Mechanism and characteristic of rain-induced vibration on high-voltage transmission line

Under the rainy weather, rain-induced vibration on high-voltage (HV) transmission line often occurs, which intensifies fatigue conductors and tower callapses. Mechanism and control measures of the rain-induced vibration have aroused wide attention in power engineering. The mechanism can be explained that the droplets suspended to the conductors amplify corona discharges with ionic wind, forms non-circular cross-sections, and the rain-induced vibration is due to the coupling action of vortex-induced vibration by ionic wind and galloping vibration by external wind force. Based on the mechanism, a valid model on the rain-induced vibration on high-voltage transmission line is proposed based on the finite element theory and the Newmark algorithm. Taking the conductor LGJ-240 as an instance, we investigate the effects of ionic wind and non-circular cross-sections with different parameters on amplitude of the conductors. The result shows non-circular cross-sections have obviously effects, and the ionic wind have a certain influence and easily to coupling with wind force. Mechanism and conclusions in this paper can be used as references to construct High-voltage transmission lines, upgrade the existing lines and control vibration.     

超长斜拉索风阻系数及风雨激振的试验研究

结合主跨为1088m的世界最大跨度斜拉桥苏通大桥,对拉索的抗风问题进行了系统的研究。通过横桥向、顺桥向拉索风阻系数的风洞测量试验,得到了光索、螺旋线及压痕凹坑3种表面情况拉索的风阻系数;并模拟人工降雨,在风洞中重现了拉索的风雨激振现象,研究了风速、降雨量、拉索表面情况以及机械阻尼对风雨激振的影响。结果表明,拉索的阻力系数与表面情况、倾角、Re数密切相关,螺旋线、压痕凹坑及机械阻尼均可有效抑制拉索风雨激振现象。本文的试验方法及结果为超长斜拉索抗风研究提供了有益的参考。     

运行工况下风电传动系统机电耦合建模及其动态特性分析

为研究风电传动系统在变速变载运行工况下的机电耦合动态特性,构建的包括齿轮系统动力学模型、永磁同步发电机有限元模型以及风机运行控制模型的风电传动系统机电耦合模型,计入了齿轮时变啮合刚度以及发电机齿槽效应、磁饱和等非线性因素.仿真分析了风电传动系统在启动、发电运行工况下的动态响应和机电耦合动态特性.研究结果表明:启动工况下...     

考虑时变刚度的齿轮振动响应仿真分析

利用MASTA软件建立齿轮传动系统实体模型,并在MASTA环境下调用ANSYS软件完成齿轮传动系统刚度有限元分析,计算得到由齿轮时变啮合刚度引起的传动误差,以此作为齿轮箱体响应分析的激励源,利用ANSYS软件对箱体进行振动响应分析,分析了时变刚度对箱体振动响应的影响.本文所采用的方法,可用于实际工程中分析预估齿轮传动装...     

随机风作用下风力发电机齿轮传动系统动载荷计算及统计分析

针对风力发电机齿轮传动系统在随机风作用下失效率高的问题,在模拟真实风速的基础上,建立考虑外部随机风载及内部齿轮时变啮合刚度、轴承时变刚度及综合传递误差等激励因素的风力发电机齿轮传动系统齿轮-轴承耦合动力学模型,通过对动力学模型进行仿真计算,得到各齿轮副的动态啮合力和各支承轴承的动态接触力。结合有限单元法和赫兹接触理论,得到关键零部件的应力时间历程,采用雨流计数法对应力时间历程进行统计分析,得到传动系统各关键零部件承受载荷的应力谱及概率分布函数。研究结果为风力发电机齿轮传动系统的动态可靠性分析和疲劳寿命预测奠定基础。     

变风速运行控制下风电传动系统的动态特性

基于齿轮系统动力学的方法对风电传动系统进行研究。运用基于自回归模型的线性滤波法(Auto-regressive,AR)建立的风速模型对实际风场的随机风速进行模拟;根据风力发电机在实际情况中的运行控制策略获得风力发电机齿轮传动系统的时变输入转矩激励;综合考虑风力发电机齿轮传动系统中各个齿轮副的时变啮合刚度、各个滚动轴承的刚度、各个轮齿综合啮合误差等内部激励,采用集中参数质量法建立风力发电机齿轮传动系统的耦合动力学模型;在此基础上建立风力发电机齿轮传动系统的动力学微分方程并进行仿真计算,分别求解风力发电机齿轮传动系统的固有频率、振动响应、动态啮合力和滚动轴承动态轴承力。研究结果为风力发电机传动系统的动态性能优化设计和可靠性设计奠定了基础。     

