Friction and wear of spindle motor hydrodynamic bearings for information storage systems during startup and shutdown

This paper investigates the friction and wear characteristics of two typical hydrodynamic bearings for hard disk drive (HDD) spindle motors (SPM), i.e., the herringbone groove and multi-taper bearings, during start-up and shut-down transient operation. The friction characteristics are calculated by a lubricated friction model which is an extension of Kogut and Etsion’s dry friction model (a modified version of the CEB model), while the wear characteristics are qualitatively evaluated in non-dimensional form by the semi-analytical wear model proposed by Holm–Archard. The average flow Reynolds equation and the pressure-compliance relationship of elastic–plastic roughness contact are used together to consider the combined effects of partial lubrication and asperity contact occurring during start-up and shut-down. Then, the friction and wear characteristics of the herringbone groove and multi-taper bearings are calculated and compared under the condition of HDD application.     

Retrieval of sea ice thickness distribution in the seasonal ice zone from airborne L‐band SAR

Although satellite data are known to be useful for obtaining ice thickness distribution for perennial sea ice or in stable thin sea ice areas, their use in the seasonal sea ice zone (SIZ) is still unresolved. In this study, we approached the problem of ice thickness retrieval by using L‐band Synthetic Aperture Radar (SAR). In the SIZ, ice thickness growth is closely related to ridging activity and therefore we expected surface roughness to be correlated to ice thickness. L‐band SAR is suitable for detecting such surface roughness and should be a useful tool for obtaining ice thickness distribution. To verify this correlation, we conducted shipborne electromagnetic (EM) inductive sounding and supersonic profiling observations with an icebreaker, coordinated with airborne L‐band SAR observations in the southern Sea of Okhotsk in February 2005. The surface elevation was estimated by representing the ship's motion with a low‐pass filter. Backscattering coefficients correlated well with ice thickness and surface roughness, defined by the standard deviation of the surface elevation. This result sheds light on the possibility of determining ice thickness distribution in the SIZ.     

Tribilogical performances of connecting rod and by using orthogonal experiment,regression method and response surface methodology

Dynamic lubrication analysis of connecting rod is a very complex problem. Some factors have great effect on lubrication, such as clearance, oil viscosity, oil supplying hole, bearing elastic modulus, surface roughness, oil supplying pressure and engine speed and bearing width. In this paper, ten indexes are used as the input parameters to evaluate the bearing performances: minimum oil film thickness (MOFT), friction loss, the maximum oil film pressure (MOFP) and average of the oil leakages (OLK). Two orthogonal experiments are combined to identify the factors dominating the bearing behavior. The stepwise regression is used to establish the regression model without insignificant variables, and two most important variables are used as the input to carry out the surface response analysis for each model. At last, the support vector machine (SVM) is used to identify the asperity contact. Compared with SVM model, the particle swarm optimization-support vector machines (PSO–SVM) can predict the asperity contact more precise, especially to the samples near dividing line. In future work, more soft computing methods with statistical characteristic are used to the tribology analyses.     

Thin water films driven by air shear stress through roughness

A model of thin water film transport over small scale surface roughness is developed in the context of a high Reynolds number boundary layer theory. The surface water is found to be described by a lubrication equation. It is shown that small scale surface roughness can first effect the water flow at roughness heights which are much less than those of first nonlinear response in the air. A number of well known phenomenon are encountered when using this model, such as pooling of water between roughness elements and rivulet formation. A linearized subsonic heat transfer analysis is also presented, and water protuberances and roughness are found to enhance the ambient heat flux. Solitons are calculated for two-dimensional films, and a linear stability analysis shows that two-dimensional film fronts can become unstable and develop into rivulets.     

Hybrid automata for linearizing the model of high-pressure thawing

The heat transfer phenomena concerned during thawing usually lead to non-linear distributed parameter systems, due to the existence of water phase change. When pressure changes, the thermodynamic effects make this model more complex. Hybrid automata allow continuous and discrete dynamics to be combined in the same method. Applied to our process, they allow a linear model to be obtained, and conserve its linearity when pressure changes are taken into account. The discrete events considered here are ice/water transitions and pressure changes. The continuous part of the model is heat transfer, either in solid, liquid or melting state of water.     

