The influence of surface roughness in elliptical contacts

The influence of surface roughness on contact behaviour is of great importance in many tribological situations. In the last decade several methods to calculate the pressure distribution and the real contact area in contacts between rough surfaces have been described. A problem arising for slender elliptical contacts, such as between gear teeth, roller and raceway, cam and follower, etc., is that the size of the contact is much greater than the size of the asperities. Accordingly the number of contact nodes necessary for an accurate solution to the problem becomes excessively large. This paper describes a method to calculate the influence of three-dimensional surface roughness in contacts that are very long in one direction. The method is based on restricting the calculations to a subpart of the real contact area, while the rest of the contact is taken into account by mirroring techniques. The results show that the real contact area is very sensitive to the amplitude of the roughness, while the waviness is less important. An equation is suggested from which the real area can be calculated if the smooth case contact parameters and two roughness parameters are known.     

Surface roughness analysis in layered forming processes

One of the main factors in present-day techniques for layered forming is characterization of the surface roughness obtainable in these manufacturing processes. To characterize effective roughness, a study of the roughness average (R_a) obtained through use of these manufacturing processes was carried out. This enabled us to establish two possible manufacturing strategies: manufacturing at constant layer height, and manufacturing with roughness confined within given limiting values. Moreover, to compare the theoretical models proposed with experimental values, prototype parts were manufactured using stereolithography technique, and an experimental analysis of resulting surface roughness was carried out. © 2000 Elsevier Science inc. All rights reserved.     

Surface roughness classification using image processing

Surface roughness is an important factor in determining the satisfactory functioning of the machined components. Conventionally the surface roughness measurement is done with a stylus instrument. Since this measurement process is intrusive and is of contact type, it is not suitable for online measurements. There is a growing need for a reliable, online and non-contact method for surface measurements. Over the last few years, advances in image processing techniques have provided a basis for developing image-based surface roughness measuring techniques. Based upon the vision system, novel methods used for human identification in biometrics are used in the present work for characterization of machined surfaces. The Euclidean and Hamming distances of the surface images are used for surface recognition. Using a CCD camera and polychromatic light source, low-incident-angle images of machined surfaces with different surface roughness values were captured. A signal vector was generated from image pixel intensity and was processed using MATLAB software. A database of reference images with known surface roughness values was established. The Euclidean and Hamming distances between any new test surface and the reference images in the database were used to predict the surface roughness of the test surface.     

Surface morphology in engineering applications: Influence of roughness on sliding and wear in dry fretting

Influence of initial surface roughness on friction and wear processes under fretting conditions was investigated experimentally. Rough surfaces (Ra=0.15-2.52 μm) were prepared on two materials: carbon alloy (AISI 1034) and titanium alloy (Ti-6Al-4V). Strong influence of initial surface roughness on friction and wear processes is reported for both tested materials. Lower coefficient of friction and increase in wear rate was observed for rough surfaces. Wear activation energy is increasing for smoother surfaces. Lower initial roughness of surface subjected to gross slip fretting can delay activation of wear process and reduce wear rate; however, it can slightly increase the coefficient of friction.     

Surface roughness evaluation by using wavelets analysis

Based upon wavelets theory, a novel reference for evaluating surface roughness is proposed here, wherein the surface roughness can be separated from the actual surface profile f(t). Some examples have shown that more precise evaluation results could have been achieved than those found using classical reference lines.     

金属数控切削表面粗糙度分析

为了适应先进制造技术的要求,使数控高速切削加工技术在我国得到更为广泛的应用,满足加工企业和加工人员的需要,研究了几种主要金属材料在数控高速切削加工中的表面质量,通过试验对不同金属在不同高速切削条件下获得的表面粗糙度进行了重点研究和分析,以期为后续研究提供借鉴。     

基于同态滤波和深度卷积模型的低照度工件表面粗糙度等级识别

为解决低照度下工件表面粗糙度等级识别正确率低的问题,提出一种基于同态滤波和深度卷积模型的低照度工件表面粗糙度等级识别的方法。该方法通过对不同照度下工件表面粗糙度图像进行等级识别,确定了同态滤波器的最优参数值,再将图像从RGB空间转换到HSV空间,在对V（亮度）分量进行同态滤波处理后,再将图像转回RGB空间并通过设计好的...     

