Exploration of heating zones in the differential heating push-bending for Ti-3Al-2.5 V tubes with small bending radius

The complexity of forming a tube escalates inversely with the bending radius; a smaller radius corresponds to increased difficulty. A differential heating push-bending (DHP-B) forming approach was proposed, which established a nonuniform temperature field, enabling the formation of bent tubes with reduced bending radius. The impact of the temperature field and heating zones on the forming of the TA18 (Ti-3Al-2.5 V) bent tube (D = 20 mm, t = 1, r = 0.9 D) was investigated through finite element methods and experiments. The findings reveal that unilateral heating on the outer side of the tube results in the inward displacement of the neutral layer of the wall thickness, thus reducing the thickening on the intrados of the tube. Conversely, heating on the inner side of the tube instigates an outwards displacement of the neutral layer, leading to an increase in the inner thickening of the bend. Despite increasing the stress on the bent section, heating the outer side mitigates the material flow to the thickened area due to the nonuniform yield stress induced by the nonuniform temperature field, thereby reducing the generation of compressive strain. Furthermore, the study reveals that when heating is confined to the bent section or the straight-line section, the thickening is greater than when the entire outer side is heated. Finally, based on the finite element results, a TA18 bent tube with a bending radius of 0.9 D was successfully formed.