Analysis of the active profile of grinding wheel surfaces

Tests have been carried out on simulated surfaces (produced by a signal generator in conjunction with an analogue computer) and on real surfaces to determine the effect of limited depth of stylus penetration in the characterization and specification of surface texture. This work is directed mainly to the working surface of grinding wheels.     

Assessment of surface roughness based on super resolution reconstruction algorithm

In this work, an attempt has been made to use a super resolution image processing algorithm for preprocessing the images over and above existing image quality enhancement techniques. The improved quality images processed using a machine vision system have been used to assess the quality of the surfaces. To ensure the validity of the approach the roughness values quantified using these images are then compared with widely accepted standard mechanical stylus instrument values. Quantification of digital images for surface roughness is performed using two Fourier transform parameters (major peak frequency and principal component magnitude squared value) and the standard deviation of gray level intensity values. Then the group method of data handling (GMDH) technique was used to obtain an analytical relationship of the roughness parameters calculated using the digital surface image and the stylus instrument values. We present in this paper an analysis based on the comparison to make sure that the present approach of estimation of surface finish based on the digital processed image could be implemented in practice.     

A computer system for the measurement of cell and nuclear sizes

A semi-automated system has been developed for the measurement of cell (perikaryal), nuclear and nucleolar areas. The system consists essentially of a Graf/Pen data tablet (with its associated acoustical stylus and tablet electronics), an optical input system such as a camera lucida, and a small digital computer. The perikaryal, nuclear and nucleolar outlines are traced in sequence with the stylus which, on contacting the tablet surface, emits a high frequency acoustic wave that is sensed by X and Y strip microphones along the left and upper edges of the tablet. The acoustic signal is converted by a simple program into a series of X and Y coordinates which are sampled at several points around the perimeter of the profile. When the stylus tip re-enters a 1 mm stationary window set up around the starting point, the measurement is automatically terminated and the data for this profile is printed out and stored in memory for subsequent statistical analysis. The system has an overall accuracy of about 1% and in practice it has been possible to measure objects at least ten times more rapidly than by any of the other currently available methods. The hardware and software features of the system are detailed and a number of additional uses for the system are described.     

Noncontact surface roughness measurement of engineering surfaces by total integrated infrared scattering

As precision engineering surfaces are gaining in importance in industry, so are the surface quality requirements. These surfaces have rms roughness typically ranging from some nanometers up to a few micrometers. Although numerous techniques exist for rough surface characterization, from traditional line-scanning stylus profilometers to modern three-dimensional (3-D) measurement instruments, there is a need for a fast, area-covering technique. An efficient method for the characterization of smooth surfaces is elastic light scattering. At visible wavelengths, the limits on roughness range and spatial frequency range make the method unsuitable for characterizing engineering surfaces. By increasing the wavelength of the incident light from the visible to the infrared, elastic light scattering turns out to be applicable for engineering surfaces. We have used total integrated scattering at 10.6 μm wavelength to measure rms roughness up to two micrometers. In this paper, the instrument design and properties are reviewed. We also present results from measurements on ground steel surfaces. Excellent correspondence with mechanical stylus measurements exists for surfaces with rms roughness in the range from 0.1–1.7 μm. The technique shows potential for rapid quality inspection of engineering surfaces.     

Roughness measurement by electronic speckle correlation and mechanical profilometry

A practical optical sensor for rough surface diagnostics has been developed for applications in mechanical engineering. The principle of the sensor is based on digital speckle correlation. First, the measuring principle and the optical system arrangement are described, then optical measurements on different rough surfaces are compared with mechanical stylus measurements and the results are discussed with consideration of the advantages and differences of the two methods.     

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.     

On the Use of Silicon Rubber Replica for Surface Topography Studies

Silicone rubber is often used to obtain replica of surfaces which are hard to study directly. Here we discuss under what conditions engineering stylus measurements can be used to obtain the correct surface roughness from the replica. We also show how thin vertical slices of the silicone rubber can be used to obtain the surface roughness power spectra for the long-wavelength roughness on even very rough surfaces, such as road surfaces, which may be hard to probe directly with standard optical or stylus instruments.     

Assessment of surface finish on bulk scattering materials: A comparison between optical laser stylus and mechanical stylus profilometers

The accuracy of autofocusing laser stylus measurement systems based on the compact disk pick-up technique has been discussed in recent years, in particular for surface roughness measurement in the submicron-micron range. In this article we present a thorough comparison between an optical laser stylus measurement system and a Talystep mechanical stylus profilometer. Sixteen surfaces having root mean square roughnesses from 0.002 μm to 3 μm for cut-off lengths <0.8 mm have been used in the study. Both bulk scattering (paper, white ceramic) and surface scattering (metal sheet) types of samples were included. Our study shows that the laser stylus exaggerates the surface profile, in particular on surfaces having laterally small but steep local slopes. For the paper surfaces the laser stylus data were on average off by a factor of two for a cut-off length of 0.68 mm.     

