Dynamic Wheel/Rail Rolling Contact at Singular Defects with Application to Squats

摘要: Squats, as a kind of short wavelength rail surface defects, have become one the main rolling contact fatigue problems in railways worldwide. The purpose this work is to better understand squatting phenomenon, contribute reduction and even prevention squat occurrence, thereby reduce related costs. To such an end, new modeling approach has been developed dissertation, i.e. three-dimensional finite element (FE) model vehicle–track interaction. Both wheel set are simulated continua. A detailed surface-to-surface algorithm integrated within FE order solve frictional between rail. Different traction/braking efforts simulated. Detailed ensures consideration important eigen-modes squats, mainly high frequency range. Other structures system also modeled appropriate extents. An estimate stresses with sufficient accuracy basis further dynamic, stress, analyses squats. validated for both normal tangential solutions by comparing it widely accepted Hertz theory Kalker’s CONTACT program. Due fact that only applicable static problems, steady-state smooth wheels rails, occurring middle top, validation. results show reliable solution contact. On other hand, can take into account actual geometry, material non-linearity, transient effects, which required more complicated cases like wheel–rail at squat. Therefore, newly provides valid promising tool problem presence friction. With model, influence plastic deformation on investigated. bi-linear elasto-plastic employed. It found geometry change caused significantly modify solutions. When type defects added calculated dynamic forces good agreement observed squats field. This means vibrations captured proving applicability treating dynamics containing Furthermore, based simulations field observations, growth process from light mature state postulated. postulation track monitoring conducted Netherlands. Further excite two frequencies. vibration component lower transfer down ballast layer, especially support close similar magnitude several fastenings near negligible layer. For investigated speed range 40 140 km/h, components increase speed. higher be absent when sufficiently low, e.g. km/h system. By evaluating stress under strength, derived initial defect indentation grow over critical size 6–8 mm typical Dutch railway condition. verified tests. dissertation formed ‘Guideline Best Practice Squat Treatment’, written upon invitation International Union Railways.