Slip resistant properties of footwear on ice

Current research on slipperiness of footwear has mainly focused on floors and lubricated floors. Slips and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in winter season in many parts of the world. However, in comparison with the size of the problem, research on slips and falls on icy and snowy surfaces has been scarce. The objective of this paper is to explore the slip resistant properties of footwear (soling materials, roughness and hardness) on ice. The coefficients of kinetic friction of four different soling materials (synthetic rubber, nitrile rubber, natural rubber and polyurethane) were measured on ice (-12 degrees C). The outsole roughness and hardness were also measured. Results showed that the polyurethane soling did not perform better than synthetic rubber, nitrile rubber and natural rubber on pure hard ice (-12 degrees C). Soling roughness was positively correlated with the coefficient of kinetic friction. The most slip resistant soling material (polyurethane) on floors and lubricated floors may not provide sufficient slip resistance on ice.     

Slip resistant properties of footwear on ice

Current research on slipperiness of footwear has mainly focused on floors and lubricated floors. Slips and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in winter season in many parts of the world. However, in comparison with the size of the problem, research on slips and falls on icy and snowy surfaces has been scarce. The objective of this paper is to explore the slip resistant properties of footwear (soling materials, roughness and hardness) on ice. The coefficients of kinetic friction of four different soling materials (synthetic rubber, nitrile rubber, natural rubber and polyurethane) were measured on ice (? 12°C). The outsole roughness and hardness were also measured. Results showed that the polyurethane soling did not perform better than synthetic rubber, nitrile rubber and natural rubber on pure hard ice (? 12°C). Soling roughness was positively correlated with the coefficient of kinetic friction. The most slip resistant soling material (polyurethane) on floors and lubricated floors may not provide sufficient slip resistance on ice.     

电动自行车鼓式制动器的有限元仿真

利用ANSYS/LS-DYNA分析软件对某电动自行车鼓式制动器进行瞬态动力学仿真,以非等载荷数组施加于与领蹄、从蹄相连的摩擦衬片,模拟制动过程中制动鼓和摩擦衬片的应力分布,并以摩擦衬片为研究对象,从材质、厚度、起始角三方面对制动器进行结构改进,为电动自行车鼓式制动器设计软件的开发提供数据参考。     

基于空气、冰与水相对介电常数差异的电容感应式冰厚传感器

基于空气、冰与水的物理特性差异实现冰生消过程的实时检测是一种新的冰情检测方法,基于这一思路,本文介绍了电容感应式冰层厚度传感器结构,并将研制成功的电容感应式冰层厚度传感器在黄河内蒙河道进行了冰层厚度连续监测应用试验,结果验证了利用电容感应技术测量冰层厚度方法的可行性.新型传感器具有结构简单,灵敏度高等特点,可以应用于冬季结冰河道冰层厚度及冰下水位的连续自动监测.     

无人机螺旋桨三维积冰计算与积冰控制检测

为降低中小型无人机螺旋桨结冰现象对其飞行造成的危害,为无人机测试工作减少障碍,采用考虑离心力的旋转部件的欧拉-欧拉法两相流模型及考虑离心力的旋转表面薄水膜流动三维积冰模型,对螺旋桨表面积冰进行三维计算检测,通过Fortran程序对积冰进行检测,形成完整的积冰过程.对比分析了 2714型螺旋桨下的不同温度、水滴含量和水滴直径对螺旋桨表面积冰的影响,控制不同环境的积冰条件,从而得出不同的积冰结果.结果表明,随着温度的降低,冰层厚度增大,位置基本不变;随着水滴含量的增大,冰层厚度增大,位置基本不变;随着水滴直径的增大,积冰厚度增大,覆盖区域扩大.本研究为无人机积冰的检测提供了基础,为更有效地进行无人机防冰提供了保障.     

