Two-process Surfaces Research Articles

Characterization of the Maximum Height of a Surface Texture.

Average surface height and maximum amplitude can affect surface functions. In the industry, these parameters can be obtained based on profile measurements. However, variability in maximum profile height is high. A more stable parameter can be obtained from the results of the areal surface topography measurements as the average value of the parallel profiles. The aim of this study is to establish this parameter directly from the result of the areal surface texture by correcting the maximum surface height to material ratios in the range of 0.13-99.87%. This method was tested by measuring 100 surface topographies with a stylus profilometer and a white light interferometer. It can be utilized correctly for deterministic textures and random one- and two-process surfaces for which the correlation between neighboring profile ordinates is not very high. In other cases, the method should be modified. Employing this method, the maximum profile amplitude Pt and parameters characterizing the average profile height Pq, Pa, and the ratios Pq/Pa and Pp/Pt describing the shape of the profile ordinate distribution can be correctly estimated. Pq/Pa and Pp/Pt were more stable than the kurtosis Pku and skewness Psk. The corrected maximum height S±3σ can be adopted as a parameter that characterizes the areal surface texture as more stable than the maximum surface height St. Pq/Pa and Pp/Pt were more steady than kurtosis Pku and skewness Psk.

Parametric Characterization of Machined Textured Surfaces

Surface topography in general is not easy to characterize due to a great number of different features that appear on it. It is still more challenging for machined textured surfaces that are of high functional significance for tribological purposes. For practical reasons, there is a need to describe such surfaces using only a small number of parameters. Which of them represent surface details the best is still an open issue. To find out which parameters can be the most suitable in that case, three groups of machined textured surfaces were prepared. They were plateau-honed cylinder surfaces made of gray cast iron, steel, and bronze surfaces with isolated dimples and steel surfaces after abrasive blasting followed by lapping. All of them were measured by means of a white light interferometer. Different parameters and relationships were evaluated and based on them correlation and regression analyses were used. The basic description contained statistically independent parameters that can be used in production control, while the wider description in scientific research. In general, parameters of random surfaces were more intercorrelated than those of surfaces with isolated dimples. As was found for the basic description of random two-process surfaces, five parameters were enough while description of textured surfaces with isolated oil pockets needed six. In wider, scientific description, regardless the surface type seven parameters contained the necessary information about the surface. It was also proved that a pair of parameters, the emptiness coefficient Sp/Sz and Sq/Sa, can describe the shape of the ordinate distribution of machined textured surfaces better than, for example, skewness Ssk and kurtosis Sku, commonly used for that purpose.

A new method of layered superposition reconstruction modeling on grinding-shot peening surfaces

Shot peening for semi-finished or finished parts is a high-performance precision manufacturing process, and the final micro-surface morphology has layered superposition features, that is, the original surface features and shot peening features coexist on the part surface. The existing layered superposition theory is based on the idea that the surface is superimposed under different baselines, but it cannot characterize the two-process surface where the characteristic baseline cannot be separated after shot peening. To solve this problem, a new layered surface superposition modeling method is proposed in this paper with the grinding-shot peening surface as the research object. In this method, the main texture features of the grinding surface are extracted by B-spline surface fitting, and the spatial distribution of craters in the shot peening surface is adjusted by this texture feature. The initial profile of the grinding-shot peening surface is constructed according to the Pawlus superposition theory, and its height parameters are adjusted by the time-frequency iteration method. In this paper, the modeling method is verified by the measured grinding-shot peening surfaces with a coverage of 100% and 200%. The results show that this method can not only ensure the uniformity of crater texture on the reconstructed surface, but also ensure that the maximum error of spatial parameters is less than 2%. Moreover, the symmetrical autocorrelation functions of the reconstructed surface are consistent with the characteristics of the measured surface.

Two-Process Random Textures: Measurement, Characterization, Modeling and Tribological Impact: A Review.

