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The purpose of this work is to study the effect of oil pocket shape and density on friction in reciprocating sliding. The experiments were conducted in reciprocating motion under starved lubrication conditions. Tribological tests were performed using an Optimol SRV5 tribotester. The frictional pair consisted of two discs of 42CrMo4 steel. One disc was laser textured. The oil pockets had circular and sandglass shapes. Disc samples of various texture shapes were characterized by the same pit-area ratios. The operating parameters were the same for all friction pairs. In most cases, surface texturing led to reductions in friction force value and scatter. For both dimple shapes, the best tribological properties were achieved for oil pocket density of 9%. When discs with circular dimples were tested, the highest resistance to motion was received for the highest pit-area ratio of 9%. On the contrary, the worst tribological performance of discs with sandglass-shaped oil pockets of sandglass shape were obtained for the largest oil pocket density of 22%.

The effect of the apex angle of triangular oil pockets created on a disc surface on friction was studied. Experiments were carried out using an Optimol SRV5 tribotester equipped with a pin-on-disc module under unidirectional lubricated sliding. Both the sample and counter sample was made of steel of 45 Hardness Rockwell C (HRC) hardness. Only 1 ml of oil was put to the inlet side of the contact area at the beginning of each test. All textured surfaces had the same pit-area ratio and an average depth of dimples. Oil pockets were positioned in the spiral array. It was found that the effect of the apex angle of triangular dimples on friction reduction was important. When the normal load was lower, the smallest coefficient of friction was achieved for the sliding pair with a disc apex angle of 60°. Under a larger normal load, a higher apex angle corresponded to a higher coefficient of friction.

The constant development of environmental protection causes the necessity to increase the efficiency of machines. By increasing the efficiency of machines, energy losses can be limited, leading to lower energy consumption. Friction reduction leads to an increase in efficiency and a decrease in wear. In this paper, selected surface texturing methods, such as burnishing and abrasive jet machining, with their limitations are presented. Thanks to those processes, various surface textures can be obtained. Examples of applications of these methods for friction and wear reduction are shown.

Surface texturing is an option of surface engineering resulting in reduction of friction due to the creation of isolated dimples or grooves on sliding surfaces. The purpose of this work is to find the effect of the groove bottom profiles on the reduction of the friction force. Investigations were conducted using an Optimol SRV5 tribotester equipped with a pin-on-disc module. A disc made of 42CrMo4 steel, with a 100 mm diameter acted as a sample. A counter-sample was made of the same material, however, its diameter was 20 mm. The sliding conditions were selected to be similar to those of a sliding crankpin bearing pad operating in a high-performance internal combustion engine. Surface texturing was found to be beneficial for a reduction in the friction coefficient up to 55% in comparison to the untextured disc. Tribological performances of discs with spiral groove patterns were better than those with a radial layout. In most cases the convergent profile of the groove bottom was superior to the dam shape.

This paper presents the results of the tribological experiments conducted using an oscillating wear tester under lubricated conditions. Specimen from piston ring slid against counter-specimen from cylinder liner. Various surface textures of cylinder liners resulted from honing and/or plateau honing. Tests were carried out for two normal loads of 100 and 300 N at a temperature of 80 °C, the stroke was 3 mm, the frequency was 10 Hz. Each experiment was divided into four time intervals. During breaks between the particular parts of the test, the surface topography of cylinder liners was measured by a white light interferometer. It was found that an increase in the normal load led to an increase in changes of the liner surface textures.

A reduction in frictional loss is an important aspect of efficiency in high-performance internal combustion engines. This can be achieved by the well-designed surface texturing of the cylinder bore, which can reduce friction at the ring/bore interface. In this work, dimples were created using plastic deformation on the cylinder surfaces of high-performance motorcycle engines. Prior to texturing, these cylinders had Nikasil coating. One cylinder was subjected to the deposition of DLC coating and then surface texturing. The results of the functional performance of internal combustion engines with textured cylinder surfaces were compared to untextured ones. The engine performance was analysed in terms of maximum power and maximum torque output. The results showed that cylinder surface texturing improved the functional properties of internal combustion engines. The maximum power increased by up to 5.8%. Best performance was achieved for internal combustion engines with textured cylinders and DLC coating. Such surface modification allows the powering of the motorbike with higher maximum speed and provides better vehicle dynamics at high speeds.

