Original scientific paper

Inhomogeneity and forming limits of copper sheets

Feliks Stachowicz ; Rzeszów University of Technology, Faculty of Mechanical Engineering and Aeronautics, Department of Materials Forming and Processing, 35-959 Rzeszów, POLAND *

* Corresponding author.

Abstract

In many calculations of the forming limit diagram (FLD) of sheet metal, based on the M-K theory, the imperfection parameter f, was chosen arbitrarily or for the best fit of calculations with experimental results. The main purpose of this work was to replace the fitting inhomogeneity coefficient with a measurable one. In the proposed model it was assumed that the material inhomogeneity was the result of surface roughness and internal defects (voids). It was also assumed that the value of the
inhomogeneity coefficient changes with the increasing strain. The experiments were carried out for the copper sheets, annealed to produce different material structures. As a result of the experimental work original equations were proposed describing the relationship between inhomogeneity coefficients and effective strain and grain size. These equations were used in the theoretical calculations of the FLD. The theoretical calculations of the strain limits of the tested sheets were based on the associated flow rules, assuming strain hardening and strain softening processes.

Keywords

forming limit diagram (FLD), M-K theory, inhomogeneity coefficient, copper sheets

Hrčak ID:

313897

URI

https://hrcak.srce.hr/313897

Publication date:

21.12.2003.

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