Hard disc drive air bearing design: modified DIRECT algorithm and its application to slider air bearing surface optimization

Hard disk drives continue to increase in areal data density. This requires air bearing sliders with lower and lower flying heights (FH). Also the uniformity of the FH and the flatness of the roll profile with radius become more critical as the FH gets lower. By using modern optimization techniques, it is possible to optimize slider air bearing surface (ABS) designs according to multiple design goals. In this paper, we discuss two modifications to the DIRECT algorithm: one to handle tolerance and one to deal with hidden constraints. Some numerical experiments were carried out using these modifications and the modified DIRECT algorithm was applied to slider ABS optimization. The results show that these two modifications can improve the efficiency of the DIRECT algorithm and they also provide more flexibility in slider ABS optimization.     

磁记录非牛顿液膜润滑仿真

随着记录密度的不断提高，头盘浮动间隙不断减小。目前近场光、磁混合记录已经在研究10nm以下的浮动系统。由于浮动间隙已远小于空气分子平均自由程(室温下约65nm)而有使气膜浮动技术有失效的危险。非牛顿液膜浮动技术就是在这种背景下在近几年备受关注的。该文提出了一个新的非牛顿润滑液膜，建立了考虑表面粗糙度影响的非牛顿液膜浮动系统模型，对不同表面粗糙度形状系数进行了仿真研究。研究表明，非牛顿液膜浮动系统的性能与气膜的情况有很大的差异。     

Wear of Cobalt Base and Stainless Materials in High Purity Water

Results of wear tests in clean water at room temperature and at 500F are presented. The differences in result with 0.08 in. diameter and line contact riders and with much larger riders are shown. The contact stress range is from 10 psi to 9000 psi for large contact areas and from 3000 psi to over 100,000 psi for small contact areas. The majority of the testing is at a linear velocity of about 2 in. per sec. The concept of wear per unit load and per unit distance traveled for a unit wear area is used for converting sliding wear data from various test machines to a common basis for comparison. The same concept can be used for calculating from wear data the expected wear in a new design. The range and trend of friction values encountered in some of the tests is presented.     

3D thermohydrodynamic analysis of a textured slider

Analysis of a 3D inlet textured slider bearing with a temperature dependent fluid is performed. Numerical simulations are carried out for a laminar and steady flow. Hot and cold lubricant mixing in the groove is modelled and examined for different operating conditions. Thermohydrodynamic performance of the bearing is analyzed for different texture lengths.Results show that texture has a stronger and positive influence on load carrying capacity when thermal effects are considered. This beneficial effect is at a maximum for the longest dimples with a length shorter than the pad length. Texture is also beneficial for the load carrying capacity when the sliding speed and inlet flow rate are varied. The load carrying capacity of the slider can be increased by up to 16% in severe operating conditions (high sliding speed).     

折弯机滑块的敏感度分析及结构优化

为寻找影响折弯机滑块直线度的关键因素,掌握滑块弹性变形的理论数据,为折弯机滑块的结构设计和刚性校核提供理论指导和依据,利用Pro/E分析软件,结合折弯机的工作情况和受力状态,通过建立有限元分析模型,进行受力分析和敏感度分析,找到各模型尺寸与弹性变形的数据关系,并确定经济可行的优化方案。     

DMC复合材料自动切割机的研发

研发一台自动切割机,对DMC复合材料进行自动切割,用于制造窨井盖。要求切割机边输送复合材料边进行纵向和横向切割,且使得切口形状尽可能平齐。纵切机构是转轴带动圆盘切刀对复合材料进行纵向切割。横切机构是采用曲柄滑块机构驱使切刀对复合材料进行横向切断。运用MATLAB仿真,对横切机构切刀运动轨迹进行优化,得出物料切口最接近垂直的轨迹线。结果表明:当切刀口距离连杆与曲柄转心的距离为55 mm,曲柄角速度为26 r/min时,物料横向切口形状的左右最大偏差最小,最接近平齐标准,满足生产要求。     

基于有限元技术的折弯机滑块分析与改进设计

滑块是数控板料折弯机的重要组成部分,对加工工件的精度有着重要影响。本文采用ANSYS有限元分析软件建立了折弯机整体有限元模型,对折弯机滑块进行了静力学分析,研究了滑块的应力分布与变形情况,研究发现液压缸活塞杆与滑块安装的方形开口周围应力过大。为提高该处结构强度,提出几种改进设计方案,通过有限元计算结果的比较,最终确定最合理的设计方案。     

An analytical approach for analysis and optimisation of slider bearings with infinite width parallel textures

This paper introduces an analytical approach to study the textured surfaces in hydrodynamic lubrication regime. For this purpose, a method of integrating the Reynolds equation for slider bearings with surface discontinuities is presented. By introducing appropriate dimensionless parameters, analytical relations for various texture profiles in both indented and projected forms are delivered. These relations express the nature of mathematical dependence between textured bearing performance measures and geometrical/operational parameters. An optimisation procedure is employed to achieve the optimum texturing parameters promoting maximum load capacity, load capacity to lubricant flow rate ratio and minimum friction coefficient for asymmetric partially textured slider bearings.     

基于UG的手机电池扣注塑模具设计与制造

以手机电池扣为例,设计了一套具有对称抽芯机构的注塑模具,阐述了UGMoldwizard自动设计注塑模具的过程和要点,以及其之于传统设计的优势所在。介绍了模具材料的选择,以及模具制造方法的要点因素。     

Hydrodynamic lubrication of rough slider bearings with couple stress fluids

The combined effects of couple stresses and surface roughness on the performance characteristics of hydrodynamic lubrication of slider bearings with various film shapes, such as plane slider, exponential, secant and hyperbolic, are studied. A stochastic random variable with non-zero mean, variance and skewness is used to mathematically model the surface roughness of the slider bearing’s. The Stokes couple stress fluid model is used to characterize the rheological behavior of the lubricant with polymer additives. The modified expressions for the bearing characteristics, namely pressure, load carrying capacity, center of pressure, frictional force are obtained for the general lubrication film shape on the basis of Stokes microcontinuum theory for couple stress fluids. Results are computed numerically for various film shapes under consideration. It is observed that, for all the lubricant film shapes under consideration, the negatively skewed surface roughness increases the load carrying capacity, frictional force and temperature rise, while it reduces the coefficient of friction. On the contrary, the reverse trend is observed for positively skewed surface roughness. Further, these effects are more pronounced for the couple stress fluids.