Effect of the Mechanical Parameters Used as Input Data in the Yield Criteria on the Accuracy of the Finite Element Simulation of Sheet Metal Forming Processes

Abstract

The accuracy of the finite element simulation of sheet metal forming processes is mainly influenced by the shape of the yield surface used in the mechanical model and, in particular, by the number of input values used in the identification of the yield surface. This paper investigates the effect of the input values used for identifying the BBC 2005 yield criterion on the accuracy of the finite element predictions. The accuracy assessment of the simulation is based on the comparison of the numerical predictions obtained using the commercially available FE programme AUTOFORM and experimental measurements obtained from the hydraulic bulging of sheet metals. Thickness and strain distributions, as well as the geometry of the bulged specimen were taken as comparison parameters. The accuracy of the finite element predictions obtained using the Hill-48 and Barlat-89 yield criteria is also studied and discussed in comparison with the results provided by the BBC 2005 yield and the experimental data.

Comparison of different yield criteria in various deep drawn cups

“…The experimental data in Table 4 yield that σ 0 =σ 90 < 1 for both SS304 and DKP6112 steels, verifying weakness of the Hill'48 model to simulate the real yield behavior of the material in the experiments. The Hill'48 model uses only the uniaxial yield stress in the rolling direction to describe the anisotropy coefficients [40,46] whereas Hu2003, Yld2003-8p and BBC2008-8p criteria use yield stresses and r-values found from uniaxial and biaxial tension tests.…”

Malzeme Modellerinin Sac Metal Sonlu Elemanlar Analizi Tahmin Performansına Etkisinin Değerlendirilmesi

“…Buna ek olarak Barlat-89 modeli bu prosesin şekillendirme adımını dahi tahmin edememiştir. Barlat-89 modelinin alüminyum alaşımları için daha uygun bir model olduğu literatürdeki çalışmalarla doğrulanmıştır [34,35]. Bu durum yapılan çalışmada da gözlemlenmiş olup çelik malzemelerde Barlat-89 modeli özellikle şekil bozukluğu açısından başarısız olmuştur.…”

Influence of the characteristics of the experimental data set used to identify anisotropy parameters

“…Moreover, it has been shown that the ability of a yield criterion to describe the material's anisotropic behaviour depends on its flexibility, which in turn is related to the number of anisotropic parameters. As a consequence, the necessary number and type of experimental tests for the calibration of flexible yield criteria increases [13,25,26]. However, the cost associated with a large number of different types of experimental tests along with the mathematical complexity of the advanced yield criteria are the major shortcomings contributing to a limited use in an industrial environment.…”

“…The predictions obtained with BBC2005, Hill48 and Yld89 yield criteria are compared to experimental ones, showing that BBC2005 leads to the best agreement. Lazarescu et al [26] provides a rough guide, stating that the Yld89 criterion is better at predicting the biaxial yield stress than Hill48, which underestimates the experimental data for the AA6016-T4 aluminium alloy. As an alternative to the extensively used conventional calibration procedures which are based on uniaxial tensile and equibiaxial tests, Aretz put forward a calibration method involving three directional uniaxial tensile tests and two plane strain tensile tests, performed in the rolling and transverse directions.…”

“…They have shown that the use of seven or eight input values leads to a good level of agreement between predicted and experimental results. Lazarescu et al [26] investigated the influence of the input data used to calibrate yield criteria parameters on the accurate prediction of hydraulic bulge test results. The predictions obtained with BBC2005, Hill48 and Yld89 yield criteria are compared to experimental ones, showing that BBC2005 leads to the best agreement.…”