Effects of sputtering on the surface of graphite

We present STM images of the sputtered surfaces of graphite after different sputtering times. The roughness (r.m.s.) and the peak-to-valley distance were calculated from the digitized STM signals. The roughness versus etching time graph shows that the roughness increases with etching time initially, but does not change with increased sputtering later. The peak-to-valley distance is proportional to the roughness with a coefficient of 8·7. The Fourier transform shows peaks corresponding to the size of mountains created on the sputtered surfaces.     

基于反射镜表面粗糙度计算极紫外望远镜分辨率

针对短波段成像系统中的散射问题,提出了一种基于反射镜表面粗糙度来计算极紫外太阳望远镜工作波段分辨率的方法.首先分析了两镜系统中散射光线的传播,讨论了反射镜表面粗糙度相对波长的比值与像面光强分布的关系.分频段测量了反射镜的表面粗糙度,利用k-相关模型拟合出全频段的一维功率谱密度(PSD).数值计算结果表明:在1/D到1/...     

Influence of surface roughness on normal-sliding lubrication

Contact between machine components can involve normal, sliding and rolling motion, either singly or in combination. Combined normal and sliding motion, which occur for example in the meshing of gear teeth and in heavily-loaded rolling elements, can present problems for lubrication. The purpose of the present experimental study was to investigate how surface roughness affects the lubricant film characteristics under conditions of combined normal and sliding motion. The experimental arrar gement consisted of a rotating roller which impacted a stationary ball in the presence of a lubricant. Under the same conditions of normal surface approach, increasing the surface roughness significantly decreased the level of roller sliding that could occur without breakdown of the lubricating film. This behaviour was similar to a step function. Of the several surface roughness parameters investigated, only those which involved the maximum peak-to-valley height correlated well with experimental results. In general, surface roughness had a greater effect on oil film breakdown than did either viscosity or load.     

Measuring the influence of materials composition on nano scale roughness for wood plastic composites by AFM

Composition of mango wood Polypropylene composites (WPCs) are prepared through melt compounding with the help of micro conical twin screw co-rotating extruder then injection molding of WPCs pellets. Polymer matrix composites are formulated for five compositions with a different weight ratio of wood, virgin polypropylene, recycled polypropylene and coupling agent. Average roughness (Ra), mean peak-to-valley height (Rz) and maximum roughness (Rmax) used to evaluate surface characteristics of samples by AFM. Also measures the 3D surface and surface roughness profile to examine the same. Result from this work clearly shows that recycled Polypropylene based composites with and without coupling agent have a smooth surface in comparison with virgin Polypropylene based composites for same operating variable conditions. The surface smoothness of WPCs improved with decreasing of wood flour content for all samples. By addition of coupling agent surface smoothness of the WPCs increases and the value of Ra decrease from 2.17 to 1.04 nm for recycle polypropylene wood based composite. Surface of composites is also examined with the help of FESEM images. FESEM feature proved that MAPP coupled is shown good bonding strength and smoothness in comparison to none coupled composite for the same class.     

The study of machined surface roughness by random analysis

The effects of various parameters on surface roughness were studied by measuring R_a (c.l.a. value) or R_t (peak-to-valley height). The effect of cutting speed, feed, rake angle and depth of cut on the randomness of the surface profile were studied from the auto-correlation function of the surface profile.     

Prediction of scratch resistance of cobalt chromium alloy bearing surface, articulating against ultra-high molecular weight polyethylene, due to third-body wear particles

