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The purpose of this paper is to investigate the influence of fluor‐oligomeric coat on the mechanical properties of steel surface, as well as the chemical interaction of fluor‐oligomeric films with surface and theoretical‐phenomenological interpretation of structural processes in friction surface.

Four groups of specimens were studied: two groups of specimens without any wear tests – initial steel specimen as control version and a specimen which was ten times coated by fluor‐oligomer, and two groups of specimens, which were tribologically tested for one million cycles – without any coating and coated specimens. Closed kinematical profile scheme roller‐roller of steel 45 was chosen for tribological tests. Wear of friction surface after those tests was investigated. The interaction between fluor‐oligomer and iron was studied by means of Mössbauer spectroscopy. The micro‐hardness of matrix was also measured.

Affecting the surface of steel by the fluor‐oligomer and friction produces the complicated processes of carbide decay and formation occur. The mechanisms are found which are related to the weakening of chemical bond in steel during the absorption, to the generation of microscopic ruptures, to the decrease (30‐50 per cent) of the amount of carbides and its increase during the friction (up to 50 per cent). The mechanical effect which causes the regeneration of carbides during friction is revealed. Tribological efficiency of fluor‐oligomeric coats (five times lower wear of coated specimens) is explained by the balance of three processes – the softening of matrix during adsorption, the detention of dislocations, and formation of hard particles in the matrix.

The complex mechanism of the increase of wear resistance is explained by filling of ductile matrix with carbide particles.

The possibilities increasing the wear resistance of friction pair radial lip seal/shaft were tested using fluoroligomeric materials and selective transfer technologies. Measurements of friction moment, temperature in contact spot and wear of friction surfaces show that fluoroligomeric coat and selective transfer technologies (metallpolymeric oil additives and NABA‐coat on shaft) can considerably decrease the friction losses and increase the wear resistance of friction pair. The microscopic analysis of surfaces shows that using tribotechnical materials in contact spot of friction surfaces forms virtually different structures which can explain the different efficiency mechanisms of the mentioned materials. These tests show that in friction pair radial lip seal/shaft the tribomaterials could be used which create selective transfer effect and have regenerating properties.

The purpose of this paper is to conduct research on the possibility of improving the tribological and utilization properties of lard and rapeseed oil bio-based greases by mixing it with ethanol and selection of thickener and modification with special biological additives.

Rapeseed oil- and lard-based greases with sodium and lithium soap thickeners were mixed with either water or ethanol and modified with a special biological anti-wear additive. Tribological properties of modified lubricants evaluated on a four-ball machine.

Rapeseed oil- and lard-based greases suspended in ethanol and modified with bio-additive have the same wear resistance as the industrial non-biological lubrication grease and much higher wear resistance as bio-based reference grease. The tribological efficiency of the additives is higher in greases of rapeseed oil and less efficient in lard-based greases. Oxidation and wear tests show that investigated bio-based greases have comparatively stable tribological properties also after their aging. Modified greases have sufficient consistence according penetration measurements and high thermal resistance according drop-point temperature measurements. All produced experimental greases pass within the category of the easily degradable materials.

The greases mixed with the ethanol make possible to form more homogeneous and stable grease mixture. Modified bio-based greases have significantly higher wear resistance as bio-based reference grease, their lubrication properties are stable also after the aging and are categorized as easily degradable materials.

The purpose of this paper is to report on the tribological properties of beef tallow grease and improvements therein through modification with special processing, polymeric compounds and additives.

Pure original beef tallow grease was used as a biological lubricating grease reference material for the tribological research. Beef tallow was modified and synthesized by adding special biological anti-oxidant additives, LZ anti-wear additives, waste polyethylene terephthalate (PET) polymer compounds and thermally processed graphite.

Rheometric measurements indicate that the beef tallow grease modification technology used in this study enables control of the synthesis process to produce lubricants with the required microstructure. Investigation results of the tribological properties of differently modified greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The grease compound with thermally processed graphite has good tribological properties at 300 N load levels. The critical load level of lubricating greases could be significantly increased through the use of anti-wear additives and thermally processed graphite.

Investigation results of the tribological properties of differently modified beef tallow greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The critical load level of lubricating beef tallow greases could be significantly increased using anti-wear additives and thermally processed graphite.

The purpose of this paper is to investigate the possibility of using the iron nanoparticles and iron nanoparticles coated with copper layer as additives to base oils.

Fe and Fe+Cu nanoparticles were synthesized by a reduction modification method and added to mineral oil. The size and structure of prepared nanoparticles were characterized by SEM, TEM, XRF, AAS and XRD analysis. Tribological properties of modified lubricants were evaluated on a four‐ball machine in a model of sliding friction pairs.

Spectral and microscopy analysis evidently displayed the formation of Fe and Fe+Cu nanoparticles in suspensions of colloidal solutions and oil. The size of formed nanoparticles was in 15‐50 nm range. Tribological experiments show good lubricating properties of oils modified with Fe and Fe+Cu nanoparticles: higher wear resistance (55 per cent and 46 per cent accordingly) and lower friction coefficient (30 per cent and 26 per cent accordingly). The tests show that nanoparticles provide decreasing tendency of friction torque during the operation of friction pair.

The paper demonstrates that iron nanoparticles and iron nanoparticles coated with copper layer, not only reduce the wear and friction decrease of friction pairs, but possibly also can create layer in oil which separates two friction surfaces and have some self‐organisation properties.

