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.     

Enhancing tribological performance of the magnetic tape/guide interface by laser surface texturing

The friction coefficient is an important parameter in designing magnetic tape transports. We have introduced a novel approach to reduce the friction coefficient between guides and magnetic tape by laser surface texturing the cylindrical guides. The surface features enhance the formation of an air bearing and hence reduce the friction coefficient.     

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.     

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.     

Effects of Different Magnetic Tapes and Operating Parameters on Lateral Tape Motion in a Linear Tape Drive

The need for increased storage capacity in today's data storage technology has created a continuing need to study the tribological performance of magnetic tape. Lateral tape motion (LTM) is one important area of ongoing tribological research. The objective of the study presented in this article is to determine the effects different magnetic tapes and operating parameters have on LTM. Specifically, the research focuses on LTM in five different tape samples and the effects the varying operating parameters have on LTM. The tapes studied include metal particulate (MP), thin MP, and three advanced metal evaporated (AME) tapes, as well as MP tapes with different edge quality and tapes from staggered packs. The operating parameters studied include tension, speed, and head and bearing setup. Experimental methods used to collect and analyze the LTM data are discussed and the findings are presented.     

A finite element simulation of the two-dimensional head/tape interface for head contours with longitudinal bleed slots

The two-dimensional (2D) steady-state linear head/tape interface with surface asperity contacts and tape shear deformations is analyzed using the finite-element method. A non-uniform mesh is utilized to improve the computational efficiency and to simulate cylindrical heads with longitudinal slots. Numerical results for the head/tape spacing and contact pressure are obtained for 2D head/tape interfaces using cylindrical heads with longitudinal slots. In addition, numerical examples are presented for the head/tape spacing and the pressure distribution using heads consisting of triple arc elements with and without longitudinal slots.     

Tribology of helical scan tape drive systems

The future direction of the designs of the metal evaporated tape for higher density recording in the helical scan tape drives which use MR heads was investigated. Static friction force between a tape and a roller guide increases the force with which the tape edge is pressed against the flange of the roller guide and wear debris is produced from the tape edge. The wear debris is driven to the recording area on the tape and increases a rewrite ratio, which indicates the ratio of failure of reading data. A solid lubricant at operating temperature was found to reduce the coefficient of static friction. However, the combination between the solid lubricant and MR heads which are heated by sense current may cause tape damage in dwell tests at low temperature. The increase in a melting temperature of the solid lubricant was found to improve the durability in dwell tests at low temperature.     

Tribology of metal evaporated tapes—for improvement of recording density

Increased recording density in video tape recorders and tape drives for data storage has been achieved by the increase in areal recording density and the decrease in tape thickness. Areal recording density can be increased by introducing high performance tapes, like metal evaporated tapes, with superior magnetic characteristics and smooth magnetic surfaces to reduce the spacing loss. However smoother surfaces often produce a higher friction coefficient, which could result in tape damage by the scanning heads and unstable runnability of tapes in VTRs or tape drives. Also thinner tapes show lower mechanical stiffness in general, which could result in damage of the tape edges during tape transportation. Superior durability and runnability are thus required of high performance tape in addition to magnetic characteristics, in spite of the trend towards smoother surface and thinner tapes. Therefore the development of practical new magnetic tapes requires research into their tribology. It was found that the durability and runnability of metal evaporated tapes with smoother surfaces can be improved by DLC coating, and that the edge damage of thinner tapes can be eliminated by decreasing the static friction coefficient, but not the kinetic one. Though the durability and the runnability of metal evaporated tapes themselves have been improved from the tape design point of view, as mentioned above, further improvement may be expected by integrating tape design with that of the VTR/tribo-elements tape drive design and thus further increasing recording density in the future.     

