Head and media design considerations for reducing thermal asperity

Recent use of magnetoresistive (MR)/giant-magnetoresistive (GMR) heads in disk drives requires tighter control on particle contamination that may generate thermal asperities at the head/disk interface. In this study, the effects of slider air bearing surface (ABS) design and media on TA reduction capability are investigated. The motion of particles at the head/media interface is simulated numerically. Drive level TA tests are performed using a particle injection chamber. It is observed that a new ABS design, that has an aerodynamic U-shaped rail and a central airflow passage, is beneficial in reducing the particle contamination on the slider. Scratch-resistance of the media surface is correlated to TA reduction capability of the media; more scratch-resistant media produced less TA. On the other hand, the adhesion properties of the media have minor effects on TA reduction, as the particles that usually generate TA in a drive are too small to spin off the media.     

A study of three-body particle generation and subsequent pole tip recession in linear tape recording heads

The Pole Tip Recession (PTR) and transferred material (stain) are major causes of magnetic spacing losses in magnetic recording system. The recorded signal amplitude is only independent of the data being read if the spacing is zero. Thus, the level and more specifically the variation in head media spacing with device life must be a minimum to maximise signal output and minimised errors. It was the purpose of this research to isolate and identify the mechanisms responsible for pole tip recession using the Linear Tape Open format as an experimental platform, but the results have implications for any head where the tape-bearing surface is Al₂O₃/TiC (AlTiC).All experiments were conducted within a matrix of pressure and humidity, which encompassed the system operating extremes. Atomic force microscopy (AFM) was used to analyse the surface topography of the heads and monitor the development of PTR after 100, 1000 and 5000 passes of tape. Auger electron spectroscopy (AES) was employed to analyse the chemical changes on the surface of the heads after 5000 passes of tape and X-ray Photoelectron Spectroscopy (XPS) was used to identify the chemical changes that occurred at the head surfaces. Optical Microscopy was employed to identify the head surface changes before and after wear. Environment was found to have a significant influence on the head/tape interface. Head wear and PTR were highest at high temperature and humidity.Wear between the head and tape was found to transform the surface layers on the TiC grains in the tape-bearing surface to TiO₂. This process results in the production of TiO₂ fragments that become trapped in the recessed pole tip region, acting as three-body abrasive particles. The presence of Ti on the surface of head thin film region confirmed that the three-body particles originated from the head AlTiC ceramic. The TiO₂ (thickness and possible areal coverage) increased with the water content increase, wear of head increased in the high water content condition.     

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.     

Thermometric design considerations for temperature monitoring in machine tools and CMM structures

Temperature measurement is an essential element in monitoring and studying the thermal deformation response of machine tools and CMM structures. In this context, temperature measurement is required for model verification, for control purposes and for determining the thermal contact resistance and other thermal boundary conditions. In these applications, where heat flux and temperature rise levels are relatively low, a proper thermometric design is a must to ensure accurate and precise results. This paper addresses the problem of thermometric design in the case of temperature measurement inside a solid body and on its surface. Results and recommendations regarding the interactions between neighbouring thermocouples, the effect of the distance between the thermocouple and the contact interface (i.e. the heat input surface), and the effect of heat flow along the thermocouple wires on the measurement error are presented. The issue of the effect of the unknown thickness and thermal conductivity of the surface paint on the uncertainty in surface temperature measurement is also addressed.     

柴油机气缸盖的热流耦合分析

对某柴油机气缸盖的热流体与热应力进行耦合分析.首先运用CFD(Computational FluidDynamics)分析软件SC/Tetra计算温度场及流场,然后将得到的节点温度映射到用于结构分析的网格,再用有限元分析软件进行结构的热应力计算.通过对结果的分析发现设计的气缸盖的缸盖鼻梁区温度偏高,且温度梯度较大,热应力集中,说明鼻梁区冷却效果差,易出现裂纹.因此该处为危险区域,应该视为重点研究对象.还发现水套进水口布置的不够合理,调整进水口布置将不但有利于降低第四缸处最高温度,还有利于改进鼻梁区冷却.     

The heat transfer between a heated tip and a substrate: fast thermal microscopy

Here we describe a new mechanism of heat transfer between two solids separated by a distance. This mechanism does not involve the ambient air or adsorbed vapour films, and is therefore expected to remain active under perfect vacuum conditions. As will be described in detail, thermal charge fluctuations of one solid substrate kept at finite temperatures create an electromagnetic field—at infrared frequencies and of a short coherence length—which extends across the gap and effectively transports heat to the other solid. In our view this mechanism is responsible for the effective heat transfer observed recently by C. C. Williams and H. K. Wickramasinghe between a heated tip and a substrate.     

