高频颤振激励下金属塑性成形过程表面效应及其致成机理研究

Aiming at the difficult problem that common exciting methods cannot meet the needs for high frequency and large exiting force in complex part forming process, electro-hydraulic vibration tech is adopted in metal plastic forming. The basical scientifical problem of surface effect and its friction-reducing principle under high frequency exciting is emphasized on. The research contents are: 1) Analyse the effect and principle of exciting parameters, such as frequency and amplitude, on surface effect and micro-friction, establish the mathematic model of surface effect and its affecting factors. 2) Obtain the changing principle of friction following the surface effect of metal plastic forming under the high frequency exciting, establishing the macro describe and mathematic model of friction in plastic forming under high frequency exciting. 3) Design the orthogonal table for anisomerous universal node plastic forming FEM simulation and experiments to verify the effect of deforming resistance reducing under high frequency exciting, amend the models of surface effect and forming friction. In this project, the high frequency exciting tech is innovatively applied in metal plastic forming. Theoretical models, which can be instructive in engineering, will be established. This research can solve the basical problem of complex part vibrative forming, and has certain theoretical value and upstanding engineering application foreground.

针对普通激振方式难以满足难成形零件冷挤压过程的高频率和大激振力需求这一难题，提出将电液高频激振技术应用于金属塑性成形，着重研究高频颤振激励下零件成形过程表面效应及其降低变形抗力的机理等基本科学问题。内容包括：1）分析挤压过程中颤振频率、振幅等主要施振参数对成形面上接触应力、微观摩擦力及其分布等的影响及其规律，进而建立表面效应及其影响因素数学模型；2）探明金属塑性成形过程摩擦力在高频颤振激励表面效应作用下的随动变化规律，建立高频颤振激励下塑性成形摩擦力的宏观描述及其数学模型。3）设计正交试验进行不对称万向节叉塑性成形有限元仿真分析和实验研究，验证高频颤振对降低塑性成形变形抗力的效果，完善表面效应及摩擦力相关理论模型。本项目创新性地将高频颤振技术应用于金属塑性成形加工，研究建立具有一定工程指导意义的理论模型，可解决难成形零件的振动挤压加工基本问题，具有一定的理论研究价值和良好的工程应用前景。

项目针对汽车零件冷挤压的难成形问题，提出了一种电液颤振冷挤压成形方法；通过引入摩擦系数和滑动速度关系式以及冲头与坯料之间周期性的脱离和接触效应，获得挤压过程模具与坯料边界面摩擦接触应力分布规律，给出非局部形式的冷挤压成形挤压力计算公式；研究电液颤振平台振动特性，设计通用冷挤压模具，搭建电液颤振冷挤压实验平台，结合有限元分析方法，分析电液颤振对所需挤压力、微观表面形貌、表面硬度、金属流线及边界面摩擦系数等指标的影响规律，揭示电液颤振对冷挤压成形的表面效应及致成机理；设计制作典型汽车零件冷挤压模具系统，实验研究电液颤振频率、幅值对挤压成形力、成形件表面质量（包括微观表面形貌、表面粗糙度、表面硬度等）、材料组织等的影响规律，获得电液颤振冷挤压关键工艺；提出二维电液颤振冷挤压成形方法，分析比较轴向、径向两种电液颤振共同激励下的降载效果、速度场、应力场及网格流线变化。高频颤振激励下金属塑性成形过程表面效应及其致成机理研究为电液激振技术在汽车零件冷挤压加工中的实际应用提供理论基础及技术支撑。