On Self-Adaptive Surface Grooves

Self-adaptive, microscale grooves improve the load-carrying capacity of the lubricated surfaces by providing a “flexible surface texturing.” These grooves use mechanical deflection to change the surface texture based on the loading condition. To accurately predict the behavior of a self-adaptive groove, the surface deformation is computed by treating the classical plate deflection equation simultaneously with a mass conservative formulation of the Reynolds equation. The results of a series of simulations reveal that the self-adaptive groove provides a greater load-carrying capacity in comparison with conventional grooved surfaces. Comparisons between the mass conservative formulation and Reynolds boundary condition for small length-to-width ratios show that the Reynolds boundary condition largely underestimates the cavitated area, leading to inaccuracies in the prediction of the load-carrying capacity.     

Tribology issues in nanoimprint lithography

Nanoimprint lithography (NIL) is one of the most promising technologies for nanofabrication because it can create nano- and microscale structures and devices in a cost-effective manner. In the NIL process, a mold with patterns on its surface comes in contact with a polymer film on a substrate. The patterns are transferred to the polymer film and then the mold is separated from the film. Mechanical contact between the mold and the polymer film, and between the film and the substrate, is inevitable. In some cases, during the separation process, adhesion and friction forces at the interfaces can deform and fracture the transferred patterns and detach the polymer film from the substrate. Thus, controlling the adhesion and friction between the materials in contact is very important in achieving a successful pattern transfer and making the NIL process a robust nanofabrication technique. Many theoretical and experimental research efforts have been made to clarify the tribological phenomena in NIL and to reduce defects due to adhesion and friction. This article describes the tribological problems encountered and reviews the related research.     

双列深沟球轴承内圈两沟道间距尺寸测量方法的改进

通常双列深沟球轴承内圈两沟道间距尺寸是采用沟间距样板测量,该样板只能定性判断两沟道间距尺寸合格与否,不能定量测量。采用百分表结构的测量方式后,能准确测出两沟道间距尺寸的实际值,提高了测量精度,且该测量装置的通用性强。     

BONDING OF MINIATURE PARTS WITH ADHESIVES AND VISION BASED PROCEDURE INSPECTION

Bonding with adhesives is an important technique for building up hybrid microsystems.Some adhesives are tested with capillary dispensing system for microassembly, and volume of dropletsless than 10 nl with good repeatability can be acquired. 1-part UV curing adhesive hardens rapidly andis suitable for bonding of transparent microparts. Light-activated adhesive starts the curing process inan adjustable short period of time after the radiation of visible light, and thus suits bonding ofnon-transoarent microparts. A method is proposed for bonding the guides of a miniature linear motorbeing developed by collaborate research center 516 (SFB516) in Germany.With the method high as-sembly accuracy in the vedical direction can be guaranteed. By making small grooves on the stator forcontaining adhesive, the deterioration of the accuracy due to the thickness of adhesive layer can beavoided. The criteria on deciding the size of the groove are given and analyzed. Vision based inspec-tion method is introduced for aut     

Simulation of elliptical patterns based on grinding with wheel dressed by elliptical tool

Dressing is a sharpening operation aimed to produce a specific groove shape on the active surface of the wheel. The preparation of grinding tools in special way is the most important enabling factor in the grinding process. It greatly influences the subsequent geometry of the workpiece. As the groove shape of the wheel surface determines the shape of the surface patterns, therefore, it is essential to produce desired groove on the wheel cutting surface before grinding. Therefore, an elliptical groove surface pattern model is proposed based on grinding with dressed wheel. An elliptical tip tool is used for the dressing process to make grooves on the wheel instead of sharp tip tool or rounded tip tool in the previous work. The dressing tool passes helically over the surface of the grinding wheel for making grooves. After that, the grooved wheel passes over the flat surface to generate elliptical patterns. The results showed the three-dimensional geometry of the surface patterns with elliptical groove which are uniformly distributed on the workpiece. An experiment is carried out for the verification of the simulation results and it is revealed that the simulation results agreed well with the experiment.     

