Weiqin Tang

A Crystalline Plasticity Finite Element Method for Simulation of the Plastic Deformation of AZ31 Magnesium Alloys

In this paper, a constitutive framework based on a crystalline plasticity model is employed to simulate the plastic deformation of AZ31 magnesium alloy, which posses the hexagonal close packed (HCP) crystal structure. Dislocation slip and mechanical twinning are taken into account in the model. The successive integration method is used to determine the active slip systems, and the contribution of twinning to the grain reorientation is treated by the PTR method. The FE model is introduced into ABAQUS/Explicit through a user material subroutine (VUMAT). Three deformation processes of AZ31 magnesium alloy, including tension, compression and a stamping process, are simulated with the present method. The simulation results are compared with experiment and those presented in the literature.

Crystal plasticity finite element modelling of the extrusion texture of a magnesium alloy

In this paper, a crystal plasticity finite-element model (CPFEM) is developed to simulate the hot extrusion texture of the magnesium alloy AZ31. The crystal plasticity model is implemented in ABAQUS™ via user interface VUMAT subroutine. The elasto-plastic self-consistent (EPSC) model is used as the basic polycrystal framework to simulate the slip and twinning during the extrusion. Furthermore, this framework is extended to account for the effects of the dynamically recrystallized (DRX) grains on the extrusion textures. Good agreement is found between the experimentally measured and simulated textures. The simulation results show that the presence of a secondary texture component around || extrusion direction (ED) can be attributed to the lattice rotation around the c-axis during the formation of the DRX grains. In addition, the shear strain imposed on the extruded material affects the resulting texture by enhancing the basal slip mode as the material passes through the extrusion opening.

Forming limit diagram analysis based on crystal plasticity for magnesium alloy sheets

In the sheet metal forming industry, forming limit diagram (FLD) is a useful tool for quantifying metals formability. However, the experimental measurement of FLD is difficulty, time consuming and expensive process. It would be useful if FLD calculated with a theoretical model could replace experimental measurements. In this research, a rate independent crystal plasticity model is developed to analyze the plastic deformation of hexagonal close packed (HCP) materials by incorporating the crystallography of deformation twinning in plasticity model. The numerical simulations of FLD for AZ31 magnesium alloy are performed based on the crystal plasticity model incorporated within the Marciniak- Kuczynski (M-K) approach. The approach allows for the incorporation of initial texture, evolution of texture, and texture-induced anisotropy. The effects of mechanical twinning on plastic deformation and FLD behavior for AZ31 alloy are also incorporated. Finally, the calculation of the FLD for AZ31 alloy successfully pre...

Simulation of cylindrical cup drawing of AZ31 sheet metal with crystal plasticity finite element method

As a light-weight structural material, magnesium alloys show good potential in improving the fuel efficiency of vehicles and reducing CO2 emissions. However, it is well known that polycrystalline Mg alloys develop pronounced crystallographic texture and plastic anisotropy during rolling, which leads to earing phenomenon during deep drawing of the rolled sheets. It is vital to predict this phenomenon accurately for application of magnesium sheet metals. In the present study, a crystal plasticity model for AZ31 magnesium alloy that incorporates both slip and twinning is established. Then the crystal plasticity model is implemented in the commercial finite element software ABAQUS/Explicit through secondary development interface (VUMAT). Finally, the stamping process of a cylindrical cup is simulated using the developed crystal plasticity finite element model, and the predicting method is verified by comparing with experimental results from both earing profile and deformation texture.