振动塑性加工是近年来振动利用工程在塑性成形领域发展起来的一门新兴边缘交叉学科，振动场与塑性力场的耦合能产生诸如材料流动应力下降的体积效应和接触面摩擦力降低、零件表面质量提高的表面效应。而目前振动塑性加工的研究成果主要以超声辅助微成形为主，用于塑性加工的大功率超声激振器实现难度大，而低频振动大功率激振器容易构建，但低频振动作用于塑性变形过程的机理研究不足。本文为解决低频大功率振动在实际工业中的应用问题，基于材料.工艺.装备的一体化研究思路，对振动场和塑性力场耦合机制、振动场下接触面摩擦机理、复杂壳体零件齿形离合器毂振动塑性成形工艺及分散多动力振动塑性成形试验平台的研制等问题进行了系统深入的研究。 本文以汽车轻量化用的DC04低碳钢板材齿形离合器毂冲压件的高效精密低能耗省力塑性成形技术为研究背景，开展该板材不同振动方向、不同振幅(0～0.4㎜)以及不同频率(0～50Hz)下振动拉伸实验，获得不同振动参数下宏观力学性能和微观组织演变规律。研究表明：板材宽度方向(TD)振动能引起瞬时振动软化效应，而轧制方向(RD)、厚度方向(ND)振动引起振动硬化；TD方向振动能引起局部位错运动加强，导致材料流动应力下降，振动频率与振幅可以统一用振动能量表示，TD方向振动能量越高振动软化越明显；RD／ND／TD方向振动后试验中间区域小角度晶界均出现下降趋势，振动产生的周期性波动应力，提高了异号位错的接触概率，并导致位错湮灭加剧和位错密度降低，是残余软化现象的主要原因。 基于塑性变形理论、热激活理论和位错动力学模型，采用实验研究、理论推导和数值模拟相结合方法，开展振动场和塑性力场耦合作用下的统一弹-粘塑性本构模型理论研究。根据Chaboche本构理论，建立DC04低碳钢率相关本构模型。基于热激活理论模型和实验结果，引入归一化能量密度和归一化传递效率，推导了与振动能量、传递效率有关的振动软化模型。基于位错动力学模型，模拟了振动场下位错密度降低现象，根据模拟结果建立振动移除后的残余软化模型，并通过引入与振幅和非弹性应变有关的参数描述后继变形时的屈服应力下降和短时硬化率上升现象。通过振动软化模型和残余软化模型修正Chaboche模型中初始屈服应力，建立振动场下统一弹-粘塑性本构模型，准确预测了振动场下应力叠加、振动软化和残余软化效应耦合作用下的应力-应变曲线。 基于振动减摩实验规律和动态摩擦模型理论，建立振动场下摩擦模型。根据干摩擦与脂润滑条件下不同振幅、频率和正压力的纵向振动摩擦实验，获得了振动对稳态摩擦的影响规律。结果表明：干摩擦条件下，振动提高模具与坯料相对滑动速度是干摩擦条件下摩擦力下降的主要原因，并随着正压力增加振动减摩效应变弱，脂润滑条件下振动减摩现象是相对滑动速度提高和润滑条件改善复合作用的结果，与干摩擦相比，脂润滑具有更宽的振动减摩振幅和正压力范围，研究了纵向振动对表面形貌的影响规律。通过理论推导，建立稳态摩擦力与正压力和相对滑动速度函数关系，并修正Dahl动态摩擦模型中的稳态摩擦力，提出改进的Dahl动态摩擦模型，准确预测了振动场下摩擦力波动以及最大摩擦力下降现象，数值计算结果显示，不同振动条件下最大摩擦力下降与实验结果吻合较好，相对误差为6.1％。 制定了齿形离合器毂振动冲挤复合成形新工艺方案，通过数值模拟揭示了材料塑性流动行为，并通过成形实验研究了振动参数对载荷下降和表面质量的影响规律。有限元模拟结果表明：变形以板材成形为主，在外齿顶部发生局部体积塑性变形，提高板材初始厚度有利于齿形成形精度，同时也伴随成形力剧烈上升和损伤的发生，坯料内径对成形精度和成形力无影响。振动成形实验结果显示：当振幅在0.2㎜和0.6㎜之间变化时，最大载荷下降比与振幅成正比，并随着振幅的增加外齿表面划痕减少。当频率在20Hz以下时，频率对载荷影响较小，当频率为30Hz时载荷下降明显，随着频率升高外齿表面质量提升明显。齿形离合器毂振动冲挤成形中载荷的下降主要来自振动的表面效应，并将改进的Dahl模型应用到Forge有限元计算中，模拟了振动成形中载荷下降现象，验证了本文提出的改进的Dahl模型的广泛适用性。 研制了分散多动力振动塑性成形试验平台及其计算机控制系统。该装置由伺服主传动系统、无油泵变频变幅激振系统、电动伺服拉深垫系统及计算机控制系统组成，实现了滑块复杂曲线加载，模具振动加载以及拉深过程中压边力分区、分时调整功能。伺服主传动系统采用伺服电机加滑动丝杠方案，使用PID三环控制算法实现滑块位置的精确控制，测试结果表明系统跟踪误差小于0.1㎜；无油泵变频变幅激振系统由凸轮激振器、阀块和振动液压缸组成，采用圆锥滚子线接触方式降低了凸轮接触面的表面应力，通过改变伺服电机转速和阀块中的双节流阀开口面积实现振动液压缸振动频率和振幅分别在0～75Hz和0～1.5㎜范围变化，并通过AMESim软件和试验验证了方案可行性；电动伺服拉深垫系统由伺服电机、皮带和滚珠丝杠组成，充分利用了系统中的弹性环节，提出了压边力主动控制算法，试验结果表明系统跟踪误差小于1.2％，实现了压边力的精确控制。 关键词：振动塑性成形；本构模型；摩擦模型；塑性流动行为；齿形离合器毂 论文类型：应用基础 本研究得到国家自然科学基金重点项目(编号：51335009)和面上项目(编号：51675414)的共同资助。

 In recent years, vibration-assisted plastic processing (VPP) is an emerging edge interdisciplinary subject developed by vibration utilization engineering in the field of plastic forming. The coupling of vibration field and plastic deformation field can induce flow stress drop, friction reduction and surface roughness improvement, which are named volume effect and surface effect. In the field of vibration plastic processing, most of the reseach focused on ultrasonic assisted micro-forming due to its convennice. However, the mechanism for volume effect and surface effect, although have been studied for 60 years, is still not clear. And less studies have been focused on low-frequency vibration assisted plastic processing technique (LVPP), which showing a gearter potential in industrial applications. In this study, in order to accularte the industrialization for LVPP, we used an integrated research method based on material-process-equipment, and studied the following questions: the coupling mechanism of vibration field and plastic field, the friction mechanism for contact surface under vibration field, geared clutch hub forming technique using LVPP and design of decentralized multipower vibration plastic forming test platform with micro-amplitude. Low carbon steel DC04, used for geared drum manufacturing, was selected as the research materials. And its mechanical properties and microstructure undergoing a vibration