[SY-F1] Symposium F-1

[SY-F1] Development of a multiscale simulation system based on microstructure of fine-grained aluminum

^○ATSUSHI SAGARA, YOSHITERU AOYAGI (Dept. of Finemechanics, Tohoku Univ., Japan)

In plastic working of metal plates, spring back and generation of cracks and sticks cause defective products. The finite element method is widely used to predict and control behavior of plastic working. Since press forming that is a sort of plastic working consists of various processes such as deep drawing, stretching, and bending, a multiaxial stress state dominates plastic deformation. The von Mises yield function is well known as a theory to express yielding behavior of mechanical isotropic metals under a multiaxial stress state. The mechanical properties for the von Mises yield function are usually identified by a uniaxial tensile test. In the case of ultrafine-grained metals produced by severe plastic deformation, they have strong orientation in mechanical properties due to a rolling texture. Therefore, the isotropic yield function cannot fully express the yielding behavior of ultrafine-grained metals. Some models such as Hill yield function, Barlat Yld-2000, etc. are proposed to express the mechanical anisotropy of metals. However, a large number of material parameters are required for determination of yield function and it is difficult to determine these parameters only by uniaxial tensile test. Tests reproducing a multiaxial stress state such as a biaxial tensile test and a compression-torsion test, which requires a tremendous labor, are necessary to obtain a yield surface identifying the material parameters. Numerical prediction of yield surface is anticipated on the basis of multiscale simulation considering information of microstructure of metals.
In this study, we aim at seamless bridging of design, development, and practical use of mechanical anisotropic metals with CAE system. Mechanical anisotropy of severe rolled aluminum is predicted by crystal plasticity analyses reflecting information of rolling texture. Furthermore, biaxial tensile tests were conducted and the mechanical anisotropy was evaluated by comparison of the experimental and numerical results. We developed a user subroutine for a commercial CAE software. Simulation result calculated by the CAE software was compared with microscopic deformation behavior of practical plastic working to evaluate the effect of predicted anisotropic yield function.