Title: Strain path influence on size effects during thin sheet copper microforming

Authors: Pierre-Antoine Dubos; Eric Hug; Simon Thibault; Antoine Gueydan; Clément Keller

Addresses: Laboratoire CRISMAT/ENSICAEN/UCBN/CNRS, UMR 6508, 6 Bd du Maréchal Juin, 14050 Caen, France ' Laboratoire CRISMAT/ENSICAEN/UCBN/CNRS, UMR 6508, 6 Bd du Maréchal Juin, 14050 Caen, France ' ENSICAEN, 6 Bd du Maréchal Juin, 14050 Caen, France ' Laboratoire CRISMAT/ENSICAEN/UCBN/CNRS, UMR 6508, 6 Bd du Maréchal Juin, 14050 Caen, France ' Ermeca-GPM, UMR 6634 CNRS – Université de Rouen, INSA de Rouen, avenue de l'université 76800, Saint-Etienne du Rouvray, France

Abstract: The influence of the size effects on the forming processes for micro-sized parts is not yet well known. This work follows experimental and numerical studies of the effect of a reduction in thickness (t) over grain size (d) ratio on the mechanical properties of high purity copper. Under tensile conditions, copper exhibits softer mechanical properties if t/d < 6, in agreement with previous results concerning Al or Ni. To assess the influence of complex loadings linked to forming processes on size effects, Nakazima tests were performed with 20 mm hemispherical punch on a universal sheet metal testing machine associated to a 3D video extensometer. Our results revealed that size effects are strongly sensitive to strain paths. Depending on these latter, the deterioration of the mechanical properties shown for tension is modified.

Keywords: size effects; forming limit diagrams; polycrystalline copper; microformability; strain paths; thin copper sheet; formability; microforming; thickness reduction; mechanical properties.

DOI: 10.1504/IJMPT.2013.058964

International Journal of Materials and Product Technology, 2013 Vol.47 No.1/2/3/4, pp.3 - 11

Received: 04 Feb 2013
Accepted: 14 Sep 2013
Published online: 28 Jun 2014 *

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