Studies on Degradation Mechanisms of Tape Lubricants in a High Vacuum Environment

Degradation and tribological performance of several tape lubricants were studied during sliding in a high vacuum environment. Gaseous products generated from the head–tape interface and friction force were detected and monitored as function of sliding distance by using a quadrupole mass spectrometer and strain gauges. Chemical analyses of the commercial tape lubricants were done to better understand the degradation processes and degradation products in the sliding tests. Experimental results showed that the commercial metal evaporated (ME) tape lubricants include fatty acid and perfluoropolyether (PFPE) compounds. The degradation products from the commercial tape include small fluorine containing fragments from the PFPE lubricant and small hydrocarbon fragment from fatty acid. In addition, three other species, H₂, C₂H₅ and CO₂ were detected in the case of ME tapes and they were generated from the degradation of the diamond-like carbon (DLC) coating on the tape surface. The commercial metal-particle (MP) tape used fatty acid and fatty acid ester lubricants. Only hydrocarbon fragments were detected in the MP tapes' sliding tests, no H₂, C₂H₅ and CO₂ were found. The coefficient of friction of these two tapes increased with sliding and depletion of lubricant on the tape surface. The trend of the coefficient of friction was different for ME and MP tapes because of the differences in the lubricant and lubricant distribution on these two tape surfaces. Z-Dol and stearic acid were used to lubricate ME tapes, their test results were analyzed and compared with the commercial tapes' test results.     

Measurement and Origin of Tape Edge Damage in a Linear Tape Drive

Integrity of the magnetic tape edge is the key to maintaining high performance of modern tape drives. Damage to the tape edge under normal drive operation results in the change in tape dimensions and debris generation, both leading to degradation in the reproduction of the recorded signal. The objective of the present study is to develop a methodology for evaluation of tape edge quality and to apply the methodology to monitor tape edge degradation under normal drive operation. Optical microscopy, atomic force microscopy and scanning electron microscopy are employed to study and quantify the quality of the tape edge. AFM measure-ments were made on both individual tape layers and the tape reel. An edge quality measurement technique is used to quantify the damage to tape edge. A technique for the tape lateral motion measurement is used to study the effect of continuous sliding on tape guiding. A lateral force measurement technique is developed to measure the force exerted by the tape edge on the guide flange. The effect of normal drive operation on tape edge quality and on tape guiding in a linear tape drive is studied. It is shown that two edges of a factory-slit tape are imperfect and different, with cracking of the magnetic coating occurring at one edge. Under normal drive operation, one edge experiences more wear with larger amount of debris produced. This larger debris generation occurs on the edge with cracks developed during manufacturing. A possible mechanism of tape edge wear under normal drive operation is proposed.     

酚醛树脂基玻璃纤维预浸带缠绕圆筒工艺参数优化

相较于传统的复合材料成型方法,预浸带缠绕技术凭借其独特的成型特点已发展成为筒形类构件重要的制造手段。缠绕过程中,多种工艺参数耦合作用,不可避免地使制品存在残余应力,继而引起不同形式的制品缺陷。基于此,针对预浸带缠绕圆筒工艺进行分析,以缠绕张力、缠绕温度及缠绕速度为参数变量,并采用Box-Behnken方法进行实验设计;同时,利用二次多项式回归模型建立制品残余应力与输入参数之间的映射模型,并通过方差分析验证了模型的可靠性及有效性,继而讨论了工艺参数耦合对残余应力的影响规律;最后采用响应面法对获得最优工艺参数组合进行实验,实验结果表明最小残余应力为22.52 MPa,最大预测误差为6%,结果满足工程要求。     

高时空分辨率动态星模拟器设计

针对大口径空间天文望远镜稳像精度测试的难题,提出了一种高时空分辨率运动导星模拟方案。利用硅基液晶作为运动导星模拟源,结合光束准直系统为空间天文望远镜提供无穷远运动导星,并且通过在光路中加入物镜来提高模拟导星的运动分辨率。针对望远镜像面结构的特殊分布,提出利用多路模拟的方法,分别为望远镜两侧精密导星仪以及巡天像面提供实时运动导星。最后,对影响运动导星模拟精度的各项误差进行分析,进而建立了误差模型。仿真结果表明:在运动导星模拟精度优于0.5″的概率为95%,时间分辨率为3 ms的前提下,动态星图星间角距误差小于0.04″,单星张角小于0.02″。通过实验验证了导星模拟模型的正确性,该模型基本满足空间天文望远镜稳像精度测试所需运动导星目标高时空分辨率的要求。     