Analysis on microfinger with grooved patterns and its application in electric�Cthermal microgripper

The properties of a microfinger with groove patterns etched on its surface were discussed in this paper. An analytical model of the deflection was built up to study the effect of the groove size on the bending stiffness and the deflection of the grooved finger. The calculation of the analytical model is consistent with the simulation and experimental results. When the grooves depth is 0.5???m, the spring constant of grooved microfinger is 22.8%, smaller than that of flat finger without grooved patterns. The spring constant of the finger decreases with the increasing of the depth of the grooves. A stable novel microelectric?Cthermal gripper is introduced based on the grooved finger. It consists of four sub-cantilever beams positioned at the diagonal lines of a square frame in the end of the main cantilever structure suspended from the silicon substrate, which guarantees an effective contact by the four-point contact area on the top surface to grab components of importance. The thermal-expansion-induced deflection makes the fingers moving vertically from an ??open?? position to a working one. The grooved finger helps to decrease the bending stiffness of the finger and increase the deflection and the initial gap. The simple fabrication process has a feasibility of compatible and mass production.     

用于光盘存贮器沟槽参数测试的光学衍射方法

光盘存贮器有非常精密的沟槽.用衍射法进行测量,由于要引用大衍射角计算,沟槽的菲涅尔系数不再恒定,因此应用很广的弗朗和费理论不适于描述光盘沟槽的衍射.这种情况下,我们提出了一个研究此种衍射的方法,进一步讨论了一些基本因素.例如:沟槽形状的影响,基底多重反射对衍射图样的影响,特别是当基底不完全平行时的影响等等.最后,建立了一种测量沟槽参数的技术.     

Research on Effects of Groove Shape Optimization on Cavitation and Lubricating Characteristics for Microgroove Rotary Seal

This article studies the effects of groove shape optimization on cavitation and lubricating characteristics of microgroove rotary seals (MGRS). A lubrication model considering cavitation effects for MGRS is established to obtain the variation in cavitation and lubricating characteristics with operating conditions. Furthermore, an optimization model of groove shape based on the lubrication cavitation model is developed and an optimal groove is obtained by co-designing the parameters of both groove shape structures and molded lines. The effects of optimal grooves and ordinary spiral grooves on cavitation and lubricating characteristics are compared and validation tests are carried out. Theoretical and experimental results indicate that the lubrication cavitation model based on the mass conservation boundary condition for MGRS could accurately predict the cavitation region of ordinary spiral grooves. Optimal grooves improve the pressure distribution of the groove area and restrain the generation of a cavitation region; therefore, the fluid bearing capacity and dynamic stiffness of optimal grooves are much larger than those of ordinary spiral grooves.     

橡胶合金螺旋槽水润滑轴承流体域仿真分析

对水润滑轴承内部由于凹槽不同而形成的不同形貌动压流体域进行数值分析。借助ANSYS建模模块的流体自动生成技术,建立不同偏心条件下稳态动压流体域;利用ANSYS CFX专业流体分析软件,对直槽和螺旋槽水润滑轴承动压流体域进行稳态数值仿真,得出偏心率、转速、水膜形貌对流场动压效果的影响;对流体内所产生的漩涡的流速和压力进行理论分析和仿真分析验证,得到不同形貌水槽内部的漩涡强度。结果表明:动压流体域流场压力会随着转速、偏心率的增加而增加,承载力也随之增加;动压流体域内部由于形貌的改变,动压效应不同,沟槽对流体域的影响较为明显,直槽的流体域承载能力较大,螺旋槽的局部压力较大;在沟槽内部出现明显的漩涡效应,有利于泥沙等杂质的流出,螺旋槽的涡流效应要明显高于直槽,对排污更有效。     

A Study on the Mechanism of Generating Wear Track Grooves

The mechanism of generating wear track grooves on metallic materials was investigated to elucidate the cause of similar wear track appearance based on pin-on-disk wear test results. As previously shown, most wear tracks on metallic materials appear similar in appearance irrespective of test conditions and materials. This phenomenon is attributed to the similar scales of prominent grooves in wear tracks, as wear tracks have common characteristic groove sizes in terms of width and depth. The ploughing by transfer particles adhering to counter surface initially generates these grooves, which become larger along with the growth of transfer particles. Pin-on-disk wear tests revealed that transfer particles adhering to the pin surface stopped growing at a certain size upon being enclosed by ridges forming along the sides of grooves on the disk and penetrating the pin surface. This final transfer particle size determines the characteristic scales of wear track grooves. We supposed that this enclosure by ridges terminated particle growth. Based on this supposition, the formation of ridges had a key effect on determining the sizes of grooves. Ridges form when the grooves grow to a certain size; thus, characteristic grooves could be expected to be a bit larger than this size. Therefore, these processes generate the characteristic scales of wear track grooves which lead to similar wear track appearance.     

