On the Determination of Forming Limits in Polycarbonate Sheets
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Department of Mechanical and Manufacturing Engineering, University of Seville, Camino de los Descubrimientos s/n, 41092 Sevilla, Spain
2
IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
*
Author to whom correspondence should be addressed.
Materials 2020, 13(4), 928; https://doi.org/10.3390/ma13040928
Received: 4 December 2019
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Revised: 7 February 2020
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Accepted: 9 February 2020
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Published: 19 February 2020
(This article belongs to the Special Issue Formability of Materials)
By proposing an adaptation of the methodology usually used in metal forming, this paper aims to provide a general procedure for determining the forming limits, by necking and fracture, of polymeric sheet. The experimental work was performed by means of Nakajima specimens with different geometries to allow to obtain strains in the tensile, plane, biaxial and equibiaxial states for Polycarbonate sheet with 1 mm of thickness. The application of the time-dependent and flat-valley approaches used in metals has been revealed appropriate to characterize the onset of necking and obtain the forming limits of polycarbonate, despite the stable necking propagation typical of polymeric sheets. An analysis of the evolution of the strain paths along a section perpendicular to the crack allowed for a deeper understanding of the steady necking propagation behaviour and the adoption of the methodology of metals to polymers. The determination of the fracture strains was enhanced with the consideration of the principal strains of the DIC system in the last stage, just before fracture, due to the significant elastic recovery typical of polymeric sheets. As a result of this analysis, accurate formability limits by necking and fracture are obtained for polycarbonate sheet, together with the principal strain space, providing a general framework for analysing incremental sheet forming processes where the knowledge of the fracture limits is relevant.
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Keywords:
polymer sheet forming; formability limits; necking; fracture; polycarbonate
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MDPI and ACS Style
Rosa-Sainz, A.; Centeno, G.; Silva, M.B.; López-Fernández, J.A.; Martínez-Donaire, A.J.; Vallellano, C. On the Determination of Forming Limits in Polycarbonate Sheets. Materials 2020, 13, 928. https://doi.org/10.3390/ma13040928
AMA Style
Rosa-Sainz A, Centeno G, Silva MB, López-Fernández JA, Martínez-Donaire AJ, Vallellano C. On the Determination of Forming Limits in Polycarbonate Sheets. Materials. 2020; 13(4):928. https://doi.org/10.3390/ma13040928
Chicago/Turabian StyleRosa-Sainz, Ana, Gabriel Centeno, Maria B. Silva, Jose A. López-Fernández, Andrés J. Martínez-Donaire, and Carpoforo Vallellano. 2020. "On the Determination of Forming Limits in Polycarbonate Sheets" Materials 13, no. 4: 928. https://doi.org/10.3390/ma13040928
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