Longhui Li

Longitudinal T-shaped finned tubes are important heat-transfer components in spacecraft thermal control systems, and their forming accuracy and quality during bending have a significant influence on heat-transfer efficiency. Therefore, the analysis and control of nonuniform sectional deformation and nonlinear springback are essential for precision forming. In this study, a semi-analytical springback correction model coupling neutral-axis shift and equivalent unloading modulus degradation was proposed based on axial force equilibrium and sectional stress integration. Based on numerical simulations and experiments, the relationship between free-bending die eccentricity and formed curvature was established, and the effects of forming radius and bending angle on springback were analyzed. The results show that the formed curvature increases approximately linearly with die eccentricity, the radius springback increases with forming radius, and the springback angle first increases and then decreases with increasing bending angle. The constant-modulus model systematically underestimated springback, whereas the equivalent unloading modulus correction improved agreement with experimental measurements. Furthermore, a coupled angle-curvature inverse compensation method was proposed to determine the pre-compensated forming radius, free-bending die eccentricity, and over-bending angle from the target geometry. After compensation, the forming accuracy reached ±0.28° for bending angle and ±0.33 mm for bending radius, compared with ±3.16° and ±2.51 mm before compensation, respectively. The proposed coupled prediction-compensation framework provides an effective approach for precision free bending of longitudinal T-shaped finned tubes.