Research and application of methods of technical diagnostics for the verification of the design node

Research and application of selected diagnostic methods for assessing the condition of the gearbox of machining center accrued from collaboration applied between our work location and the company Regada, Ltd. Prešov. The requirement of our partner was directed to identify the current state of the abrasive particles in oil, to assess the condition of the contact surfaces in the running-in period and to assess the condition of the lubricant. Implemented analysis of gear oils have been prefentially oriented to identify the wear particles produced during running-in period and in the first hours of operation of contact surfaces. At the same time the correlation between total content of Fe (iron) particles in oil and accrual of kinematic will in tooth meshing of toothed ring of the gearbox was monitored. In quantification of the content of ferrous wear particles the impact of the running-in processes on the contact surfaces (bearings, toothing), which can cause negative side effects, was assessed.     

锅炉用封头与压力容器用封头标准的对比

通过对锅炉用封头与压力容器用封头标准的对比 ,有效地防止了在封头加工过程中发生差错 ,避免了在锅炉封头和压力容器封头检验中因为不熟悉标准而造成的损失。     

小型数控车床热态性能的分析优化与实验辨识

针对CMK系列小型数控车床运行过程中普遍存在的主轴"翘头"问题,试图通过热变形分析与实验辨识相结合的方法找出上述问题的成因,并给出相应的优化方案,因此,建立了基于有限元法的机床热态特性分析模型来解析整机温度场,同时,通过热应力耦合分析预测了机床各部分的热变形以及主轴的热倾斜,随后,利用红外热成像仪测量、验证了整机温度分布,通过特别设计的六个测点三个方向的热变形实验辨识了主轴系统的热倾斜特性,最后,以降低主轴热倾斜角为目标,给出了提升机床热态性能的两种方案,热优化设计和采用人造花岗岩床身。     

封头自动上下料及码垛设备的研制

针对封头生产过程中存在的劳动强度大、产品质量差、生产成本高、环境污染等问题,提出了一种基于大直径、重载荷、大变形坯料板的新型自动定心、上料和成型封头码垛自动化设备设计方案。该方案根据液压机结构及生产特点,采用上下料布局于液压机两侧,并设计了坯料车、上料、定心、取料和下料系统;依据坯料板和成型封头外形特点,设计了不同的吸盘结构和上下料方式,并与封头压制工艺相结合,实现自动化生产。实践应用表明该封头自动上下料及码垛设备不仅具有安全可靠、自动化程度高、降低工人劳动强度等特点,而且可有效提高作业效率,提高产品质量。     

基于Pro/E香皂冷打印机构的虚拟设计与运动分析

在产品的开发竞争日益激烈的今天,为缩短产品的研发周期,利用软件对产品进行虚拟设计已经成为一种趋势。在所有设计环节中,机构的运动仿真是产品开发设计过程中的重要环节,基于Pro/E软件的高级功能,实现了香皂冷打印零部件的三维造型设计及冷打印机构虚拟设计及运动仿真。对冷打印机构的虚拟装配,干涉检查和运动仿真分析表明:运动模拟与实际机构运动相吻合,能够达到机构的运动要求,为机构优化设计提供了一种简明有效的思路。     

On the prediction of the design criteria for modification of contact stresses due to thermal stresses in the gear mesh

The mechanism of surface failure due to temperature rise is a very important problem in gear design. Thermal considerations have received considerable attention from the gear researchers but only for scoring failures when the destruction of lubrication film occurs as a result of temperature rise. In spite of the wealth of literature on this subject, this problem is not fully analyzed.The objectives of this paper are to consider the mechanisms of thermal stresses and the thermal cycling in contact zone, during the gear mesh. This research has been conducted for the first point of contact based on consideration of transient heat transfer, elastohydrodynamic lubrications, and surface roughness and gear material.A procedure presented in this paper evaluating the stresses (thermal and mechanical) and predicting the design criteria for modifying the contact stresses due to thermal stresses. The effect of the material, oil film thickness, surface roughness and geometric operating parameters on modification parameter is illustrated. Also the effects of a load on the temperature rise and the modification parameters are evaluated.     

