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Characterization of anisotropy evolution and its application on deep drawing finite element simulation of aluminum alloy 5754-H22

In the present paper, an extensive study was carried out to characterize the plastic anisotropy and its evolution with straining in tensile testing for aluminum alloy sheet AA5754- H22. The yield stress ratios and Lankford coefficients are considered as variables dependent on the plastic strain. Lankford coefficient (r-value) was calculated as an instantaneous value based on the polynomial fit of the transverse versus longitudinal true plastic strain diagram. The directional dependences of yield stress ratios and r-values corresponding to the selected amounts of plastic work are determined. The capabilities of the simplest orthotropic stress function Hill (1948) under the associated/non-associated flow rule in predicting observed plastic material behavior were examined. In order to describe the plastic anisotropy evolution, the anisotropy parameters of Hill (1948) yield function/plastic potential are set as the polynomial functions of the equivalent plastic strain. The developed model based on the non-associated flow rule and Hill (1948) stress functions with variable anisotropy parameters is further analyzed in predicting the cylindrical cup drawing process. The implicit algorithmic formulation of the analyzed constitutive description is implemented into the finite element program ADINA. The predictions of cup drawing process are compared with the experimental data for the considered material. Based on the obtained results, the influence of plastic anisotropy evolution on the final predictions as well as the capabilities of developed constitutive descriptions are assessed.

anisotropy evolution ; sheet metals ; constitutive modeling ; non-associated flow rule ; cylindrical cup drawing

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