压电梁弯曲振动振幅分布特性的实验研究

对压电梁进行了弯曲振动模态有限元分析,讨论了压电陶瓷片与梁的组合方式对压电梁弯曲模态的影响,在此基础上,对压电梁B1和B3阶弯曲模态、振幅分布进行了实验研究。结果表明,当压电梁振动阶数较高时,陶瓷片的横向布置对梁的振动特性影响很小。研究结果对压电驱动技术具有指导意义。     

轴类加工工件系统弯曲振动固有频率的计算方法

从动力学观点来看,当外激振力的频率接近于加工机床工件系统固有频率时,就有可能发生共振,因而会有一定的危险;另外,共振会导致数控机床的驱动装置、检测装置不能正常地工作,因此,为避免发生共振,有必要计算工件系统的固有频率.下面介绍的方法是一种适用机械动力学中传递矩阵法,结合FORTRAN语言及连续性要求,利用计算机计算工件系纺固有频率的方法,该方法通过实验验证是可行的,计算结果也是正确的.     

黏弹性梁弯曲振动的复模态分析

发展复模态分析研究黏弹性梁的弯曲振动。将梁的控制方程写作状态变量的形式，然后利用复模态的正交性可解耦为无穷多个彼此独立的常微分方程组。基于固有频率和模态函数，可以得到黏弹性梁对于任意初始条件和外激励的响应。在固支梁的边界条件下确定黏弹性梁的固有频率、衰减系数和模态函数，并计算梁受两种典型的外激励时的响应。     

分布参数压电层合梁的振动主动控制

建立了悬臂梁上粘贴一段压电陶瓷片实现振动控制的动力学方程,定义了压电层合梁的压电消耗功率,并针对悬臂梁这一分布参数控制系统,提出了确保控制系统闭环稳定的设计方法。最后通过数值算例证明了该方法的有效性。     

压电陶瓷用于智能梁结构的振动控制研究

从理论和实验两方面分析了利用压电作动器进行柔性梁结构振动主动控制的机理,建立了相应的实验系统,得出了智能梁结构的振动位移和驱动电压及传感电压之间的关系。实验中采用直接负反馈和趋势预测反馈控制方法,对智能梁结构进行了有效的振动主动控制,得到了良好的效果。     

变截面压电智能梁的频率分析

建立了变截面压电智能梁的动态模型,分析了表面粘贴压电元件的均质梁的固有频率。在分析中考虑了压电元件和粘结层的影响,同时,还考虑了梁的剪切变形和转动惯量。研究表明,压电元件的刚度和惯量对梁的频率影响很大,粘结层剪切的弹性模量对一阶频率影响较小;当考虑梁的剪切变形和转动惯量时,则对梁的高阶频率影响较大。     

电脑刺绣机横梁弯曲振动固有频率研究

以2头电脑刺绣机横梁为研究对象,分别运用简单梁理论,ANSYS有限元模拟和实验测试三种方法计算分析了电脑刺绣机横梁弯曲振动的固有频率,所得结论可用于电脑刺绣机横梁长度、截面形状和固定方式的改进设计。     

变截面智能压电梁的动态特性研究

建立变截面智能压电梁的动态模型,分析表面粘贴压电元件的均质梁的固有频率。在分析时考虑坟电元件、粘贴层、梁的剪切变形和转动惯量。研究表明,压电元件的刚度和惯量对梁的频率影响很大,变截面智能压电梁的一除非 固有频率总是高于等截面梁的固有频率。粘结层剪切 对一阶频率影响较 剪切变 转动惯量时,对梁的高阶频率影响较大。考虑梁的惊动国惯量和剪切谱形时,智能阶梯梁的频率比没有时的要低。     

叠层平面圆环的振动行为

为了研究叠层平面圆环的振动行为和叠层对其振动影响,用有限元法对系列均质平面圆环进行振动分析以获得试验比较参照,对系列均质圆环和不同夹紧压力下的系列叠层圆环进行大量试验。理论分析和试验结果表明,叠层平面圆环的振动行为是由组成该叠层圆环的单片圆环的振动行为所支配,但叠层对圆环的振动有着重要影响,且这种影响与模态类型、夹紧压力和叠层层数有很大关系。随着叠层层数和夹紧力的增加,圆环纵向振动模态将很快消失,而平面模态得以保留并支配叠层平面圆环的振动。     