Surface roughness measurements in finish turning

A new approach is proposed for the on-line measurement of the maximum peak-to-valley roughness,R _max, of a finished-turned surface in the feed direction. The method is based on solving the inverse problem of light scattering by using a linear least-square estimate of the angular scattered light pattern reflected from a surface. A laser system has been developed to capture the light reflected under different cutting conditions. The effects of the ambient room light as well as the workpiece's rotational speed and methods for thier compensation are also discussed. Good correlation was found between the optical and stylus-measuredR _max.Nomenclature R _max maximum peak-to-valley roughness within the sampling length - R _q RMS surface roughness within the sampling length - R _a arithmetically averaged roughness within the sampling length - _z r.m.s. surface height within the sampling length - u r.m.s. slope of the surface within the sampling length - T correlation distance of the surface, defined as the distance in which the correlation coefficient,C(), equals e^–1 - I(₁,) intensity of reflected light - I _m(₁,₂,) measured intensity of reflected light at instant - ₁ angle of incidence of laser beam - ₂ scattering angle defining a CCD pixel location (₁ and ₂ are measured with respect to the normal of the surface of the workpiece coincident with the centre of the laser beam) - v scattering vector of reflected light - _x,_z components ofv in thex andz direction, respectively - L sampling length associated with the laser spot on the surface of the workpiece - j representative location of a CCD pixel - j CCD pixel location corresponding to the mean light level - p _j density function of the light intensity of thejth pixel - wavelength of laser light - nose radius of the cutting tool - ASLP angular scattered light pattern - K correction factor for the measured light intensity - S _m standard deviation of the measured ASLP - S _c standard deviation of the ASLP calculated from an estimatedR _max - K control step size ofK - computational error, defined as =|S _m–S_c|/S _m - K _a,K_b starting and ending point, respectively, within the search range forK - K _c,K_d two points within (K _a,K_b), determined by the golden section search method - V cutting speed (m/min) - f feed rate (mm/rev) - d depth of cut (mm) - H hardness of workpiece (found on Rockwell scale C) - CCD charge-coupled device     

Surface roughness effects on curved pivoted slider bearings with couple stress fluid

In this paper the effect of surface roughness on the performance of curved pivoted slider bearings is studied. A more general type of surface roughness is mathematically modelled by a stochastic random variable with nonzero mean, variance and skewness. The averaged modified Reynolds type equation is derived on the basis of Stokes microcontinuum theory for couple stress fluids. The closed‐form expressions for the mean pressure, load‐carrying capacity, frictional force and the centre of pressure are obtained. Numerical computations show that the performance of the slider bearing is improved by the use of lubricants with additives (couple stress fluid) as compared to Newtonian lubricants. Further, it is observed that the negatively skewed surface roughness increases the load‐carrying capacity and frictional force and reduces the coefficient of friction, whereas the positively skewed surface roughness on the bearing surface adversely affects the performance of the pivoted slider bearings. Copyright © 2006 John Wiley & Sons, Ltd.     

An in-depth study of tool wear monitoring technique based on image segmentation and texture analysis

We present a new micro-vision system for tool wear monitoring, which is essential for intelligent manufacturing. The tool wear area is divided into regions by a watershed transform, then subjected to automatic focusing and segmentation. The individual pixel gray values in each region are then replaced with the corresponding regional mean gray value. A hill climbing algorithm based on the sum modified laplacian (SML) focusing evaluation function is used to search the focal plane. In addition, we implement an adaptive Markov Random Field (MRF) algorithm to segment each region of tool wear. For our MRF model, the connection parameter value is adaptively determined by the connection degree between regions, which improves image acquisition of more integral tool wear areas. Our findings suggest that automatic focusing and segmentation of the tool wear area by region (within the tool wear area) enhance accuracy and robustness, and allow for real time acquisition of tool wear images. We also implement a complementary tool wear assessment procedure based on the surface texture of the workpiece. The optimal texture analysis window is determined using the entropy metric – a texture feature generated using a Gray Level Co-occurrence Matrix (GLCM). In the best texture analysis window, entropy remains monotonic as tool wear increases, demonstrating that entropy can be used effectively to monitor tool wear. Information from combined measurements of tool wear and workpiece texture can reliably be used to monitor tool wear conditions and improve monitoring success rates.     