PASSIM卷烟机布带轮张紧臂的改造

PASSIM卷烟机布带轮是烟支成型的关键部件之一。烟支成型过程中,布带轮驱动布带,并由布带牵引烟丝束和卷烟纸以一定速度进入烟枪。在生产过程中,由于布带轮与布带之间打滑容易引起烟丝束在烟枪内瞬时停滞甚至堵塞,从而影响成品烟支的烟丝分布,导致烟支重量不稳和烟支空头等质量问题。针对该问题,系统从布带打滑现象产生的原因出发,并根据布带张紧机构相关动力学机理进行分析论证后,对布带张紧轮机构中张紧臂的运动摩擦方式进行改造,由改造前的滑动摩擦改为滚动摩擦。改造后,能有效地解决布带轮与布带间相对打滑的问题,保证产品质量。     

直流无刷电机驱动曲柄压力机动态仿真与实验研究

研制了由直流无刷电机驱动的250kN伺服曲柄压力机试验样机,以直流无刷电机取代普通异步电机,取消了机械飞轮和离合器,驱动电路中配有大电容,以储存和释放电能。对压力机驱动和传动系统进行了理论分析,建立了机电系统的数学模型;根据样机参数进行了数值仿真和实验研究,二者结果十分接近,证明了数学模型的正确性;实验样机可以获得滑块的任意工作曲线,实现工作特性的柔性化;电容器可以起到“电子飞轮”储放能量的作用,在实验条件下,冲裁时电网瞬时峰值电流可减少86.3%。     

Simultaneous five-wavelength interferometry for head/tape spacing measurement

An improved five-wavelength interferometer with high-speed shutters in the light path was designed and implemented. The interferometer allows switching between two sets of three wavelengths, keeping one wavelength in each measurement in common. The set-up allows nearly simultaneous acquisition of fringe intensities and can be used to measure the head/tape spacing in a moving linear tape drive. The precision of the new five-wavelength interferometer was investigated and was found to be superior to the precision obtained with a three-wavelength interferometer.     

剑杆织机引纬系统的分析

分析了剑杆织机的引纬系统,阐述了在引纬机构中取消剑带齿轮和导带轮小齿轮,可杜绝齿条断啬,并可提高整机的综合性能.     

Recent research of tape/drive tribology

Decreasing track width and tape thickness to increase the volumetric recording density of helical scan-tape-drive systems, which is suitable for higher volumetric recording density, will result in the failure of tracking. The displacement of tape forwarding position, which causes failure of tracking, is caused by static friction coefficient between a tape and a roller guide. It was found that surface roughness and materials of roller guides are very important to reduce static friction coefficient.     

Investigation of roller interactions with flexible tape medium

Lateral tape displacement and roller axial runout are measured on an experimental tape transport. The effect of roller axial runout on lateral displacement of tape is investigated. Tape lateral displacement is found to be generated at the roller surface, and is observed to be correlated to roller axial runout. A number of typical roller types are investigated to determine the mechanism causing lateral tape displacement. Edge contact and friction are each shown to play a role in the creation of lateral tape displacement in the tape path.     

摩擦带传动的最大有效拉力分析计算

分析了考虑离心力作用时的摩擦带传动的最大有效拉力，并推导出了理论公式，进而讨论影响摩擦带传动工作能力的有关因素。     

Wear of tribe-elements of video tape recorders

The helical scan magnetic recording equipment, like the video tape recorders (VTR), consist of many tribe-elements. The wear of these tribe-elements is an essential problem affecting the reliability of the equipment. The rotating magnetic head in high-speed rubbing with the magnetic tape needs a self-cleaning effect by mild wear. A simple trial of reducing the head wear often brings partial recession, friction polymer and brown stain. The summary of the current study of head wear is given by dividing it into the head factors, the tape factors, the system factors and the atmosphere factors. The computational analysis of head contour change caused by wear is compared with the experimental results. The outline of the tribology of motor, capstan and tape path in the VTR is introduced.