Vývoj nových metod zvyšování únavové pevnosti železničních dvojkolí

Abstract

PhD work deals with the development of new methods of increasing the fatigue life of railway wheelsets. This job aims to clear up effects of metallurgical and technological factors influencing the limits of fatigue life to increase the service life and reliability of railway wheels and axles in the railway traffic. From the metallurgical factors the most studied is an influence alloying strategies of materials used for the railway axles on achieved fatigue attributes and optimization of chemical composition steel in relation to strength and fatigue properties. In terms of technology the work is aimed on clearing up the effects of heat treatment and result strenght limit on achieved fatigue attributes and on quantification and rating the application of new technological processes, especially shot peening, rolling of surface, thermal spray coatings and influence of induction hardening of axles on increasing the limits of fatigue life of railway wheelsets. In the PhD work there are described the basic theoretical parameters influencing the fatigue life of materials, which are the strenght influence, the influence of stress concentrators, residual internal stresses, character of the surface layers and size of body on the fatigue life. In the PhD work is present methodology of testing railway wheels and axles in the special testing equipment, that were built during the work solutions to test the limits of fatigue life. There are discuss the materials commonly used for production of railway wheels and axles, their mechanical characteristics defined by basic standards and methods for increasing the limits of the fatigue life of the railway wheels and axles. The main contribution of the PhD work is the development of new technology and introduction of axle induction hardening in EA4T quality on operation requirement BONATRANS GROUP a.s. The results of resolutions lead to the discussion, where are quantified benefits of new produce technology the fatigue life of railway wheelsets.