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电流变液研究进展及最新动态——第5届国际电流变液,磁悬浮体及相关技… 总被引:15,自引:0,他引:15
通过评介第5届国际电流变液、磁悬浮体以及相关技术研讨会,指出电流变液和磁流变液的应用研究有重要进展,磁流变液的剪切应力比电流变液大一个数量级,近来又受到重视,有机理研究中,要注意电流变液的表面效应,损耗对电流变效应的影响,本文还归纳了一些电流为液材料设计的思路。 相似文献
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电流变液和电流变效应 总被引:26,自引:1,他引:25
电流变液是一种极有发展前景的新颖材料,通常由不导电的母液和均匀散布在其中的电介质微粒组成。对于外加电场的变化,它的力学性能可以作出迅速的响应,因而在工业上极具应用前景。本文将就电流变液的研究进行综述,涉及的内容有:电流变效应的机理、电流变液材料及其力学性能、应用和展望. 相似文献
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电流变阻尼器的动态特性实验研究 总被引:7,自引:0,他引:7
设计制造了一种多层滑动极板式电流变阻尼器,使用自制的电流变液,采用正弦激励,进行了这种电流变阻尼器的阻尼特性试验。研究了电流变阻尼器的载荷-位移迟滞特性和载荷-速率迟滞特性,同时研究分析了这种电流变阻尼器的周期能耗特性及等效粘性阻尼特性。结果表明,阻尼器的周期能耗量随外加电场强度的增加而增加,外加电场强度越大,阻尼器的等效阻尼系数越大。阻尼器的阻尼特性体现为库仑阻尼和粘性阻尼的组合,其中随外加电场强度可控的主要是库仑阻尼力,而且库仑阻尼力不仅与外加强度有关,也与阻尼器的运动速度有关。该阻尼器系统是一个强非线性系统,极板间电流变液在低剪切应变率时表现为Bingham塑性流体,在高剪切应变率时流变性态比较复杂,导致载荷-速率迟滞环出现多区域闭合现象。 相似文献
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电流变液与压电陶瓷复合的自耦合阻尼器 总被引:1,自引:0,他引:1
基于智能结构的思想,率先提出设计制作电流变液和压电陶瓷复合的自耦合阻尼器.相比于通常的电流变液阻尼器,该自耦合阻尼器采用压电陶瓷响应外界振动而输出高电压,激励电流变液体工作,从而省去了外加高压电源.随外作用力变化,激励电流变液的压电陶瓷电压自动改变,阻尼器具有自适应的特征,省去了通常的计算机等控制系统.研制的第1代电流变液/压电陶瓷阻尼器实现了自适应的控制过程,显示了良好的减振性能.在第2代产品中采用了新的设计,提高了阻尼器的结构稳定性和可靠性,使阻尼器整体性能得到提高. 相似文献
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基于油膜内屈服面位置可能出现的4种情况,Tichy提出了用于Bingham流体滑动轴承特性及其屈服面位置的计算方法,在将该计算方法推广到电流变液滑动轴承的计算时,发现随着外加电场强度的变形,出现了轴承风屈服面位置不变的非物理结果,而且Tichy的方法只能适用于无限宽滑动轴承,为了对有限宽度的电流变液滑动轴承进行数值研究,采用了类Bingham模型,通过差分离散和超松驰迭代的方法对雷诺方程进行求解,计算结果表明:电流变流滑动轴承内的压力分布可以通过外加电场强度来控制,轴承间隙内屈服面位置随电场强度变化而产生的移动是使轴承润滑性能得以改变的重要力学机制;在轴承以高剪切速率运转时,由于电流变液表观黏度随电场强度的变化已经很小,该机制在轴承的设计中尤为重要。 相似文献
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用 HAAKE RV2 0型流变仪 ,在不同外加电场强度和不同颗粒体积分数下测试了基于沸石和硅油的电流变液的剪切应力变化 .结果表明 :随着外加电场强度升高 ,电流变液的零电场粘度急剧增加 ,电流变液的剪切屈服应力增加 ;随着电流变液中沸石颗粒体积分数升高 ,电流变液的剪切屈服强度急剧上升 .这种变化可以用颗粒间作用力与颗粒间距的关系、单位面积的颗粒链数目变化以及多体作用对电流变液性能的影响来解释 相似文献
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An electrorheological (ER) response is defined as the dramatic change in rheological properties of a suspension of small particles
due to the application of a large electric field transverse to the direction of flow. ER fluids are typically composed of
nonconducting or semiconducting particles dispersed in a nonconducting continuous phase. A sufficiently large electric field
will cause ER fluids to solidify, giving rising to a yield stress. Many applications in torque and stress transfer devices
were proposed employing the reversible yielding behavior of ER fluids. Successful applications depend on a large yield stress
of ER fluids and therefore accurate measurements of the yield stress of ER fluids are required. Reported experimental yield
stresses of ER fluids have been dynamic yield stresses obtained by extrapolating the shear stress–shear rate data to zero-shear
rate. It would be very helpful to the understanding of ER behaviors and the applications of ER fluids to be able to measure
the static yield stress of ER fluids accurately. The slotted plate technique has been shown to be a successful method to determine
the static yield stress of suspensions. The values obtained via the slotted plate method are static yield stress as the platform
is designed for extremely low-speed motion. In this study, we modified the slotted plate device for the application of large
electric fields and measured the static yield stress of TiO2 ER fluids under various electric fields. The measured static yield stress values are also compared with the static yield
stress values from a commercial rheometer. 相似文献
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近年来发生的许多事故表明,按传统方法设计和评定工程结构不能保证其损伤后的安全性,人们试图引入新的余度衡准来解决这一问题.余度密准的概念和定义十分繁杂,并且还在不断发展之中,本文给出了余度的定义,对各种分度衡准进行了归纳分类,评述和研究了它们的特点及应用,并讨论了与余度相关的几个概念. 相似文献
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The rheological behavior of a dielectric fluid is studied in nonuniform electric fields which are generated by an electrode
covered with flocked fabrics. Although no electrorheological (ER) effects are observed in uniform fields between metal electrodes
with smooth surfaces, striking increases in viscosity and elastic response are induced by the electrode with flocked fabrics.
