磁头局部结构的优化设计和数值分析

在磁头磁盘系统中,磁头尾端与磁盘的气膜最小,局部结构承受很大的气膜压力,其气膜压力的大小和分布对磁头飞行稳定性有重要的影响.采用优化设计理论对磁头尾端局部结构进行设计,可明显改善气膜承载性能.最后,采用提出的优化设计方法对负压型磁头结构进行设计.数值分析和实验测试表明,优化后的磁头结构飞高性能参数明显得到改善.     

摄动法研究硬盘磁头滑块动态飞行特性

硬盘工作时,磁头滑块飞行在磁盘上方,其动态飞行特性对硬盘工作性能有重要影响。该文利用摄动法推导了磁头滑块的气膜刚度和阻尼摄动方程,且通过有限体积法进行求解,获得了初始摄动条件下的气膜刚度和阻尼矩阵。结合磁头滑块动力学方程,研究了扰动速度、扰动俯仰角和扰动侧倾角对磁头滑块动态飞行特性的影响。研究结果表明:①扰动速度会导致磁头滑块向磁盘表面作竖直方向的移动,增加了与磁盘接触碰撞的风险;②扰动俯仰角或侧倾角的增加都会导致磁头滑块振动幅度的增加,但扰动俯仰角更容易引起磁头滑块的振动。     

头/盘界面均匀化Reynolds方程及其高效数值求解

当硬盘工作时,磁头滑块飞行在高速旋转的磁盘上方,头/盘界面产生了一层只有几个纳米的气膜,该气膜润滑方程为考虑气体稀薄效应的修正Reynolds方程。为了提高磁记录密度,人们正在考虑用离散磁道（Discrete Track Recording,DTR）磁盘取代传统的光滑磁盘。由于这种DTR磁盘表面磁道和沟槽的影响,在数值求解修正Reynolds方程的过程中,就需要足够多的离散网格来分辨出DTR磁盘表面几何形状,从而带来了计算效率问题。基于均匀化理论和修正Reynolds方程的线性流率（Linearized Flow Rate,LFR）模型,该文推导了一个适合分析DTR磁盘气体润滑特性的均匀化Reynolds方程,并采用有限体积法对均匀化Reynolds方程进行了求解和验证。其结果显示:相对于修正Reynolds方程,求解均匀化Reynolds方程只需要很少的离散网格,从而节省了大量的计算时间,大幅提高了计算效率,且两者压力分布、压力中心和承载力的最大相对误差都小于3.5%。     

粗糙度模式对硬盘气膜承载特性的影响

当前硬盘中磁头磁盘之间气膜的厚度已经接近或低于分子平均自由程,在这种情况下表面粗糙度及气体稀薄效应的影响不容忽视.应用最小二乘有限差分法,求解考虑气体稀薄效应并引入压力流因子和剪切流因子的量纲一雷诺方程,研究了不同粗糙度模式下硬盘超低飞高(1nm~2nm)气膜的承载特性.数值结果表明:粗糙度模式对超低飞高气膜压力分布及承载力的影响较大,而对压力中心的影响较小;在各种粗糙度模式情形下,磁头取横向粗糙度模式时,可使气膜压力分布升高,并提高气膜的承载力.     

微型硬盘驱动器工作状态下的冲击特性仿真

为了研究微型硬盘驱动器在受到外界冲击激励时的动态特性,对磁头/盘界面的磁头悬臂与支承件接触面系统建立了力学模型,对施加不同冲击持续时间和加速度幅值的半正弦冲击的系统响应进行了仿真,探讨了在不同激励下磁头浮动块的冲击响应及影响空气轴承力变化的主要因素。仿真结果表明,在冲击过程中,气膜的挤压效应对空气轴承力具有一定的影响,冲击加速度幅值和持续时间的变化将影响浮动块的运动稳定性。研究结果为硬盘结构的抗冲击设计提供了理论参考和分析方法。     

