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Contact Thermal Analysis and Wear Simulation of a Brake Block

DOI: 10.1155/2013/878274

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The present paper describes an experimental test and a coupled contact-thermal-wear analysis of a railway wheel/brake block system through the braking process. During the test, the friction, the generated heat, and the wear were evaluated. It was found that the contact between the brake block and the wheel occurs in relatively small and slowly moving hot spots, caused by the wear and the thermal effects. A coupled simulation method was developed including numerical frictional contact, transient thermal and incremental wear calculations. In the 3D simulation, the effects of the friction, the thermal expansion, the wear, and the temperature-dependent material properties were also considered. A good agreement was found between the results of the test and the calculations, both for the thermal and wear results. The proposed method is suitable for modelling the slowly oscillating wear caused by the thermal expansions in the contact area. 1. Introduction Applications with dry sliding friction between metal parts are common in classical mechanical engineering practice [1, 2]. However, the processes in railway brake systems are quite complex. There are many studies about the steady-state friction of such applications, some of them considering even the wear and the thermal effects [3–6]; yet the real-life braking is typically a transient phenomenon, the vehicle is usually stopped in seconds or in a few minutes. Since most of the kinetic energy of the train is transferred to heat by the friction between the wheels and the brake blocks, a big amount of heat is developing in a short time. It was found earlier that in the beginning of the braking, the edges of the brake blocks contact the wheel, even when the brake block is worn. This can be explained by the thermal expansion of the brake blocks: at the end of the previous braking, the brake block is worn, so the radii of the wheel and the brake block approximately are equal. Then, the system cools down, and since there is a great decrease in temperature, a significant thermal deformation occurs, which causes the brake block to have a shape that fits the wheel only at the edges. There is another interesting feature that is called thermoelastic instability (TEI) in the literature, which is responsible for the appearance and moving of hot spots in the apparent contact area. The TEI was investigated in a number of papers (e.g., in [7–11]), and it was found to be caused by the joint effect of wear and thermal expansion of the high-temperature hot spots. present paper shows experimental and numerical analysis of the

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