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This paper aims to present the influence of glass bead concentration in a matrix of polyamide on wear and several three-dimensional (3D) parameters of the surface texture when the composite is sliding on steel in dry contact.

There were mold disks with the following concentrations in glass beads: 2.5, 5.0, 10, 20, 30 and 50 per cent. The mix of glass beads has diameters in the range of several microns to 50 microns. Tests were done on a pin-on-disk tribotester, in dry regime, for the following parameters: average pressure (1, 2 and 3 MPa) and sliding speed (0.5, 1.0 and 1.5 m/s). Zones of 500 × 500 μm were investigated from worn tracks generated on the composite disks, and the average values of several 3D texture parameters were analyzed.

The authors plotted maps indicating no correlation between the glass bead concentration and the parameters characterizing the surface quality (amplitude parameters and functional parameters). Composites with concentrations of 10[…]30 per cent glass beads generated worn surfaces with better quality as compared to composites with extreme concentrations: low (2.5 and 5 per cent) and high (50 per cent).

This set of parameters allows for evaluating the influence of regime parameters on the surface quality, by comparing the obtained values before and after sliding, and this evolution of roughness parameters could give recommendations for selecting the friction couple of materials for particular contacts that function with repeated starts and stops.

The results encourage the researchers to use a set of 3D texture parameters instead of “classical” two-dimensional parameters, the arithmetic mean deviation of the profile, Ra, because this set of parameters better evaluate the surface quality, especially for worn surfaces.

This paper aims to present an analysis of several 3 D texture parameters for the entire wear scars obtained in severe regime, on a four-ball tester. The aim of this analysis is to correlate the tribological parameter as wear scar diameter to texture parameters.

Tested lubricants were rapeseed oil, rapeseed oil additivated with 1% Wt nano TiO₂ and rapeseed oil additivated with 1%Wt nano ZnO. The severe regime was applied for 1400 rpm and for loads increasing in steps of 50 N, from 500 to 900 N. Several analyzed roughness parameters (height parameters and functional ones) could be related to the evolution of a wear parameter, the wear scar diameter. Comparing the values for neat rapeseed oil and additivated variants, the texture parameters allow for evaluating if the additives protect or not the worn surfaces.

Measurements pointed out two groups of roughness parameters: one that has an evolution depending on wear scar diameter (WSD) and load (Sa, St, functional parameters) and one including Ssk that has shown no dependence on load and WSD. Also, the functional parameters Spk and Svk follow in a similar manner the wear parameter, WSD, but Sk is the least dependent on load. For the highest load, amplitude parameters such as Sa and St are following the tendency of WSD. Each lubricant has its particular correlation between wear parameters and texture quality, expressed by the help of a set of roughness parameters.

Such studies help tribologists to rank lubricants based on a combined analysis with wear parameters and texture parameters.

The results allow for evaluating new formulated lubricants.

The study on the quality on worn surfaces introduces the original idea of analyzing the entire wear scar surface (approximated by an ellipse with the axes as those experimentally measured) by the help of a set of 3 D roughness parameters.

This research aims to characterize the tribological behavior of polybutylene terephthalate (PBT) and PBT composites with micro glass beads (MGB) on steel, in dry conditions and on a block-on-ring tester, pointing out the influence of sliding distance and speed. The tribology of PBT and its composites is still in an early stage because this thermoplastic polyester requires accurate technological and thermal treatment.

The composites were produced by ICEFS Savinesti Romania and contain PBT grade Crastin6130NC010 (as supplied by Du Pont), 0.5 […] 1.0 per cent (weight) Relamyd B-2Nf (polyamide grade produced by ICEFS, for a better dispersion of MGB), 1 per cent (weight) black carbon for technological and tribological reasons and different micro glass beads (MGB) concentrations (10.0 and 20.0 per cent weight). Tests were done for different sliding distances (2,500, 5,000 and 7,500 m) and speeds (0.5, 1.0 and 1.5 m/s) and a normal load of 5 N.

The friction coefficient and the wear parameter (as mass loss of polymeric blocks) pointed out a good tribological behavior for these composites. Scanning electron microscope (SEM) images revealed particular aspects of PBT local transfer on steel. Also, 10 per cent MGB in PBT reduces wear, especially for longer distances (75,000 m) and higher speeds (0.5 and 0.75 m/s); the friction coefficient is only slightly increased up to 0.23, being less influenced by the speed and the sliding distance as compared to neat polymer.

PBT and PBT composites could become challengers for replacing materials in applications similar to tested ones. Even the neat polymer exhibits a good tribological behavior. The composites have a lower sensibility to higher speeds and sliding distances for the applied load.

The purpose of this paper is to establish the influence of oil concentration in oil-in-water emulsions on their flammability on hot surfaces and on their viscosity. The interest in fire test systematization is obviously developing due to many grades and applications of fluids and new design solutions asking for higher parameters in exploitation, including pressure and temperature. Higher temperature and pressure have a synergic effect on fire risk; thus, a special attention has to be given to selecting fluids based on fire tests.

This test simulates a hazardous event when a fluid drops on a hot surface: 10 ml of fluid is dropped during 40-60 seconds on a manifold kept at a constant temperature, from a distance of 300 ± 5 mm above the surface. Tests were done under the procedure of SR EN ISO 20823:2004, with an original equipment. The apparent viscosity of the tested fluids was determined using a rheometer Rheotest 2. The tests were done for the fully mineral oil (Prista MHE-40) and for emulsions with different oil volume in water: 5, 10, 20, 30, 40, 50, 60, 70, 80 and 90 per cent, respectively.

The mineral oil MHE 40 Prista does not burn repeatedly for manifold temperature lower than 440°C, but it burns at 450°C on the clean surface and at 425°C on dirty surface, as obtained after testing the same oil, but at a temperature for which the oil burns. The emulsions do not burn even at 90 per cent oil in water, but the apparent viscosity of the emulsion is too high and unstable, above 20-30 per cent (volume) oil in water. No evident relationship was found between the apparent viscosity of the emulsions and their behavior on hot surface.

The hydraulic fluids were ranked, taking into account the flammability characteristics determined with the help of this test.

This paper aims to reduce the risk of fire in hazardous environments using fire-resistant fluids.

Testing hydraulic fluids under the procedure of SR EN ISO 20823:2004 is required by European and national regulations to avoid large-scale accidents produced by the ignition of hydraulic fluids.

As far as the authors have known, the test procedure was only used for establishing whether a certain fluid passes or does not pass this test. The authors did not find any references for establishing the influence of oil concentration on the flammability characteristics. Also, the equipment has an original design, allowing for a good repeatability and a high protection of the operator.

The paper aims to present results on the friction and the wear of polytetrafluoroethylene (PTFE) and eight commercially available composites with PTFE matrix, for tests done on shoe/roller tribotester with water lubrication in open circuit. There are pointed out particular tribological processes within the superficial layers of the composites with the help of optical microscopy.

Analysing the tribological behaviour of eight grades of PTFE composites sliding in water on shoe/roller tribotester.

Good results of wear behaviour under water lubrication for all the composites. PTFE exhibits severe wear under the tested regime.

The research could support PTFE composite application for water lubricated systems.