Six-axis free bending and twisting (6FBT) technology is suitable for the integral bending of complex profiles with torsional characteristics for the cross-section. However, the influence and mechanism of section torsion on bending deformation during the forming process of this technology have not been studied. In this paper, a new theoretical analysis model describing the relationship between a torsion angle of a section and the radius after bending springback is proposed for 304 stainless steel flat oval section hollow profiles. Using the proposed model, the trend of the influence of section torsion on bending deformation when bending along the long and short axes of the flat oval profile is derived, and the theoretical derivation matches well with the simulation and experimental results. The findings show that when the flat oval profile is bent along its long axis, the springback of the bending radius is positively related to the torsion angle, while when bending along the short axis direction, the rebound of the bending radius is negatively correlated with the torsion angle. The paper also explains for this phenomenon in terms of stress and strain, and establishes for the first time a “U-R-γ” model that introduces section torsion and reflects the relationship between the radius and eccentricity.

六轴自由弯曲和扭转（6FBT）技术适用于截面具有扭转特性的复杂型材的整体弯曲。但该技术成形过程中截面扭转对弯曲变形的影响及机理尚未得到研究。本文针对304不锈钢扁椭圆截面空心型材提出了描述截面扭转角与弯曲回弹后半径之间关系的新理论分析模型。利用所提出的模型推导了扁平椭圆型材沿长轴和短轴弯曲时截面扭转对弯曲变形的影响趋势，理论推导与仿真和实验结果吻合良好。研究结果表明，扁平椭圆型材沿长轴方向弯曲时，弯曲半径的回弹与扭转角呈正相关，而沿短轴方向弯曲时，弯曲半径的回弹与扭转角呈负相关。扭转角。论文还从应力应变的角度对这一现象进行了解释，并首次建立了“UR-γ ”模型，引入截面扭转，反映半径与偏心率的关系。