotive Cylindrical Shallow Panels

XING Zhongwen¹  ZHAO Lihong ¹  YANG Yuying²

(1. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001)

Abstract: The finite element models of cylindrical shallow shells that could represent automobile panels are established. Numerical simulations of forming, springback and stiffness of the cylindrical shallow shells are carried out. The geometric information and the stress of three simulation processes are obtained. Springback observed in cylindrical shallow shell is influenced by the variation of blank holder force (BHF), and the mechanism of influence of springback on the stiffness is achieved. Based on the analysis of distribution of the stress-strain after cylindrical shallow shell forming and springback, it is found that great residual compressive stress exists along the cylindrical and curved direction of shell. The residual compressive stree is in a state of uneven distribution, and the residual compressive stress is the mechanical condition for the variation of stiffness. The spring back after stamping of the part results in a geometrical change, so the curvature radius of shell is the geometrical condition for the variation of stiffness. The greater the springback is, the greater the residual compressive stress will be, and the more uneven the distribution will be, and the smaller the stiffness will be. The greater the curvature radius is, the smaller the stiffness will be, and vice versa.

Key words: Cylindrical shallow shells Numerical simulation Springback Blank holding force

CLC No: TG386

Received 200770519, received in revised form 20071227

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