Flow visualization in an annulus between co-axis rotating cylinders with a circular jet on stationary outer cylinder

This work experimentally investigated the effects of jet flow and flow outlet configuration on the fluid flow in an annulus between co-axis rotating cylinders. By using the incense and the laser light, smoke flow visualization in a rotating annulus can be obtained. Firstly, the flow behavior in a rotating annular without jet flow and flow outlet was investigated. When Taylor number (Ta) exceeded 1708, the well-known Taylor vortices were successfully observed. Subsequently, the flow characteristics in a rotating annular with a jet flow and various flow outlet configurations were investigated. The circle jet nozzle was located at the middle position of the stationary outer cylinder. In addition, two flow outlet configurations were employed. One was the model of single outlet at the right side of the annulus, the other was the model of double outlets at both side of the annulus. The jet Reynolds number (Re) was 1351. The Taylor number (Ta) varied from 545 to 24,217. When the impinging force and the inertia force from the jet flow interacted with the Coriolis force and the centrifugal force due to rotation, the fluid flow should become very complicated. The experimental results indicated that the rapid rotation broke the original stream line of the jet flow. On the other hand, when the jet flow turned 90° to be the axial flow, it would suppress the onset of Taylor vortices. Finally, fixing the Re and Ta, the model of single outlet more suppressed the onset of Taylor vortices than the model of double outlets did.     

Scratching by pad asperities in chemical-mechanical polishing

In the fabrication of micro- and nano-scale semiconductor devices and electromechanical systems, the chemical-mechanical polishing (CMP) process is extensively employed. During the CMP process, undesirable scratches are produced on metal-interconnect and low-k-dielectric surfaces by the softer pad asperities. This paper presents contact mechanics models for the initiation of scratching in terms of the pad asperity geometry, the interfacial friction, and the mechanical properties of materials. Results of dry, wet and lubricated experiments on Cu coatings qualitatively validate the theoretical models. To mitigate scratching by pad asperities during CMP, the developed models suggest that the friction coefficient be kept below 0.2.     

An inductance-based technique for the measurement of magnetic moment of the magnetorheological fluids

We presented a detailed study of the inductance properties of a MRF-based system with different MRF volume fractions under a magnetic field. The inductance of the system raised firstly and then decreased while the magnetic field kept increasing. We theoretically analyzed the mechanism of the field-induced variation of the inductance and deduced that the magnetic field dependence of the inductance could be represented by the derivative of the magnetic moment of MRF, thus the M–H curves of the MRF could be derived from the inductance measurement proceeded in our work. This method for the magnetization calibration was very convenient and economic for manipulation compared with the traditional magnetization meter techniques and has been proved to be feasible according to the experimental results which showed a satisfactory measurement precision.     

基于矩形凸块的盘式磁流变制动器设计与仿真

基于磁流变液的流变特性,设计了一款盘面加工有矩形凸块的盘式磁流变制动器,推导了其制动力矩计算公式,基于Matlab/simulink建立了仿真模型,不断优化矩形凸块的尺寸参数。仿真结果表明,当加工有12个宽度为2 mm、深度为1.5 mm的矩形凸块时,产生的制动力矩达到626 N·m,比未加工凸块时的制动力矩提高了31.5%,表明设计的磁流变制动器可以有效地提高制动力矩。     

磁流变阻尼器非线性动力学行为的实验研究

磁流变阻尼器具有阻尼力大范围高度可控且耗能功率小的优点,在结构的半主动控制中有广泛的应用。磁流变流体及其元器件的动力学行为因其磁流变现象而存在滞回效应,对这种滞回效应的研究是其相关应用的基础。对磁流变阻尼器在多种激励电流与加载频率下的滞回动力学行为进行了实验研究,并进行了数学建模与参数识别。结果表明:磁流变阻尼器的阻尼力大小由激励电流控制,其非线性滞回特性具有频率依赖性;实验数据与模型仿真值的比较显示,模型可以准确模拟磁流变阻尼器滞回阻尼特性。     

多尾鳍仿生推进器多推进模式运动仿真研究

提出了一种新型水下仿生推进器,采用多尾鳍协调驱动方式实现了鱼类波动推进模式和水母射流推进模式的有机复合,建立了多尾鳍波动-射流推进的运动学模型,着重利用计算流体动力学方法对多尾鳍波动-射流推进运动进行了仿真分析。研究结果表明:在特定运动参数下,多尾鳍波动推进模式能提供持续均匀的推进力,游动稳定性好;而射流推进模式,能产生瞬间的大推进力,加速性能好。研究内容为进一步探索多模式推进理论提供了依据。     

新型磁流变刹车装置设计与性能研究

设计了一种兼顾盘式与筒式结构优点的新型磁流变刹车装置,采用Maxwell软件结合田口算法思想对结构进行仿真优化。搭建实验测试平台,测试了磁流变液刹车装置的静态以及动态性能,验证了所设计的结构是有效的,实验结果达到预期目标,建立了制动力矩与输入电流的关系式,修正了τ-H经验公式,修正后的理论计算值与测量值基本一致,验证了磁流变液在高速剪切情况下存在剪切变稀的现象。     

应用射流器改造混合机加水系统

玻璃生产中混合料的主要工艺指标为均匀度、水份和温度。通过应用射流器对原加水系统进仃改造，使混合料加水系统操作简单，质量稳定，维护方便，从而达到稳定混合料的水份和温度这一目标。     

Prediction of the pumping capacity for reverse-flow diverter pumps

Reverse-flow diverter pumps have no moving parts that are in direct contact with the fluid; as a result, they are applicable for the transport of hazardous liquids or liquid–solid mixtures. To date, there is no method available for predicting the pumping capacity of reverse-flow diverter pumps. In this study, we experimentally investigated the pumping performance of reverse-flow diverters in the reverse-flow mode. Two dimensionless performance equations, expressed as q = 0.9597exp(−Eu_r/0.9237) + 0.4946exp(−Eu_r/7.360) + 0.1765 and q = kα + I, were determined from the experimental data. Based on these two equations, a method for predicting the pumping capacity of reverse-flow diverter pumps was proposed.     

Distribution of contact pressure over the surface of ceramic floor tiles during the polishing process

Assisted with computational simulation this work quantitatively determined the distribution of contact pressure over the surface of porcelain stoneware tiles during the industrial polishing process. In modern polishing lines there are basically three movements responsible for the scratching velocity and the position of the abrasives. Combining the kinematic equations obtained by these movements with a pre-existing model the contact pressure between abrasive tool and tile surface could be determined as function of time. The spatial distribution of average, standard deviation and maximum values of contact pressure were then obtained and mapped over the entire surface. The simulation results showed that the contact pressure tends to be 50% higher near to the center, in regions worked by the innermost abrasives. Additionally, periodical variations of up to 10% were found to occur due to the partial retreat of the abrasive tool.