大型飞机复杂板件表面微沟槽的超声辅助柔性滚压成形与强化

Shark-skin-inspired surface micro-riblets have prominent drag reduction effects and are recognized as an effective way to achieve higher speed and less energy consumption for large aircrafts. However, currently available manufacturing processes cannot produce extensive, precise and wearproof micro-riblets on the surfaces of sheet metal parts with complex shapes. Hence, this project proposes an ultrasonic-assisted flexible rolling process, which can produce precise micro-riblets and enhance the wear resistance of the micro-riblets. This project mainly focuses on constructing a constitutive model considering ultrasonic effect and size effect; characterizing the dynamic loading process and material flow behavior under ultrasonic vibration to obtain the stable filling mechanism of micro-riblets; investigating the spatio-temporal evolution rule of microstructure and residual stress under the coupled influence of ultrasonic vibration and plastic deformation, so as to acquire the wear-resistance strengthening mechanism of micro-riblets; and establishing ultrasonic-assisted rolling process schemes according to the influences of process parameters on the macro/micro geometrical profiles and wear resistance property of micro-riblets. The research outputs of this project have essential significance for revealing the regularity and mechanism of ultrasonic-assisted micro forming, as well as promoting the practical engineering application of bionic drag-reduction micro-riblets.

仿鲨鱼皮表面微沟槽结构具有卓越的减阻效果，是实现大型飞机提速降耗的有效途径。但现有工艺无法在复杂板件表面加工出大面积的精密耐磨微沟槽。为此，本项目提出一种基于超声振动的微沟槽柔性滚压成形新工艺，在获得精密微沟槽的同时改善微沟槽的耐磨性能。主要研究内容包括：建立考虑超声塑性效应和尺寸效应的本构模型；研究超声振动作用下材料的动态受力过程和流动规律，获得微沟槽的稳定填充机理；研究超声振动和塑性变形耦合作用下材料微观组织和残余应力随时间和空间的演变规律，得到微沟槽耐磨性能强化机理；基于工艺参数对零件宏微观外形轮廓和微沟槽耐磨性能的影响规律，建立超声辅助滚压成形工艺方案。本项目研究成果对于揭示超声辅助金属微尺度塑性成形规律和机理，以及推进仿生减阻微沟槽的实际工程应用具有重要意义。

针对现有工艺无法在已经具备复杂形状的金属板件表面大面积加工精密耐磨微沟槽的难题，本项目提出基于超声振动的微沟槽柔性滚压成形新工艺。在项目实施过程中，项目团队研究了超声辅助滚压成形工艺并设计制造了相关成形设备；通过多尺度超声辅助压缩实验和微观组织表征，研究了超声振动作用下的材料力学性能变化规律及机理，并建立了材料本构模型；采用超声辅助滚压成形数值模拟探究了工艺参数对成形质量的影响规律，并通过实验进行了验证。本项目的实施取得了以下结果：超声振动成形过程中，超声加载使材料得到显著软化，应力下降幅度与超声振动能量密度有关，超声卸载后的材料力学性能曲线相比无超声作用下的力学性能曲线表现出轻微的残余硬化；由于超声振动对材料的软化效应，滚压成形载荷显著减小，材料能够更好地填充微沟槽型腔；微沟槽的填充率随滚压成形中压印辊角速度的增大而减小，但这个趋势在超声振动的软化作用下变得几乎可以忽略；由于材料主要在压印辊的挤压作用下发生变形，横向挤压变形很小，摩擦系数几乎不对填充率产生影响。本项目的研究为超声辅助金属塑性成形工艺提供了重要科学依据，也将有力推动微沟槽减阻技术的应用。