Surface roughness modeling in Laser-assisted End Milling of Inconel 718

Inconel 718 is a difficult-to-machine material while products of this material require good surface finish. Therefore, it is essential for the evaluation and prediction of surface roughness of machined Inconel 718 workpiece to be developed. An analytical model for the prediction of surface roughness under laser-assisted end milling of Inconel 718 is proposed based on kinematics of tool movement and elastic response of workpiece. The actual tool trajectory is first predicted with the consideration of overall tool movement, elastic deformation of tool, and the tool tip profile. The tool movements include the translation in feed direction and the rotation along its axis. The elastic deformation is calculated based on the previously established milling force prediction model. The tool tip profile is predicted based on the tool tip radius and angle. The machined surface profile is simulated based on the tool trajectory with elastic recovery, which is considered through the comparison between the minimum thickness and actual cutting thickness. Experiments are conducted in both conventional and laser-assisted milling under seven different sets of cutting parameters. Through the comparison between the analytical predictions and experimental measurements, the proposed model has high accuracy with the maximum error less than 27%, which is more accurate for lower feed rate with error less than 3%. The proposed analytical model is valuable for providing a fast, credible, and physics-based method for the prediction of surface roughness in milling process.     

提高活塞表面光洁度的叶轮抛光工艺

通过对剪板机、折弯机产品活塞杆表面质量、加工原理分析及阐述,提出了"叶轮"抛光加工工艺及其在生产中的广泛应用。实践证明,"叶轮"抛光工艺能很好地满足活塞杆等高精度表面零件的设计要求。     

Surface roughness and material strength of tribo-pairs in ring compression tests

The quantification of friction by means of simple models such as Amonton-Coulomb’s and the law of constant friction is questionable because the influence of surface roughness and material strength, among other factors, is not considered.This paper provides a comprehensive analysis on the influence of surface roughness and material strength in friction and proposes a new operator based on a sigmoid function to incorporate the combined influence of both phenomena in a modified version of the Amonton-Coulomb’s law.The presentation is supported by thoroughly researched quantitative data obtained from experimentation and finite element modelling of the ring compression test.     

The influence of surface roughness and the contact pressure distribution on friction in rolling/sliding contacts

A numerical contact model is used to study the influence of surface roughness and the pressure distribution on the frictional behaviour in rolling/sliding contacts. Double-crowned roller surfaces are measured and used as input for the contact analysis. The contact pressure distribution is calculated for dry static contacts and the results are compared with friction measurements in a lubricated rolling/sliding contact made with a rough friction test rig. The mean pressure is suggested as a parameter that can be used to predict the influence of surface roughness on the friction coefficient in such contacts. The results show two important properties of the friction coefficient for the friction regime studied in this paper: (1) there is a linear decrease in friction coefficient as a function of the slide-to-roll ratio, and (2) the friction coefficient increases linearly with increasing mean contact pressure up to a maximum limit above which the friction coefficient is constant. The absolute deviation of experimental results from the derived theory is for most cases within 0.005.     

Surface roughness measurement based on fiber optic sensor

The multi-wavelength fiber sensor for measuring surface roughness and surface scattering characteristics were investigated. In this paper, specimens with different surface roughness were analyzed by using 650 nm, 1310 nm and 1550 nm laser as the light source, respectively. The working distance of 2 mm was chosen as the optimum measurement distance. The experimental results indicate that multi-wavelength fiber sensor can accurately measure surface roughness, and can effectively reduce the unsystematic error. The light scattering intensity ratio has a good linear relationship with the surface roughness. The minimum relative error of the surface roughness is 2.92%, the maximum relative error is 13.4%, and the average relative error is about 7.48%. The accuracy for measuring surface roughness by multi-wavelength fiber sensor is about twice as large as that by single-wavelength fiber sensor.     

