Thermal elastohydrodynamic lubrication simulation model for the tooth guidance contact of a single tooth gearbox under mixed friction conditions

This article presents a simulation model for thermal elastohydrodynamic lubrication of the tooth guidance (piston/cylinder) contact of a single tooth gearbox. A finite-element analysis provides the boundary conditions for the thermal elastohydrodynamic lubrication simulation. The finite-element analysis under dry conditions allows calculating the macroscopic deformed contact surfaces for the elastohydrodynamic simulation model. The Hertzian deformation should be calculated in the presence of a lubricant and not with a dry finite-element analysis. A recently presented method, based on the finite-element submodeling technique, is extended to remove the Hertzian deformation of the macroscopic deformed lubrication gap from the dry finite-element analysis. A mixed friction with measured rough surfaces using the averaged flow model and mass conserving cavitation is implemented as well. An example shows how optimization of the gearbox by application of the simulation model is possible.

The Possibilities of Using Ecological Liquids in Tribological Gliding Systems with a Selected Surface Created by the Radial Welding Technology

Presented paper deals with the issue of lubricating tribological systems formed by a double pair operating under mixed conditions of mixed friction before and after experimental tests, which were conducted in accordance with the selected methodology using Tribotestor M‘06 test machine. The lubricating media included ecological oils Plantohyd 46 S by Fuchs and EAL Hydraulic 46 manufactured by the Mobil company. Applied ecological oils can be used in agricultural mobile machines as a replacement for conventional lubricants. The tests were conducted on designated material double pairs. The shaft was made of steel 16MnCr5. The second observed friction element in terms of glide angle test was a steel plate made of S235JR, gliding surface of which was produced utilizing flame powder coating technology. The results were statistically processed and are presented in the form of graphs, tables and figures.

Theoretical Model and Experimental Research on Friction and Torque Characteristics of Hydro-viscous Drive in Mixed Friction Stage

The hydro-viscous drive (HVD) has been widely used in fan transmission in vehicles, fans, and scraper conveyors for step-less speed regulation or soft starting. In the mixed friction stage, the contact, friction, and torque characteristics of friction pairs are very complex and change at any time. The characteristics of the frictional and hydrodynamic lubrication states were studied in order to calculate and predict the friction and torque characteristics of the friction pairs in the mixed friction stage. The fluid torque was calculated by applying the average shear stress model and the load-carrying capacity of asperity was determined on the basis of the fractal contact theory. In addition, the contact friction coefficient of the friction pairs was taken into consideration and measured by using the MM1000-III friction and wear testing machine. The asperity friction torque and total torque in the mixed friction stage were obtained and finally, the test rig for the torque characteristics was set up. The results show that the contribution to the total torque is shared by the oil film and the asperity friction. The friction coefficient decreases sharply at first and then increases with a change in the relative rotational speed, following the Stribeck curve closely, and the contact frictional coefficient slowly decreases with increase in the pressure between the friction pairs. The torque between the friction pairs is provided by the asperity friction, and the torque due to the oil film reduces to zero. When the thickness of the oil film is small, a major contribution to the total torque is due to the asperity friction. The total torque also increases with the decrease in the film thickness ratio. Therefore, by theoretical analysis and experimental verification, the torque of the friction pairs in the mixed friction stage can be accurately calculated using the average shear stress model and asperity friction torque model.

Influence of pitch and exploitation on the frictional behaviour of the silent chains

The silent chain transmissions are widely used in automotive industry as part of the distribution transmission for the combustion engines. The investigation of friction loses in chains is important in order to find out the influence of their constructive and exploitation parameters. The paper presents the results of the tests performed on a test rig used in the case of transmissions with parallel axes. The main contribution of the paper is represented by determining the influence of speed, tensioning force, temperature and pitch on the friction loses of silent chains. Two types of silent chains are tested: LD6 with the pitch equal with 6.35 mm and LD8 with the pitch equal with 8 mm. The tests have been achieved with the following test parameters: the driver sprocket rotations with the values of 500, 1000, 1800 and 5000 r/min; the tensioning force with the values of 0.5, 1, 2 and 3 kN; the lubrication oil temperature equal with 40°C, 90°C and 115°C. Conclusions are drawn regarding the influence of the chains’ pitch and of the exploitation parameters on the frictional torque. The presence of boundary or mixed friction in the joints of the chain explains the frictional behaviour of the chain.