The entrapment of abrasive particles within the articulation between a cobalt chromium alloy (CoCrMo) femoral component and an ultra-high molecular weight polyethylene (UHMWPE) cup of artificial hip joints or tibial inserts of artificial knee joints usually scratches the metallic bearing surface and consequently increases the surface roughness. This has been recognized as one of the main causes of excessive polyethylene wear, leading to osteolysis and loosening of the prosthetic components. The purpose of this study was to use the finite element method to investigate the resistance of the cobalt chromium alloy bearing surface to plastic deformation, as a first approximation to causing scratches, due to various entrapped debris such as bone, CoCrMo and ZrO2 (contained in radiopaque polymethyl methacrylate cement). A simple axisymmetric micro contact mechanics model was developed, where a spherical third-body wear particle was indented between the two bearing surfaces, modelled as two solid cylinders of a given diameter, under the contact pressure determined from macro-models representing either hip or knee implants. The deformation of both the wear particle and the bearing surfaces was modelled and was treated as elastic-plastic. The indented peak-to-valley height on the CoCrMo bearing surface from the finite element model was found to be in good agreement with that reported in a previous study when the third-body wear particle was assumed to be rigid. Under the physiological contact pressure experienced in both hip and knee implants, ZrO2 wear particles were found to be fully embedded within the UHMWPE bearing surface, and the maximum von Mises stresses within the CoCrMo bearing surface reached the corresponding yield strength. Consequently, the CoCrMo bearing surface was deformed plastically and the corresponding peak-to-valley height (surface roughness) was found to increase with both the hardness and the size of the wear particle. Even in the case of CoCrMo wear particles, with similar mechanical properties to those of the CoCrMo bearing surface, a significant plastic deformation of the bearing surface was also noted; this highlighted the importance of considering the deformation of the wear particles. These findings support the hypotheses made by clinical studies on the contribution of entrapped debris to increased surface roughness of CoCrMo femoral bearing surfaces.     

曲面圆弧包络磨削表面粗糙度特性研究

对曲面磨削表面粗糙度成型原理进行了分析,得出曲面磨削时其表面粗糙度由磨粒划痕和砂轮两步距间的残留高度构成。探讨了其分布均匀性的原理,揭示了各参数对其均匀性的影响。通过砂轮进给速度的变速控制,可以降低约60%的表面粗糙度波动率。根据理论分析可知,在加工凹曲面时,其理论残留高度值约为凸曲面的两倍。实际加工时,采用较小的砂轮进给步距或砂轮圆弧半径可达到凸曲面的表面粗糙度效果。     

Optical interference artifacts in contact atomic force microscopy images

Atomic force microscopy images are usually affected by different kinds of artifacts due to either the microscope design and operation mode or external environmental factors. Optical interferences between the laser light reflected off the top of the cantilever and the light scattered by the surface in the same direction is one of the most frequent sources of height artifact in contact (and occasionally non-contact) images. They are present when imaging highly reflective surfaces, or even when imaging non-reflective materials deposited onto reflective ones. In this study interference patterns have been obtained with a highly polished stainless steel planchet. The influence of these artifacts in surface roughness measurements is discussed, and a semi-quantitative method based on the fast Fourier transform technique is proposed to remove the artifacts from the images. This method improves the results obtained by applying the usual flattening routines.     

Effect of lighting conditions in the study of surface roughness by machine vision - an experimental design approach

In the evaluation of surface roughness by machine vision technique, the scattered light pattern reflected from the machined surface is generally captured and optical surface finish parameters from the images are correlated with the actual roughness. Capturing of the image at appropriate conditions is required for the good correlation of the optical parameters with the roughness. Lighting conditions is a major factor that influences the image pattern and hence the optical parameters. In this work the lighting conditions like grazing angle, the light to specimen distance, the orientation of the striations on the surface to the light are varied and its influence on the optical surface finish parameter are studied. A plan of experiments based on the techniques of Taguchi was designed and executed for conducting the trials and to obtain valid conclusions. The analysis of variance and the signal to noise ratio of robust design are employed to investigate the influence of different lighting conditions on the optical surface finish parameter. The results of both the approaches confirm that grazing angle is the most influencing factor affecting the image parameter.     

Roughness and wear characteristics of spark-eroded surfaces

Measurements of surface roughness H_r.m.s were made on spark-eroded samples of tungsten carbide, high speed tool steel, high carbon steel and mild steel machined with graphite, copper and tungsten tools. The roughness increased with increasing pulse energy for particular work-tool combinations. The surface finish improved as the melting point of the work material increased for a particular tool material and as the work function of the tool material decreased for a particular work material.The surface roughness profile records were graphically analysed to obtain the average and maximum peak-to-valley height and the free polishing depth. The heterogeneity of the surface, expressed as the ratio of the range of microirregularities to its average value, was between 1.1 and 1.5. Reduction in pulse energy, which resulted in a better surface finish, correlated with reduction in the free polishing depth. The average diameter of the crater increased with increasing pulse energy.     

考虑纵向粗糙度的点接触微观热弹流润滑数值分析

主要研究了纯滑动点接触热弹流润滑在考虑纵向单粗糙峰／单粗糙谷这一因素时，油膜的厚度、压力、温度随粗糙波高度、波长的变化而变化的情况，结果表明粗糙度对油膜的压力、膜厚和温度均有很大影响。     

Topographic quantification of non-planar localized surfaces

The topography of non-planar localized surfaces can be quantified by roughness indices as well as by height and angular distributions of the surface elements. For the roughness indices general relationships between the profile and spatial quantities including overlapping have been established. Some measurement methods are briefly considered. The profile analysis has proved to be a reliable, easy and fast way to characterize the topography of surfaces.     

