Study on anti-barrel deformation of ultrasonic-assisted upsetting

Anti-barrel shape is a typical phenomenon for a cylinder deformed in the upsetting process superimposed with sufficiently high intensity of ultrasound. In this paper, the cylindrical specimens of aluminum 6061, ϕ 4.08mm×4.8mm, were performed as the experimental object. With the different temperatures of 350°C, 400°C and 500°C and the longitudinal vibration amplitudes of 6μm and 10μm, the anti-barrel forming law of cylindrical specimens was studied, as well as the material flow law in the forming process. Results show that, the anti-barrel profiles may show up elliptic and hyperbolic curves, as well as the circular arc. The forming process of anti-barrel profile consists of multiple processes of high-speed collision, low-speed collision, high-speed compression and low-speed compression. The formation of anti-barrel profile may effectively promote the uniform flow of the end material and avoid upward-moving of the lateral material which is inevitable in conventional upsetting. The barrel and anti-barrel profiles perform almost opposite types of hot-working streamline, of which the layout of arcs opening inward and outward respectively.