振动攻丝的研究及发展前景

对振动攻丝的优点、运动机理做了介绍，对影响振动攻丝的相关参数进行了分析并对振动攻丝的提出了其发展前景，对于振动攻丝研究中的相关课题研究进行了总结和阐述。     

正交车铣细长轴的切削稳定性研究

为解决传统车削细长轴类工件时易出现振动、变形、加工质量不易控制等难题,应用正交车铣加工技术,由于其独特的切削运动,使其成为了细长轴等弱刚度工件切削加工的良好解决方案。建立了考虑刀具-刀柄-主轴结合面的电主轴以及不同装夹下的工件的有限元模型,并对其进行了频率响应分析。运用半功率点法对动力学参数拾取并进行计算,对不同装夹方式以及切削参数下的极限切削深度进行了分析。以车铣切削振动系统传递函数为基础,建立了正交车铣细长轴的切削深度计算模型。研究表明,正交车铣细长轴的极限切削深度随进给量的增大而减小,随铣刀半径的增大而增大,为实现细长轴类工件的车铣加工应用打下理论基础。     

基于典型正弦路面的履带车辆振动试验台研制

为了研究履带车辆在正弦典型路面下的振动情况，必须对其振动参数和特性进行测试。实车实验由于成本高、仪器不便安装等缺点而导致实验不能很好地进行。所以利用相似定理，结合车辆行驶时的振动情况，来制作实验台架是进行车辆实验的有效途径。通过振动实验台，可以模拟履带车辆在典型路面上以不同速度行驶时的情况。通过外加传感器和信号处理装置，可对非耦合情况下垂直振动和纵向角振动车辆的振动参数进行测量和分析，进而对车辆悬挂系统的减振效果进行定量的分析和研究。     

汽车纵向动力学系统的模糊-PID控制

在对汽车纵向动力学控制系统进行分析的基础上，探讨了基于两车的车列纵向自动跟踪的控制问题，建立了二阶车间纵向相对距离控制模型，并设计了汽车发动机／制动器的逻辑切换规律。应用参数自整定模糊-P1D控制，对P1D的3个参数进行调节，控制被控车与导航车的车间纵向相对距离误差和纵向相对速度误差的变化范围，以实现汽车纵向控制。仿真结果表明，这种方法与模糊控制相比，减小了系统的超调量，增强了动态抗干扰能力，具有一定的鲁棒性，较好地解决了控制系统快速性和小超调之间的矛盾。作者简介：李以农，男，1961年生。重庆大学机械传动国家重点实验室教授、博士研究生导师。主要研究方向为汽车系统动力学控制、汽车主动安全性、振动控制等。发表论文70余篇。     

发动机悬置系统参数的优化设计

发动机悬置系统的动态特性对整车的行驶平顺性有一定的影响，通过调整发动机悬置系统的悬置结构参数，可降低汽车行驶时的振动响应，对发动机悬置系统优化设计进行了分析，并针对某车振动较大的问题，对其发动机悬置系统进行了动态计算与优化设计，通过改进设计，使原车的整车振动状况得到了改善。     

基于MATLAB的捣固装置机构运动仿真

捣固装置是铁路捣固车的核心设备,用于完成铁路道床石碴的捣固作业。通过其偏心轴的高频振动和液压缸的夹持运动,使铁路道床的道碴重新排列并变得密实。本文介绍了捣固装置工作原理和MATLAB软件中SimMechanics模块的功能,并建立了捣固装置机构仿真模型,通过对其运动进行仿真分析,得到了捣固镐头和夹持液压缸的相关运动特性参数,并指出了有关参数对捣固机构的影响。     

侧倾互联悬架系统特性研究

车辆行驶过程中,其运动是垂向运动、侧倾运动和俯仰运动等多种运动模式的叠加。本文通过AMESIM软件建立侧倾互联悬架模型,根据某SUV车参数以及不同工况研究侧倾互联悬架参数对系统输出特性的影响规律,为分析参数对整车性能影响提供依据,具有较强的工程应用价值。     

人椅系统振动特性及其集中参数模型研究

结合实车振动舒适性试验,对人椅系统的振动特性进行了分析,结果表明:除坐垫外座椅靠背、人体头部振动对驾乘人员的舒适性具有较大影响。根据底板-坐垫传递函数、底板-头部传递函数,采用Matlab编程及遗传算法对集中参数人椅模型进行了参数识别,并利用所识别出的参数计算了各模型传递函数理论值。借助视在质量验证了模型参数的合理性,并通过分析各模型传递函数理论值与试验值的拟合优度,得出三自由度带框架质量的并联人椅模型,能够较准确地预测实车振动特性。     