考虑强度退化和失效相关性的风电齿轮传动系统动态可靠性分析

针对随机风作用下风力发电机齿轮传动系统失效率高的问题,研究了随机风引起的风力发电机传动系统外部风载荷以及内部由齿轮、轴承刚度及综合啮合误差等引起的内部动载荷激励,基于集中质量法建立了风电齿轮传动系统齿轮-轴承耦合动力学模型。在对模型进行仿真求解的基础上,分别求得了传动系统中各齿轮和轴承的动态接触应力-时间历程。将载荷作用过程视为随机过程,推导出随机载荷作用下的等效载荷累计分布函数,从系统层面上建立了基于应力-强度干涉理论的风力发电机齿轮传动系统动态时变可靠性模型,模型考虑了零件的失效相关性和强度退化因素,研究了失效相关性和强度退化对风电齿轮传动系统可靠度和失效率的影响规律,为风力发电机齿轮传动系统动态设计和可靠性优化设计奠定了基础。     

大型风力发电机复合材料叶片动态特性分析

以1.2 MW风力机叶片为研究对象,采用参数化建模技术建立大型风力机复合材料叶片的三维有限元壳模型,在此基础上采用拟波前子空间迭代法准确计算了基于多因素耦合作用下复合材料叶片的固有频率和振型。进而分析了不同形式的振动对旋转叶片的影响机理,该计算方法对大型复合材料风力机叶片的结构设计具有一定的参考价值。     

基于有限元法的准双曲面齿轮时变啮合特性研究

准确计算准双曲面齿轮的时变啮合参数是其系统动力学分析的基础。基于接触有限元分析原理,应用有限元分析软件ABAQUS对齿轮进行加载接触分析(Loaded tooth contact analysis,LTCA),准确计算准双曲面齿轮时变等效啮合参数,包括时变等效啮合点位置、时变等效啮合力作用方向、等效啮合力作用方向上的线位移传动误差和时变等效啮合刚度,并研究转矩大小对时变啮合参数的影响。对比有限元法与经典齿轮接触分析(Tooth contact analysis,TCA)方法求得的传动误差曲线,并对比有限元法计算与加载啮合试验获得的齿面啮合印迹,验证有限元模型和计算的正确性。该方法求得的时变等效啮合参数能够准确体现准双曲面齿轮的时变啮合特性,为进一步研究准双曲面齿轮系统动力学特性提供依据。     

暂态扭矩在多支承转子系统中的传递特性

以北卫碳纤维复合芯导线用于输电线路增容改造的实例为工程背景,运用有限元软件ANSYS建立三塔四线的有限元模型,并通过Matlab模拟沿高度变化的Kaimal风速谱,得到作用于输电塔和导地线的脉动风速时程曲线。由于碳纤维复合芯（aluminum conductor composite core,简称ACCC）导线具有重量轻、强度大和弧垂小等特点,计算得出了改造前使用的普通钢芯铝绞线及改造后使用的ACCC塔线体系的位移随时间的变化规律,以及在档距和塔高各自变化的情况下ACCC塔线体系的位移和应力,并与工程实际的塔线体系进行比较。结果表明,ACCC导线用于输电线路上的优越性及改造后模型的合理性可以节省工程造价,为以后的设计提供参考。     

Imaging vibrations of electromechanical few layer graphene resonators with a moving vacuum enclosure

Imaging the vibrations of nanomechanical resonators means measuring their flexural mode shapes from the dependence of their frequency response on in-plane position. Applied to two-dimensional resonators, this technique provides a wealth of information on the mechanical properties of atomically-thin membranes. We present a simple and robust system to image the vibrations of few layer graphene (FLG) resonators at room temperature and in vacuum with an in-plane displacement precision of ≈0.20 μm. It consists of a sturdy vacuum enclosure mounted on a three-axis micropositioning stage and designed for free space optical measurements of vibrations. The system is equipped with ultraflexible radio frequency transmission lines to electrically actuate resonators. With it we characterize the lowest frequency mode of FLG resonators by measuring its frequency response as a function of position on the membrane and by extracting its effective mass. We use the background noise of the undriven vibrational spectrum to calibrate in-plane displacement. Finally, we measure the first three vibration modes of a resonator whose membrane is partially folded and find that folds locally suppress vibrations.     

基于接触有限元的齿轮-转子系统动态特性分析

考虑齿轮-转子系统各部件的弹性,基于接触有限元理论提出一种能够高保真模拟齿轮副连续啮合过程的动态特性分析方法。该方法利用实体有限元进行系统建模,可体现各部件的结构特征;基于接触有限元进行啮合过程仿真,可模拟系统的时变刚度、啮合冲击等真实激励进而得到全面准确的响应信息。以一直齿轮-转子系统为例进行啮合过程的数值仿真,利用中心差分法求得系统各动力学参量在时域上的响应,通过中心距偏差、动态传递误差、动态接触力等参数分析系统的弯曲振动、扭转振动、齿轮副的啮合特性及其耦合关系。研究结果表明：考虑各部件尤其是转子的弹性后,系统的非线性振动特性显著,齿轮副啮合存在明显的双边冲击及脱啮现象。     

斜齿圆柱齿轮传动系统的耦合振动分析

建立了斜齿轮传动系统（斜齿轮、轴与轴承）的弯曲-扭转-轴向-扭摆耦合振动的动力学模型，推导了其振动微分方程，计算了风力发电机组增速箱FH660的传动系统的振动响应，并进行了三维有限元模态分析。对斜齿轮传动系统进行了很好的数值模拟，为斜齿轮传动系统的动态设计提供了有效的方法。     

Vibration characteristics and power transmission of coupled rectangular plates with elastic coupling edge and boundary restraints

Coupled-plate structures are widely used in the practical engineering such as aeronautical,civil and naval engineering etc.Limited works can be found on the vibration of the coupled-plate structure due...     