基于接触面优化方法和整体仿真的压缩式压电振动传感器固有频率优化

振动传感器的固有频率范围决定了工作带宽上限,其固有频率的优化是设计中的重要一项.在压缩式压电振动传感器的固有频率优化中,存在缺少ANSYS的适应性优化方法和缺少整体仿真的问题.针对这2个问题,分析了压电振动传感器的结构和ANSYS有限元分析工具的特点,提出了一种基于ANSYS接触工具和网格分布分析的整体仿真接触面优化方...     

压电智能悬臂梁结构振动主动控制仿真

为了提高LQR最优控制方法对压电类智能结构的振动控制效果,推导了表面离散分布压电元件的柔性悬臂梁结构的驱动和传感方程以及梁的弯曲振动方程,用模态分析方法对方程进行解耦和模型降阶,建立控制系统的状态空间方程。利用有限元分析方法来衡量压电元件对梁固有特性的影响,对状态空间方程的自振频率和振型函数进行修正,得到更为精确的数学模型。通过一悬臂梁的LQR最优控制仿真实例表明,经过模型修正后的最优振动控制效果更好。     

两自由度悬臂梁压电发电装置的宽频发电性能

研究一种两自由度悬臂梁压电发电装置,以提高悬臂梁式压电发电装置在环境振源振动频率波动情况下的发电能力。建立了两自由度悬臂梁压电发电装置的频率特性理论模型,并对该理论模型进行了有限元仿真验证,结果显示理论计算与有限元仿真结果基本一致。对两自由度悬臂梁压电发电装置的频率特性模型进行了数值模拟,模拟显示:装置的前两阶模态频率比随着长度比、宽度比、厚度比及质量块的质量比的增大均出现一个最小值,且在长度比为0.8,宽度比为2.0,厚度比为1.0,质量块的质量比为0.5时,装置的前两阶模态频率比最小,结果表明通过合理设计两自由度悬臂梁压电发电装置的结构参数,可以使得装置的前两阶模态频率最接近。最后,实例设计了两自由度悬臂梁压电发电装置,并进行了试验测试,证实了优化后的两自由度悬臂梁压电发电装置具有宽频带发电能力。     

弯曲振动圆盘振动特性试验研究

对超声振动系统中弯曲振动圆盘的振动特性进行了试验研究,结果表明,减小圆盘厚度,谐振频率减小;减小圆盘直径,谐振频率增大。在振动系统设计中,将变幅杆与弯曲振动圆盘设计成一体,克服了原来由于螺纹连接所造成的缺陷。通过试验得知,弯曲振动圆盘是以弯曲振动为主,存在一定反射波的干扰,并且圆盘具有增幅特性,圆盘的最大振幅约为18μm。所获得的结论对振动系统结构设计以及在超声深孔珩磨中的应用有一定的参考价值。     

Analysis of dynamic characteristics for vibration of flexural beam in ultrasonic transport system

An object transport system is an essential device in the factory automation system (FAS). Generally, an object transport system is driven by a conveyor belt system or a magnetic levitation system. However, contact force in the conventional transport system can damage precision optical components, while the magnetic field can destroy the inner structure of the semiconductor. The ultrasonic transport system transports objects on an elastic body using an ultrasonic wave. When an ultrasonic wave is applied to a flexural beam, the flexural beam vibrates to excite the air layer, which lifts up the object on the beam to transport. In this paper, the dynamic characteristics of the ultrasonic transport system are theoretically analyzed. Through normal mode expansion, the modeling equation for steady state response of ultrasonic vibration is expressed and the natural frequency of the flexural beam in each mode is also estimated by using the finite element method (FEM). This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin Sang-Hwa Jeong received his M.S. degree in Mechanical Engineering from KAIST, Korea, in 1985 and his Ph.D. degree from North Carolina State University, USA, in 1992. Dr. Jeong is currently a professor at the department of Mechanical Engineering of Chosun University in Gwangju, Korea. His research fields are microactuator design, ultrasonic transport system, and SMA actuator of robot finger.     