正交车铣切削层几何形状的仿真与分析

针对现有正交车铣切削层几何形状仿真方法复杂及解析法无法明确其几何形状变化规律的问题,根据正交车铣的运动规律,结合NX 8.5软件提出了正交车铣切削层几何形状的仿真方法,并进行了试验验证和仿真分析。研究结果可为正交车铣切削力和加工振动的分析提供基础,并为正交车铣切削参数的优化提供指导。     

振动磨机稳态工作模型的试验研究

通过对振动磨机磨介群运动及工作过程的分析，研究了工况参数对振动磨机工作状态及其粉磨效果的影响，运用“灰箱”理论方法，建立了包括能量，给料和设备工况参数在内的振动磨机稳态工作模型，通过试验对模型进行论证。结果表明，该模型不仅客观地反映了其工作运行过程，而且还可有效地对磨机工作过程进行控制，可为拓动磨机的进一步应用和开发提供理论依据。     

超声振动磨削运动学分析

建立了超声振动磨削加工过程数学模型,对超声振动磨削运动学特性进行了分析,通过引入速度系数K探讨了砂轮的位移和加速度的变化规律及其对加工过程的影响.分析了单颗磨粒在超声振动磨削过程中的运动特点及运动速度的变化规律.指出切削速度方向超声振动磨削具有分离、熨压和冲击的特点.     

On the improvement design of dynamic characteristics for the roller follower of a variable-speed plate cam mechanism

Without modifying the cam contour, a cam mechanism with a variable input speed trajectory offers an alternative solution to flexibly achieve kinematic and dynamic characteristics, and then decrease the follower’s residual vibration. Firstly, the speed trajectory of cam is derived by employing Bezier curve, and motion continuity conditions are investigated. Then the motion characteristics between the plate cam and its roller follower are derived. To analyze the residual vibration, a single degree of freedom dynamic model of the elastic cam-follower system is introduced. Based on the motion equation derived from the dynamic model, the residual vibration of the follower is yielded. The design procedure to improve the kinematic and dynamic motion characteristics is presented and two design examples with discussions are provided. Finally, the simulations of the kinematic and dynamic models by ADAMS are carried out and verified that the design models as well as the performances of the mechanism are feasible.     

单辊驱动轧机水平自激振动定性分析

应用非线性力学模型分析了轧辊水平振动。在分析轧辊轧件接触界面之间相对运动及其相对变形与接触面上摩擦力的关系基础上,建立了轧辊水平振动的非线性动力学方程。分析了粘滑共存摩擦转变为全滑动摩擦对轧辊水平振动的影响。用相平面方法分析了轧辊水平运动规律,并确定了粘滑—滑动运动的极限环。定性地分析了轧辊水平运动的动力学特性,着重分析单辊驱动轧机水平自激振动产生的条件及其机理,得出影响轧辊水平自激振动的因素。提出轧辊水平自激振动模型。     

混沌振动磨机力学模型的建立与运动分析

随着工业化的不断发展,各应用领域对粉体的产量和超细化的需求越来越大,现有的粉磨设备普遍存在能耗大、效率低、物料粉碎单一等不足,从工艺到设备还有待于进一步的研究。本文在普通振动磨机的基础上,提出了混沌振动磨机并建立了混沌振动磨机的力学模型。通过对其进行运动分析和与普通振动磨机的对比得出,混沌振动磨机较普通振动磨机效率更高,节能性更强,同时混沌振动磨机可生产出普通磨机很难生产加工的纳米级颗粒。     

空间机械手动力学及轨迹优化问题研究

机械手的动力学模型用在连接处施加控制扭矩的2杆模型来模拟，考虑了因整体运动而引起的柔性杆的局部振动问题，使用了基于Hamilton定律的结构动响应算法对模型进行动力学分析。研究了使局部振动最小的整体运动的轨迹优化方案。出末时速度和加速度双变量的优化结果，并与仅仅考虑加速度的单变量优化结果进行了比较。     

NONLINER VIBRATION ANALYSIS OF THE PLATE WITH DRY FRICTION SUPPORT CONDITION

The rigid-interface friction model is usually used in the nonlinear vibration of the rectangular plate with dry friction support edges. The present study provides an extension by using a hysteretic spring friction model and taking account of the stick-slip motion of the plate. Results for a range of problem parameters have been obtained. The results show that the nonlinear frequency response behavior of the system can be quite different from the rigid-interface friction model. The effects of the stiffness at friction interfaces and the stick-slip motion on the nonlinear vibration of the plate are significant and hence cannot be neglected.     