assited tensile test have been investigated. The test results showed that: (1) TD vibration could cause instantaneous vibration softening effect, while RD/ND vibration caused vibration hardening effect; (2) TD vibration could stenghten the local dislocation motion, which caused the material flow stress decrease. Vibration frequency and amplitude could be uniformly expressed by the vibration energy. The higher vibration energy in TD, the more obvious vibration softening; (3) After RD/ND/TD vibration removal, there appeared a downward trend wtih low-angle grain boundaries in the middle region of the sample, and the periodic wave stress generated by the vibration increased the contact probability for dislocation dipole, leading to increased dislocations annihilation and reduced dislocation density. It is the main reason for residual softening. Based on plastic deformation theory, thermal activation theory and dislocation dynamics model, an unified elastic-viscoplastic constitutive model under the coupling of vibration field and plastic force field has been studied. Through the analysis of Chaboche constitutive model, rate-dependent constitutive model for DC04 low carbon steel has established. According to the thermal activation theory model and experimental results, we introduced normalized energy density and normalized transfer efficiency, a vibration softening model related to vibration energy and transmission efficiency is derived. The phenomenon of dislocation density reduction under vibration field was simulated using the dislocation dynamics model. With the results acquired from the simulation works, we established a residual softening model after vibration removal to describe the phenomenon of the yield stress reduction and shorttime hardening rate increase. The initial yield stress in the Chaboche model was then replaced by the vibration softening model and the residual softening model. The unified elastic viscoplastic constitutive model under the vibration field is established, and stress superposition, vibration softening and residual softening effect in the vibrational plastic field is accurately predicted. Based on the vibration reduction experiment results and the dynamic friction model theory, the vibration induced friction redution model was established. The influence of vibration on steady-state friction were obtained by the tangential vibration friction experiments with different amplitudes, frequencies and positive pressures, and dry friction condition and grease lubrication condition were both considered. The results showed that under dry friction state, vibration increased the relative sliding speed between the mold and the workpiece, which was the main reason for friction reduction under dry friction condition. The vibrational antifriction effect was weakened with the increase of positive pressure. Vibrational antifriction effect under grease lubrication condition is a combined result of the relative sliding speed rise and lubrication condition improvement. Compared with dry friction condition, vibrational antifriction effect has a wider range of amplitude and positive pressure under grease lubrication condition. The influence of tangential and normal vibration on surface morphology also was studied. Through theoretical derivation, the relationship between steady friction and positive pressure, relative sliding velocity is established. By modifying the steady-state friction force in the Dahl dynamic friction model, an improved Dahl dynamic friction model is proposed to predict the frictional fluctuation and the maximum frictional force drop under the vibration