Combinatorial materials research applied to the development of new surface coatings VII: an automated system for adhesion testing

An automated, high-throughput adhesion workflow that enables pseudobarnacle adhesion and coating/substrate adhesion to be measured on coating patches arranged in an array format on 4x8 in.(2) panels was developed. The adhesion workflow consists of the following process steps: (1) application of an adhesive to the coating array; (2) insertion of panels into a clamping device; (3) insertion of aluminum studs into the clamping device and onto coating surfaces, aligned with the adhesive; (4) curing of the adhesive; and (5) automated removal of the aluminum studs. Validation experiments comparing data generated using the automated, high-throughput workflow to data obtained using conventional, manual methods showed that the automated system allows for accurate ranking of relative coating adhesion performance.     

Theoretical Analyses and Design Guidelines of Oil-Film-Lubricated Mechanical Face Seals with Spiral Grooves

The oil-film-lubricated mechanical face seal is a kind of pure hydrodynamic lubricated noncontacting mechanical face seal with zero leakage. On the basis of systematic theoretical analyses, the design calculation formulas under zero-leakage condition for mechanical face seals with different spiral groove patterns, including double-row spiral grooves such as splay pattern and single-row spiral grooves, are derived. The effects of groove geometry including number of grooves, balance ratio, spring force, rotating speed, and differential pressure on the seal performance are discussed in detail. Finally, the design guidelines of this kind of seal with zero leakage and no wear are put forward. The seals designed according to the guidelines can withstand the pressure disturbance and speed change by means of a slight change of oil-film thickness. Seals developed according to the design guidelines have been tested on a test rig in detail and applied successfully in high-speed turbocompressors of the oil refinery and petrochemical industries.     

液黏离合器油槽结构参数对油膜剪切转矩的影响分析

合理确定油槽的结构参数能有效地改善摩擦副间流体的流场特性和油膜剪切摩擦转矩性能。为了揭示摩擦副油槽结构对油膜剪切转矩的影响,以双圆弧油槽为研究对象,建立了集油槽结构参数化设计、流场数值模拟与试验设计方法(DOE)为一体的油槽结构参数影响分析平台。重点分析了液黏离合器摩擦副双圆弧油槽宽度、油槽对数、偏心距与内圈偏心圆直径对油膜剪切转矩的影响,并探究了各个参数的敏感性。结果表明,液黏离合器油膜剪切转矩随着摩擦副油槽宽度、油槽对数及内圈偏心圆直径的增大而增大,随着偏心距的增大而减小。摩擦副油槽宽度与内圈偏心圆直径是影响液黏离合器油膜剪切转矩的敏感参数。     

表面凹槽对滚子链套筒-销轴摩擦副热弹流润滑影响的数值模拟

以工业滚子链为工程背景,研究表面沟槽对套筒-销轴铰链副在充分供油条件下的热弹流润滑问题的影响。分析基于长椭圆接触假设,建立稳态热弹流润滑的数学模型,采用纵向和横向2种凹槽的表面织构形式。结果表明:在椭圆接触区长轴两端布置2个对称的纵向凹槽时,可以起到储油的作用,增加局部油膜厚度;在椭圆接触区长轴两端各布置3个对称的横向凹槽时,会引起油膜厚度、压力与温度的急剧变化,增加了动压效应。在接触区端部设置横向凹槽的效果要好于设置纵向凹槽。     

Numerical Simulations of Groove Topography Effects on Film Thickness and Friction in EHL Regime

The effects of depth and top width of transverse rectangular grooves on film thickness and friction in elastohydrodynamic lubrication (EHL) regime were investigated through numerical simulations. Results were obtained in the form of pressure profiles and Stribeck curves for central and minimum film thickness and for friction coefficient. The results indicate that grooves with narrow top widths reduce the minimum film thickness and that this reduction is greater for deeper grooves. Lubricant shearing inside these grooves was further identified as a dominant factor contributing to friction. Near the groove edges, however, no evidence of micro-EHL effect was observed. Based on the results, a groove volume parameter was proposed to characterise the groove lubrication efficiency. We found that the parameter was linearly related to the average central film thickness and by increasing the groove wavelength the film could be made thicker than that of a smooth contact.     

Experimental Investigation Regarding the Effects of Grooves on Conical Bearing Performance

An experimental investigation is made regarding conical bearing characteristics related to the introduction of grooves. Load capacities of three bearing types are compared, i.e., smooth bearings, bearings with radial grooves, and bearings with inclined grooves rotated in both directions. The obtained results indicate that the presence of grooves significantly affects conical bearing performance. It is concluded that for the maximum load capacity, a bearing with inclined grooves should be used with forward rotation, i.e., when the entry part of the groove advances ahead of the exit of the groove.     

