Study on Multi-Pass Steel Ball Push Bending Process of 5A02 Aluminum Alloy Thin-Walled Tube with 0.8 D Bending Radius

During multi-pass push-bending, the supporting behavior at process interfaces may induce microscopic surface damage and thereby adversely affect the bonding performance of subsequent surface treatments. To address the excessive cross-sectional ovality in conventional tube push-bending and the difficulty of recovering liquid filling media, this work proposes a novel multi-pass push-bending process using discrete steel balls as filling and supporting media, with 5A02 aluminum alloy tubes of Φ32 × 1 mm selected as the research object. A corresponding finite element model is established, and orthogonal simulations are performed to optimize the parameters, including steel ball diameter, tube blank length, and tube–die friction condition. The results show that a steel ball diameter close to the inner diameter of the tube blank provides stronger internal support and remarkably restrains cross-sectional distortion. A shorter tube blank facilitates material flow in the bending zone and alleviates excessive inner-wall thickening. Reducing the tube blank–die friction effectively suppresses excessive outer-wall thinning. While achieving favorable macroscopic forming quality, the proposed process also exhibits promising potential for reducing surface scratches and improving surface integrity.