INVESTIGATION OF FEATURES OF DUAL WEAR OF PADS IN BRAKE SYSTEM OF FREIGHT CARS

Abstract

Purpose. This research is aimed at revealing features of dual wear of pads in the brake system of freight cars. Methodology. The complex of theoretical and operational research concerning the causes and consequences of dual wear of pads, as the most widespread one in the freight cars, was conducted. Using the theory of planning the experiment based on the collected statistical material an adapted mathematical modeling of the dual wear process was performed and negative factors were determined. The Mathcad software and STATISTIKA software application were used. Findings. A comparative analysis of various devices for the uniform wear of brake pads showed insufficient efficiency. It has been established that typical devices of uniform wear of brake shoes (up to 95%) are in damaged condition due to the effect of significant dynamic loads. Therefore, the shoes are bent, pressed with their upper edges to the wheel threads and when driving in trains without braking do harmful friction with the formation of double frictional wear of the working body of the shoes. It has been theoretically proved that in a hinged connection of a vertical lever with a brake beam king post a harmfully acting torque from the gravitational forces is formed, which becomes the main cause of the dual wear of the brake shoes. Kinetostatic analysis, taking into account the dynamic forces in the unsprung parts of the bogie, has allowed establishing the cause of dual wear and determining the possibility of eliminating the specified torque in the existing brake system. According to the R & D and the Ukrzaliznytsia`s order the operational tests on 10 gondola cars constructed by Kriukiv Railway Car Building Works were performed. They confirmed the results of the theoretical studies. Originality. For the first time, it was discovered, the research was initiated and the definition – the dual deterioration of brake pads was proposed. A mathematical regression model was developed for determining the main cause of dual wear of pads in a typical mechanical braking system of three-element bogies. It was adapted the mathematical approach to the planning of experiments with the construction of the corresponding schemes-models, which revealed the malignant moment of forces, bending the break beam on the pendulum suspensions until the upper edges of the brake pads will be pressed to the wheel thread. Practical value. The results of the research can be used in the design, modernization and operation of brake systems for both the operational fleet, as well as a new generation of three-element bogies.