Numerical study on the effect of anisotropy on deformation behavior of aluminum bilayer sheets in single point incremental metal forming

Abstract

The anisotropy of metals is an important property that has a significant impact on the dimensional accuracy of components in manufacturing. In metal forming processes significant attention has been given to multilayer composite sheets as they may combine the advantages of materials with various mechanical properties. In this study, the effect of anisotropy is investigated in the process of single point incremental forming (SPIF) of aluminum bilayer sheets. The finite element method (FEM) is used to study the effect of layer arrangement and the anisotropy of metal sheets relative to the rolling direction. For the effective description of sheet metal anisotropy, the two-dimensional Yld2000-2D yield function is implemented in Abaqus software using a material subroutine (VUMAT). The calculation and calibration of the coefficients of Yld2000-2D in accordance with the experimental data were performed using a MATLAB code. For comparison, the anisotropic coefficients of Yld2000-2D were replaced by unit values in the same VUMAT to investigate forming behavior in the isotropic case with the von Mises yield function. Anisotropic and isotropic models are compared in a conical geometry by assessing equivalent plastic strain, sheet thickness, and forming tool reaction forces. Our findings show that anisotropy of sheet metal causes less variation in material properties compared to the isotropic case, significantly affecting the stiffness and, subsequently, the final shape dimensional accuracy of the formed component. The results of the study have a practical application in that they can be used to identify strategies for anisotropic bimetal sheets to improve such material forming processes