field. The numerical calculation results showed that the maximum frictional force drop under different vibration conditions was in good agreement with the experimental results, and the relative error is only 6.1%. A new process combined drawing and extrusion under the assisted vibration for forming of geared clutch hub is proposed. The materals flow behavior during plastic deformation is revealed by numerical simulation. The influence of vibration parameters on load drop and surface quality is studied by forming experiments. The finite element simulation results showed that the deformation zone in the extrusion forming was mainly attribuated to sheet metal forming, and local volume plastic deformation occured at the top of the external tooth. The equivalent stress and equivalent strain were graded distributed in the height direction, and showed larger value at the outer edge of the part. Increasing the initial thickness of the sheet was conducive to the accuracy of teeth formation, which was accompanied by a sharp rise in the forming force and the occurrence of damage. The inner diameter of the blank had no effect on the forming accuracy and the forming force. The results of the vibration forming experiment showed that when the amplitude changed from 0.2 ㎜ to 0.6 ㎜, the maximum load drop ratio was proportional to the amplitude, and the external tooth surface scratches decreased as the amplitude increased. When the frequency was below 20Hz, the load is less effected by vibration frequency. When the frequency was 30Hz, the load droped most obviously. As the frequency increased, the surface quality of the external tooth improved significantly. The cause for load reduction in vibration-assisted geared clutch hub forming is atrribuated to vibration surface effect. In addtion, the improved Dahl model was integrated into the Forge software to simulate the load drop phenomenon during vibration forming, which was verified the widely application for the improved Dahl model proposed in this paper. A decentralized multi-power vibration plastic forming test platform with micro-amplitude and its computer control system were developed. The device consists of servo drive system, nonuse pump excitation system with adjustable amplitude and frequency and electric servo deep drawing pad system. These three system realizes the complex curve loading of the slider, vibration loading on mold and adjustment blank holder force. By using the PID closed loop control, the servo drive system achieved a precise control on the slider position. The test results showed that the movement tracking error is less than 0.1㎜; the nonuse pump excitation system is composed of a cam shaker, valve block and the vibration hydraulic cylinder. A tapered roller line contact method to reduce the surface stress of the cam contact surface. The vibration frequency (0～75Hz) and amplitude (0～1.5㎜) of the vibration hydraulic cylinder can be adjusted by changing the servo motor speed and the opening area of the double throttle valve. The feasibility of the excitation system is passed the test of AMESim software and experiment. The electric servo deep drawing pad system is composed of servo motor, belt and ball screw. Making full use of the elastic link in the system, an active blank holder force control algorithm is proposed. The experimental results show that the tracking error of the system is less than 1.2%, and the precise control of the blanking force is realized. KEY WORDS: Vibration plastic forming; Constitutive model; Friction model; Plastic flow behavior; Geared clutch hub TYPE OF DISSERTATION: Application Fundamentals