Pawel Pawlus

A study on the functional properties of honed cylinders surface during running-in

Abstract The hypothetical possibilities of effects of surface topography of honed cylinders on their wear resistance during running-in are presented in this paper. In order to confirm theoretical considerations, experimental investigations were conducted. The cylinders tested had various surface topographies as a result of honing by abrasive tools of different design. The results of wear measurements of the cylinders during running-in of an automotive gasoline engine are presented and analysed. Some connections between the initial cylinder surface topography and the selected engine operating parameters after running-in are also studied.

Change of cylinder surface topography in the initial stage of engine life

Abstract The paper is concerned with the change of cylinder liner surface topography in the early stage of engine life. The analysis of surface topographies of the great number of cylinders after engine operation was performed. Wear within the limit of original topography of cylinder liner was studied. Surface topographies of worn cylinders were compared with the microgeometry of the honed cylinders. The changes of the profile and waviness parameters were studied. The tendencies of the changes of autocorrelation and power spectral density functions during engine operation were also analysed. It is shown in the paper that the assessment of the amplitude parameter, preferably R 1 , is sufficient to monitor final wear on a cylinder bore provided that the general shape of the initial surface is known. In calculation profile cumulative distribution plot on a normal probability graph was used. Parameters of the worn surface were evaluated and compared with the values experimentally achieved. Prediction of the space between the deep valleys on the worn cylinder surface was also made. Since this paper is concerned mainly with the 2-D parameters, the new ‘zero-wear’ model was useful for three dimensional analysis. It can be also used for the profiles after running-in process of initially deterministic piston skirt surface.

Description of honed cylinders surface topography

Abstract A review of the existing methods describing the cylinder bore surface roughness was presented. An analysis of the surfaces of a large number of honed cylinders was performed. The relationship between conventional and proposed roughness parameters was studied using the principal components method as well as correlation and regression analysis. It follows from the analysis that one can fairly precisely describe a cylinder surface roughness profile using the following parameters: the emptiness coefficient R p / R t , the normalized rough core depth R k / R t , one of the height parameters ( R tm or R 3y are proposed) and the mean distance among deep valleys. A wider description includes also the real oil capacity and one of the horizontal parameters.

Tribological behaviours of textured surfaces under conformal and non-conformal starved lubricated contact conditions

Wear tests were carried out using a pin-on-disc tester. The sliding friction experiments were made using textured and untextured discs of 50 HRC hardness, under starved lubricated conditions in unidirectional sliding. Two batches of tests were done. The special construction was made to obtain conformal contact in the first type of tests. In the second test type in non-conformal initial point contact condition, a steel disc was put in contact with a ball from bearing steel of 3.175 mm radius. Two kinds of textured discs were tested; the oil pockets were positioned in spiral and radial arrays the number of oil pockets within friction track also varied. It was found that in conformal contact conditions the presence of dimples resulted in considerable decrease of the friction force compared to untextured samples. Surface texturing caused transition from point to conformal contact during test, which resulted in decrease of friction force but increase of wear of balls. The tribological behaviour of assembly with spiral dimples layout was better than that with radial array of oil pockets.

The Effect of Determining Topography Parameters on Analyzing Elastic Contact Between Isotropic Rough Surfaces

Elastic contact between two computer-generated isotropic rough surfaces is studied. First the surface topography parameters, including the asperity density, mean summit radius, and standard deviation of asperity heights of the equivalent rough surface, are determined using an 8-nearest neighbor summit identification scheme. Second, many cross-sections of the equivalent rough surface are traced and their individual topography parameters are determined from their corresponding spectral moments. The topography parameters are also obtained from the average spectral moments of all cross-sections. The asperity density is found to be the main difference between the summit identification scheme and the spectral moments method. The contact parameters, such as the number of contacting asperities, real area of contact, and contact load for any given separation between the equivalent rough surface and a rigid flat, are calculated by summing the contributions of all the contacting asperities using the summit identification model. These contact parameters are also obtained with the Greenwood-Williamson (GW) model using the topography parameters from each individual cross-section and from the average spectral moments of all crosssections. Three different surfaces characterized by a different autocorrelation length, and three different sampling intervals were used to study how the method to determine topography parameters affects the resulting contact parameters.

