Influence of Surface Effect On Nickel Micro Deep Drawing Process

In this paper, the forming behavior of nickel sheets is investigated as a function of the number of grains across the thickness by finite element simulations. Experimental tensile tests were carried out on nickel samples of approximately 100 μm grain size and thicknesses ranging between 12.5 μm and 3.2 mm. The decrease of the number of grains across the thickness involves a decrease of tensile stress due to the apparition of surface effects. These latter were taken into account for the deep drawing simulation of samples with 250 μm thickness by the use of two different constitutive elasto-plastic laws for surface and core grains. The simulations with two laws predict a modification of the distribution of the V.M. equivalent stress and of the damage zones compared to results from simulations using a simple average law. © 2010 American Institute of Physics.Book subtitle: DEDICATED TO PROFESSOR O. C. ZIENKIEWICZ (1921-2009)status: publishe