Two-process random textures seem to present better functional properties than one-process surfaces. There are many random two-process textures. Plateau-honed cylinder surfaces are the most popular example. Two-process surfaces are also created during the initial periods of life of machined elements. However, knowledge about two-process textures measurement, modeling, and behavior is low. Two-process surfaces are very sensitive to measurement errors. It is very difficult to model them. Special methods of their characterization were created. Their functional significance was studied in a small number of publications. In this paper, measurement, characterization, and modeling of two-process textures were presented. The functional impact of them was analyzed, the effects on contact mechanics and friction and wear were mainly studied. Finally, considerations of future challenges were addressed. The nature of two-process random textures should be taken into account during analyses of properties of machined elements. The plateau part decides about the asperity contact, and the valley portion governs the hydrodynamic lubrication.

Conditions of the Presence of Bimodal Amplitude Distribution of Two-Process Surfaces

Two-process surfaces are functionally important. They contain plateau and valley parts. They are created by superimpositions of two one-process textures of Gaussian probability height distributions. It is expected that the resulting two-process surface would have bimodal height probability distribution. However, typically two-process textures have unimodal ordinate distribution. The present authors developed limiting conditions of presence of bimodal ordinate distribution. These conditions depend on the material ratio at the plateau-to-valley transition (the Smq parameter), and on the ratio of heights of the plateau and valley surface parts (Spq/Svq). Generated stratified textures and measured two-process surfaces of cylinder liners were taken into consideration.

Characterization of the shape of height distribution of two-process profile

Two-process surfaces are more important than one-process topographies from the tribological point of view. However, most researchers understood the surface texture from a single-stratum viewpoint. Two-process topographies are more difficult to describe than one-process textures. The aim of this work was to select parameters characterizing the shape of the ordinate distribution of two-process profiles. A traditional description by the skewness Rsk and the kurtosis Rku used for one-process profiles is inadvisable for two-process profiles, since these parameters are strongly interrelated. Statistical dependencies among 17 non-dimensional parameters were analyzed on the basis of the linear coefficient of correlation. About 70 modeled and measured profiles were studied. The pair of ratios: Rp/Rz and Rq/Ra was selected. These parameters stable on typical surfaces are easy to calculate, the emptiness coefficient Rp/Rz is also tribologically important. It was also found that this pair of parameters could also describe the shape of the ordinate distribution of one-process profile. Especially the Rq/Ra ratio is a good alternative to the kurtosis Rku; these parameters are strongly inter-correlated, but the variation of the Rq/Ra ratio on typical surfaces is much lower.Sets of the following parameters: ypp–del and a–b from BETA distribution can also describe the shape of the ordinate distribution of two-process profiles.Extensions of the recommended parameters can be also used in the areal 3D analysis.

The Effect of Isotropic One-Process and Two-Process Surface Textures on the Contact of Flat Surfaces.

The contact of random modeled one- and two-process textures with smooth, flat surfaces is discussed in this paper. An elastic-plastic contact model was applied, assuming a distributed radius of summits. A one-process surface was characterized by the standard deviations of height and the correlation length; however, it also had a two-process texture by the standard deviations of the plateau and valley structures, the material ratio at the transition point, and the correlation lengths of the plateau and valley parts. It was found that the contact characteristics depended on the height and spatial properties of the surface texture. The plateau part governs the contact characteristics of two-process surfaces, while the effect of the valley surface portion is smaller. The plastic deformation leads to a smaller effect of the surface texture on the contact characteristics.

Edge-area form removal of two-process surfaces with valley excluding method approach

This paper analyses the influence of edge-area form removal on surface texture parameters (from ISO 25178 standard). The study focused on assessing the effect of near-edge dimples on surface texture analysis. Areal form removal was performed by means of digital filtering methods (regular Gaussian filter, robust Gaussian regression filter, median filter and/or other algorithms). For minimisation of dimples distortion the valley digital excluding method (VDEM) with standard deviation determination procedure was applied to measure plateau-honed cylinder liner surfaces (more than 20 measured and/or 20 with digitally added dimples surfaces were studied). The measurements were performed with a stylus instrument, Talyscan 150, or a white light interferometer, Talysurf CCI Lite. It was assumed that application of VDEMwith further application of proposed digital filtering algorithms caused the decrease in dimples distortion with accordance to regular Gaussian regression and/or robust Gaussian regression filtering methods. It was also found that the near-edge dimples were more vulnerable to distortion than the centre-located oil pockets.

