Attenuation of lateral tape motion due to frictional interaction with a cylindrical guide

Lateral tape motion (LTM) is a function of tape path and tape properties, design parameters such as speed, tension, and friction between tape and tape path components. This investigation deals with the LTM of a tape moving over the surface of a cylindrical guide. Starting from the equation of motion for a moving tape on a cylindrical guide surface, the effects of friction, tape properties and design parameters are examined by calculating the ratio of LTM before and after a cylindrical guide. Attenuation of LTM is found to be mainly dependent on the guide radius and the wrap angle.     

Measurements and theoretical predictions of head/tape spacing over a flat-head

Experimental measurements and theoretical calculations of the head/tape spacing are presented for the self-acting subambient foil bearing phenomenon at the interface of a flexible tape and a flat surface (e.g., tape-head). The air entrained at the flat-head/tape interface forms a subambient pressure layer which creates suction on the tape to pull it down to contact the head. The head/tape spacing for flat-heads is measured with a commercially available, two-wavelength, digital interferometer by using transparent tape and Al₂O₃-TiC flat-heads. Measurements for a large array of tape speed, tension, wrap-angle values, and head-lengths are presented. The interferometric spacing measurements show that, in general, the tape contacts the flat-head in the central region of the head and forms displacement-bumps adjacent to the edges of the head in the upstream and downstream corners. Experiments also show that the length of the displacement-bump affects whether a central contact region will form. The length of the displacement-bump is proportional to tape tension and wrap angle and inversely proportional to tape speed. The experimental results compare favorably to results of a mathematical model of the flat-head/tape interface.     

多线切割机排线机构参数优化设计

多线切割机排线机构是走线系统正常运行的主要机构。传统的排线机构存在各导轮之间钢丝张力波动较大、易造成钢丝拉断的缺陷。文中介绍了一种新的设计方法:通过建立导轮张力包角模型,得出导轮两边张力与包角大小和摩擦系数之间的关系;由排线机构中导轮与滑轮之间相对的几何位置,推导出钢丝张力和包角与设计参数L1、H之间的关系表达式。利用优化方法确定导轮与滑轮之间最佳的几何位置,使排线机构工作时钢丝张力波动最小,在多线切割机往复走线过程中,有利于放线辊上的钢丝会逐渐过渡到收线辊上,保证了收放线系统平稳、有序地运行。     

The effect of tape overwrap angle and head radius on head/tape spacing and contact pressure in linear tape recording

Linear tape recording devices typically employ contact recording to minimize head/media magnetic spacing and thus maximize recording density. Successful contact recording is a delicate balance between spacing and contact pressure. If an air bearing develops, spacing will exceed the 100 nm upper limit for current high recording density devices. Conversely, high contact pressure can lead to head wear or tape damage. Most recording heads produced today for linear tape devices consist of one or more cylindrical wafer sections that are bonded together to form a rigid structure. Each individual tape bearing surface is cylindrical with straight edges. The tape is held over the head contact surface by tape guides so that the tape is wrapped sharply around the edges where cylindrical surface and flat surface meet. Overwrap angle is defined as the angle between the tape after it leaves the head and a tangent to the cylindrical head surface at the edge where cylindrical surface and flat surface meet. This paper will use one-dimensional finite element modeling to explore how overwrap angle and bump radius affect head/tape spacing and contact pressure. The effects of tape stiffness, tape tension, and tape velocity will be investigated. Feasible combinations of overwrap angle and bump radius will be presented which minimize head/tape separation, yet keep contact pressure within bounds.     

Head/Tape Spacing Measurements for Digital Linear Tape Drives Using Three-Color Interferometry

The spacing of the head/tape interface in a digital linear tape (DLT) drive was measured using replica glass heads and three-color interferometry. A modified load-unload method was used to calibrate the light intensity. Class heads with different island widths and zero and nine degree skew angle were used to investigate the effect of head contour on the head/tape spacing. In addition, thin and thick metal particle tapes were evaluated to study the effect of tape compliance, tape speed and tape tension. “Tape tenting” was observed for heads with a narrow center island.     

Influence of blade wrap angle on centrifugal pump performance by numerical and experimental study

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.     

Analysis of sprocket load distribution

A study was made to determine the load distribution for an elastic roller chain on an elastic sprocket. The equations developed for the distribution include, as a subset, those for a rigid roller chain on a stationary rigid sprocket. The effect of friction and sprocket rotation on load distribution is discussed. Results are presented for a 20-tooth sprocket with a 180° angle of roller chain wrap, for various tight-to-slack side tension ratios of both driver and driven sprockets, with various spring constant ratios.     

