| Brake disc is one of the important basic braking devices for high-speed trains,and its safety and reliability in service directly affects the operational safety of trains.in the braking process,the brake disc by the repeated cycle of friction and thermal stress,after a long period of service,the brake disc will produce fatigue leading to a decline in braking efficiency or even failure.Wear is also one of the causes of brake disc failure,serious wear will also significantly reduce the braking efficiency of the brake disc,so the study of the brake disc in the braking process temperature,thermal stress distribution law and the brake disc wear mechanism,and to predict the service life of the brake disc,the high-speed train driving safety is of great importance.In this paper,24 Cr Ni Mo cast steel material brake discs are studied for the temperature field,stress field,wear behavior and service life of brake discs during the braking process in the following aspects:(1)Based on Catia 3D modeling platform to build simplified brake disc model as well as full-size brake disc model.Combined with the theory of thermal-mechanical coupling analysis,ABAQUS finite element analysis software is used to simulate the temperature and stress distribution patterns of two brake disc models under a variety of different operating conditions.The simulation results of the two models were compared with the relevant test results,and the comparison results showed that the simulation results of the full-size brake disc model deviated less from the actual results.In order to avoid the chance of results,a set of full-size brake disc model simulations were supplemented and compared with the test results,and the results still matched the reality.In the numerical simulation process,the structure of the brake disc model has a greater impact on the simulation results,the simplified model does not have a heat dissipation structure,the phenomenon of high local temperature,the full-size model brake disc heat dissipation performance is better,the temperature and stress of the disc body is at a normal level.(2)A full-size brake disc model was used to simulate the temperature and stress distribution pattern of the brake disc surface under emergency braking conditions at 380km/h braking initial speed for the 24 Cr Ni Mo cast steel material.The braking process lasted94 s.The temperature on the surface of the brake disc was distributed in a ring pattern,and the highest temperature ring was near the outer side of the brake disc with a maximum temperature of 830°C.The stress distribution pattern of the brake disc is basically the same as the temperature distribution pattern,and the maximum equivalent force on the disc surface is 855 MPa.(3)Based on the brake disc temperature field,stress field and normal thermal expansion field of the disc surface,the bias grinding mechanism of the brake disc is analyzed in combination with the actual wear shape of the brake disc surface.The brake disc will have uneven temperature distribution during the braking process,and the temperature gradient along the radial direction of the brake disc surface is large,with high temperature on both sides of the disc surface and low temperature in the central region.Disc thermal expansion by the temperature field,both sides of the expansion is larger,the middle region expansion is smaller,the expansion of the large part of the contact with the brake pad more tight,serious wear,after many braking cycles,the surface of the brake disc is concave on both sides,the middle slightly convex "W" shape.Using the Manson-Coffin formula and the empirical formula summarized by the four-point correlation method,combined with the simulation results under the emergency braking condition at 380 km/h braking initial speed and the material thermodynamic properties of 24 Cr Ni Mo,the service life of the brake disc under the emergency braking condition at 380 km/h braking initial speed was predicted,and the results showed that the number of failure cycles of the brake disc was 1527. |
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