磁头与离散磁道式磁盘瞬态接触行为研究

 离散磁道式磁盘在与磁头瞬态接触过程中极易损坏.为改善离散磁道式磁盘的瞬态接触状况,采用有限元仿真方法,建立了平整化前后离散磁道式磁盘与磁头的瞬态接触模型,分析了平整化前后离散磁道式磁盘接触应力分布特点,研究了磁头冲击速度、径向速度、磁盘表面摩擦系数等接触条件及平整化对离散磁道式磁盘最大等效塑性应变、塑性应变总体积的影响.结果表明：磁头冲击速度、寻道速度增大均可导致磁盘最大等效塑性应变、塑性应变总体积增大;摩擦系数增大可增大磁道最大等效塑性应变、减小塑性应变总体积;在接触初期,平整化离散磁道式磁盘可以减小磁道最大接触应力,缓解应力集中现象;在接触全过程中,平整化离散磁道式磁盘可以减小磁道最大等效塑性应变及塑性应变总体积;平整化所用2种弹性模量等力学特性不同的填充材料,即磁道材料与类金刚石碳,对于磁道接触状况的改善作用区别较小.以上结论可为降低离散磁道式磁盘的破坏程度提供理论指导．     

磁头结构表面刻蚀深度对磁头飞行姿态影响的实验研究

随着磁盘容量的不断增大,测试技术也不断得到发展.本论文中,工作在纳米级条件下的磁头飞行姿态由动态飞高测试仪获得.通过实验测试方法分析了3层2台阶负压型磁头表面结构的刻蚀深度对磁头飞行姿态的影响.实验测试结果表明刻蚀深度的变化对磁头飞行姿态有明显的影响:随着次景层深度的增加,最小飞行高度和俯仰角都有明显增大趋势;最小飞行高度随着基层深度的增加基本呈增大趋势,而俯仰角呈下降趋势;侧翻角对次景层和基层深度变化不敏感.实际的磁头结构设计中可实验测试结果和优化组合方法选择最佳结构表面刻蚀深度来降低磁头的飞行高度,从而达到增大磁盘存储容量的目的.     

分子间作用力对硬盘磁头承载力的影响

当硬盘驱动器的磁头飞高降至5nm以下时,磁头与磁盘间的分子间作用力不能忽略.以皮米磁头和飞米磁头为模型,模拟了分子间作用力对飞高低于5nm的磁头总承载力的影响.模拟结果表明,分子间作用力改变了飞高低于5nm的磁头承载特性.分子间吸引力使总承载力减小,甚至出现负值,以致使磁头失去承载能力.当飞高进一步降低时,分子间斥力的作用显现出来.由于分子间引力和斥力的作用范围不同,磁头有一段失去承载能力的临界飞高区间.磁头的尺寸因子不同,临界飞高区间也有差别.     

液晶玻璃面板光学检测仪器气浮平台系统参数优化设计

液晶玻璃平板在线检测流程当中,气膜的流场压力和速度的分布需要较高的稳定性,为了比较不同的气浮平台供气方式对气膜稳定性的影响,结合气体润滑理论,分析得出气膜稳定后的压力分布情况。通孔在气浮板上通常采用阵列排布,使用Gambit对气浮平台三维模型进行网格的划分,再将其导入软件Fluent中,对正压供气方式和正负压供气方式进行仿真计算,分析得到2种不同供气模式下气浮力的分布以及速度分布。由以上分析可得,若气浮系统中其余变量保持不变,正负压同时供气方式优势更加明显,气膜稳定后气浮力和速度分布平缓,所需气体的质量流量较正压供气方式更少。以正负压同时供气方式自制玻璃基板光学缺陷检测样机,实验结果表明气膜间隙变化量小于1μm。     

热压镍锌铁氧体磁头材料的研制

一、前言为了配合电子计算机外存贮设备——磁鼓或磁盘的研制,克服国内磁头材料——热压铁氧体材料供求不足的现状,以适应我国磁记录技术进一步发展的需要,研制磁头材科热压铁氧体是具有一定的现实意义的。随着磁记录技术的发展,对磁头材料的要求有下列几点: 1.饱和磁感应强度Bs高; 2.在高频范围内有适当的导磁率μ,     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.