新型内嵌式地线融冰电流计算

针对湖南电网研发的新型内嵌式地线地线新型直流融冰技术,提出地线直流融冰的所涉及的两个重要的参数(临界融冰电流和最大融冰电流)概念和计算方法。基于有限元法,以 GJ-70电线为模型,建立3D热-电耦合仿真模型,仿真得出不同气候、温度条件下的临界融冰电流,以及地线正常运行所允许的最大电流,与试验人员得出的实验数据进行对比,进一步验证这种融冰技术的优越性,并为运行人员有效的融冰电流范围提供了参考依据。     

Energy efficient control of HVAC systems with ice cold thermal energy storage

In heating, ventilation and air conditioning (HVAC) systems of medium/high cooling capacity, energy demands can be matched with the help of thermal energy storage (TES) systems. If properly designed, TES systems can reduce energy costs and consumption, equipment size and pollutant emissions. In order to design efficient control strategies for TES systems, we present a model-based approach with the aim of increasing the performance of HVAC systems with ice cold thermal energy storage (CTES). A simulation environment based on Matlab/Simulink^® is developed, where thermal behaviour of the plant is analysed by a lumped formulation of the conservation equations. In particular, the ice CTES is modelled as a hybrid system, where the water phase transitions (solid–melting–liquid and liquid–freezing–solid) are described by combining continuous and discrete dynamics, thus considering both latent and sensible heat. Standard control strategies are compared with a non-linear model predictive control (NLMPC) approach. In the simulation examples model predictive control proves to be the best control solution for the efficient management of ice CTES systems.     

Water diffusion in polymer nano-films measured with microcantilevers

We present a method to measure the absorption of water molecules from the liquid and the vapour phase into polymer nano-films and the diffusion inside these films. Film thickness can be down to 45 nm. To demonstrate the possibilities of this method we use polymer films that are deposited on the upper side of a silicon cantilever by plasma polymerization of norbornene. When a microdrop of water is deposited onto the initially straight cantilever, the drop causes the cantilever to bend while it evaporates. Evaporation of such small water drops usually takes less than a second. An upwards bending is due to capillary forces and a downwards bending is due to the diffusion of water into the polymer film – and the consequent volume expansion (swelling) of the film. The magnitude of the capillary forces and the extent of swelling continuously change during drop evaporation. When drop evaporation is over the cantilever returns to its initial straight position. We simulate the time dependent bending with a numerical model that qualitatively agrees with the experiment. From the time dependence of cantilever bending we are able to determine the diffusion coefficient of water in the thin polymer film.     

基于车用电涡流缓速器温度场分析控制系统设计

随着车辆向大型化、高速化发展,车辆正常行驶制动能量增加,传统的摩擦制动器已经难以满足使用要求,很容易诱发一些故障;电涡流缓速器以其非接触无摩擦,响应时间短,无明显时间滞后,工作时噪声很小,能够提供车辆正常行驶85%的制动功率等优点成为新型的车辆辅助制动系统;采用ANSYS软件实现电涡流缓速器转子盘的二维温度场分析,对不同宽度的转筒式电涡流缓速器的温度分布进行数据采集,建立转筒式电涡流缓速器转筒的二维模型,采用虚拟边界法进行简化处理,然后根据系统不同的载荷和约束条件进行温度场控制系统建模;最后做了大量的仿真实验,模拟了依据不同的制动力矩,不同的磁路结构以及转子盘温升来分析对汽车制动性的影响。     

双电层对纳米流体润滑与摩擦影响的MD模拟 (2.东南大学MEMS教育部重点实验室 南京 210096）

采用分子动力学方法对带电和不带电两硅板之间的水分子润滑薄膜进行模拟研究,通过加双电层的水分子薄膜润滑与未加双电层薄膜润滑摩擦属性的对比,发现摩擦系数在存在双电层的情况下比未加双电层时要小,两板相对滑动速度对摩擦系数的影响与未加双电层时相似,相对滑动速度越大,摩擦系数在一定的速度范围内平稳增大.当速度大于某个数值时,摩擦系数增大变快.两板之间水分子以及离子密度或数目分布在靠近壁面的地方较大,中间密度相对较小.     

