An Enhanced Johnson–Cook Model for Hot Compressed A356 Aluminum Alloy

Abstract

The isothermal compression experiments with the strain rates of 0.01–10 s−1 and deformation temperature range of 300–420 °C are performed to investigate the hot deformation behavior of A356 aluminum alloy. Also, the complex deformation mechanisms are analyzed. It is found that, as the strain is gradually increased, the flow stress first rises, and then the stable stress appears without a tangible peak. The microstructures exhibit large elongated grains, and only a few small new grains appear under most deformation conditions. It is because the dynamic recovery (DRV) is the dominant softening mechanism. Based on the measured data, both the original Johnson–Cook (O–JC) model and modified Johnson–Cook model (M–JC) are built for the tested aluminum alloy. However, there are different deviations between the experimental and the predicted true stresses by O–JC model and M–JC model. Considering the obvious DRV features, an enhanced Johnson–Cook (EH–JC) model is proposed by introducing the stress–dislocation relation. The accuracy of the EH–JC model is validated because the correlation coefficient between the experimental and predicted results is as high as 0.997, whereas the average absolute relative error is merely 2.84%.

Nanomechanical Characterization of the Deformation Response of Orthotropic Ti–6Al–4V

“…The difference between the strain rate selected for identifying the isotropic hardening law and that present in the nanoindentation simulation and experimental tests produces small variations in the stresses and overall plastic material response. [12,13,16,91,92]…”

Prediction of Exit Thickness and Its Compensation after Snake Rolling of Aluminum Alloy Thick Plate

“…Constitutive relation [25][26][27] is a key content for establishing the relationship between loads and deformation degree and has been researched for a long period. Based on the theory of the elastoplastic body, the constitutive relation of the thick plate is set as a bilinear kinematic model with an elastic modulus of the thick plate being 0.8 GPa and yield strength being 60 MPa and no hardening effect [28].…”

A Strain Rate‐Dependent Constitutive Model for Asymmetric Hardening Behavior of TB9 Titanium Alloy

“…No apparent difference in the values of B c and C c is observed for different strain rates, and the values of B c and C c are 2900.01 and 5675.12, respectively. The shear stress-plastic strain curves under different strain rates are fitted by Equation (10), as shown in Figure 13. The B s and C s are material constants that are obtained from the fitting results in Figure 13.…”

“…[ 7,9 ] Johnson–Cook constitutive equations are a very useful model for describing the temperature effect and strain rate effect of materials; however, it adopts the isotropic hardening and cannot be used to describe the plastic deformation process of tension and compression asymmetric materials. [ 10–12 ]…”

“…[7,9] Johnson-Cook constitutive equations are a very useful model for describing the temperature effect and strain rate effect of materials; however, it adopts the isotropic hardening and cannot be used to describe the plastic deformation process of tension and compression asymmetric materials. [10][11][12] Constitutive models should provide correct description of the asymmetric yield behavior of tensile and compression with simplified yield function for user-friendly finite element implementation. [13,14] For a given strain magnitude, it is generally assumed that the tensile and compressive flow stresses of metallic materials are the same as each other.…”