https://espace.library.uq.edu.au/view/UQ:b7acbc0/UQb7acbc0_OA.pdf

Monitoring and modelling of false brinelling for railway bearings

The friction behavior of the formed antifriction films and their effect on the functional properties of the composite based on the powder nickel alloy EI929 with solid lubricant CaF2 at high temperatures was investigated. An antifriction film was formed on the contact surfaces during the friction process. Such a film was the result of the interaction of the contact surfaces with atmospheric oxygen at high temperatures. It contains oxides of alloying elements from materials of the frictional contact and solid lubricant calcium fluoride. The quantitative ratio of formed oxides depends on the temperature operating conditions of material. The data of thermodynamic simulation of the high-temperature interaction of the composite with oxygen coincide with the experimental data obtained by studying the fine structure of surface antifriction films. Antifriction films consist of oxide phases in combination with solid CaF2 lubricant. Anti-friction films provide high wear resistance of the self-lubricating composite in the range of temperatures 1073–1173 K due to the balance between the rate of their formation and wear. When the temperature exceeds 1200 K, the film loses its lubricating properties and acts as an abrasive substance due to the intense oxidation. Abrasive surfaces of materials were subjected also to microscopic examination, in which the mechanically mixed layer (MML) was described. The study of the friction surface roughness parameters confirmed the presence of the formed friction self-lubricating film and allowed to determine its parameters. The friction mechanism was the formation of an oxide layer combined with a solid lubricant, which provides high antifriction properties in the range of 1073–1273 K.

Friction Mechanism Features of the Nickel-Based Composite Antifriction Materials at High Temperatures

The influence of different types of loading on false brinelling

Electrical contacts involve complicated electrical, thermal, and mechanical phenomena. Fretting wear as a surface damage mechanism significantly weakens the performance of electrical contact components. In this study, a numerical approach is developed to investigate the electrical-thermal-mechanical-wear coupling behavior of electrical contacts. An electrical contact conductance law is used with the current conservation model to evaluate the electrical behavior. A transient heat transfer model, including the Joule heating behavior and a thermal contact conductance law, is employed to calculate the temperature field. Both contact conductance laws are related to the contact pressure distribution obtained by the contact stress analysis. Based on the predicted contact stress and relative slip on contact surfaces, the energy wear model is used to study the evolution of fretting wear depth and contact surface geometry. The material properties in these models are temperature-dependent. The proposed numerical approach is implemented in a finite element modeling of electrical contacts, which is validated by comparing the predicted and experimental results of the wear scar profile. The effects of the fretting wear on the electric potential, current density, contact resistance, temperature, and contact pressure are numerically studied.

A.L. Sotnikov

Papers

Scale levels of damage to the raceway of a spherical roller bearing