The presence of flocked fabrics does not have a significant effect on the fluid rheology without electric fields. The ER behavior
and current density are influenced by the fiber length even at a constant field strength. When a very small amount of fine
particles is introduced in the electrified fluid without shear, we can see the rapid and large-scale motion of particles between
the tips of fibers and plate electrode. In high DC fields, the Coulomb force acting on a free charge often gives rise to the
secondary motion of fluid. The local motion of fluid in high electric fields is refereed to as electrohydrodynamic (EHD) convection.
The additional energy may be required to change the periodic patterns of EHD convection by forced shear. Therefore, the ER
effect demonstrated by the modification of electrode with flocked fabrics can be attributed to a combined effect of EHD convection
and external shear.
Received: 10 March 1998 Accepted: 1 June 1998 相似文献
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高雷诺数流动理论、算法和应用的若干研究进展 总被引:3,自引:0,他引:3
在黏性流体力学的历史发展中,Navier-Stokes (NS)方程组的
简化理论、相应算法和应用构成了不同历史时期的学科前沿、核心内
容的应用热点。以此为线索,简要评述经典边界层、多层(三层)边界
层、干扰边界层、扩散抛物化(DP) NS方程诸理论、相应算法和应用的
若干研究进展;诸理论之间以及他们与实验的关系;简化湍流计算的
一点注释以及物理分析和数值模拟相结合的一些问题。 相似文献
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The dynamic responses of the electrorheological fluid in steady pressure flow to stepwise electric fields are investigated
experimentally. First of all, the transient responses of the ER fluid under various electric field strengths and flow velocities
are obtained from the pressure behaviors in the flow channel with two parallel-plate electrodes. The response times are exponentially
decreased with the increase of the flow velocity and the decrease of the electric field strength. Next, the relationship between
the dynamic pressure behaviors of the ER fluid and the cluster structure formation processes of the ER particles is investigated
using the flow visualization technique. Through the comparison study, it is verified that the dynamic responses of the ER
fluid in the flow mode are mainly caused by the cluster densification process in the competition of the electric field-induced
particle attraction and the hydrodynamic force, unlike those in the shear mode determined by the particle aggregation process. 相似文献
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Dielectric liquids that show striking electrorheological (ER) effects are formulated by controlling the conductivity. Although the viscosity is increased on the application of a d.c. field, the flow of electrified fluids is Newtonian in the plain electrodes with smooth surfaces. When the liquids are sandwiched between the electrodes with flocked fabrics, the viscosity behavior is converted from Newtonian to shear-thinning flow. In electric fields, the convective flow is induced over the system due to the electrohydrodynamic(EHD) effect. The interactions between EHD convection and external shear give rise to the additional energy dissipation and in turn the increase in viscosity. The ER effects of simple liquids are very attractive in application to new fluid devices. 相似文献
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综述了国内和国外学者研究连续介质分析动力学问题的进展,阐明了本文主要论述将Lagrange方程应用于连续介质动力学的问题.论文采用Lagrange-Hamilton体系,分别论述了非保守非线性弹性动力学、不可压缩黏性流体动力学、黏弹性动力学、热弹性动力学、刚--弹耦合动力学和刚--液耦合动力学的Lagrange方程及其应用.论述了应用Lagrange方程建立有限元计算模型的问题. 最后,展望了将Lagrange方程应用于连续介质动力学问题的研究前景. 相似文献