Characterization and Thermo Elasto Viscoplastic Modelling of Cunip Copper Alloy in Blanking Process

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Mechanics, Materials Science & Engineering, March 2016

ISSN 2412-5954

Characterization and Thermo Elasto Viscoplastic Modelling of Cunip Copper Alloy in Blanking Process A. Touache1, S. Thibaud2, J. Chambert2, P. Picart2 1 Mechanical Engine Fez, Morocco 2

Institute FEMTO-ST, Applied Mechanics Laboratory, University of Franche-

DOI 10.13140/RG.2.1.3289.0645

Keywords: strain rate/temperature sensitivity, blanking process, copper alloys, FEM

ABSTRACT. Numerical simulations of blanking process are performed to investigate CuNiP copper alloy behavior under blanking conditions. Numerical simulations are mostly dependant of a correct modeling of the material behavior with thermo-mechanical sensitivity. A thermo-mechanical characterization by a set of uniaxial tensile tests at different temperatures and strain rates is presented. A thermo elasto - viscoplastic approach was investigated to propose the mechanical behavior model based on a phenomenological way in the framework of the thermodynamic of irreversible to the numerical simulation of precision blanking operations and developed at the Applied Mechanics Laboratory. Numerical results are presented and compared with experiments.

1. Introduction. In precision blanking for very thin sheet about 0.254mm thickness, accurate predictions of maximal blanking load and cut edge profile are essential for designers and manufacturers. A finite element code untitled Blankform [1-2] has been developed at the Applied Mechanics Laboratory to simulate the blanking operation from elastic deformation to the complete rupture of the sheet. In blanking operation like many metal forming processes the material undergoes very large strains, high strain rates and significant variations in temperature. So to obtain an acceptable prediction of the maximal blanking load by FEM simulation, it needs an adapted model for mechanical behavior which takes into account large strains, strain rate and thermal effects. In this paper, a specific thermo-elastoviscoplastic modelling has been developed for CuNiP copper alloy used for manufacturing electronic components by high precision blanking. In first, tensile tests are carried out at room temperature with various strain rates. The temperature distribution in the specimen is observed using a thermal CCD camera. Then a second set of tensile tests are carried out in various isothermal conditions. Considering locally the temperature evolution as a function of the strain rate, the analysis of the tensile curves obtained for these experiments allows to propose a new thermo-elasto-viscoplastic modelling for a copper alloys. The identification of the associated material parameters is investigated and presented. The proposed mechanical behavior is implanted in the finite element code Blankform. Finally the capability of the new modelling to predict the maximum blanking force is presented and discussed. 2. Experiments. To study strain rate sensitivity, tensile tests are performed at room temperature with four strain rates: and . During each tests, a thermal camera allows the measurement of the heating in the specimen due to the mechanical energy dissipation. The second set of tests is performed at a constant strain rate with three different temperatures T=20 MMSE Journal. Open Access www.mmse.xyz

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