管状构件超声辅助颗粒介质内高压成形变形行为及增塑机制

Aim to deal with the forming problems of light alloy tube with complex sections, a new technology of Ultrasonic-assisted Granules Hydroforming (UGHF) is proposed, which uses granules as medium to form the tube combined with ultrasonic vibration process. The project focuses on deformation mechanism of tube, ductility enhancement mechanism of light alloy material and other basic scientific problems during UGHF process. Its main contents include: 1) Pressure transmission characteristics of granules medium with complex boundary, and mechanical characteristics of metal materials under granules vibration; 2) The deformation behavior and metal material dynamic response of tube during UGHF process will be studied; To reveal the surface effect and volume effect mechanism; The dynamic ductility enhancement mechanism of metal material of UGHF technology will be expounded from macroscopic and microscopic aspects; The friction stress and contact pressure distribution of different deformation regions of the tube will be analyzed, and then the mathematical model of forming force of UGHF technology is established. 3) UGHF scheme for typical tube of magnesium alloy will be designed and the loading path will be optimized through coupling simulation; To research its deformation and instability mechanism, and then establish the forming theory and process specifications. This project will provide a new effective way to solve the hydroforming problems of special-shaped tubes of light alloy.

针对目前轻合金复杂截面管状构件成形中存在的难题，提出超声辅助颗粒介质内高压成形(Ultrasonic-assisted Granules Hydroforming, UGHF)新工艺，该工艺将固体颗粒作为介质，融合超声振动对管状构件实施内高压成形。本项目重点研究UGHF中的管件变形机理及轻合金材料增塑机制等基本科学问题。内容包括：1)复杂边界颗粒介质传力特性及颗粒体振动下的金属材料力学特征。2)研究管件UGHF过程中的变形行为及材料动态响应，揭示表面效应和体积效应致成机理，从宏观和微观层面阐明该工艺下的材料动态增塑机制；分析管件各变形区域的摩擦应力、接触压力分布规律，进而建立UGHF工艺成形压力的数学模型。3)设计镁合金典型管件UGHF试验方案并运用耦合仿真优化内压加载路径，探索其变形规律和失稳机理，建立相应成形理论及其工艺规范。本项目将为解决轻合金异形管件的成形技术难题提供新的有效途径。

针对轻合金管状构件塑性较低、成形困难的问题，提出超声辅助颗粒介质内高压成形工艺。该工艺将固体颗粒介质作为传力介质，并结合超声振动辅助成形技术对轻合金管材进行内高压成形。以铝合金凸环六边形成形零件为目标，着重研究了管状构件超声辅助颗粒介质内高压成形理论和成形过程中表面效应及体积效应，探明了本工艺条件下金属材料的增塑机理。获得如下具有科学意义和应用前景的重要成果：(1)研究超声振幅、颗粒粒径、传力距离对颗粒介质曲线传力性能的影响规律，建立了振动激励下颗粒介质传压模型。(2)通过分析超声振动下金属坯料-颗粒介质、金属-模具圆角间摩擦力的分布特点和变化规律，构建了振动条件下的摩擦模型。(3)基于单向拉伸、单向压缩实验，结合理论分析，建立了超声振动条件下振动镁合金AZ31B，铝合金6061材料本构方程，阐述了表面效应和体积效应机理。(4)针对铝合金目标工件超声振动颗粒介质成形进行FEM-DEM耦合仿真分析和试验研究，探明了管材变形规律、增塑机制，揭示了超声辅助颗粒介质成形中管材成形性提高的机理，并最终建立了管材超声振动颗粒介质成形理论及其相应工艺规范。本项目的开展为难成形材料(轻合金)管状构件加工提供了新的方法和手段，具有一定理论价值和广阔工程应用前景。