Tests were carried out using a pin-on-disc tester under starved lubrication conditions. To achieve a conformal contact, a special construction was used with an adjustable counter sample. Textured surfaces with two dimple patterns (spiral an radial) and four shapes (circle, oval, triangle, and chevron) were tested. The contact area was lubricated with L-AN-46 oil. Before the tests, surface topographies of the discs were measured by a white light interferometer Talysurf CCI Lite. Tests showed that, in starved lubrication conditions, oil pocket shape and pattern affected the friction force.

The experiments were carried out using a block-on-ring tester. The block samples made from bronze CuSn10P of 138 HB hardness were burnished to obtain surfaces with circular oil pockets. Rings were made from 42CrMo4 steel of hardness 40 HRC. Friction tests were conducted at a constant normal load of 900 N. Tests were carried out at increasing sliding speeds of the range 0.08 – 0.82 m/s, starting from the lowest speed. The every speed was maintained for two minutes. The tested assembly was inserted in the reservoir of mineral oil L-AN 46. It was found that the dimple presence on block surface reduced the friction coefficient substantially compared to non-textured turned surfaces. The area density of dimples smaller than 15% (particularly 4.5% and 6%) was beneficial.

The experiments were carried out using an Optimol SRV5 oscillating wear tester under lubrication. Specimens were cut from gray cast iron cylinder liners honed and/or plateau honed with diamond or ceramic stones. Counter-specimens were cut from chromium-coated compression ring. Short time tests of 30 min duration were conducted at a temperature of −20 °C, with a stroke of 3 mm. In addition, for a few sliding assemblies, durations of tests at the low temperature were extended to 24 h. For comparison, similar tests for a smaller number of sliding pairs were carried out at a temperature of 80 °C. Before and after tests cylinder liner surface topographies were measured by a white light interferometer Talysurf CCI Lite. It was found that the changes of liner height and frictional resistance at the low temperature were smaller from those tested at the elevated temperature. Two-process textures tested at the low temperature led to a smaller final coefficient of friction, compared to one-process surfaces; opposed results were obtained at the high temperature.

Tribological tests were conducted using a pin-on-disc tester in unidirectional sliding under starved lubrication. A specimen of 25.4 mm diameter with a hardness of 50 HRC and a counter-specimen of 5 mm diameter with a hardness of 40 HRC were made from 42CrMo4 steel. Specimens were textured by abrasive jet machining. An average depth of oil pockets was 10 μm, a mean diameter was 0.5 mm and a pit-area ratio was 17%. Tribological behavior of sliding pairs with textured and untextured (polished) discs were compared. Friction tests were conducted at normal loads of 10, 20, 30, 40, 50 and 60 N increased in a stepwise manner, a sliding speed was set to 0.6 m/s. Friction behaviors were evaluated at room temperature and at elevated temperature (80 °C). The tested assemblies were lubricated by different oils. Surface texturing always led to beneficial performance of sliding pairs. However the best effect of surface texturing was observed at smaller loads and elevated temperature. Under these conditions, the effect of kind of oil on tribological behavior was negligible.

Experiments were carried out using a pin-on-disc tester in conformal contact starved lubrication and unidirectional sliding with constant normal load of 20 N and sliding speed of 0.8 m/s. Different combinations of co-acted samples were studied: textured specimen and untextured counter-specimen, both samples textured and untextured. Samples with the following densities of dimples were tested: 2.25%, 5%, 9%, 14% and 20.25%. The best tribological performance was achieved for both surfaces textured with the smallest pit-area ratio. For large area densities tribological behaviors of sliding pairs with one sample textured were better than those with both samples textured.

The experiments were conducted using an oscillating wear tester under lubricated conditions. Specimens were cut from cylinder liners made of gray cast iron. As the results of honing and/or plateau honing various surface textures of cylinder liners were obtained. Counter-specimens were cut from chromium-coated compression ring. Short time tests were carried out at temperature of 80 °C, stroke was 3 mm. The other operating parameters, like normal load and frequency varied. Before and after tests surface topographies of liners were measured by a white light interferometer. It was found that one-process textures led to smaller coefficients of friction than two-process topographies for test duration of 0.5 h. The frictional resistance increased when honing angle increased.

Experiments were carried out using pin-on-disc tester in conformal lubricated contact conditions for different normal loads. Surface texturing was done using abrasive jet machining with the application of laser cut mask. In order to eliminate the effect of different input variables in all the experiments, pit-area ratio and sizes of oil pockets were very similar. Five types of oil pocket arrays were tested: radial, concentric, spiral, of a square arrangement, and of a random arrangement for 5% and 17% of pit-area ratio. Different dimple diameters caused various oil pocket densities. The experiments were also made for untextured polished discs. During tests, the friction force was monitored as a function of time. Before and after tests, disc surface topography was measured using a white light interferometer Talysurf CCI Lite. The beneficial effect of surface texturing was obtained for spiral arrays of dimples on disc surface. The presence of a radial array of oil pockets resulted in the worst tribological properties of tribological assemblies containing textured discs.