空间变化地震动下输电塔-线体系振动控制研究

在考虑输电线的几何非线性基础上,建立了输电塔-线体系的三维有限元计算模型.依据现行《电力设施抗震设计规范》,模拟生成了适合输电塔-线体系的多点地震动时程.利用质量、弹簧单元和阻尼单元模拟了调谐质量阻尼器,并对控制参数进行了优化.运用非线性时程分析方法,研究了多点地震激励对高压输电塔-线体系振动控制的影响.研究结果表明调谐质量阻尼器的减震效果显著,能够有效地减小输电塔的地震响应;仅考虑行波效应和多点激励对输电塔的减震效果影响较小,并且多点激励对输电塔的减震效果优于一致激励,但仅考虑相干效应减弱了输电塔的减震效果.     

输电线路风雨激振分析模型及数值分析

在分析电晕放电激振机理的基础上,基于有限单元法和Newmark积分法建立了输电线路风雨激振有限元分析模型。基于试验和数值分析方法,以输电线型号LGJ-240的相关参数为参考,分别研究了电晕放电离子风的产生及响应、电晕力和风载作用下的瞬态响应和谐响应特性。研究表明,电晕放电对舞动具有显著作用,并在特定输电线结构条件下,易于与外界风载耦合作用引起舞动。分析方法和结论可为多风雨区域的特高压输电线路设计、已有线路升级改造以及振动抑制提供必要参考。     

Contact-induced off-track vibrations of air bearing-slider-suspension system in hard disk drives

Contact-induced vibration of air bearing-slider-suspension system is a crucial issue for slider flying stability and head positioning precision of 1 Tbit/in² hard disk drives. In this paper, the contact-induced off-track vibrations of air bearing-slider-suspension system are investigated by simulation. A dynamic simulator is developed to calculate the interactions between the air bearing dynamics and vibrations of slider-suspension assembly. The simulation model consists of a finite element model of suspension assembly, an air bearing model based on the generalized lubrication equation, and a slider–disk contact model based on the probability distributions of surface roughness. A sequential method is used to couple all these models and analyses. The time history of the slider and suspension motions, together with the time-varying forces including air bearing force, air shear forces, contact force and friction force can be obtained. The effects of different contact conditions, such as the contact intensity, friction coefficient, and disk surface waviness on off-track vibrations are investigated numerically in details. The results reveal some mechanisms on how these factors contribute to the off-track vibrations of suspension assembly.     

考虑ARMA风速模型半直驱风电行星齿轮传动系统动力学分析

针对半直驱风电行星齿轮系统的变速变载的特点,考虑风速变化引起的外部载荷激励,采用自回归-滑动平均(ARMA)方法建立模拟风速模型,在考虑时变啮合刚度、啮合阻尼等因素的基础上,采用集中参数法建立了行星齿轮传动系统平移-扭转耦合动力学模型。并采用四阶龙格-库塔法,求解1.5 MW半直驱风力发电行星齿轮传动系统的动态响应。     

Multibody dynamics study on galloping of power transmission line

When the power transmission line (PTL) passes through a region of high mountains and heavy snowfall, maintaining the stability of the PTL and avoiding sleet jump and galloping are necessary. In this study, PTL is modeled as the mass-spring-damper system by using the multi-body dynamics analysis program, RecurDyn. The lumped mass model is compared with the finite element model based on deflection. To analyze the dynamic behavior of the PTL under icing and wind conditions, we obtained a damping coefficient for a multibody model from the free vibration test and Rayleigh damping theory. The icing cross-section of the transmission line is assumed to have ellipse and triangle shapes. The aerodynamic coefficients for each cross-section are derived by using the commercial CFD program, ANSYS Fluent. The occurrence of galloping is simulated for each shape according to the attack angle. Results indicate that the dynamic behavior of the PTL and the galloping conditions such as the icing shape, thickness, and attack angle, can be analyzed. Furthermore, the effects of each factor are evaluated. In the elliptical icing section, the effect of icing thickness is high; whereas in the triangular icing section, the wind velocity highly affects galloping.     

Vibration reduction of automotive transmission control cables

A reduction in the level of vibration in the gearshift lever module in the cabin of automobiles may have a positive effect on driver comfort. The vibration to the gearshift lever module is transferred through transmission control cables (TCCs) connected to the shift lever attached to the body of a transmission or transaxle. Ways to reduce vibrations are evaluated by analyzing vibration characteristics of TCCs employed in conventional gearshift lever modules. The analysis was carried out by both analytical and experimental approaches, including the construction and analysis of a finite element model of the module. By utilizing the results from the analysis, a vibration reduction method was proposed and its applicability was also investigated. It is observed from the investigation that the proposed method is a viable solution for both the reduction of vibration-related issues in gearshift level modules and improvement of ride quality.