Inhibiting thinning in tube bending by considering a coupling effect of material compensation and friction under a boosting movement

Abstract Pressure die boost is an effective method to inhibit the thinning in the manufacturing process of aerospace tubes, and its mechanism is concerned by scholars at home and abroad. Finite element and experimental methods were conducted to analyze the tube thinning with and without boost. The effects of boosting velocity and friction on the outer wall thickness of the tube are studied. Results show that frictional force generated by the boost and the material compensation effect combine to resist the outer wall thinning during the bending process. When the boosting velocity is higher than the tube bending linear velocity, the frictional force of the boost generates a specific compressive stress, which weakens the tensile stress during the bending process of the outer wall. In the meantime, the boosting effect transfers the material from the feed section to the bending section, compensating for the thinning of the tube wall during the bending process. A new theoretical model of tube bending and thinning under boost conditions is proposed to explain this coupling effect. The relative error between the new theoretical model and the experimental value is less than 1.5%, and the accuracy is improved by 5.3% compared with the traditional no-boost condition. It overcomes the poor accuracy of the existing thinning model when fitting to boosted conditions and reveals the boosted effect's mechanism on the tube thinning.