ANALYSIS OF IMPACT FORCES BETWEEN RAILWAY WHEELS AND TRACK

Abstract

Impact loads essentially result when a railway wheel encounters discontinuities on the track. Other factors that substantially influence the impact loads include track surface irregularities, track subsoil properties and vehicle suspension parameters.The safety and control of railway vehicles is largely affected by these impact forces which are a function of normal load between wheel and track along with many other parameters. The impact (dynamic) loads, together with longitudinal and lateral forces, cause damaging effect on the wheel and/or the track and eventually lead to the failure of the wheel/track. Few of the typical failures may be wheel wear, wheel cracks, gauge face corner cracking, track wear, rolling contact fatigue. On the other hand, the railway vehicle ride behavior is concerned with the vibrations of the vehicle body, which are the function of the mass and moment of inertia parameters of the both the car body and bogie frames, suspension properties and wheel/rail surface irregularities. The vehicle parameters like suspension, mass and inertia values and geometrical parameters, etc.,form a vital part of the input data for vehicle simulation studies. A nine degrees of freedom railway vehicle with rigid track model has been considered for the study of ride behavior and impact force analysis. The railway vehicle model in consideration consists of car body, two bogie frames, primary and secondary suspensions, and four wheel sets. The car body and each bogie frame are subjected to bounce, pitching and rolling motion (each having 3-degrees of freedom). Equations of motion (nine) based on the Newton's second law of motion have been derived, one for each corresponding DOF and are written in the matrix form