Influence of Yield Stress and Material Area Ratio on Bondability and Formability in Drawing Processes of Bimetallic Rods

Finite element simulations were conducted to investigate the drawing process of bimetallic rods, a key manufacturing technique used in aerospace, automotive, and advanced engineering applications. The study focused on how independent variations in the yield stress of the core and sleeve (150, 200, 250, 300 and 350 MPa) and differences in the initial core ratio (10%, 30%, 50%, 70% and 90%) affect bondability, formability, and fracture behavior. Simulations showed that the maximum achievable reduction ratio varied from approximately 50% to 55%, and hence, we focused on this range. By analyzing the maximum achievable reduction ratio and the distribution of effective strain, the simulations provided insights into the deformation mechanisms and failure modes of these composite structures. The results reveal that increasing the yield stress in either the core or the sleeve reduces the drawing limit by promoting stress concentrations at the interface, leading to premature failure and weakened bondability. Moreover, the core ratio critically influences performance: high core ratios result in thin, vulnerable sleeves prone to early fracture, while low core ratios produce thin cores that fail under high deformation loads. Strain analysis indicated that higher core yield stress increased interfacial shear stress, leading to localized failure, while a lower core yield stress resulted in more uniform material flow. A balanced core ratio (approximately 50%) yields a more uniform strain distribution, though it requires robust interfacial bonding to prevent delamination. These findings underscore the importance of optimizing both material properties and geometric configurations to enhance bondability, formability, and structural integrity during the drawing process of bimetallic rods.