Surface topography and roughness of high-speed milled AlMn1Cu

The aluminum alloy AlMn1Cu has been broadly applied for functional parts production because of its good properties. But few researches about the machining mechanism and the surface roughness were reported. The high-speed milling experiments are carried out in order to improve the machining quality and reveal the machining mechanism. The typical topography features of machined surface are observed by scan electron microscope(SEM). The results show that the milled surface topography is mainly characterized by the plastic shearing deformation surface and material piling zone. The material flows plastically along the end cutting edge of the flat-end milling tool and meanwhile is extruded by the end cutting edge, resulting in that materials partly adhere to the machined surface and form the material piling zone. As the depth of cut and the feed per tooth increase, the plastic flow of materials is strengthened and the machined surface becomes rougher. However, as the cutting speed increases, the plastic flow of materials is weakened and the milled surface becomes smoother. The cutting parameters (e.g. cutting speed, feed per tooth and depth of cut) influencing the surface roughness are analyzed. It can be concluded that the roughness of the machined surface formed by the end cutting edge is less than that by the cylindrical cutting edge when a cylindrical flat-end mill tool is used for milling. The proposed research provides the typical topography features of machined surface of the anti-rust aluminum alloy AlMn1Cu in high speed milling.     

Classification of esophagitis grade by neural network and texture analysis

Esophagitis is divided into four grades according to the progress degree of disease by the LA classification method. This research was carried out on image processing with endoscope images for quantifying the four grades under the LA Classification. In a previous paper, which presented our work, the algorithm for detecting abnormal parts from one image was developed. This paper was conducted to classify esophagitis grade of one image itself. Whole 30 images were used in an experiment and included normal images and abnormal images with four grades. GLCM (gray level co-occurrence matrices) factors were extracted. The distributions of the texture image histogram were analyzed from each image for texture images. The algorithm to determine esophagitis grade used BPN (Back propagation network) that was composed of the texture histogram distribution for input data. It learned 20 images and verified with 10 images to diagnose under the LA classification system. Recognition ratio of learning result was 93.0% and verification result 77.0%. With features of the neural network, the success rate could be improved with this result by learning the data which were errors. Consequently, the recognition success rate appeared at 96% by total re-learned 30 images in addition to 10 images. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim     

A Study of Computer Vision for Measuring Surface Roughness in the Turning Process

The paper presents a system for measuring the surface roughness of turned parts using a computer vision system. The images of specimens grabbed by the computer vision system are processed to obtain parameters of their grey levels (spatial frequency, arithmetic mean value, and standard deviation). These parameters are used as input data to a polynomial network. Using the trained polynomial network, the experimental result shows that the surface roughness of a turned part made of S55C steel, measured by the computer vision system over a wide range of turning conditions, can be obtained with reasonable accuracy, compared to that measured by a traditional stylus method. Compared with the stylus method, the computer vision system constructed is a useful method for measuring the surface roughness of this material faster, at a lower cost, and with lower environmental noise.     

Surface roughness measurement in turning carbon steel AISI 1045 using wiper inserts

Surface roughness of the workpiece is an important parameter in machining technology. Wiper inserts have emerged as a significantly class of cutting tools, which are increasingly being utilized in last years. This study considers the influence of the wiper inserts when compared with conventional inserts on the surface roughness obtained in turning. Experimental studies were carried out for the carbon steel AISI 1045 because of its great application in manufacturing industry. Surface roughness is represented by different amplitude parameters (R_a, R_zD, R_3z, R_q, R_t, R_a/R_q, R_q/R_t, R_a/R_t). With wiper inserts and high feed rate it is possible to obtain machined surfaces with R_a < 0.8 μm (micron). Consequently it is possible to get surface quality in workpiece of mechanics precision without cylindrical grinding operations.     

三维表面粗糙度的表征和应用

表面粗糙度会直接影响零部件的耐磨性、密封性以及抗腐蚀性等,是评定机械加工和产品质量的重要指标。现代科技水平的不断提高对零件表面性能的要求也日益严苛。传统的二维表面粗糙度的测量和表征已经不再能够满足技术发展的要求,三维表面粗糙度由于能够更加全面、真实地反映工件表面的状态而受到人们的重视,成为研究热点。本文回顾了三维表面粗糙度的发展历史,系统地介绍了三维表面粗糙度参数及标准的发展现状,分析了表面形貌与功能特性的联系,概述了三维粗糙度参数在制造业、生物医疗、摩擦学与材料科学等领域的广泛应用,并进一步指出了三维表面粗糙度表征和应用的发展方向。未来随着相关研究(比如,三维测量的溯源性、重复性、参数表征体系等问题)的深入以及三维表面测量手段的发展,三维表面粗糙度参数也将不断完善和推广,并更多地与实际功能相结合来预测并指导生产,确保工件的表面质量。