Design method of worn rail grinding profile based on Frechet distance method

Due to the large volume and high running density of railway freight lines, rail deterioration occur frequently. Thus, it is necessary to grind the rail in time to improve the wheel-rail relationship. The profile data of the worn rail were measured at different measuring points in a section, and the Frechet distance method was adopted to analyze the data. The representative profile reflecting the overall condition of rail wear in this section is obtained. Combined with NURBS curve theory, a fitting algorithm in which the rail profile with certain discrete points was established. Taking the reduction of the amount of grinding material removed as the objective function, setting wheel-rail matching characteristics, and the reduction of rail wear as the constraint conditions, a calculation model for rail grinding profile was established. The dynamic characteristics of standard profile CN75 and g grinding profile OP75 were analyzed by the vehicle track dynamics model. The results showed that compared with the standard profile CN75, the amount of grinding material removed of the grinding profile OP75 is reduced by 44.7%, and the height reduction of the rail top is reduced by 0.39 mm. After [Formula: see text] km of running, the wear amounts of grinding profile OP75 is about 36.1%–36.5% less than that of standard profile CN75.In the small curve section, the derailment coefficient of grinding profile OP75 is reduced by 11.7% compared with that of standard profile CN75. The dynamic performance is improved. The grinding target profile has better dynamic characteristics and is beneficial to reduce wheel-rail wear.

Analysis of the Impact Factor of Rail Grinding on Their Condition

The Doctoral Thesis “Analysis of the impact of rail grinding on their condition” is developed by Viktors Ivanovs to obtain a Doctoral Degree in Engineering. The scientific supervisor is Assoc. Professor Dr. sc. ing. Pāvels Gavrilovs. In this Doctoral Thesis rail steels are considered according to standards EN 13674-1:2011 and GOST R 51685-2013. Rail steel defects and reasons for their causes are reviewed. The statistics of damaged and heavily damaged rails in the network “Latvijas dzelzceļš” in the period 2011–2019 is studied and analysed in detail. The statistics of rail grinding train operation in “Latvijas dzelzceļš” within the year period 2011–2019 is gathered and analysed. A research of hardness of 60 E1 type rail running surface, of metal chemical composition of the damaged rail with code X 10.1., and structure analysis was performed. Likewise, statistics of wheelset rejection in the network “Latvijas dzelzceļš” in the period 2016–2019 are gathered and analysed, as well as the number of wheel rim defects in the railway of Russian Federation. The main defects of wheelsets are reviewed. The actual wear of wheels and rails in Latvia and the stated wear in the railway of Russia are modelled. Repair profiles of rail head grinding for Latvian rail ways are modelled and their influence on side wear determined due to the rail and wheel surface interaction. Calculations regarding the wheels with flange angle of 66.8° from worn out profile durability coefficient were performed for Latvian railway according to the entry conditions on rail profiles, developed in this dissertation. A rail grinding method was developed. The wheelset repair and wheel grinding economic expenses were calculated. Recommendations for wheel and rail side wear reduction are presented.

Contact Model And Simulation Analysis of Rail Grinding With Open-Structured Abrasive Belt Based On Pressing Plate

Recently, the emerging rail grinding method with open-structured abrasive belt based on pressing plate which adopts full contour copying grinding method to extend the working length of abrasive belt and is more suitable for preventative grinding and maintenance of rail corrugation in high-speed railway has been proposed. The essence of its grinding process is the complex nonlinear interaction among the pressing plate, abrasive belt and rail. The research on the contact mechanism of the rail grinding method with open-structured abrasive belt based on pressing plate is still very lacking, which limits the practical application of the emering rail grinding method to a certain extent. In this paper, a theoretical model of the contact between pressing plate, abrasive belt and rail is established. The contact area morphology and contact stress distribution were obtained, and validity of the theoretical model was verified by finite element simulation. At the same time, the distribution characteristics of contact stress under single concentrated force, uniform force and multiple concentrated force were studied based on the contact model. It is concluded that the multiple concentrated force is the optimal loading method, and the contact stress is more uniform, which is more conducive to repair the standard contour of rail.

Rail Corrugation of High-Speed Railway Induced by Rail Grinding

Rail corrugation is a common railway defect that involves diverse and complex factors. Rail grinding is also the most commonly used method to address corrugations. Through numerous irregularity tests and one-third octave frequency spectrum analyses, this study determined the characteristics and development process for rail corrugation on high-speed rail tracks. The vibration transmission properties of the grinding train were tested using the force hammer impacting method. Thereafter, using a simulation, the influence of the vertical vibration behavior of the grinding stone and the stiffness of the hydraulics were determined. Through a series of field tests and numerical simulations, this study revealed a clear correlation between rail corrugation and rail grinding and confirmed that the technical operation of rail grinding is closely associated with regular grinding marks at a wavelength of approximately 60 mm on rail surfaces. The combination of the natural vibration of the grinding stone (frequency of 60 Hz) and an inappropriate operational process can aggravate the grinding marks on the rail surfaces, thereby forming an initial excitation of rail corrugation. Although a large number of irregularity tests are performed after rail grinding, these wavelength-fixing grinding marks can cause the formation and development of rail corrugation. Suggestions for improving the high-speed rail-grinding technology are also provided.