Comparison of optical and stylus methods for measurement of surface texture

Optical methods are increasingly used for measurement of surface texture, particularly for areal measurements where the optical methods are generally faster. A new Working Group under Technical Committee (TC) 213 in the International Organization for Standardization is addressing standardization issues for areal surface texture measurement and characterization and has formed a project team to address issues posed by the optical methods. In this paper, we review the different methods of measuring surface texture and describe a classification scheme for them. We highlight optical methods and describe some of their characteristics as well as compare surface-profiling results obtained from three optical methods with those obtained from stylus profiler instruments. For moderately rough surfaces (Ra?≈?500 nm), roughness measurements obtained with white light interferometric (WLI) microscopy, confocal microscopy, and the stylus method seem to provide close agreement on the same roughness samples. For surface roughness measurements in the 50 to 300 nm range of Ra, discrepancies between WLI and the stylus method are observed. In some cases the discrepancy is as large as about 75% of the value obtained with the stylus method. By contrast, the results for phase shifting interferometry over its expected range of application are in moderately good agreement with those of the stylus method.     

The influence of stylus flight on change of surface topography parameters

Theoretical and experimental work on stylus flight is described. The paper describes the development of a simulation model for assessing the magnitude of surface topography distortion by stylus flight. Experiments on the surfaces support the theoretical model, which predicts stylus flight. The measurements of different surface topographies (including surfaces after grinding, turning, honing, milling) were done using Talyscan 150 measuring instrument with four traversing speeds (0.5, 1, 2 and 3 mm/s). The results of theoretical considerations and experiments were compared. The effect of stylus flight on surface topography parameters of measured surfaces basing on experimental investigation was assessed. The tendency was found that slope decreased, decrease of amplitude parameters and increase of horizontal parameters took place, but these effects were different for various surface types. The simulation procedure assured good accuracy of surface topography parameters changes.Based on theoretical investigation, the effect of stylus flight and stylus tip radius on parameters of computer-generated profiles was predicted. The choice of traversing speed to different types of surfaces was done. The parameters of biggest changes caused by error in measurement due to stylus kinematics were selected.     

Roughness measurement with a laser scanning analyser

In the laser scanning analyser a laser beam is reflected from a rotating polygonal mirror so as to scan the workpiece surface at high speed, where it is again reflected into a photodetector which measures the reflected intensity. If the surface is rough, in addition to the specular reflectance the diffuse reflectance due to diffraction is measured as a function of the off-specular angle. In effect the system when used in this mode is a glossmeter which measures the optical properties of a section through the surface and is thus highly suitable for comparison with a stylus instrument. Experiments are described in which reflectance measurements on surfaces finished by various machining processes are compared with stylus roughness measurements. It is found that reflectance measurements are sensitive both to roughness and to the orientation of the lay. Reflectance measurements are found to vary as the average roughness and as the fourth power of the profile slope. There is no correlation with curvature and no evidence of the effect of longer surface wavelengths. There is some evidence that two different scattering mechanisms are involved. Possible applications of such a real-time non-contacting roughness measuring system are described.     

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.     

Methods of measuring and characterising the surface geometry of road stones

Methods of measuring and characterising random rough surfaces have always been of interest in the field of engineering. Measurement and analysis of finer scales of texture of a surface are now mainly effected by the use of a stylus instrument.Because of the finite radius of the tip of the stylus, this instrument cannot sense all the scales of texture on a surface. Evaluation of scales of texture finer than that sensed by the stylus instrument is of interest in many fields of engineering and in the prediction of hysteretic friction and of abrasion of rubber in particular. Two new methods which meet this demand to a great extent are described and their application is illustrated by actual measurements on stone surfaces. A scanning electron microscope is used in one method and an optical microscope in the other. Numerical methods of solution using electronic computers are adopted for the evaluation of texture parameters in both methods.     

磨合试验及磨合吸引子初探

为了表征磨合过程和磨合状态,掌握磨合过程中表面形貌的变化规律,在销-盘式试验机上对45#钢摩擦副进行了润滑条件下的磨合试验,用T1000型表面粗糙度测量仪和计算机数据采集系统测量磨合过程中的表面形貌和粗糙度值,并用分形方法对表面形貌进行分形表征和分形参数计算。研究表明:随着磨合过程的进行,摩擦副表面的粗糙度和分形参数逐渐变化,当达到磨合状态时,2个表面具有互适匹配的稳态参数值。因而从非线性科学原理出发,将磨合过程当作摩擦学系统的自组织过程,提出磨合吸引子的概念,并进行了初步的探讨。     

SPECKLE METHOD EVALUATION OF THE ROUGHNESS OF ELECTRODISCHARGE MACHINED SURFACES

Abstract

This paper describes the applicability of the speckle method to evaluate the roughness of surfaces produced by non-traditional machining processes such as EDM, ECM or USM, where material removal occurs randomly. The method is based on the digital correlation of two speckle images produced by interference phenomena arising when a coherent light beam is incident on a rough surface. The basic principle of the speckle pattern correlation is presented and the theoretical analysis based on a hypothesis concerning the morphology of the machined surface is reported. An experiment has been set-up in order to assess the feasibility of applying the speckle method to evaluate the roughness of machined surfaces. In the experimental tests, two speckle patterns produced from the same rough surface under two different illumination conditions have been correlated. The two different conditions have been obtained by varying the angle of incidence of coherent light on the surface being analysed. The roughness of electrodischarge machined surfaces, as measured by the speckle method, is found to be in good agreement with that of a stylus instrument.     