皮带传动中动弧角曲面的分析

通过推导,得到皮带初拉力、皮带有效拉力和皮带动弧角这三个重要参数形成曲面所列应的曲面方程,并定义为动弧角曲面方程,在已知其中任意两参数的情况下,可计算第三参数的大小.分析动弧角曲面特性,研究当量摩擦系数对动弧角曲面的影响,及曲面三参数之间的重要关系.     

包角对中比转速泵流场及无过载性能的影响

以D82-19-2型中比转速离心泵为研究对象,根据无过载叶轮约束公式确定叶轮设计方案,选取四种叶轮包角（150°、170°、190°和210°）开展中比转速泵流场及无过载性能的模拟研究。与实验结果相比,模拟所得扬程、效率和功率值误差不超过9%,模拟方法可行。结果表明：当叶片包角由150°增大到210°时,叶轮进口压力提高24%,低速区面积扩大至整个叶轮流道的1/3,叶片对流体的约束能力及抗汽蚀性能增强,但叶轮出口压力降低,大包角下导叶的湍流损失加剧了动能损耗;功率备用系数由1.145减小至1.025,且功率曲线出现极大值,泵的无过载特性更显著,但扬程和效率分别下降了15.4%和4.48%。研究结果为中比转速离心泵的无过载设计提供了理论依据。     

转载式多点驱动带式输送机设计计算

介绍中间驱动单元数量及位置的确定方法。论述了等功率及等围包角３种不同方案的转载式多驱动带式输送机计算方法，推导出了适合于任意多个中间驱动单元的胶带张力计算公式。对一带式输送机算例，分别按４种不同的设计方案进行了计算，并与单点驱动方案进行了比较。     

基于CFX正交试验的深井离心泵导叶的优化设计

为提高深井离心泵的水力性能,针对100QJ16型深井泵,按照L9(34)正交表,选取空间导叶的进口冲角、包角、叶片出口安放角和叶片数等4个因素,每个因素取3个水平,设计出9个导叶模型,并分别与同一个叶轮装配。基于CFX软件,对两级模型泵进行了全流场数值模拟,获得9组方案在额定工况下的扬程和效率。采用极差分析法分析了各几何参数对扬程和效率的影响规律以及影响空间导叶性能的主要因素和次要因素。空间导叶进口冲角和叶片包角对两级泵的扬程和效率的影响较大。将优化方案进行了样机试验,其效率达到了设计要求。     

Use of phase imaging in atomic force microscopy for measurement of viscoelastic contrast in polymer nanocomposites and molecularly thick lubricant films

Phase contrast microscopy, using an atomic force microscope, is used to detect and quantify changes in composition across polymer nanocomposites and molecularly thick lubricated surfaces. The technique takes advantage of the contrast in viscoelastic (viscous energy dissipation) properties of the different materials across the surface. Some materials, especially polymers, are found to display viscoelastic behavior. For such materials, the strain response lags the stress by a phase angle that is characteristic of the material. In tapping (or intermittent contact) mode, phase angle contrast is found to be highly dependent on vibration amplitude and mean tip-to-sample distance (setpoint). Phase angle contrast seems to be a stronger function of viscoelastic properties at relatively high vibration amplitude and low mean tip-to-sample distance. In this regime the effects of sample deformation, and thus viscoelastic properties, are dominant. In these contrast images, low phase angle corresponds to materials with low viscoelastic properties. This technique was used to find fairly reproducible phase angle contrast for polyethylene terephthalate (PET) films with embedded ceramic particles, metal particle (MP) magnetic tape, and Si(100) with a nonuniform Z-15 lubricant film. Very little correlation is found between phase angle images and friction force images for PET films with embedded ceramic particles and MP tape; phase angle images give information that cannot be obtained from topography or friction images. A numerical vibration model verifies that viscoelastic properties are dominant for high vibration amplitude and low mean tip-to-sample distance. For these conditions, the model also verifies that low phase angle corresponds to low viscoelastic properties.     

Influence of test parameters on the measurement of the coefficient of friction of magnetic tapes

The cylinder friction and the normal stress distribution were calculated for the general case of a magnetic tape wrapped around a cylinder. The coefficient of friction was found to depend on the radius r of the cylinder and the initial tension T₀ according to the relation $\text{(}\text{r}\text{T}{}_0\text{)}{}^{\mathrm{1?n}}$ and to be independent of the wrap angle θ₀. On the basis of tests conducted on five commercial magnetic tapes and on a typical tape substrate (poly(ethylene terephthalate)), n was found to be close to 1. Hence r, T₀ and θ₀ in the ranges used in the tests reported here have no significant influence on the coefficient of friction.For the speed range from 27 to 80 mm s^?1, the sliding speed has no influence on the coefficient of friction, but temperature and humidity do have a significant influence. Therefore, temperature and humidity conditions should be selected on the basis of the application of the machine.     