The Effect of Valley Location in Two-Process Surface Topography Analysis

The Effect of Valley Location in Two-Process Surface Topography Analysis

The effect of sampling interval on the predictions of an asperity contact model of two-process surfaces

AbstractContact of random machined two-process steel textures with a smooth, flat steel surface is discussed in this paper. Two-process surfaces were machined by vapour blasting followed by lapping. An elastic-plastic contact model was applied, assuming distributed radius of asperities. Calculation procedures allowed the mean surface separation, contact pressure, and area fraction to be computed as functions of sampling intervals. Parameters characterizing the summits important in contact mechanics were calculated for different sampling intervals. Plasticity index of two-process textures was calculated using the modified procedure. It was found that the influence of sampling interval on normal contact depended on the rough surface ability to plastic deformation. The use of a traditional method of calculation overestimated the plasticity index. Peaks from plateau surface region governed contact characteristics of two-process surfaces.

Calculation of plasticity index of two-process surfaces

This paper presents the method of plasticity index calculation of isotropic two-process surfaces on the basis of index developed by Greenwood and Williamson for random surfaces of Gaussian ordinate distribution. This method was applied to computer generated isotropic two-process textures. The proposed plasticity index of two-process surface was compared with that of plateau surface and of the whole surface calculated by traditional manner. It was shown that plasticity index and generally the contact properties of two-process surfaces depended not only on plateau but also in a smaller degree on valley roughness. The method of estimation of summit radius of plateau surface from the analysis of two-process surface was presented too.

THE EFFECTS OF SURFACE ROUGHNESS ON FRICTION REDUCTION AS THE RESULT OF SURFACE TEXTURING BY ABRASIVE JET MACHINING

Various machining methods are currently used to obtain the best co-action of sliding surfaces. Application of two-process surfaces led to a decrease of frictional resistance. Textured surfaces after abrasive jest machining are practical examples of two-process topographies. The results of the application of textured discs with the same array of oil pockets of similar sizes, but with different roughness in areas free of dimples, are presented in this paper. It was determined that after this type of machining, the effect of the friction force decrease was caused by surface texturing.

Comparison of tribological behaviors of one-process and two-process steel surfaces in ball-on-disc tests

Wear tests were conducted using a ball-on-disc tester. In the experiment, 42CrMo4 steel disc of hardness 40 HRC was put in contact with 100Cr6 steel ball of 6.35 mm diameter. Hardness of ball was 60 HRC. Disc samples were created using vapor blasting and/or lapping techniques in order to obtain one-process and two-process isotropic surfaces. Dry and lubricated tests were carried out. During tests, the friction force was monitored as a function of time. Wear of discs and balls was measured after the test using white light interferometer. Under dry friction conditions, two batches of tests were performed. In order to decrease variation of the experimental results, during tests the wear debris was continuously removed from the disc surface. Tests under starved lubrication conditions were carried out using L-AN 46 oil. One drop of oil was supplied into the inlet side of the contact zone. It was shown that beneficial effects of two-process surfaces on tribological behavior of sliding pairs depended on the operating conditions.

Description of two-process surface topography

After two machining processes, a large number of surface topography measurements were made using Talyscan 150 stylus measuring equipment. The measured samples were divided into two groups. The first group contained two-process surfaces of random nature, while the second group used random-deterministic textures of random plateau parts and portions of deterministic valleys. For comparison, one-process surfaces were also analysed. Correlation and regression analysis was used to study the dependencies among surface texture parameters in 2D and 3D systems. As the result of this study, sets of parameters describing multi-process surface topography were obtained for two-process surfaces of random and of random-deterministic types.

