Study On The Improvement Of Evaluation Technology Of Composite Brake Shoes In Speed-Raising And Heavy-Haul Train

China railway freight is walking towards heavy-haul and speed-raising. The freight train has reached120km/h while the axle weight has increased from23ton to27ton, reaching even30ton in some special transportation routes for coal. As a key part of a braking system, the performance of high friction coefficient composition brake shoes are tightly related with the safety of railway trains. This paper focuses on the parts to be improved in the evaluation criteria of the composition brake shoes, which is based on the study of massive field application, as well as theoretical analysis and experimental tests. This paper mainly includes three parts as follows:investigation of brake shoes’ current use; study on the physical and mechanical performance; study on the tribological properties of composition brake shoes. According to the analysis and discussion on the research results, the following conclusions can be drawn:(1)The research starts from the investigation of the composition brake shoes’current use and has carried out large-scale, in-depth, extensive collection about a variety of problems arising in the utilization. Then statistical analysis was employed for the data obtained, after which the condition of using of composition brake shoes can be known well. And this paper also analyzes the category, reason and probability of the problem occurrence.(2)Composition brake shoes collected in the research were made into standard modules, whose change of physical and mechanical performance such as impact strength, compressive modulus, compression strength and rockwell hardness were analyzed under the condition of a temperature variation from room temperature to300℃. Through the Pro/Engineer modeling and ANSYS finite element analysis of the braking process, breakage process of the composition brake shoes was given:deformation—cracking—plum hole’s loosing—friction part loosing. A rank correlation method was taken to judge the correlation between mechanical performance and breakage.(3)Compared with some foreign advanced composition brake shoes, friction coefficients and abrasion loss under various experimental conditions were tested via constant-speed testing machine and inertia brake testing machine, where the effects of elements such as braking pressure, initial velocity and contact area on composition brake shoes’ friction and wear performance were analyzed. Metal mounting problem of the composition brake shoes was studied, where a relation model between influence factors causing the problem occurrence and metal mounting rate was given:P=-6.337-0.193H+5.628Rpm, Where H is the hardness, Rpm is the average height of microscopic surface contours. This model can quantitatively foresee the metal mounting condition in the future, which fills up the gap in the detection and prediction of metal mounting problems occurring in the composition brake shoes.This paper begins with the current use of composition brake shoes under the guidance of the current evaluation criteria, providing important test data and theoretical analysis for the wear reduction and probability decrease of metal mounting and abnormal wear occurrence, thereby offering a useful reference for the modification of current evaluation technology of railway composition brake shoes.