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IASS-SLTE Symposium 2014: Shells, Membranes and Spatial Structures: Footprints


IASS Symposium 2014

SESSION: General 10: ETFE - Design and Experiments

TensileTensile property of ETFE foil after viscoplastic-forming process

< Table of Contents for General 10: ETFE - Design and Experiments
  • Proceedings Name: IASS-SLTE Symposium 2014: Shells, Membranes and Spatial Structures: Footprints
  • ISSN: (Electronic Version) 2518-6582
  • Session: General 10: ETFE - Design and Experiments
  • Title: TensileTensile property of ETFE foil after viscoplastic-forming process
  • Author(s): Minger WU, Yintang LI, Weitao XU
  • Keywords: ETFE foil, viscoplastic-forming, tensile property, yield point, modulus
Abstract
ETFE cushion traditionally forms its shape by cutting pattern, cutting and welding plane foil to curved surface. Recently, a novel form finding process, called viscoplastic-forming process, has been studied. This method utilizes unrecoverable deformation of ETFE foil to form designed structural shape, which makes the form finding process of ETFE cushion simpler. Two series (S-1 and S-2) of viscoplastic-forming tests were performed to investigate factors that affect the unrecoverable deformation, namely the objective strain in loading process and the time in creep process. Three objective strains were set in S-1 and four kinds of time were set in S-2. While the objective strain determined plastic deformation in the viscoplastic-forming process, the time in creep process determined that viscoplastic deformation. Results of these tests showed unrecoverable deformation increased with the enhancement of the objective strain and the time in creep process. Also, in most cases, the objective strain contributed more than the time in creep process to the final unrecoverable deformation. For the objective strain must being above the first yield point, the tensile mechanical property of ETFE foil after viscoplastic-forming process was different with that in original material. Uniaxial tensile tests were performed to investigate the tensile property of ETFE foil. Results showed that the first yield point moved to the new yield surface and the second yield point also changed. Strain and stress of the first yield point both increased, strain of the second yield point decreased and stress of the second yield point kept the same. Meanwhile, after the viscoplastic-forming process, initial tangent modulus of ETFE foil kept identical, and modulus between two yield points increased.

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