基于ANSYS的电热产品热场分析方法与应用

针对CAD＼CAE软件的特点，给出了三维模型温度场分析的一般方法，并就CAD软件和CAE软件之间的数据交换问题提出了相应的解决方案。以电热产品为例，介绍了对具有内热源的三维稳态问题的分析流程和具体应用。     

旋转控制头密封胶芯力学行为和失效分析

针对欠平衡钻井中旋转控制头的密封胶芯经常失效的问题,根据旋转控制头的工作原理以及胶芯的材料特点,分析胶芯在几种典型工作状态下的受力与变形规律,以及胶芯失效的形式和原因。结果表明：胶芯的主要失效形式为胶芯侧面拉压疲劳开裂、顶部剪切疲劳开裂、底部疲劳膨胀开裂,以及胶芯内锥面与内圆柱面交界处橡胶的脱落和胶芯内表面划伤、形成沟槽等;胶芯失效主要是由铁芯与橡胶连接部位的应力集中、起下钻中胶芯所受变应力的反复作用、胶芯与钻具间的摩擦力等方面引起的。提出在结构设计、材料选取、操作使用过程中合理地控制上述因素,以改善胶芯性能,提高其使用寿命和可靠性。     

高速铣削床鞍温度场建模与热变形分析

以安阳鑫盛机床厂生产的高速CX系列立式车铣复合加工中心CX8075的移动部件床鞍为研究对象,简化了加工中心的整机模型,研究了床鞍部件的主要发热点和热力学参数,分析了床鞍的发热量,合理地选择了滚珠丝杠的滑动摩擦系数,确定了热边界条件,建立了床鞍的三维数字化模型。利用有限元法对床鞍进行加载,研究了稳态温度场的分布[1],完成了床鞍热变形的分析与计算,从而正确认识了床鞍部件的热变形,实现了高速高精密机床的优化设计和热变形分析。     

核电蒸汽发生器下封头内壁堆焊预(后)热工艺方案探讨和实施

从传热学理论出发,对形状较复杂的核电蒸汽发生器下封头不锈钢堆焊预热和后热工艺方法进行了讨论,提出了详细的实施方案,并对具体的加热工艺从加热方法、工装、加热过程和温度控制等方面进行了描述。实践证明,采用的加热工艺方法是可行的。     

New device and method for measuring thermal conductivity of thin-films

Thermal sensitive paints (TSPs) are used for global nonintrusive detection of boundary layer transition in flow over the surface of wind tunnel research models. Since the transition is a transient process, the TSP should have a fast response characteristic. A low paint thermal conductivity is required for fast response. A thin-film thermal conductivity meter (TFTCM) was designed and built to measure thermal conductivity of the TSPs, which are typically between 50 and 150 microm thick. In this paper, the design and operating features of the TFTCM are described. Measurement of the thermal conductivity with this TFTCM of three standard thin-film low conductivity specimens, Kapton, Teflon, and Borofloat glass, showed good agreement with the manufacturer quoted values, thus validating the instrument and the procedure. Consistently repeatable values for thermal conductivity (k=0.41 +/- 0.02 W/m K) were also obtained for the TSP specimen (TSB-B, 75 microm) tested.     

燃气机气缸盖水腔流场及刚强度优化

针对某燃气机气缸盖"鼻梁区"冷却不足及缸盖整体刚强度不足的问题,采用高热负荷区域强迫冷却和布置加强筋的方法,对气缸盖水腔流场及刚强度进行优化设计。通过对原气缸盖和优化方案气缸盖进行冷却水腔计算及刚强度计算并进行对比分析,结果表明:优化方案气缸盖底板"鼻梁区"冷却能力明显改善;气缸盖整体刚强度明显增强,尤其是排气道下壁及排气道间"鼻梁区"等区域刚强度得到有效增强。     

万能自动镗铣头的建模与运动仿真

在Pro/E环境下通过镗铣头三维数字模型的建立,可以在数字模型上检查机构动、静干涉情况,消除设计错误,进行机构的运动仿真,验证机构的工作原理。     

长传动链摆头主轴高加速度启停控制策略研究

摆头主轴是高附加值关键功能部件,在航空结构件加工机床中大量采用。摆头主轴的传动链长,对伺服控制系统施加的高加速启停指令响应能力低,造成启停时间长,影响加工效率。在辨识某摆头主轴机械传动环节模态的基础上,建立了机械动力学模型和伺服控制模型,分析发现机械传动环节低频和高频模态限制伺服控制带宽的提高,进而限制了启停加速度的提高。针对低频和高频模态的限制,提出模态滤波器与双T网络陷波滤波器综合控制策略,将伺服控制带宽由12 Hz提高到110 Hz,启动加速度由10 r/s²提高到40 r/s²,启动加速时间由7.05 s下降至1.76 s。