Accurate assessment of plastic anisotropy is essential to many material models used in computer-aided sheet metal forming simulations. In this analysis, the influence of discontinuous yielding (yield point elongation or YPE) on normal anisotropy (R-value) measurements was examined. A laboratory-annealed, non temper-rolled, aluminum-killed drawing quality (AKDQ) steel was considered. It was found that discontinuous yielding significantly influences R-value calculations by imposing an effective offset to the width strain measurement during a sheet tensile test if the R-value is defined in terms of total strains (R = epsilonW/ epsilonT). The effect may be positive or negative and shows considerable variability between tests. For a more accurate and consistent representation of normal anisotropy, the incremental R-value (R' = d epsilonW/d epsilonT) should be used in cases of significant YPE. A procedure has been developed to account for the low-strain effects of discontinuous yielding on plastic anisotropy measurements, where the R'-value is determined in a region of stable, uniform deformation on the stress/strain curve. For adequately temper rolled materials (with minimal YPE) and for inherently YPE-free materials, the R-value may be determined in the conventional way.
Influence of discontinuous yielding on normal anisotropy (R-value) measurements
Einfluss der Streckgrenzenverlängerung auf die R-Wert Messung
Journal of Materials Engineering and Performance ; 14 , 5 ; 616-622
2005
7 Seiten, 12 Quellen
Aufsatz (Zeitschrift)
Englisch
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