1 Toward the wheels calculation and validation in multiaxial fatigue under service loads F. COCHETEUX 1 , J. BENABES 1 ,T. PALIN-LUC 2 , N. SAINTIER 2 , F. BUMBIELER 1 1 SNCF : Agence d’Essai Ferroviaire 21, avenue Salvador Allende - 94407 Vitry-sur-Seine Cedex France; 2 ENSAM - Laboratoire Matériaux Endommagement Fiabilité et Ingeniérie des Procédés (EA2727), Esplanade des Arts et Métiers - 33405 Talence Cedex France Abstract Dimensioning methods currently allow to design against fatigue the axisymmetric plate of a railway wheel. For drilled wheel plates, fatigue calculation methods enacted in UIC leaflets (International Union of the Railroads) [1] or European standards [2] are not adapted. Those are based on an assumption of often checked simplification: whatever the zone of the plate, the maximum principal stress is radial. A recent application, for which the plate of the wheel is drilled, showed that the principal stress field directions vary during the wheel rotation. Consequently, classical monoaxial fatigue criterion as GOODMAN or HAIGH [3] are not applicable. A reliable design of industrial parts against high-cycle multiaxial fatigue requires a fatigue criterion capable of predicting both the load-type and the stress gradient effects. Gradient effects are of prior importance for the applicability of fatigue models to real structures. By using the concept of volume influencing the fatigue crack initiation proposed by Palin-Luc and Banvillet [4], an extension of the criterion, based on an energy approach, is applied to design wheels against fatigue. To evaluate the fatigue strength in multiaxial stresses zones, it is initially necessary to estimate the stress fields according to the real service loadings. This is done by a numerical approach using a finite element model correlated by strain gauges measurment during on line tests. For most critical points of the modeled wheel, the application of the LAMEFIP volumetric criterion [4] to numerical results allowed to evaluate the theoritical safety level for the fatigue strength in theoretical way. In parallel, a validation test protocol is under development. It consists in applying vertical and transverse bidirectional forces (test bench with two actuators) to a full scale wheel with a drilled plate. Introduction New designs of railway wheels can present drillings at the core of their plate to allow the brake disc assembly, a sound-proofing system or any other element. Currently the failure risk evaluation, related to the use of such wheels, is only possible by the experience feedback. Within the framework of an optimized design and in order to estimate its safety margin, it is necessary to approach the service loading. Although calculations with finite element analysis (FEA) allow to evaluate the stress levels in a correct way, the assumptions of the current dimensioning methods in fatigue are not applicable because of the multiaxiality of the stress field near the geometrical singularities. The first part of the study consists in determining loading characteristic of a wheel at the time of various configurations of circulation. In a second stage, measurements of vertical and transverse forces allow to work out the sections of life which will be integrated in numerical simulations. The second part deals with the FE computation on a real wheel and presents the procedure used introduce the service loading records in the calculation. Finally, a postprocessing is applied to check if a fatigue life calculation must be implemented or if an equivalent stress calculation is enough [5]. An application of the method suggested for fatigue life calculation is finally presented.