Effect of triangular oil pockets on friction reduction

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.

TECHNOLOGY OF COMBINED ELECTROMECHANICAL TREATMENT WITH PROFILE ROLLING

The technology of combined electromechanical treatment with profile rolling is presented, which is a combination of electromechanical treatment and surface plastic deformation, which allows to create on the surface directed regular microrelief. The proposed technology is tested during processing of parts of multipurpose tracked and wheeled machines operating under difficult loading conditions, signalternating dynamic loads, often with limited lubricant or presence of abrasive in its composition. Reasonable selection of relief (pattern) of treated surface makes it possible to maximize retention of lubricating material in zone of tribocontact, as well as to increase wear resistance of parts and to create residual compression stresses in surface layer. The mechanical properties of the surface layer of the sample with a strengthened geometric pattern by changing the microhardness of the smoothed surface and oil pockets (channels) obtained by surface plastic deformation were examined. Electromechanical treatment by rolling the profile makes it possible to create on the surface a strengthened surface layer with naturally varying parameters with the specified regular micro-relief including oil pockets (channels) and reinforced tracks, at the same time considerable increase of wear resistance of triboscreating is provided.

Controlling the Properties of the Surface Layers of Parts by Forming Regular Micro-Reliefs

The paper focuses on a combined processing method developed to control the properties of the surface layer of parts. A regular micro-relief was obtained on the surface, with oil pockets to hold the lubricant during the friction process. Profilograms of samples processed by different modes and a model of the process of obtaining regular micro-relief are presented. We carried out comparative endurance tests of the samples processed by various methods. For the study the samples of steel 5140 (41Cr4) were selected. The results obtained allow us to recommend combined processing for the parts operating under conditions of intense friction with lubrication.

CONTROLLING THE PROPERTIES OF THE SURFACE LAYERS OF PARTS BY COMBINED PROCESSING

The paper focuses on a combined processing method developed to control the properties of the surface layer of parts. A regular micro-relief was obtained on the surface, with oil pockets to hold the lubricant during the friction process. Profilograms of samples processed by different modes and a model of the process of obtaining regular micro-relief are presented. We carried out comparative endurance tests of the samples processed by various methods. For the study the samples of steel SA-240 TP 310S were selected. The results obtained allow us to recommend combined processing for the parts operating under conditions of intense friction with lubrication.

Analysis of dimples distribution in surface topography measurements

In this paper the influence of distribution of oil pockets on areal form removal in surface topography measurement was taken into consideration. Surface topography of plateau-honed cylinder liners with burnished oil pockets was analyzed. The effect of dimples distribution on surface topography parameters (from ISO 25178 standard) after form removal by commonly used algorithms (cylinder fitted by the least square method, polynomials of nth degree, robust Gaussian filter) and/or other procedures (plateau-part filtering method, digital extraction of valleys) was taken into account.

THE EFFECT OF SURFACE TEXTURING ON THE FRICTIONAL RESISTANCE OF STEEL-BRONZE ASSEMBLY IN LUBRICATED SLIDING

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 EFFECT OF OIL POCKET ARRAYS ON FRICTION COEFFICIENT

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.

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.