A novel method for micro-gap control in electrogenerated chemical polishing

In the electrogenerated chemical polishing (EGCP), material removal rate (MRR) is inversely proportional to the processing gap. To polish a workpiece with a large area, high and uniform MRR is necessary, which prefers a small and uniform processing gap. Based on the principle of the hydrostatic support, a novel micro-gap control method is proposed. The method uniformly controls the gap between the electrode and workpiece to a micro level over a large area. A relationship between the gap size and the inlet pressure is derived theoretically and verified experimentally. The proposed method is successfully applied to the polishing of a Cu surface with a diameter of 50 mm. Promising results are obtained that surface roughness and flatness are reduced from average roughness (Ra) 82 nm and peak-to-valley (PV) value 290 nm to Ra 4 nm and PV 120 nm, respectively.     

Effects of Surface Roughness on Point Contact EHL

The effects of orientation of surface roughness, entrainment (rolling) velocity, and slide/roll ratio on micro-elastohydrodynamic lubrication (micro-EHL) are investigated under pointcontact conditions using the optical interferometry technique. Long bumps with constant height and wavelength produced artificially on the surface of a highly polished steel ball are used as a model roughness. It is shown that the asperities are elastically deformed and the magnitude depends on the film factor A, defined by the ratio of the central film thickness based on smooth surfaces to the composite surface roughness, as well as the surface kinematic conditions and the orientation of the asperities. It is also found that a thin or thick oil film formed at the inlet of the contact by a moving rough surface travels through the contact region at a speed very close to the average speed of the contacting surfaces. The possible mechanism is discussed.     

Development of electrically controlled polishing with dispersion type ER fluid under AC electric field

This paper shows that a dispersion type functional fluid and AC electric field may be used to control the distribution of abrasives in free-abrasive polishing and to improve surface roughness and finishing time. In the case of polishing conductive materials, such as cemented carbide, an AC electric field created by a mono-pole electrode has concentrated abrasives in the polishing area. To obtain a minimum surface roughness, a peak-to-valley voltage of 2 kV at a frequency of 0.8 Hz has been applied. Then the surface roughness of a cemented carbide plate was reduced from 0.65 μm Ra to 0.02 μm Ra in 5 min. But to polish non-conductive materials, such as glass and semiconductors, a multi-layered concentric electrode must be introduced. The surface roughness of borosilicate glass plates has been reduced from 13.5 nm Ra to 7.5 nm Ra in 3 min under the optimum AC electric field gradient of 2 kV/mm and 0.8 Hz frequency.     

Spectral analysis of the finish of polished optical surfaces

Surface finish is a critical factor in many high performance optical components with major limitations arising from scattering due to topographic surface roughness. Scattering theory shows that the relevant statistic of the residual surface height fluctuations is their power spectral density. In this paper, methods of estimating such spectra from surface profile measurements are described and are illustrated by the analysis of mechanical stylus measurements of several polished surfaces which have nanometer height fluctuations over the surface wavelength range of about 10⁰–10³ μm.     

Evolution of matt surface topography in aluminium pack rolling. Part II: effect of material properties

A model has been presented in a companion paper [1] to predict the generation of roughness on the matt surface in pack rolling of aluminium foil. The model is based on the finite element method using isotropic plasticity. This model is used in the current paper to investigate the effect of material properties on the generation of surface roughness. There is a large inhomogeneity of strain during deformation, with harder grains generally deforming less than softer ones. It is found that the roughness amplitude is roughly proportional to the standard deviation of the initial grain yield stress distribution, normalised by the initial mean yield stress, so that a wider distribution of the initial yield stress results in greater surface roughness. It is shown that a suitable linear hardening law can be used to approximate the roughening behaviour for real material flow stress curves.     

Modelling of surface finish and material removal rate in rough honing

In the present work influence of different parameters of the rough honing process on surface roughness and material removal rate were studied. Specifically, second order mathematical models are presented for mean average roughness Ra (μm), maximum peak-to-valley roughness Rt (μm) and material removal rate Qm (cm min⁻¹), obtained by means of regression analysis.