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.

The effect of random surface topography height on fretting in dry gross slip conditions

This paper describes the tribological effect of surface topography on friction and wear under dry fretting regime of a point contact. Experiments were made using SRV4 ball-on-disc tribotester. 100Cr6 sphere of 64 HRC (Rockwell method, scale C) hardness co-acted with a disc made of 42CrMo4 steel with hardness of 40 HRC. Fretting tests were carried out under dry gross slip conditions. The diameter of ball was 10 mm. During tests, normal load was kept constant at P = 50 N within the contact. Duration of each test was 15 min. Tests were performed in 26 ℃ temperature in the chamber at 39–43% of relative humidity. Displacement amplitude was 0.1 mm (stroke was 0.2 mm) with frequency of 20 Hz. The disc samples had different textures obtained after one process (grinding, vapor blasting, or polishing) and two process (grinding or vapor blasting followed by lapping). During tests, the friction force was monitored as a function of time. Wear of disks and balls was measured after the test using white light interferometer. Surface roughness height of discs, determined by the Sq parameter was in the range: 0.01–4.5 µm. It was found that initial surface roughness height had a significant influence on friction and wear in dry gross slip conditions. For rougher disc surfaces, the friction force in initial test stage and wear of co-acting parts were higher.

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.

Effects of metallurgical structure and cylinder surface topography on the wear of piston ring-cylinder assemblies under artificially increased dustiness conditions

Abstract The aim of this work is to determine the effects of metallurgical structure and cylinder surface topography on the abrasive wear of piston-piston ring assemblies. The cylinders tested were made of grey cast irons of different structures. They had also various surface topographies as a result of honing by abrasive tools. These cylinders were tested during automotive gasoline engine operation under artificially increased dusty conditions. Similar investigations were carried out using a tribotest machine. After the engine tests, it is evident that cylinders of pearlitic-ferritic structure show the best abrasive wear resistance. This result can be explained by the possibility that quartz particles can be embedded in the comparatively big graphite flakes located within a soft ferrite matrix. The effect of the presence of phosphorus eutectic on the wear of piston ring-cylinder assemblies in comparison to the pearlitic structure is negligible. However, the influence of the surface topography of grey cast iron cylinders on abrasive wear during engine operation under increased dusty conditions is substantial.

Variability of areal surface topography parameters due to the change in surface orientation to measurement direction

Several random surface topographies were analyzed. They were measured by optical (Talysurf CCI Lite) method. They represent one- and two-process anisotropic and isotropic surfaces. These surfaces were rotated of ± 1° and ± 2° by two methods: on the plane table (before measurement) and virtually (after measurement) using the software TalyMap Gold. After each measurement or surface rotation, each surface was levelled. Then, the forms were removed using polynomial of the 3rd degree. Areal surface topography parameters from standard ISO 25178 were calculated. The relative deviations of parameters were determined. The tendency of surface topography changes characteristic to various surface types were analyzed. It was found that change in orientation to the measurement direction of both isotropic and anisotropic surfaces could be substantial source of the measurement uncertainty. Functional parameter Smr and also feature parameters Sda, Sha, Sdv, Shv, and Spd are the mostly sensitive on measurement orientation. Statistical amplitude parameters Sa and Sq are more stable than parameters describing maximum surface height, like Sz, Sp, and Sv. The effect of surface orientation to measurement direction on values of functional parameters from V group was small. It was shown that changes of Sdq, Sdr, and Spc parameters describing hybrid properties due to surface rotation before measurement were smaller than those caused by change in surface orientation after measurement.