间隙液压粘滞阻尼器特性参数分析

主要介绍用于桥梁上的间隙液压粘滞阻尼器,分析其工作原理及影响其工作性能的参数。建立数学模型,在MATLAB的中进行仿真,通过改变工作介质的特性参数,如动力黏度、体积弹性系数和间隙量,研究参数对阻尼器性能的影响。     

带梯形截面导磁环的全通道有效车用磁流变减振器设计

车用磁流变减振器(MRD)往往结构尺寸较小,且传统的车用MRD阻尼通道有效工作长度较短,输出阻尼力小,导致其工程应用受到限制。针对这一问题,提出一种带梯形截面导磁环的新型全通道有效MRD以增大阻尼通道有效工作长度,减缓磁饱和,并基于磁流变液流变特性和流体动力学理论给出了具体的结构与磁路设计计算方法,将5种不同结构的MRD进行有限元仿真对比。通过阻尼特性测试试验,分析其阻尼特性并与普通MRD、带弯曲磁路全通道有效MRD进行对比,应用线性二次高斯(LQG)控制器进行减振性能分析。研究结果表明：新型全通道有效MRD能够显著提高阻尼通道有效工作长度,达到阻尼通道全长的99%以上;新型全通道有效MRD能改善小尺寸MRD易发生磁饱和的问题;在相同电流激励与尺寸约束下阻尼通道的磁场强度分布更均匀,平均磁场强度更大,具有更大的输出阻尼力;新型全通道有效MRD在结构尺寸小的同时具有更大的输出阻尼力;新型全通道有效MRD相对于普通MRD具有更好的减振性能,能够进一步降低车辆的簧上质量加速度与轮胎动变形21.51%和1.43%。该研究能有效扩宽小尺寸MRD的实际应用范围,具有一定的工程应用价值。     

考虑平-扭耦联效应黏弹性阻尼器最优位置研究

为了研究控制平-扭耦联效应黏弹性阻尼器最优位置问题,推导不同偏心形式单层偏心结构,采用不同方式布置黏弹性阻尼器减震结构考虑平-扭耦联效应的振动方程,建立基于结构平动与扭转位移响应相关性的目标函数。利用随机振动理论中的李雅普诺夫方程和最优控制理论,建立并求解偏心结构平面几何中心位移响应协方差矩阵,通过求得目标函数最小值找到阻尼器的最优偏心位置。在此基础上编制相应程序对典型算例进行数值计算,分析不同偏心形式下,地震荷载输入条件、等效阻尼比、静力偏心率、扭平频率比、结构周期、结构尺寸效应对考虑平-扭耦联效应时黏弹性阻尼器最优位置的影响规律。     

动调频液柱阻尼器基于遗传算法的LQR控制优化设计

ATLCD由调频液柱阻尼器(Tuned Liquid Column Damper,TLCD)发展而来,在TLCD液柱端部连接气压控制箱,通过引入控制气压对结构实施主动控制。采用被动TLCD优化设计方法设计阻尼比及频率比,采用LQR算法确定ATLCD系统的主动控制力,并对LQR算法中权矩阵采用遗传算法进行优化。以一五层钢框架结构为例,顶层装ATLCD用LQR算法进行主动控制,加载El-Centro地震波进行时程响应分析,比较无控结构及被、主动控制结构的时程响应结果表明,采用ATLCD的减振效果明显优于采用被动装置。     

基于MR大数据的LTE网络结构评估方法

随着4G网络的快速发展和用户的迅速增长,传统的基于测试、网管指标和客户投诉的网络质量提升手段已经不能满足客户感知的需要。本文提出一种基于MR大数据的网络质量分析方法,首先从网络结构的角度出发,评估现网网络质量情况,然后发现网络问题短板,定位网络质差的根本原因,最后输出针对性的网络优化调整方案,从而改善网络结构,提升客户感知。     

滚珠丝杠副精度保持性试验装置及加载方案研究

滚珠丝杠副的精度保持性对数控机床的加工精度稳定性与高精度加工持久性有重大影响。采用电涡流制动器加载螺母的方案,设计了一套滚珠丝杠副精度保持性测量装置,解决在大载荷运动过程中对滚珠丝杠副实际工况的模拟及传感器数据实时采集等难题。在此基础上,对滚珠丝杠副精度保持性的试验方法进行了研究。结果表明该试验装置具有加载载荷大,实际工况仿真度高,被测件易拆卸装配,测量精度高,适用范围广的优点;该试验方法能够较好地完成精度保持性的测量及验证,对同类产品试验方法的研究也具有指导意义。     

Application of coupled multi-body dynamics–discrete element method for optimization of particle damper for cable vibration attenuation

With the application of the particle damping technology to cable vibration attenuation, the rootless cable damper overcomes the limit in installation height of existing dampers. Damping is achieved through energy dissipation by collisions and friction. In this paper, a coupled multi-body dynamics–discrete element method is proposed to simulate the damping of the damper–cable system under a harmonic excitation. The analyses are done by combining the discrete element method in EDEM and multi-body dynamics in ADAMS. The simulation results demonstrate the damping efficiency of rootless particle damper under different excitations and reveal the influence of the design parameters on its performance, including the filling ratio, particle size, coefficient of restitution, and coefficient of friction.     

基于Simulink的油压减振器动态特性研究

以某型号一系垂向减振器的实际结构参数为基础,利用流体力学和油膜理论,建立了考虑泄漏的油压减振器的数学模型。根据油压减振器的具体参数和公式,在MATLAB/Simulink中建立了减振器的系统仿真模型。利用所建立的仿真模型,分析了单一变量下阻尼阀截面积、活塞杆面积、活塞面积、弹簧预压缩量等减振器关键参数对减振器阻尼性能的影响,为减振器的阻尼特性优化设计提供了参考。     

Temperature Effect on the Torque Characteristic of a Magnetorheological Clutch

In this article the torque characteristic of a permanent magnet magnetorheological (MR) clutch is investigated focusing on the influence of temperature. An experimental campaign was carried out on a test bench equipped with a caulk oxen, heating up to 80°C. The torque characteristic was measured monitoring both fluid and clutch case temperature. Torque data were processed and well fitted by a formula where the temperature dependence is expressed by Arrhenius law. In particular, a loss of transmitted torque for increasing temperature was found. An approximate dependence of MR fluid shear stress on temperature, useful for similar devices, was also obtained.     

Rheological Characterization of MR Polishing Fluid Used for Silicon Polishing in BEMRF Process

The finishing mechanism of the ball-end magnetorheological finishing (BEMRF) process mainly depends on the stiffened hemispheroid, which is formed at the tool tip. Magnetorheological (MR) polishing fluid imparts strength to the polishing spot because of the effect of magnetic field strength. Behavior of this polishing fluid mainly depends on the size and shape of its constituents, volume concentration, particle size distribution, and applied magnetic field strength. A detailed study was undertaken on the role of carbonyl iron particle (CIP) size on the rheological behavior of the MR polishing fluid under various magnetic flux densities. Evaluation of the behavior of MR polishing fluid for silicon polishing was attempted through designing and fabrication of a parallel-plate magnetorheometer. Rheological characterization study was carried out using the Casson fluid model and the MR polishing fluid rheological properties, namely field-induced yield stress and shear viscosity were evaluated.