Abstract : The railway study presented in this thesis deals with three types of wheel and rail service degradations. Every solid which has a contact connection, wheel and rail, are subject to degradations such as wear and fatigue. Wheel-rail wear may be considered in two forms. The first is a uniform loss of cross section, the second is a non-uniform loss of cross section. This second form results in rail corrugation or wheel polygonisation. Initially, the first type of wear of wheel and rail profiles was of interest. This type of wear affects vehicle stability, consequently ride quality and safety. Our model for numerical simulations of this type of wear is presented; its validation is supported by comparisons of computed wear profiles to measured profiles over the S.N.C.F. network. The irregular longitudinal wear of high speed wheel profiles is studied. A new hypothesis is applied for dealing with the generating mechanism for corrugation. This is coupling of the wheel set axle torsional vibrations to the lateral dynamic vibrations of the bogie which generate corrugation wear. The coupling occurs through the wheel-rail contact. This is supported by numerical simulations with two models. The hypothesis is validated and the mechanism of irregular longitudinal wear is shown up. The last part is devoted to rail Rolling Contact Fatigue, where Head Checking is studied. At first, the parameters most influencing the vehicle-track system were isolated by studying contact forces induced by the behavior of some railway vehicles in curves. Secondly, two methods are used to deal with crack initiation: the Dang Van criterion and the Damage Mechanics. Results allow to propose appropriated devices to avoid Head Checking.