Subglacial water presence classification from polar radar data

Ground and airborne radar depth-sounding of the Greenland and Antarctic ice sheets have been used for many years to remotely determine characteristics such as ice thickness, subglacial topography, and mass balance of large bodies of ice. Ice coring efforts have supported these radar data to provide ground truth for validation of the state (wet or frozen) of the interface between the bottom of the ice sheet and the underlying bedrock. Subglacial state governs the friction, flow speed, transport of material, and overall change of the ice sheet. In this paper, we utilize machine learning and classifier combination to model water presence from airborne polar radar data acquired on Greenland in 1999 and 2007. The underlying method results in radar independence, allowing model transfer from 1999 to 2007 radar data to produce water presence maps of the Greenland ice sheet with differing radars. We focus on how to construct a successful set of classifiers capable of high classification accuracy. Utilizing multiple machine learning algorithms is shown to be successful for this classification problem, achieving 86% classification accuracy in the best case. Several heuristics are presented for constructing teams of multiple classifiers for predicting subglacial water presence. The presented methodology could also be applied to radar data acquired over the Antarctic ice sheet.     

The effect of roughness, floor polish, water, oil and ice on underfoot friction: current safety footwear solings are less slip resistant than microcellular polyurethane

Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.     

低温等离子体辅助聚乳酸表面接枝乳酸链球菌素 及抗菌性

该文主要通过低温等离子体处理聚乳酸薄膜,并研究了不同处理时间(0、15 s、30 s、45 s 和 60 s)后薄膜的表面形貌及亲水性。在此基础上,将低温等离子体处理后的聚乳酸薄膜浸泡到乳酸链球 菌素溶液中,对其抗菌性能进行测定。通过调节等离子体处理时间,可以明显改善聚乳酸薄膜的表面 亲水性及粗糙度。结果表明,随着处理时间的增加,聚乳酸薄膜表面粗糙度先增加后减小,接触角先 降低后增加。经过 60 s 低温等离子体处理的聚乳酸薄膜,浸泡乳酸链球菌素溶液进行接枝,可有效降 低单核增生李斯特菌的菌落总数。因此,低温等离子体处理聚乳酸薄膜,为其在食品抗菌包装领域提 供了一个非常好的思路。     

Application of triple-deck theory to the prediction of glaze ice roughness formation on an airfoil leading edge

A viscous–inviscid interaction triple-deck structure is developed to describe the thermomechanical interaction of an air boundary layer with ice sheets and liquid films. Linear stability results are compared with nonlinear triple-deck computations, and a number of nonlinear simulations of air–water–ice interactions are presented. An icing instability is encountered in regimes with simultaneous wall and air cooling that is believed to admit small scale and highly irregular surface roughness. The stabilization of the smallest scale icing disturbances is obtained through the Gibbs–Thomson relation. This local thermodynamic condition relates the freezing temperature of a pure substance to the surface tension and the mean curvature of the interface and provides a short scale stabilizing mechanism for icing instability modes. Comparison with available experimental data on glaze ice roughness diameters, accreted on NACA 0012 airfoil leading edges under glaze icing conditions, is provided. It is also found in all cases computed in this study that water beads can be formed on a wetted ice surface once the water film is locally ruptured by ice roughness elements.     

基于连接式螺旋体结构的FBG冰层厚度传感器研究

河冰现象是进行水资源开发利用时需要考虑的一个重要现象,冰层厚度检测是冰情状况检测的主要对象。研制了连接式螺旋体结构的光纤Bragg光栅（FBG）温度传感器。基于冰与水温度变点的机理,通过检测冰层与水的温度和传感器纵向分布阵列之间设置的间距得到冰层厚度。该FBG温度传感器使用导热系数较好的毛细紫铜管作为制作螺旋体结构材料。对不同厚度的冰在冰消过程中的厚度检测,实验结果表明：最大测量误差为12mm,最小测量误差为0mm。可通过调节U型管所在斜面和直通管所在平面角度改变各测点之间的间距。