Static And Dynamic Analyses Of Metro Fastening System

Rail fasteners are important components of the track, therefore, their failure can intensify the wheel/rail interaction force, accelerate components of the track and vehicle structure to damage, and even endanger running safety. According to the clips fracture of the two common fasteners in metro lines frequently, based on the theory of nonlinear contact and vehicle/track dynamics, the thesis studies the rail fastening clip static and dynamic force analysis, explores the clips fracture to provide a scientific basis for the rail fastening clip design, optimization, installation, maintenance and repair. In this thesis, the main work and conclusions are as follows:(1) A lot of field experiments on the installation and usage of type III and type PR rail fastenings indicate that the root cause of their failures is fatigue fracture. Detailed finite element models of type III and type PR rail fastenings are established to investigate the effects of installation state of the clips and vertical displacement of their fingers on the clamping force and stresses. The numerical results show that the distance of the center leg of the clip inserting into the shoulder has a little effect on the clamping force, but its effect on the maximum equivalent stress of the clip is significant. The contact state between the clip and the shoulder becomes multi-point contact instead of line contact with an increase in the distance, and a local extrusion occurs between the rear arch of the clip and the shoulder end, which finally results in a local stress concentration in the clip. Under the cyclic train loading, crack initiation comes out in the clip’s stress concentration area easily, and the fatigue fracture finally occurs with the crack propagation. In track operation and maintenance, the distance of the inner rear arch and the shoulder end should be controlled within8-10mm.(2) The detailed analyses on the clip clamping force, the maximum equivalent stress, the shear stress and the first principal stress were carried out to investigate the effect of the shoulder radius of iron plate end on the static behavior of the type III rail fastenings. Results show that the optimal fillet radius of the shoulder is about8mm, and a suitable fillet radius can reduce the stress concentration after the excessive installation. (3) rail corrugation has a significant influence on the dynamic behavior of rail fastening system. With an increase in rail corrugation amplitude and a decrease in its wavelength, the rail fastening force and the maximum equivalent stress increase rapidly.(4) When the train running speed ranges from90km/h to120km/h, some of the resonant frequencies of type III and type PR rail fastening clip are close to the passing frequencies of typical rail corrugation observed on metro lines, which would accelerate the fatigue damage of the rail fastening clips.