This study covers the design of mobile standalone unit for continuous monitoring of lubricating oil properties and for particle counting. A user-interface controls the operation of the unit and displays data that are obtained. The operation of the unit was experimentally tested on a specially designed laboratory gear test rig, where contamination of gearbox oil was performed to simulate changes in oil state.
COBISS.SI-ID: 26487591
The aim of this research was to confirm skewness and kurtosis parameters as two main roughness parameters which describe tribological properties of contact surfaces, especially pointing out their application in surface texturing. Based on our previous virtual texturing findings, steel samples were laser textured in a manner to achieve micro-channels with different spacing and width of the channels. Lubricated tests under different contact conditions were done to evaluate their influence on friction. It was confirmed that higher Sku and more negative S[sub]sk can be used for planning surface texturing.
COBISS.SI-ID: 12440347
For steel contacts it is usual for the longer molecular chain lengths of saturated linear hydrocarbons and their acids and alcohols to reduce the coefficient of friction in the boundary-lubrication regime. However, the effect of these lubricant properties on DLC contacts is still unknown. Since the boundary- lubrication mechanisms between DLC coatings and conventional additives do not appear to be as effective as with metals, other potential mechanisms, even though based on weaker interactions or the oils physical andrheological properties, may thus be very relevant. In this study we focus on the influence of the base oils chain length and viscosity on the friction and wear in DLC/DLC contacts, and we compare this behaviour with conventional steel/steel contacts, using several simple linear hydrocarbons, i.e., alkanes, and complex branched hydrocarbons, i.e., polyalphaolefins. The results show that in both the steel/steel and DLC/DLC contacts the wear decreases with a longer molecular chain length and a higher viscosity of the oil. However, in DLC/DLC contacts the coefficient of friction increases when oil with a longer molecular chain length or a higher viscosity is used, and decreases with the lower oil viscosity and shorter chain lengths, which is just the opposite to conventional steel/steel behaviour. These results are analysed and discussed in view of lubricant cohesive energy, surface tension, shear strength, viscosity and chain length.
COBISS.SI-ID: 12266267
Several types of nanoparticles have been experimentally investigated as possible lubrication agents and the results suggest that this is a promising idea. However, so far, MoS2 nanotubes have not been experimentally evaluated in this respect. Accordingly, this study is focused on the tribological behavior of MoS2 multi-wall nanotubes (MWNTs) as a potential additive in lubricating oils. The experiments were performed in the boundary-lubrication regime under a contact pressure of 1 GPa (Herty, max) and a sliding velocity of 0.005 m/s using a ball-on-disc tribotester. The results were compared to a reference base oil, and it was found that MoS2 nanotubes significantly decreased the friction and wear compared to the base lubricant. The friction was more than 2-times lower and the wear as much as 5-9-times lower. Several tribological mechanisms and effects due to the MoS2 nanotubes are presented. It was established that a wear-protective and low-shear film was forming on the surface. This tribofilm was formed either by (i) the adhesion of thin MoS2 nano-sheets on the surface, where these sheets were deposited on the surface by one of the four possible sub-mechanisms proposed in this work; or by (ii) the compaction and deformation of nanotube aggregates, which resulted in a thicker boundary film. Thus, in contrast to the rolling of the nanotubes, which we do not consider to be plausible, the exfoliation and deformation of the nanotubes were found to be the prevalent effects for the nanotubes in the boundary-lubrication regime.
COBISS.SI-ID: 12245787
This work focuses on a study of the parameters affecting the running-in and long-term behaviour of plastic/plastic and plastic/steel contacts at sliding distances sufficiently long to ensure steady-state sliding conditions, which is very important for an evaluation of the performance in real-scale applications. Unreinforced polyamide (PA6) was paired against stainless steel and against unreinforced polyacetal (POM). The effect of sliding velocity was studied at a constant nominal pressure of 0.7 MPa. The results show that the running-in sliding distances to reach steady-state conditions are much longer for the PA6/POM contacts than for the PA6/steel contacts.
COBISS.SI-ID: 12348699