Challenges of grinding stone localization

The above review of the current research status of whetstone from the aspects of whetstone molding (raw material and process), whetstone performance evaluation methods, rail burns, etc., summarizes that the design and manufacture of whetstone is a multidisciplinary (mechanics, materials, mechanics, etc.), multifactorial (components, processes, interfaces, working conditions, etc.) interaction of the complex technical challenges. Therefore, the following is a summary of the difficulties and challenges faced in the research and development process of whetstone from three aspects: whetstone molding, whetstone/rail interface behavior, and whetstone performance evaluation (Figure 1), aiming to provide certain references for related scientists and practitioners.

(1) Millstone Molding

The performance of whetstone is affected by the formulation (resin, filler, abrasive, etc.), molding process (mixing, curing, etc.), structure (porosity and pore size, abrasive concentration, etc.), and heterogeneous interfaces (resin/abrasive, resin/filler, etc.) bonding strength and other factors, as shown in Figure 1 (a). At present, the heterogeneous interface bonding mechanism of the abrasive system is not clear; micro/nano filler on the bond toughness, heat resistance, wear resistance of the regulatory mechanism needs to be revealed; complex abrasive stone structure of the physical and chemical properties of the abrasive stone, the mechanism of the impact of the performance of the service performance is not yet clear. The above scientific and technical difficulties bring great difficulties to the regulation of the performance of grinding stones.

Yuan Yongjie [1] utilized Abaqus and Python to establish a virtual millstone model, and carried out millstone-related research through the method of finite element calculation, which is an important inspiration for the design of millstones with more variables and complex processes. Therefore, in the future, we can use finite element and other methods to construct the millstone model quickly and efficiently, and establish a finer spectrum of synergistic response relationship between various factors to guide the design of millstones. And the model is justified by a large amount of basic experimental data.

(2) Abrasive stone/rail interface behavior

Abrasive geometry, spatial orientation has randomness, resulting in large differences in the front angle of the abrasive grinding (sliding, plowing, cutting) process, and thus the role of each abrasive on the rail material behavior (mechanical force, grinding temperature, etc.) is also random, and thus there are differences in the failure mechanism of the stone, the impact of the surface quality of the rail. Ideally: the abrasive after many cycles of abrasion - self-sharpening process, give full play to its cutting function; bond wear and shedding, so that the passivated abrasive off, the grinding stone self-sharpening; but excessive wear of the bond, resulting in premature shedding of the abrasive, abrasive utilization rate is reduced, the abrasive wear resistance of the grinding stone is reduced, shortening the service life. Therefore, the wear and self-sharpening of the grinding stone must reach a balanced state, in order to make the grinding stone both strong cutting performance and long service life. At the same time, the wear of the grinding stone directly affects the abrasive edge condition and cutting angle, which in turn affects the grinding process grinding heat and rail surface quality. Thus, it can be seen that in the process of rail grinding, under the thermal-mechanical coupling of grinding stone/rail interface, the material removal and failure of grinding stone affect each other and have a close relationship, which ultimately affects the surface quality of the rail after grinding.

At present, the interaction mechanism between material removal and whetstone failure in the rail grinding process and its influence on the surface quality of the rail are still unclear, which enhances the design difficulty of the whetstone, as shown in Fig. 1(b). Therefore, it is important to study the mechanism of material removal during rail grinding process, wear mechanism of whetstone, the evolution of rail surface quality, and to construct the physical relationship model of whetstone structure - mechanical properties of whetstone - grinding performance - failure mechanism of whetstone - surface quality of rail, which is of great value for the design and manufacture of whetstone.

(3) Evaluation of grinding stone performance

Scientific and comprehensive evaluation of grinding stone performance (especially grinding capacity), grinding stone formula, process design provides an important reference. At present, there are various methods for evaluating the performance of whetstone, and there is a lack of uniform evaluation standards for the performance of whetstone, which makes it difficult to share the research results related to whetstone, as shown in Fig. 1(c). Meanwhile, at present, many researchers carry out related research by preparing full-size millstones, which have a large size, which is not conducive to the later macro/micro characterization and analysis, and cannot obtain finer experimental data, resulting in the experimental results of the millstones with limited guidance on the regulation of the millstones' performance, which reduces the research and development efficiency of the millstones, increases the cost of the research, and results in the waste of energy and raw materials. Therefore, a multi-dimensional evaluation technology route can be adopted to scientifically design the grinding stone evaluation equipment and construct the evaluation guidelines for the performance of grinding stones in various dimensions, so as to lay the foundation for the promotion of grinding stones in rail transportation lines.

Fig.1 The key problems for the development of GS

(a) Grindstone Formation [2,3,1]; (b) Relationships between Material Removal Mechanisms, Grindstone Wear Mechanisms, and Rail Surface Quality [4,5,6,7,8]; (c) Grindstone Performance Evaluation Methods [9,2,10].

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