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.

Investigations were performed to study the effect of graphite surface texturing on the friction coefficient reduction of graphite-steel sliding pair in dry flat contact. Friction tests were carried out using an Optimol SRV 5 tester, equipped with a rotation pin-on-disc module. Graphite discs of 100 mm diameter and 10 mm thickness were tested. Surface texturing was made with abrasive jet machining. Counter samples made of 42CrMo4 steel were polished. Four types of textured surfaces were tested. The tests revealed that a direction of the converging bottom texture had a substantial effect on the scatter of the friction coefficient. High stability and low value of the coefficient of friction were achieved for the disc texture with bottom steps parallel to the arm of the chevron. Low friction forces were obtained for the angle between arms of 120°.

Experiments were carried out using a pin-on-disc tribological tester in a flat-on-flat configuration in unidirectional sliding. Both counterparts were made from steel with 50 HRC hardness. The normal load was 20 N, the sliding speed was 0.4 m/s, the number of revolutions was 10,000. Before each test, one drop of L-AN-46 oil (0.08 ml) was supplied to the inlet side of the contact zone. The discs were textured using abrasive jet machining. Tribological effects of eight chevron-based textures were compared with that of the surface having circular oil pockets. All textures had the same pit-area ratios and depths. The untextured assembly was also tested for comparison. It was found that chevron-shaped dimples were sensitive to their angular orientation to the direction of sliding. The best tribological performances were achieved for chevrons inclined to the outer sides of the rotating discs.

The aim of this work is to compare various methods of oil capacity calculation for surfaces containing cavities. In reference method, oil capacity was computed by summation of volumes contained in all the holes of measured surface using TalyMap software. Oil retention volume was calculated also on the basis of material ratio curve using the Svk and Sr2 parameters from Sk parameters group (areal extension of ISO 13565-2 standard). The second and third procedures were developed on the basis of rotation of material ratio curve axes. The fourth method is based on determination of point of maximum curvature of the normalized material ratio curve. It was found that in the most cases it was possible to obtain correct values of oil capacity using the Sk parameter family. However when the slope of material ratio curve in its middle part (core roughness) is small or high, the errors of oil capacity estimation may be large; up to 80%. In those cases the other methods gave better results–usually errors of oil capacity estimation were not higher than 10%; average deviations were about 5%. Determination of transition point between valleys and plateau regions as the point of maximum curvature of the normalized material ratio is recommended. The new proposals of oil capacity calculation can be used also for surfaces with cross-hatched pattern.

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.

This paper presents method of oil pockets creation by the burnishing (embossing) technique. Steel and ceramic forming elements were used to modify sliding surfaces. This technique allows to obtain dimples in a wide dimensional range and regular arrangement. Dimples array on machined surface depends on the forming element shape and many machining factors. Examples of textured cylinder liners surface topographies are shown. The computer software for visualization of oil pockets array on machined surface is presented in this paper.

Experiments were carried out on a reciprocating tester. The lubricant was supplied into the inlet side of the contact zone. The construction of tribological tester allows to measure the friction force between specimen and counter-specimen. Tribological behaviours of cylinder liners with and without oil pockets were compared. Specimens were cut from plateau honed cylinder liners made of grey cast iron. Counter-specimens were cut from grey cast iron piston rings. A special tool acted as a hammer to form additional dimples on the liner surfaces. The area density of oil pockets was about 13%. Specimen surfaces had dimples with average depths about 5 μm and diameters in the range 0.15–0.2 mm. Two batches of tribological tests were carried out, in regimes of full and starved lubrication. Friction tests were conducted at three mean sliding speeds: 0.44, 0.66 and 0.88 m/s. Experiments were performed with normal load in the range 50–300 N, starting from the lowest load. Normal load increased in a stepwise manner after 2 min at each load, until the maximum load was reached. Areal surface topographies of specimens and counter-specimens were measured before and after two batches of tests by white light interferometer.

The tribosystem consisted of a stationary block pressed at a required load P against a ring rotating at a defined speed. Sliding was unidirectional. Block samples, made from bronze CuSn10P with 138-HB hardness, were modified using a burnishing technique to obtain surfaces with circular oil pockets. Rings were made from 42CrMo4 steel, of hardness 40 HRC, which was obtained after heat treatment. Tests were conducted at a constant speed of 0.27 m/s. Before the test, an oil drop was added to lubricate sliding surfaces. A seizure resistance test was carried out at constant normal load of 2700 N. Tribotests were automatically stopped when the coefficient of friction reached a limit value 0.15. Selected textured samples clearly exhibited a lifetime longer than untextured reference specimens.