小尺度摩擦副润滑特性数值模拟研究

与一般大型机械设备中的摩擦副不同,小尺度摩擦副润滑油膜在表面张力的作用下不再是水平形状,从而影响到摩擦副的摩擦学特性。在考虑到表面张力作用的基础上,对小尺度摩擦副进行摩擦学理论分析,建立了二维模型并求解了雷诺方程,以研究小尺度下表面张力对摩擦副摩擦学特性的影响。研究结果显示,由于表面张力的影响,摩擦副的油膜压力分布和承载能力有较大幅度的变化。宏观状态下的摩擦学设计与小尺度摩擦副的实际情况相去甚远,对小尺度摩擦副表面张力作用下的摩擦学特性进行研究是十分必要的。     

Bi系高温超导单芯线材拉拔工艺的数值模拟

对高温超导单芯线材的拉拔工艺开展了研究，建立了单芯高温超导线材拉拔工艺的轴对称数值模型，计算分析了拉拔半模角、截面缩减率以及摩擦因数等工艺参数对拉拔工艺的影响。针对拉拔过程中径向体积应变、拉拔力、摩擦损耗能以及残余应力等多指标的优化问题，采用了线性加权和法获得了Bi系高温超导单芯线材拉拔过程中的最优拉拔半模角。     

Numerical simulation of flying phenomena of the running tape on rotating drum

This paper analyzes the running mechanism of flexible and thin tape above rotating protrusion through a numerical simulation. The scope of analysis is confined to the phenomena of elastohydrodynamic lubrication between the rotating drum with a protrusion and the running tape. This model is based on the modified Reynolds equation and the equation of plate considering the effect of geometric nonlinearity and geometry of protrusion. Finite element method of Bubnov-Galerkin type is adopted as a numerical simulation technique to solve the above two coupled nonlinear equations. In numerical simulation, the influences of tape tension and protrusion velocity are evaluated in simple model. In complex models, the reciprocal action of two protrusions is simulated.     

耦合作用下涡旋动盘形变与应力的仿真分析

运用有限元分析软件ANSYS,分析了在特定气体载荷与温度载荷耦合作用下涡旋齿的形变与应力的变化,并在气体、温度载荷变化的情况下,研究其形变的变化规律。被压缩的气体对涡旋齿产生气体力载荷,由气体被压缩、动静盘间的摩擦产生的温度载荷,会引起动盘的热变形与热应力。分析结果表明,温度载荷是影响涡旋齿变形的主要因素。由于涡旋齿头部位受到气体力最大、温度最高,耦合作用下涡旋齿最大变形发生在涡旋齿头顶部;由于主轴对轴承孔内壁的约束作用,最大应力发生在主轴承孔内壁与底盘接触的部位。     

Lateral motion and edge wear of magnetic tapes

Lateral motion and edge wear are measured on magnetic tape, and the relationship between tape edge wear and tape lateral motion is investigated. Instrumentation for measuring tape edge force is described. Tape edge force is measured at the tape guiding position using a force-calibrated cantilever spring and a linear optical probe. Typical measurements of tape lateral motion are given as a function of tape tension, tape direction, and path position. A technique for measuring tape edge wear is introduced and wear measurements are presented as a function of load and the number of passes.     

A Model for Magnetic Tape/Guide Friction Reduction by Laser Surface Texturing

The friction coefficient between a magnetic tape and a guide in a tape path can be minimized by creating micro dimples on the guide surface with laser surface texturing. The dimples enhance the formation of an air bearing and reduce the friction coefficient between the tape and the guide due to the increased spacing. A model is presented to optimize the geometry of the surface texturing parameters to maximize the average air bearing pressure and minimize the tape/guide friction coefficient.     

基于正交设计法的中比转速泵无过载优化设计

以D82-19-2型中比转速离心泵为研究对象,选取导叶喉部面积、叶片数、叶片包角、叶轮出口直径、叶轮出口宽度、叶片出口角、叶轮进口直径7个参数为变量,运用正交设计法制定七因素三水平正交方案L18(37),借助数值模拟方法对泵的性能进行预测,通过分析得到了几何参数对中比转速离心泵性能影响的主次顺序:叶片数对扬程和效率的影响起主要作用,叶片包角对轴功率的影响起主要作用;正交优化方案的数值模拟结果表明,该方案既满足无过载性能的要求,又保持了较高的效率,可为中比转速离心泵无过载设计提供参考。