Relating contact conditions to abrasive wear

Damage caused by particles within rolling/sliding contacts can severely reduce the operational life of machinery such as roller bearings, gears and pumps.Abrasive wear of spherical roller thrust bearings has been studied using a stylus apparatus and scanning electron microscopy (SEM). Both a standard bearing and a bearing with rollers coated with metal mixed amorphous carbon (Me-C:H) were studied. The SEM measurements were performed systematically across the contact surfaces so that surfaces with gradually different contact situations could be examined. These measurements were compared to the measured wear depth of the components of the roller bearing. Also, the calculated contact conditions in terms of creep, contact size and surface separation have been related to the observed wear pattern at various locations.To attempt to understand the wear behaviour of the bearing with coated rollers, the coating as well as the material content of the surfaces were examined using both SEM and energy dispersive X-ray spectrometry (EDS). This revealed that the coating did not flake off but rather was scratched off.It is possible to link the abrasive wear behaviour to the contact conditions. It is crucial to understand this relationship when building a simulation model of abrasive wear.     

Measurement of coated abrasive surfaces

The measurement and characterisation of coated abrasive surfaces are reported. Four different techniques were used with the emphasis on simplicity, sensitivity and, most important, repeatability. As a process control technique stylus measurement with simple statistical analysis was found to satisfy most of the necessary requirements for “shop floor” use.     

Uncertainty analysis of roughness standard calibration using stylus instruments

A stylus instrument was characterized and calibrated, including a dynamic calibration of the probe. This stylus instrument was used to calibrate ten roughness standards for six surface roughness parameters. The sensitivity of each parameter of each standard to such measurement conditions as stylus geometry, measurement force, cut-off wavelength, and so forth was determined experimentally. These results were used for an uncertainty evaluation of each parameter for each roughness standard. It is shown that the manufacturers’ specification for the stylus instrument (2% uncertainty in roughness parameters) is approximately correct for the most commonly used samples and parameters, but the uncertainty may range from 0.03% (for sinusoidal profiles) to 100% (for very fine surfaces), depending upon the standard and parameter to be calibrated.     

Fractal roughness structures of precision-machined WC-Co- and Inconel 625-coated steel rods

Thermally sprayed WC-Co coatings on steel rods were machined by grinding and turning using diamond tools, and thermally sprayed Inconel 625 coatings on steel rods were machined by turning using various WC tools. Four of these samples were selected for surface characterization using a stylus roughness tester. The results show that precision-machined WC-Co and Inconel-625 surfaces can be identified as self-affine fractals in the stochastic sense within the correlation length. The root-mean-square roughness (R _q ) depends on the scale of cut-off length (=sampling length in this paper) as a power law. The R _q of the machined WC-Co surface was found to be dependent on the scale of cut-off length rather than the scale of evaluation length. The roughness exponent is a very useful parameter and can be used to predict the roughness value of the surfaces at any scale length, if the scale is within the correlation length and provided that one such value of a scale is known. It may be suitable to compare surfaces using roughness exponents, even if different cut-off lengths or scanning scales are used in the measurements to obtain roughness exponents.     

Classification of Tribological Surfaces Without Surface Parameters

Quantitative measures are obtained from images of tribological surfaces. Based on these data, decisions are made regarding manufacturing and maintenance processes, machine-condition monitoring and failure analysis of engineering components. These decisions are often guided by an automated pattern recognition system. Components of this system are: surface topography data acquisition, surface characterization, surface classification and performance evaluation. The characterization and classification of tribological surfaces are major challenges that make the development of a reliable pattern-recognition system difficult. The reasons are that: (i) tribological surfaces often exhibit a non-stationary and multiscale nature, while most surface characterization methods currently used work well with surface data exhibiting a stationary random process, (ii) changes in topography that might occur between the interacting surfaces usually need to be known in advance, and (iii) the selection of surface parameters that separate different classes of surfaces is usually time-consuming and cumbersome. Because of these difficulties, characterization and classification methods which do not use surface parameters have been developed. In the classification methods, a measure of dissimilarity (e.g., Euclidean distance) calculated between a surface to be classified and already classified surfaces was used, instead of surface parameters. The unclassified surface was assigned to the class (of classified surfaces) with the lowest value of dissimilarity measure. The suitability of different classifiers; such as k-nearest neighbour classifier, linear-discriminant-analysis based classifiers and different dissimilarity measures; for the classification of tribological surface topographies (without the need for surface parameters) is investigated in this paper. Recent developments in this area, i.e., a fractal measure and a hybrid fractal-wavelet measure, are also discussed. The most suitable method for the classification of tribological surfaces has been selected.