•The maximum temperature of the gear tooth surface appears near the addendum.•Steady temperature of the meshing point whose friction heat flux is minimum is lowest.•Theoretical value of the transient ...temperature is calculated by Blok criterion.•Simulation result of the transient temperature rise is lower than the theoretical value.•Transient temperature rise obtained by the finite element method is more accurate.
Sliding velocity variation for gear meshing surface was researched based on theories of gear tribology, heat transfer and Hertz contact, and a model of contact stress considering friction force was derived. The model design process culminated in a comparison of theoretical values and simulated values. Heat flux of friction for different meshing positions and the convective heat transfer coefficient at gear tooth surface and tooth face were initially calculated accurately. The finite element method was then adopted to establish the gear bulk temperature field model and, after the steady state temperature field of the locomotive traction gear was obtained, the distribution law of the steady-state temperature for the gear teeth was analyzed. Transient thermal analysis on the gear was implemented utilizing the steady-state thermal analysis to obtain the transient temperature field of the locomotive traction gear. Applying the Blok flash temperature criterion, theoretical value of the transient temperature rise for the gear tooth surface was calculated. Comparison of the simulation values and the theoretical values for the transient temperature rise indicated that the theoretical values were higher than the simulation values as the Blok flash temperature criterion considers the heat conduction only in the direction vertical to the tooth surface and disregards heat conduction in other directions. The simulation results were then concluded to be superior in practicality and accuracy.
The present study aims at predicting the maximum temperature in line contacts depending on operating conditions. For this purpose, a thermo-elastohydrodynamic lubrication (TEHL) simulation model of a ...line contact is used to calculate the maximum temperature for a wide range of parameters. Subsequently, a neural networks (NN) approach is used to develop a surrogate model that is able to predict the maximum temperature on the basis of the operational parameters. The influence of different NN architectures and transfer functions on the accuracy is shown. A good agreement with a correlation coefficient (R) greater than 0.997 is achieved for a NN with two hidden layers. Furthermore, the impact of feature engineering on the prediction accuracy with limited data sets is presented.
•Local temperature detection in rolling contact bearings on the basis of TEHL simulations.•Efficient temperature prediction with a neural network-based surrogate model.•Influence of feature engineering on the performance of neural network model.•Impact of neural network architectures on the prediction accuracy.
Predicting tyre–road friction requires various inputs that are known with differing levels of confidence. This paper studies the prediction and associated experimental confirmation of rubber friction ...on real roads at high sliding speeds. Friction predictions are obtained from Persson’s flash temperature model: the topography of the road surface is measured using an optical profilometer, while the rubber’s viscoelastic modulus is obtained through Dynamic Mechanical Analysis. A newly developed friction tester performs in-situ friction measurements, while controlling and monitoring bulk and contact surface temperature, respectively. Local topographical road roughness variations were identified as a major contributing factor leading to predicted friction variations of over 50%, while the flash temperature predictions showed good correlation with temperature measurements from near the rubber–road interface.
•Rubber friction testing with flash temperature measurement under real conditions.•Persson’s flash temperature model without adhesion showed agreement with experiment.•Rubber background temperature is less important in practical situations.•Partial validation of flash temperature predictions.
The presence of hard, brittle, thin White Etching Layers (WELs) on rail surfaces plays a critical role in varying the tribology behaviours at the wheel and rail interface. The reciprocating sliding ...tests were carried out on the rail samples covered with two types of WELs, including thermomechanically-induced WEL (TP-WEL) and mechanically-induced WEL (SD-WEL) at room temperature and 600 °C. A WEL-free rail sample was also employed for the comparison. The wear mechanism of WEL-free rail shifts from severe abrasive wear at room temperature to adhesive dominant wear at 600 °C. Under the pressurized sliding conditions of 1.2 GPa at 600 °C, the WEL-free rail was observed to form WEL and BEL. The pre-existed SD-WEL and TP-WEL on the rail samples could transform into worn WEL at the topmost contact rail surface with Brown Ething Layer (BEL) formation beneath it. The formation of BEL is attributed to the tempered effect on pre-existed WEL. Due to their high hardness, both SD-WEL and TP-WEL-covered rails exhibit minimal abrasive behaviours at room temperature while displaying adhesive dominant wear mechanisms at 600 °C. Of the two types of WELs, TP-WEL has lower wear resistance, whereas SD-WEL promotes high friction and reduces wear loss.
•Tribological behaviours of two distinct classes of White Etching Layers (WELs) on the rail surface were measured.•Tribological properties of the rail are dependent on the existence and type of WELs and the temperature at rail surface.•The pre-existed WELs could be transferred into worn WEL at the topmost contact and underlying Brown Etching Layer (BEL).•In comparison with mechanically-induced WEL, thermomechanically-induced WEL is more prone to be worn out during service.
Heat generation at frictional interfaces is important due to its strong influence on the contacting material's deformation, microstructure, and mechanical properties. Inspired by the governing ...equations of convective heat transfer, a mathematical model is proposed to describe the microscopic friction-induced heat transfer process. The Prandtl-Tomlinson (P-T) model deals with the stick-slip motion of the sliding probe, and the energy conservation equation expresses the heat transfer process. The effect of friction on the heat transfer is represented by the frictional work in the energy conservation equation, and the thermal activation force in the P-T model introduces the effect of heat transfer on friction. Numerical results reveal that the interfacial temperature and friction force have the same period with the opposite trend. When the thermal-friction coupling effect is considered, the stick-slip motion is advanced, and the friction force decreases with the increase of the base temperature, while a barely noticeable difference is observed in the interfacial temperature rise. This work helps to improve the understanding of the heat transfer mechanisms between the rubbing surfaces, which is fundamental for various applications in friction welding and tribology.
•A model describing the atomic-scale thermal-friction coupling effect is proposed.•Friction and heat transfer have the same period with the opposite trend.•The rapid release of the strain energy leads to flash temperature.•The interfacial temperature is a power function of the sliding speed.
Dry sliding wear behavior of amorphous steel coating (ASC) and crystalline stainless steel coating (SSC) manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, ...coefficient of friction (COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation. Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness (H), reduced Young’s modulus (Er), and ratios of H/Er and H3/Er2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.
This study investigates the flash temperature rise of spur gear contacts under the tribo-dynamic condition. A transverse–torsional discrete gear dynamics model is coupled with a mixed ...elastohydrodynamic lubrication formulation to include the interactions between the gear dynamics and the gear tribological behavior. The flash temperature rises are quantified within a wide speed range under the different operating and surface conditions. By comparing the simulation results between the tribo-dynamic and quasi-static conditions, evident deviations are observed, pointing to the important role of the gear dynamics in the flash temperature rise. Very interestingly, it is found not only the line-of-action dynamic response but also the off-line-of-action vibratory motion affects the surface flash temperature.
•Bridge the gear dynamics and gear tribology disciplines.•Investigate flash temperature under the tribo-dynamic condition.•Show the importance of line-of-action dynamic response on flash temperature.•Show the importance of off-line-of-action dynamic response on flash temperature.
