Formability limits by fracture in sheet metal forming |
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| Affiliation: | 1. Institute of Forming Technology and Lightweight Construction, Technical University of Dortmund, Baroper Str. 301, D-44227 Dortmund, Germany;2. Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;1. Massachusetts Institute of Technology, Impact and Crashworthiness Laboratory, Department of Mechanical Engineering, Cambridge, MA 02139, USA;2. MINES ParisTech, Centre des Matériaux, CNRS UMR 7633, BP 87, 91003 Evry Cedex, France;2. Escola de Engenharia de São Carlos, University of São Paulo, Av. Trabalhador São-Carlense, 400, São Carlos, CEP: 13566-590, Brazil;3. Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;4. Department of Engineering, University of Reading, Box 225, Reading RG6 6AY, UK;1. Department of Mechanical and Manufacturing Engineering, University of Seville, Camino de los Descubrimientos s/n, 41092 Sevilla, Spain;2. Department of Mechanical Engineering and Industrial Construction, University of Girona, C/Maria Aurèlia Capmany, 61. 17071 Girona, Spain;1. IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;2. Institute of Forming Technology and Lightweight Construction, Technical University of Dortmund, Baroper Str. 303, D-44227 Dortmund, Germany;3. Department of Engineering, University of Reading Box 225, Reading RG6 6AY, UK |
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| Abstract: | The aim of this paper is twofold: first, to revisit the forming limit diagram (FLD) in the light of fundamental concepts of plasticity, damage and ductile fracture mechanics and, second, to propose a new experimental methodology to determine the formability limits by fracture in sheet metal forming. The first objective makes use of the theory of plasticity applied to proportional strain loading paths, under plane stress conditions, to analyze the fracture forming limit line (FFL) and to introduce the shear fracture forming limit line (SFFL). The second objective makes use of single point incremental forming (SPIF), torsion and plane shear tests to determine the experimental values of the in-plane strains at the onset of fracture. Results show that the proposed methodology provides an easy and efficient procedure to characterize the formability limits by fracture in sheet metal forming. In particular, the paper shows that the FFL determined by means of tensile and conventional sheet formability tests is identical to that determined from SPIF tests on conical and pyramidal truncated specimens. The new proposed approach is expected to have impact in the established methodologies to outline the formability limits on the basis of the forming limit curves (FLC's) at the onset of necking. |
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| Keywords: | Forming limit diagram Formability Fracture Single point incremental forming Shear tests |
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