Nonlinear dynamic analysis of coupled gear-rotor-bearing system with the effect of internal and external excitations

Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out. However, the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated. An eight-degree-of-freedom(8-DOF) nonlinear spur gear-rotor-bearing model, which contains backlash, transmission error, eccentricity, gravity and input/output torque, is established, and the coupled lateral-torsional vibration characteristics are studied. Based on the equations of motion, the coupled spur gear-rotor-bearing system(SGRBS) is investigated using the Runge-Kutta numerical method, and the effects of rotational speed, error fluctuation and load fluctuation on the dynamic responses are explored. The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion, quasi-periodic motion, chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations. Significantly, the changing rotational speed could effectively control the vibration of the system. Vibration level increases with the increasing error fluctuation. Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase, the chaotic motion may be restricted. The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.     

Analysis of nonlinear vibration response of a functionally graded truncated conical shell with piezoelectric layers

The nonlinear vibration response of a functionally graded materials (FGMs) truncated conical shell with piezoelectric layers is analyzed. The vibration amplitude is suppressed by the positive and inverse piezoelectric effects. And the bifurcation phenomenon is described to reveal the motion state of the conical shell. Firstly, a truncated conical shell composed of three layers is described. And the effective material properties of the FG layer are defined by the Voigt model and the power law distribution. Next, the electric potentials of piezoelectric layers are defined as cosine distribution along the thickness direction. Meanwhile, the constant gain negative velocity feedback algorithm is used to suppress the vibration amplitude by the electric potential produced by the sensor layer. Thereafter, considering the first-order shear deformation theory and the von Karman nonlinearity, the relationship between the strain and displacement is defined. And the corresponding energy of the conical shell is calculated. After that, the motion equations of the conical shell are derived based on the Hamilton principle. Again, the nonlinear single degree of freedom equation is derived by the Galerkin method and the static condensation method. In the end, the nonlinear vibration response of FGMs truncated conical shell with piezoelectric layers under the external excitation is analyzed via using the harmonic balance method and the Runge-Kutta method. The effects of various parameters, such as ceramic volume fraction exponent, external excitation’s amplitude, control gain and geometric parameters on the nonlinear vibration response of the system are evaluated by case studies. Results indicate that the control gain plays an important role on the suppression of the vibration amplitude. The ceramic volume fraction exponents are not sensitive to the nonlinear vibration response compared with other parameters. The bifurcation behavior is observed under different parameters. The FGMs truncated conical shell with piezoelectric layers has three types of motion state, such as periodic motion, multi-periodic motion, and chaos motion.

     

摩擦驱动型压电叠堆直线电机的工作机理

以一种典型的摩擦驱动型压电叠堆直线电机结构为例,对摩擦驱动型压电叠堆直线电机的振动摩擦驱动机理进行研究.结合电机系统的振动脱离模型,分析了电机定子与动子脱离的力学条件,进而分析电机结构参数和工作参数对椭圆运动和振动脱离性能的影响.对原理样机进行了试验研究,结果表明,压电叠堆的激励电压、激励频率和电机的预压力对电机的振动脱离性能有显著影响.     

Non-classical stiffness strengthening size effects for free vibration of a nonlocal nanostructure

New analytical solutions for free vibration of thick nanostructures are presented based on the nonlocal elastic stress field theory and the Timoshenko shear deformable nanobeam model. By applying the variational principle, new governing equations of motion and higher-order boundary conditions for these thick nanobeams are derived and their physical characteristics interpreted. The nonlinear history of straining involving higher-order strain gradients is considered in the derivation of strain energy and the contribution of higher-order strain gradients results in non-classical equations of motion thereby indicating that direct replacement of stress and moment quantities into the classical equations of motion is invalid. The Timoshenko nanobeam models are well suited for modeling and investigating the nonlocal behaviors of size-dependent carbon nanotubes. The effects of nanobeam size and various boundary conditions including simple supports, free and clamp constraints, such as a cantilevered nanotube, on the natural vibration frequency of nanotubes are discussed. The effects of nonlocal nanoscale are confirmed by comparing with molecular dynamic simulation solutions for (5,5) and (10,10) carbon nanotubes with four types of boundary conditions. The influence by nanoscale effect on the frequency ratio of nanotubes with different diameters is investigated. Further analysis based on the analytical nonlocal Timoshenko nanobeam model and the Euler–Bernoulli nanobeam model shows that the frequency ratio is more sensitive to nonlocal effect for free vibration of a nonlocal nanostructure if shear deformation is considered.