Tribological Behavior And Modification Of Friction Lining For Mine Hoist Under Severe Conditions

Friction lining is a key component of the friction hoist, and its performance is directly related to the hoisting capacity, efficiency and safety. In recent years, the studies of wire rope and friction lining were carried out mainly under low velocity, and the tribological properties of friction lining under severe conditions such as heavy load and high velocity have not been totally understood. When the non-normal slide caused by overloading and other unexpected factors occurs, a great deal of friction heat accumulates on the surface of friction lining, which results in drastic changes in temperature filed. Accordingly, the friction coefficient and wear resistance exhibit sharp decline which finally leads to serious accidents. Therefore, to carry out the investigation on tribological behaviors of friction lining and wire rope under severe conditions and consequently modify the material of friction lining, in order to improve its friction coefficient and wear resistance, is helpful to ensure safe hoisting and enhance economic and social benefits.This dissertation was financially supported by Research Fund for the Doctoral Program of Higher Education of China. Aiming at the frequent occurrence of serious slipping accidents in coal mine, the methodology of theoretical and experimental analysis was employed, and the investigation of tribological properties between wire rope and friction lining was carried out in the laboratory simulating the real working conditions of coal mine. The goal is to master the tribological behaviors of friction lining, then to develop new material of friction lining which exhibits better properties under severe condition.Firstly, the sliding experiment between friction lining and wire rope was carried out on the tester under the condition of high velocity, heavy load and grease lubrication, which simulated the severe working condition of coal mine. Then, the SEM and XPS were employed to analysis the morphology and chemical structure of worn surfaces, and the wear mechanism and failure reasons were obtained consequently.Secondly, taking the character differences into consideration, several types of whiskers were chosen as reinforcements to prepare the whisker modified material. Afterwards, the effect of whisker on the physical and tribological properties was studied with experiments, and the morphology of worn surfaces was investigated with SEM. According to the different action laws of whisker, certain type of whisker which showed the best modification effect was fixed.Thirdly, the material formulations, in which the weights of PF, CaSO4 whisker and aramid fibre were considered as factors, were designed with quasi-level uniform method. Based on the support vector theory, the prediction model of tribological properties for different formulations was established to study the effect of ingredients and their weights on the tribological properties. Considering the tribological parameters under different conditions as criteria, the optimal formulation was chosen based on the method of AHP and PROMETHEE.Finally, the friction experiments of the newly developed material were conducted with the method of central composite design. The RSM was employed to analyze the sensitivity of friction coefficient and wear rate affected by the independent and interactive effect of velocity and pressure. Furthermore, the wear mechanism of developed material under different conditions was studied on the basis of the morphology and chemical structure of worn surfaces. In the end, with the experimental data, the friction coefficient prediction model was established based on the artificial neural network covering the whole range of velocity.