A reverse receptance approach for analysis of vibration of grooved plates

A reverse receptance approach is proposed to solve eigenvalues of a plate with two orthogonally connected through grooves, two parallel through grooves and two parallel internal grooves. The procedure is a modification of the well-known receptance method commonly used to study vibrations of combined structures. In the present paper, vibrations of rectangular plates with grooves in different sizes and boundary conditions are studied analytically to illustrate the approach. A through groove is simulated by a simply supported beam, while an internal groove is simulated by a free–free beam. The accuracy is evaluated by comparing the percent differences between the natural frequencies solved using the reverse receptance method and the standard finite element method.It is verified that the reverse receptance method with both force and moment connections at the interface of each plate–groove pair and with sufficient interaction points is adequate and accurate for solving vibration characteristics of a plate with either through or internal grooves. Parametric study reveals that the percent differences are directly proportional to the length, the width and the depth of the grooves on the plate. It is found that, for good accuracy, the groove width should not exceed 3.6% of the plate width, while the groove depth should not exceed half of the plate thickness. This report demonstrates the potential of reverse receptance concept in the engineering practice of machine design, as a simple numerical or analytical approach to study dynamics of structures with complex geometries.     

新型涡流槽密封泄漏特性与动力特性研究

提出一种密封入口周向均匀设置有涡流槽的新型密封结构,建立了传统迷宫密封与新型涡流槽密封泄漏特性及动力特性求解模型,在实验验证数值计算方法准确性的基础上,通过比较分析了传统迷宫密封与新型涡流槽密封在不同进出口压比、预旋比工况下的泄漏特性与动力特性,研究了新型涡流槽结构对密封泄漏特性及动力特性的影响机理。研究结果表明：随着涡流槽数量的增加,涡流槽密封的泄漏量逐渐降低;在同一压比下,不同涡流槽数新型密封的泄漏量之间差值随着压比的增大而增大。当压比为6时,64涡流槽的新型密封较传统迷宫密封,泄漏量下降了3.37%;在高预旋比的工况下,不同涡流槽数量密封的切向气流力均与转子涡动方向相反,起到抑制转子涡动的作用,且随着涡流槽数量的增加,切向气流力也随着增大;随着转子涡动频率的增大,三种不同涡流槽数量密封的交叉刚度先减小到负值然后增大到正值。涡流槽密封的有效阻尼均高于传统迷宫密封,新型涡流槽密封可以提高转子系统的稳定性。     

Visualization of flagellar interactions on bacterial carpets

Methods for the in-depth study of the physics of microscale actuation of microfluidics environments by flagellated bacteria 'teamsters' have been developed. These methods, which include single and multi-colour fluorescent labelling and electron microscopy allow for the analysis of the effect that individual flagellar filaments have on bacterially driven microstructures, and allow for the investigation of the interaction and coordination of flagellar filaments of neighbouring bacteria on densely packed monolayers of bacteria, 'bacterial carpets'. We show that the flagella of bacteria that are immobilized on a surface often interact with each other, and that the flagella of these bacteria do not often form multi-flagella bundles that are aligned with the cell body.     

Investigation of scale effects and directionality dependence on friction and adhesion of human hair using AFM and macroscale friction test apparatus

Macroscale testing of human hair tribological properties has been widely used to aid in the development of better shampoos and conditioners. Recently, literature has focused on using the atomic force microscope (AFM) to study surface roughness, coefficient of friction, adhesive force, and wear (tribological properties) on the nanoscale in order to increase understanding about how shampoos and conditioners interact with the hair cuticle. Since there are both similarities and differences when comparing the tribological trends at both scales, it is thus recognized that scale effects are an important aspect of studying the tribology of hair. However, no microscale tribological data for hair exists in literature. This is unfortunate because many interactions between hair-skin, hair-comb, and hair-hair contact takes place at microasperities ranging from a few mum to hundreds of mum. Thus, to bridge the gap between the macro- and nanoscale data, as well as to gain a full understanding of the mechanisms behind the trends, it is now worthwhile to look at hair tribology on the microscale. Presented in this paper are coefficient of friction and adhesive force data on various scales for virgin and chemically damaged hair, both with and without conditioner treatment. Macroscale coefficient of friction was determined using a traditional friction test apparatus. Microscale and nanoscale tribological characterization was performed with AFM tips of various radii. The nano-, micro-, and macroscale trends are compared and the mechanisms behind the scale effects are discussed. Since the coefficient of friction changes drastically (on any scale) depending on whether the direction of motion is along or against the cuticle scales, the directionality dependence and responsible mechanisms are discussed.