计及轴颈轴向运动的径向滑动轴承润滑分析

以轴-径向滑动轴承系统为研究对象,综合考虑轴颈轴向运动和倾斜,建立了倾斜轴颈的轴承的流体动力润滑模型,采用有限差分法求解Reynolds方程,分析了不同的轴颈倾角、转速、偏心率和轴承间隙下的轴颈轴向运动对倾斜轴颈的轴承润滑性能的影响规律。结果表明：轴颈轴向运动对倾斜轴颈滑动轴承润滑特性影响显著,且影响程度与轴颈倾角和转速有直接的关系,倾角越大,对轴承润滑性能的影响越大,转速越低,对轴承润滑性能的影响越显著;轴承间隙越小,对轴承润滑性能的影响越大。     

Misalignment effects on steady‐state and dynamic behaviour of compliant journal bearings lubricated with couple stress fluids

This work concerns the steady‐state and dynamic analysis of misaligned compliant journal bearings considering the effects of couple stresses arising from the lubricant blended with polymer additives. Based on the Stokes micro‐continuum theory, a modified form of the Reynolds equation is derived. The displacement field at the fluid film–bearing liner interface due to pressure forces is determined using the elastic thin liner model. The effects of the misalignment and the couple stress parameters on static and dynamic performances such as pressure distribution, load‐carrying capacity, power loss, side leakage flow, misalignment moment, critical mass and whirl frequency are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

叠片联轴器不对中的力学模型建立及分析

联轴器装配不对中是引起旋转机械中异常振动的主要原因之一。将一种使用在大型风机上的长距离叠片联轴器做为研究对象 ,将联轴器及电机视作一个电机—转子系统 ,建立了不对中引起的电机—联轴器扭矩力学模型。理论分析结果表明 ,不对中引发的振动频率为电机基频的偶数倍 ,当系统固有频率接近或达到电机基频的偶数倍时 ,将发生共振 ,使不对中引发的振动放大成为系统的主振源。因此应避免系统固有频率为电机基频的偶数倍     

膜片联轴器耦合的不对中转子-轴承系统的不平衡响应分析

转子系统的不平衡是旋转机械最为常见的故障之一，它影响转子系统的振动品质。考虑了转子系统不平衡力的作用，建立了膜片联轴器耦合的转子-轴承系统的运动微分方程；并以膜片联轴器耦合的双跨转子-轴承系统为研究对象，分析了不对中状态下转子系统的不平衡稳态响应，重点讨论了两跨转子各结点之间的振幅差异，结果表明膜片联轴器具有显著的隔振效果。     

Development of a three-dimensional finite element model for a unidirectional carbon fiber reinforced plastic based on X-ray computed tomography images and the numerical simulation on compression

A unidirectional carbon fiber reinforced plastic (CFRP) was scanned by an X-ray computed tomography (CT) system. Based on the X-ray CT images, a three-dimensional model with random fiber waviness was developed. Each fiber location was identified in a sectional CT image. Subsequently, the relative displacement of fibers between adjacent sectional CT images was obtained with a digital image correlation method. This procedure was repeated to obtain fiber waviness along the axial direction. The constructed three-dimensional fiber model showed random waviness of each fiber in the unidirectional CFRP. Finite element analysis was performed using the three-dimensional model. Simulation results showed bending and twisting deformations coupled with axial contractions during axial compression, which developed due to fiber waviness. A reduction of the fiber directional Young’s modulus due to fiber random waviness was quantitatively evaluated.     

电动汽车无线充电线圈偏移情况下的效率提升

电动汽车无线充电过程中线圈偏移问题经常发生,可能造成系统传输效率的降低和增加系统的不稳定性.针对两种电动汽车无线充电过程中出现的线圈偏移问题进行了互感、传输效率的理论计算与分析.在此基础上,运用Matlab对线圈科学设计、阻抗网络优化、平板磁芯耦合的3种无线电能传输系统进行仿真.结果表明3种方法均能有效提高充电系统线圈偏移情况下无线电能的传输效率.     

基于BEER模型的人民币汇率失调研究

基于均衡汇率BEER模型,采用2000年第一季度到2008年第四季度期间的数据,运用协整技术得出基本经济因素向量对均衡汇率的影响系数,估计出样本期间内人民币汇率的失调程度。结果表明,政府支出对人民币均衡汇率影响最大,贸易条件和对外净资产对均衡汇率具有正向作用;利用模型得出的人民币均衡汇率方程对当前人民币汇率进行测算,样本期间内人民币大都处在低估的状态;另外,2005年的汇改使得人民币汇率在3个季度内连续升值并接近均衡,长期内人民币仍有升值的压力。     

Calibration of split Hopkinson pressure bar system with special shape striker

In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindri...     

光纤陀螺随钻测斜仪钻进中井眼轨迹测量方法研究

为提高光纤陀螺随钻测斜仪的井眼轨迹的测量精度,采用卡尔曼滤波组合的测量方法,对井斜、方位和工具面失准角进行估计。由于姿态失准角的估计精度与其可观测性密切相关,为了提高估计精度,文章分别在匀速、匀加速和匀速转动三种钻进运动状态下,采用分段线性定常系统(PWCS)和奇异值分解(SVD)的方法分析了姿态失准角的可观测性,并分析了钻进中井斜角和转动速率对姿态失准角估计精度的影响。由仿真结果可知,匀速钻进时,方位失准角不可观测;匀加速钻进时,方位失准角可观测且在水平井中可观测性最强,随着井斜角度增大,方位角、井斜角的测量精度逐渐提高;绕轴向匀速转动钻进时,方位失准角的可观测性和估计精度均优于匀速、匀加速钻进状态;角速率由0°/s增加到5°/s时,三个姿态失准角的估计精度均增大并逐渐趋于稳定。文中提出的轴向转动钻进运动可有效提高井眼轨迹的测量精度。     

计入轴倾斜时轴-轴承系统动力学摩擦学耦合分析

探讨了变载荷作用下计入轴倾斜时轴-轴承系统动力摩擦学耦合问题.以弹性轴多柔体动力学分析为基础,通过ADAMS与MATLAB联合仿真,解决了考虑轴倾斜时弹性轴-轴承系统在正弦激励力作用下的动力学求解问题.得到的主要结论是:考虑轴倾斜时一阶固有频率略有下降,二阶固有频率略有上升,共振时振动幅度增大,最小油膜厚度减小.分析计算轴-轴承系统的动力学和摩擦学特性时,计入轴的受力变形倾斜对于提高其分析计算的准确性和可靠性是十分重要的.