Study on Springback Straightening after Bending of the U-Section of TC4 Material under High-Temperature Conditions

Abstract

The thin-walled structures of titanium alloys have peculiar characteristics involving thin curved surfaces, complicated structures, and a poor rigidity. Therefore, bending or twisting distortion frequently occurs in forging, extrusion, drawing, transportation, cooling, and manufacturing. Straightening theory focuses on the straightening curvature or bending moment at room temperature, and a unified analytical model of the straightening curvature, the straightening bending moment, and the straightening stroke, as well as a study on springback straightening under high-temperature conditions, have not been investigated comprehensively. In order to understand the inherent mechanism of springback straightening and quantitative prediction of springback under high-temperature conditions, uniaxial tension tests were carried out to obtain the true stress–strain model of material and stress relaxation under the stress relaxation model. This paper is based on the theory of elastic-plastic mechanics and combines this with the mechanism of stress relaxation to establish springback and residual relative curvature equations of springback. The law of springback straightening is further explored, and springback and residual deflection equations are provided. The results of the study showed that the relative errors of the theoretical residual deflection of the bending deformation and residual deflections obtained by the experiment were less than 20%, with an average absolute error of less than 10%. Therefore, the hardening models adopted can achieve an allowable relative error if hardening parameters are properly selected. The proposed research provides basic data for the prediction of springback straightening, and the design of springback compensation tools can be applied in practical applications.

Deformation Characteristics, Formability and Springback Control of Titanium Alloy Sheet at Room Temperature: A Review

“…where ρa and ρb are the radius after and before springback, D and E are the hardening modulus and the elastic modulus, σs and t are the yield strength and the thickness of sheet, respectively. To predict the springback of anisotropic materials, including titanium alloys, the effect of anisotropy (asymmetry in the yielding and hardening stage) on springback cannot be neglected [100,101]. Zhang et al found that springback would be overestimated by applying the isotropic hardening model [102].…”

“…In comparison to the springback results, it was found that asymmetry would cause an increase in springback of hexagonal close-packed sheet metals compared with using a symmetric material model, as shown in Figure 13. To predict the springback of anisotropic materials, including titanium alloys, the effect of anisotropy (asymmetry in the yielding and hardening stage) on springback cannot be neglected [100,101]. Zhang et al found that springback would be overestimated by applying the isotropic hardening model [102].…”

Billet Straightening by Three-Point Bending and Its Automation

“…Different parameter settings return differently straightened billets [5]. The crucial thing is to achieve accurate prediction of spring back [20,21] after releasing the straightening force. To achieve fast calculations, analytical and semianalytical approaches are currently used.…”

Microstructure and Mechanical Properties of TC4 Titanium Alloy at the Temperature of 77K

“…The structural components in spacecraft require further improvement of the low-temperature performance required by the equipment environment. The alloy must meet the requirements of sufficient strength and toughness at low temperatures, excellent thermal properties and good machinability because of the complex shape of the structural parts [6]. At low temperature, titanium alloy has higher yield strength than traditional alloy, which is more than three times of stainless steel, and the density is only half of stainless steel [7].…”