薄壁钛合金型材多点三维热拉弯多尺度成形机理研究

The thin-walled titanium 3D curved component has the characteristics of high structural strength, excellent aerodynamic performance, and flowing geometric shape. It is an advanced lightweight structural part urgently needed in the field of aeronautics and astronautics. However, with the increase of forming dimensions, as well as the large, thin-walled, complex forming features, it is urgent to study the precise plastic forming method for this kind of difficult-to-deform materials, which integrated regulation of forming shape and performance. Therefore, this application intends to study the multi-scale deformation mechanism to solve the high precision forming problems in multi-points 3D hot stretch-bending forming process. Firstly, based on the analysis of macroscopic deformation principle and microstructure evolution characteristics, some constitutive equations will be established by considering the microstructural effects; the internal relationship between macroscopic deformation and microstructure evolution will be clarified. Secondly, the multi-scale finite element models for analyzing the whole process of 3D hot stretch-bending will be established. Then, based on the established finite element models, the effects of 3D hot stretch-bending plastic behavior on the change of material property will be investigated; the 3D springback after unloading will be predicted; and the influence of process parameters will be quantified. At last, a high precision and high quality process design strategy will be developed in this research. The completion of this project will help to improve the titanium profiles’ precise plastic forming theory system with integrated regulation of shape and performance. The research results will provide theoretical support for the development and application of this new forming process in high-end equipment manufacturing industry.

薄壁钛合金型材三维构件具有结构强度高、空气动力学性能好、几何造型流畅等结构特点，是航空航天领域迫切需求的先进轻量化结构。然而，由于弯曲维度的增加，以及大型整体、薄壁的复杂结构特征的制约，其精确成形成性方法亟待研究。为此，本项目拟通过宏微观多尺度成形机理的研究，解决钛合金型材多点三维热拉弯精确控形控性的成形难题。基于实验和理论研究，分析钛合金高温宏观变形行为与微观组织演变特征，建立考虑微结构信息的材料本构模型；阐明材料宏观变形与微观组织形貌演变之间的内在联系；构建分析多点三维热拉弯全过程的多尺度仿真模型，揭示三维热拉弯塑性行为对材料组织结构及性能改变的作用规律，预测三维回弹变形，并量化工艺参数对控形控性的影响规律；最终形成高质量、高精度的工艺方法。本课题的完成将有助于完善钛合金构件精确塑性成形成性一体化制造的理论体系，为新型多点三维热拉弯成形工艺在大型高端装备中的应用奠定理论基础。

薄壁钛合金型材三维构件具有结构强度高、空气动力学性能好、几何造型流畅等结构特点，是航空航天领域迫切需求的先进轻量化结构。然而，由于弯曲维度的增加，以及大型整体、薄壁的复杂结构特征的制约，其精确成形成性方法亟待研究。为此，本项目针对难加工材料的三维弯曲成形问题，开发了多种柔性三维弯曲成形工艺，研制了多点三维拉压复合弯曲成形装备和三维热拉弯成形装备，解决了金属型材多向曲率复杂弯曲成形加工难题；基于TC4钛合金高温热拉伸试验，高温胀形试验，以及微观组织演变的SEM-EBSD观测，分析了TC4钛合金高温宏观变形行为与微观组织演变特征，阐明了材料宏观变形与微观组织形貌演变之间的内在联系，建立了描述TC4钛合金高温流动特性与成形性的本构模型，有效预测了TC4钛合金高温条件下的塑性变形行为与断裂极限；通过TC4钛合金型材三维热拉弯成形试验，揭示了三维拉弯成形工艺参数对钛合金三维成形制件的回弹变形影响规律；构建了分析多点三维热拉弯成形全过程的宏微观仿真模型，揭示了三维热拉弯塑性行为对微观组织的改变机制，进而阐明TC4钛合金三维热拉弯成形机理；基于变形的叠加理论，建立了三维拉弯成形制件的回弹理论预测模型，提出了基于回弹预测数据反向补偿的回弹控制方法，实现了高铁列车窗口下梁的精确成形。本课题的研究成果将有助于完善钛合金构件精确塑性成形成性一体化制造的理论体系，为新型多点三维热拉弯成形工艺在大型高端装备中的应用奠定理论基础。