The fundamental aim of the present research is to study the effect of dimple shape and area density on abrasive wear in lubricated sliding. The other aims are to recommend a method of obtaining the local linear wear of a textured ring on the basis of profilometric measurement and to analyse the changes in the surface topography of this ring with selection of parameters that could monitor the “zero-wear” process. The experiments were conducted on a block-on ring tester. The stationary block made from cast iron of 50 HRC hardness was ground. The rotated ground ring was made from 42CrMO4 steel of 32 HRC hardness. The rings were modified by a burnishing technique in order to obtain surfaces with oil pockets. Oil pockets of spherical and of drop shape were tested. The pit-area ratios were in the range: 7.5–20%. The tested assembly was lubricated by oil L-AN 46. Because of the great hardness of the co-acting parts the wear resistance test was carried out under artificially increased dustiness conditions. The dust consists mainly of SiO2 and Al2O3 particles. Measurement of local microscopic ring wear was made using a three-dimensional scanning instrument. The tendencies of ring surface topography changes during wear were analysed. Various methods of obtaining the local wear value during a low wear process were proposed and compared. We found that a spherical shape of dimples was superior to a drop shape with regard to wear resistance of steel rings.

A review of literature about the effect of oil pockets on improvement of sliding elements tribological performance as well as about the changes of surface topography during “zero-wear” process is shown. The paper presents also the results of experimental investigations done in the Department of Manufacturing Processes and Production Organisation of Rzeszow University of Technology, connected with the creation of oil pockets on sliding surfaces. In order to simulate a deterministic surface a program for the visualisation of pits was written. The procedures for assessment of the oil pocket size of specific shape and oil pockets coverage are presented. The tendencies of changes of surface topography and oil pockets dimensions during “zero-wear” process are also described.

The paper reviews the current efforts being made on surface texturing and presents a literature analysis about running-in process of sliding components. The wear resistance test is described. The results of experimental investigations of the oil pockets (created by burnishing technique) existence effects on tribological performance of sliding elements under mixed lubrication conditions are presented. The block made from bronze contacted the steel ring. The wear intensity, friction coefficient and roughness were measured during the tests. Surface texturing of the block surface (area density between 20 and 26%) resulted in significant improvement in wear resistance in comparison to a system with a turned block. The paper deals also with the commonly observed behavior involving running-in followed by steady wear. We compared total wear rate of sliding elements and coefficient of friction in initial wear period with those during steady-state. It was found that running-in affected steady wear. When textured surface topography was removed, the equilibrium roughness was reached independently of the initial roughness.

The experiments were carried out using a block-on-ring tester. The stationary blocks were modified by a burnishing technique in order to obtain surfaces with oil pockets of spherical shape. The area density of oil pockets varied in order to explore their effect on wear resistance and wear intensity. Specimen surfaces had dimples with depths 45–60 μm and diameters 1–1.2 mm. The area density of oil pockets Sp was in the range 4–20%. The block samples were made from bronze B101 (CuSn10P) of 138 HB hardness. The rotated rings were made from 42CrMo4 steel, hardness of 40 HRC obtained after heat treatment. The tested assembly was lubricated by mineral oil L-AN 46. The experiment was carried out under artificially increased dustiness conditions. The dust added to oil consists mainly of SiO2 (74%) and Al2O3 (15%) particles. During the test friction force and temperature of block sample were registered. The tendencies of block surface topography changes during wear were analysed. It was found that sliding pairs with textured specimens were not superior to a system with a turned block with regard to abrasive wear resistance.

The last decade has seen a significant and increased interest in surface texturing technologies esulting in improving the overall tribological properties of mechanical components. Several techniques could be used to modify the surface topography with laser surface texturing becoming most popular recently. In this investigation, rig experiments have been performed on plain and textured-surface journal bearings with an aspect ratio of 1.1 under a variety of loads and speeds. Percussive burnishing (embossing) was used to create the dimples on the internal surfaces of the test bearings. The dimples have a spherical shape with a diameter of 1 mm and a depth of 60 micrometers. Pit-area ratio was in the range 5-20% of the total bearings surfaces. The effects of surface-texturing and dimple density on the bearing steady-state characteristics and dynamic coefficients are analyzed and discussed in this paper. Copyright © 2011 by ASME., ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011, 6 June 2011 through 10 June 2011, Vancouver, BC