Comparison of parameters describing stratified surface topography

There are a lot of methods of two-process surface topography description. Some parameters can be computed from material ratio graph. There are included in ISO standards. The methods described in ISO standards 13565-2 (Pk, Ppk, Pvk, Pmr1 and Pmr2) and 13565-3 (Pmq, Pvq and Pmq) are compared in this paper. Profiles with given values of Pmq, Pvq and Pmq parameters and wavelengths were modelled. For these profiles, material ratio curve and Pk, Ppk, Pvk, Pmr1 and Pmr2 parameters were calculated. As a result, dependencies among parameters from ISO 13565-3 and ISO 13565-2 standard were found.

Modification of Robust Filtering of Stratified Surface Topography

Abstract Various components of surface texture are identified, namely form, waviness and roughness. Separation of these components is done by digital filtering. Several problems exist during analysis of two-process surfaces. Therefore the Gaussian robust profile filtering technique was established and has been studied here. The computer generated 2D profiles and 3D surface topographies having triangular scratches as well as measured stratified surfaces were subjected to filtration. However even robust filter applications cause distortion of profiles having valleys wider than 100 μm. In order to minimize the distortion associated with wide and deep valleys, the robust filter should be modified. A special procedure was elaborated for minimizing distortion of roughness profiles caused by filtration. Application of this method to analyses of several profiles was presented. The difference between 1-D and 2-D filtering of surface topography using the same kind of filter was discussed. As a result we found that modification of a 2-D surface topography filter was not necessary.

The Study of the Tribological Properties of One-Process and Two-Process Textures after Vapour Blasting and Lapping Using Pin-on-Disc Tests

Wear tests were conducted using a pin-on-disc tester. In the experiment, a steel disc of hardness 40 HRC was put in contact with a steel pin of hardness 64 HRC with spherical end. Disc samples were prepared in order to obtain very similar values of the Sq parameter of one-process and two-process isotropic surfaces. Height of one–process disc surfaces, characterized by the Sq parameter was in the range 0.5 – 6 µm, but of two-process textures 1- 4.5 µm. Dry and lubricated tests, using different contact conditions were carried out. During testing, the friction force was monitored as a function of time. Wear of disc was measured after the test using white light interferometer. Tests under boundary lubrication condition were done using L-AN 46 oil.

Problems of surface topography with oil pockets analysis

The present paper presents method of description of two-process surfaces of random (load-bearing plateau structure) and deterministic (oil pockets) character on the basis of the probabilistic approach of material ratio curve. Examples of this method usage for textured surfaces are shown. The other application of material ratio curve for estimation of pit-area ratio of textured surfaces is discussed. Distortion of surface topography with oil pockets measurement by improper selection of areal reference plane is taken into consideration.

Tribological characteristics of one-process and two-process cylinder liner honed surfaces under reciprocating sliding conditions

This paper reports an experimental study of the effect of surface texture on cylinder liner wear. This research is important because the conjunction between piston rings and cylinder liner is one of the major sources to frictional losses in internal combustion engines. Experiments were conducted on a reciprocating tester. Specimens were cut from cylinder liners honed or plateau honed made of grey cast iron of hardness 218 HB. The honing operation was performed in order to obtain very similar values of the Sq parameter of one-process and two-process surfaces. In addition, one-process specimens characterised by different Sq parameter values were tested. Counter-specimens were made from chromium-coated steel C45. It was found that wear of two-process surfaces was lower than that of one-process surfaces characterized by the same Sq parameter. Linear wear of specimens was proportional to initial Sq parameter value. The effect of additional oil pockets created by the burnishing technique on cylinder liner wear was negligible.

Simulation of stratified surface topographies

In this paper various simulation methods of isotropic and anisotropic random surfaces of Gaussian ordinate distribution with Fast Fourier Transform are compared and the best of them are recommended. The method of numerical generation of arbitrarily oriented three-dimensional rough surfaces is presented. The procedure of digital simulation of two-process surface is introduced. An idea of the proposed method (and its possible modifications) is imposition of random surface of Gaussian ordinate distribution (second process) on the base surface (first process). The examples of using this method for the simulation of plateau honed cylinder surface, cylinder and piston skirt surfaces after “zero-wear” processes are given. In each case the matching criteria of real and simulated surface topographies are presented.