Abstract
Titanium bent tubular parts attract extensive applications, thus meeting the ever-growing demands for light weight, high reliability, and long service life, etc. To improve bending limit and forming quality, local-heat-assisted bending has been developed. However, significant springback seriously reduces the dimensional accuracy of the bent tubular parts even under elevated forming temperatures, and coupled thermal-mechanical working conditions make springback behavior more complex and difficult to control in warm bending of titanium tubular materials. In this paper, using warm bending of thin-walled commercial pure titanium tube as a case, a coupled thermal-mechanical finite element model of through-process heating-bending-unloading is constructed and verified, for predicting the springback behavior in warm bending. Based on the model, the time-dependent evolutions of springback angle and residual stress distribution during thermal-mechanical unloading are studied. In addition, the influences of forming temperature and bending angle on springback angle, thickness variation, and cross-section flattening of bent tubes are clarified. This research provides a fundamental understanding of the thermal-mechanical-affected springback behavior upon local-heat-assisted bending for improving the forming accuracy of titanium bent tubular parts and structures.
Highlights
Titanium bent tubular components are widely used in high-end manufacturing industries, such as aircraft, aerospace, nuclear energy, etc., due to their high specific strength and excellent resistance to corrosion and fatigue [1,2,3]
Accurate control of springback is of great importance to the fabrication of high-quality parts, which in turn requires a clear understanding of springback characteristics in the forming process
For the springback in warm forming of titanium alloys, Ozturk et al experimentally studied the influence of temperature on springback in bending of a commercial pure titanium (CP-Ti) sheet from room temperature to 300 ◦ C, and revealed that springback is dramatically reduced at elevated temperatures [21]
Summary
Titanium bent tubular components are widely used in high-end manufacturing industries, such as aircraft, aerospace, nuclear energy, etc., due to their high specific strength and excellent resistance to corrosion and fatigue [1,2,3]. In the tube bending processes, one of the most important problems affecting dimensional accuracy of the formed parts is springback during unloading. For the springback in warm forming of titanium alloys, Ozturk et al experimentally studied the influence of temperature on springback in bending of a commercial pure titanium (CP-Ti) sheet from room temperature to 300 ◦ C, and revealed that springback is dramatically reduced at elevated temperatures [21]. This paper takes the local-heat-assisted bending of a thin-walled CP-Ti tube as a case, attempting to clarify the springback characteristics through the coupled thermal-mechanical modeling approach. The evolutions of residual stress distribution will be revealed, and influences of temperature and bending angle on springback will be identified to provide a fundamental understanding of the springback phenomena in warm bending of titanium tubular materials
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