悬臂梁振动自适应模糊控制及DSP实现

以粘贴压电自感作动器的悬臂梁为研究对象,推导了悬臂梁振动主动控制的压电元传感方程和作动方程的传递函数,给出了压电自感作动器位置配置优化方法,设计了硬件电路以及软件流程.试验结果表明,利用压电自感作动器和模糊自适应控制器可有效地抑制悬臂梁振动.     

Repair of notched beam under dynamic load using piezoelectric patch

In this paper, the repair of a cracked beam under an external dynamic load employing the electro-mechanical characteristic of piezoelectric material to induce a local moment is presented. Conceptually, an external voltage is applied to actuate a piezoelectric patch bonded on the beam to effect closure of a crack so that the singularity at the crack tip under dynamic load may be decreased. Globally, this has the effect of altering the resonant frequency of the cracked beam towards that of the healthy beam, which is the criterion used for the repair. To demonstrate the repair methodology, a cantilever beam is used as an illustration, where the repair moment coefficient and the voltage required are mathematically derived. The relationship between repair moment coefficient, crack parameters and length of piezoelectric patch is investigated. The difference between the proposed repair criterion and an earlier published criterion for cracked beam under static load is also shown. A numerical example is used to study the effectiveness of the proposed repair methodology and its results are compared with those from 3-D finite element analyses using ABAQUS 6.4 as one means of verification.     

一种新型高低频复合振动装置的研究

针对金属材料疲劳断裂研究的现状以及实际应用中应力比r的变化情况,分析了应力比r对金属疲劳裂纹萌生和扩展的影响.运用Pro/E设计了一种新型高低频复合振动装置,对其空载运动状态下的动力学特性做了理论分析.建立了振动装置加栽金属材料时的动力学模型,以加载7A09高强度铝合金为算例,运用ANSYS对模型进行谐波分析,得到了此种情况下的幅频特性曲线图,并由此获得了在该状态下最易发生疲劳断裂的变频区间.     

Non-linear free vibration analysis of laminated orthotropic cylindrical shells

A method to predict the influence of geometric non-linearities on the natural frequencies of an empty laminated orthotropic cylindrical shell is presented in this paper. It is a hybrid of finite element and classical thin shell theories. Sanders—Koiter non-linear and strain-displacement relations are used. Displacement functions are evaluated using linearized equations of motion. Modal coefficients are then obtained for these displacement functions. Expressions for the mass, linear and non-linear stiffness matrices are derived through the finite element method (in terms of the elements of the elasticity matrix). The uncoupled equations are solved with the help of elliptic functions. The frequency variations are first determined as a function of shell amplitudes and then compared with the results in the literature.     

Vibration and buckling of cross-ply laminated composite circular cylindrical shells according to a global higher-order theory

Natural frequencies and buckling stresses of cross-ply laminated composite circular cylindrical shells are analyzed by taking into account the effects of higher-order deformations such as transverse shear and normal deformations, and rotatory inertia. By using the method of power series expansion of displacement components, a set of fundamental dynamic equations of a two-dimensional higher-order theory for laminated composite circular cylindrical shells made of elastic and orthotropic materials is derived through Hamilton's principle. Several sets of truncated approximate higher-order theories are applied to solve the vibration and buckling problems of laminated composite circular cylindrical shells subjected to axial stresses. The total number of unknowns does not depend on the number of layers in any multilayered shells. In order to assure the accuracy of the present theory, convergence properties of the first natural frequency and corresponding buckling stress for the fundamental mode r=s=1 are examined in detail. The internal and external works are calculated and compared to prove the numerical accuracy of solutions. Modal transverse shear and normal stresses can be calculated by integrating the three-dimensional equations of equilibrium in the thickness direction, and satisfying the continuity conditions at the interface between layers and stress boundary conditions at the external surfaces. It is noticed that the present global higher-order approximate theories can predict accurately the natural frequencies and buckling stresses of simply supported laminated composite circular cylindrical shells within small number of unknowns.     

确定阶梯轴扭振固有频率的混合状态方法

提出的新方法将阶梯轴分为若干段,每段可视为等截面轴,每段内所满足的扭振混合状态方程可精确地求出,然后利用两段之间的连续条件和边界条件将固有频率求出。