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Beyond the advantages in design of running gear and railway vehicles itself and introducing the active wheelset steering control systems many railroads and tram companies still use huge number of old fashion vehicles. Dynamic performance, safety and maintenance cost of which strongly depend on the wheelset dynamics and particularly on how good is design of wheel and rail profiles. The paper presents a procedure for design of a wheel profile based on geometrical wheel/rail (w/r) contact characteristics which uses numerical optimization technique. The procedure has been developed by Railway Engineering Group in Delft University of Technology. The optimality criteria formulated using the requirements to railway track and wheelset, are related to stability of wheelset, cost efficiency of design and minimum wear of wheels and rails. The shape of a wheel profile has been varied during optimization. A new wheel profile is obtained for given target rolling radii difference function ' r y ∆ − ' and rail profile. Measurements of new and worn wheel and rail profiles has been used to define the target ' r y ∆ − ' curve. Finally dynamic simulations of vehicle with obtained wheel profile have been performed in ADAMS/Rail program package in order to control w/r wear and safety requirements. The proposed procedure has been applied to design of wheel profile for trams. Numerical results are presented and discussed.

Worldwide, metallurgical rail welds are being geometrically assessed by the principle of vertical deviations satisfying given tolerances, measured with steel straightedges or occasionally with digital/electronic straightedges. In this approach, the geometrical shape of the weld in longitudinal direction has no real influence, although it has a direct relation with the dynamic wheel -rail interaction forces, which are responsible for track deterioration. In this article, different new assessment methods for rail welds are proposed and evaluated in practice, after which a choice is made for the best method. This is done in line with the situation in the Netherlands, where the chosen new method was recently introduced and standardized (2005). The proposed method is based on a limitation of the gradient of the discrete measurement signal, implying a limitation of the wheel -rail dynamic contact force.

The primary mechanisms playing a role in the dynamic wheel-rail response to rail weld irregularities in a ballasted track are pointed out. The concept of P1 and P2 forces for metallurgical rail welds, introduced in a first paper [1] concerning the present research, is further elaborated. The dynamic wheel-rail response is simulated for a number of geometrical rail weld measurements. Results show a good correlation between the gradient of the rail weld geometry and the maximum dynamic wheel-rail contact forces, whereas the correlation with vertical peak deviations is shown to be very poor. Therefore, an assessment method based on the gradient (introducing a speed-dependent quality index [1]) is more consistent than a method based on vertical tolerances. An approximate formula is presented to calculate the maximum dynamic wheel-rail contact force as a function of the train velocity and the maximum gradient of the weld geometry, in analogy to Jenkins' formulae for calculating P1 and P2 forces at dipped rail joints.

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In this contribution, attention is focused on the problem of a moving load on a Timoshenko beam-half plane system. Both the subcritical and the supercritical state will be analysed via a FE-simulation. The character of the response is explained by the analytical derivation and the elaboration of the eigen-value problem that follows from the characteristic wave equations together with the boundary conditions. It will be demonstrated that also transcritical states can occur. The total number of critical states and the values of the corresponding critical velocities are determined by the beam-half plane stiffness properties as well as the contact conditions. IntroductionImprovements in rail transport capacity are continuously required to maintain a competitive edge against other forms of transportation. The quest for the increasing transport capacity automatically results in the application of higher train speeds. In order to guarantee the safety of the passengers, it is important to adapt the maximum train speed to critical states of the railway structure (or vice versa), which are governed by considerable ampli®cations of the track response under possible generation of surface waves. Indeed, in France speed limits have been established on certain parts of the TGV-track, since at cruising speed a clearly visible surface wave was noticed in front of the train.In this contribution, we will consider the in¯uence of the load speed c l on the critical response of a Timoshenko beam-half plane model via a ®nite element analysis, in which a strongly accelerating load is applied to the con®guration. The Timoshenko beam takes into account the bending and shear deformations of the compound system of rails, sleepers and ballast, and the half plane models the subgrade. The constitutive behaviour of the structure will be considered as elastic, which is justi®ed since the response under an instantaneous load passage is mainly reversible. Although in the past a complete analytical (steady state) solution for the moving load problem has been derived for various beam-elastic support systems (e.g. [2,4,5]), the analytical solution is not known for the current system as a result of the more complex system behaviour. Also the fact that the load accelerates, complicates an analytical approach considerably, so that we have to rely on numerical techniques in order to examine the problem. The analytical treatment in this paper will be limited to the derivation of the dispersion relationships, which show that the lowest critical wave speed c crit of a stiff beam-soft half plane system lies between a value somewhat smaller than the Rayleigh wave speed of the half plane and the shear wave speed of the half plane. The exact value depends on the contact conditions and the stiffness difference between the beam and the half plane. When the beam is rigidly connected to the half plane, the total response range can be divided into a subcritical state c l`ccrit and a supercritical state c l b c crit . For a soft beam-stiff half plane system, not only...