The aim of this paper is to investigate the regularities and longevity of the recovering without takedown of the friction pairs in internal combustion engines using the lubricants with metal cladding materials (MCM).

Recovering of friction pairs of internal combustion engines by MCM was investigated using field experiments. Four automobiles were investigated. The wear of those details was evaluated according to the compression in the cylinders. The influence of MCM on the amount of toxic materials (carbon monoxide and hydrocarbons) in the exhaust gas was evaluated after measurements with a gas analyser.

Using MCM can recover on average 60 per cent of lost compression ΔP_m. MCM decreases compression dispersion among separate cylinders of the engine. Compression of recovered engine cylinders decreases according to logarithmic function. Increment of cylinders' compression ΔP_d decreased on average 40‐50 per cent after 10,000 km car run. The recovering of the details of a cylinder‐piston group with MCM decreases the emission of toxic exhaust gas to the environment.

No laboratory investigations of MCM regeneration of friction pairs were performed which could evaluate the influence of different factors on the regeneration quality.

Investigations on the use of MCM for recovering the cylinder‐piston details of engines show the expedience in using such materials during periodic technical service of engines when the lubricants are changed.

Investigations of regenerating engines by MCM using field experiments were performed for the first time.

This paper aims to present a method to measure the rolling friction coefficient in an easy and fast way. The aim is also to measure the rolling friction coefficient between a small steel ball and a cylindrical aluminum surface.

An analytical model of the tribosystem of a freely rolling ball and a cylindrical surface is established. The rolling friction coefficient is evaluated from images recorded by a high-speed camera. The coefficient between a 1.58-mm diameter steel ball and a cylindrical aluminum surface is measured. A background subtraction algorithm is used to determine the position of the small steel ball.

The angular positions of the ball are predicted using the analytical model, and a good agreement is found between the experimental and theoretical results.

An optical method for evaluating the rolling friction coefficient is presented, and the value of this coefficient between a small steel ball and a cylindrical aluminum surface is evaluated.

The optimal performance of the machinery is based on lubricants that require frequent monitoring and the analysis of characteristics such as chemical content, contamination and viscosity. The application of nanoparticles dispersed lubricant in tribology has received remarkable attention in recent years. This paper aims to investigate the tribological properties of SN500 grade lubricating oil containing garnet nanoparticles.

In this study, 45-nm-sized garnet particles are ultrasonically dispersed in SN500 grade base lubricant oil. The effects of viscosity and additive concentration on tribological properties are investigated using a four-ball tester.

Rolling, reinforcing and film-forming behaviour of dispersed nano-sized garnet additives in the rubbing zone were investigated using scanning electron microscopy equipped with energy dispersive spectroscopy. The results indicate that the garnet additives can improve the wear resistance and resistance to relative motion and decrease the friction coefficient of rubbing steel interface by surface polishing and formation of tribo-film containing Si, C and Mn.

Because of the complex two-phase solid–liquid mixture, there are still limited physical understandings of the friction and wear reduction mechanisms. Therefore, the present research was undertaken to interpret the possible phenomena.

The purpose of this paper is to experimentally investigate the effect of aluminium oxide (Al₂O₃) nanoparticles on gear oil (SAE EP 90) as a lubricant in heavy earth moving machinery (HEMM).

Particle size distribution, viscosity, density, stability and other rheological properties have been measured. The variations in rheological properties with varying nanoparticle volume fraction and temperature have been investigated at atmospheric pressure over a temperature range of 15-40°C. Classical as well as modified Krieger – Dougherty models have been used for finding out viscosity variation and a new empirical model has been presented.

Dynamic light scattering data confirm the presence of large agglomeration of about 5.5 times of primary nanoparticles in nanofluid. Nanofluid starts behaving as a non-Newtonian fluid with increasing nanoparticle volume fraction. Viscosity of nanofluid is enhanced by 1.7 times of base fluid with 2 per cent volume fraction of Al₂O₃ nanoparticles, while it significantly decreases with increase in temperature. The stability of nanofluid decreases with increase in nanoparticle volume fraction due to settling down of nanoparticles. It has also been observed that shear thinning increases with increasing nanoparticle volume fraction.

It is expected that these findings will contribute towards the improvement in rheological and thermal properties of the conventional lubricants used in HEMM. The outcome may help the designers, researchers and manufacturers of the HEMM.

Most of the previous research in this field is confined with base fluid as water, ethylene glycol, transformer oil, etc. Gear oil in HEMM performs under high mechanical and thermal load. The Al₂O₃/gear oil nanofluid is expected to have better cooling and lubrication properties.

This paper aims to investigate the friction and wear performance of Hazelnut oil with copper (Cu) nano additives.

The experiments were performed on a pin-on-disc tribometer in boundary and mixed lubrication regimes. Copper nanoparticles were added in 0.5 and 1 Wt.% concentrations and corresponding Stribeck curves were generated with a base oil and with oil containing Cu nanoparticles. Surface analysis of aluminium 6061 pins was conducted using an optical microscope, scanning electron microscope and energy dispersive spectroscopy.

The lubricant with 0.5 Wt.% Cu nanoparticles exhibited better results. An improvement of around 80 per cent in coefficient of friction and around 99 per cent in specific wear rate was observed. The film formation capability of the Cu nanoparticles led to an overall improvement in tribological properties of the base oil.

Experiments were performed to evaluate the tribological performance of a new lubricant (Hazelnut oil) using Cu nanoparticles. The results obtained herein suggest that Hazelnut oil has a great potential to replace the conventional mineral oils in the field of industrial lubrication.