Vertical Wheel-rail Contact Force Research Articles

Track Condition Analyser: Identification of Rail Rolling Surface Defects, Likely to Generate Fatigue Damage in Wheels, Using Instrumented Wheelset Measurements

Vertical wheel—rail contact forces with high magnitudes are generated in vehicle operation on track sections with periodic (rail corrugation) or discrete (rail joints, crossings) surface defects and/or in operations with out-of-round wheels. This may result in severe wheel damage, such as subsurface rolling contact fatigue and deep shelling. Based on input data in the form of contact forces measured by an instrumented wheelset, including contributions with frequencies up to about 2 kHz, a track condition analyser (TCA) has been developed. The dominating and most frequently occurring types of rail rolling surface defects can be detected, their location along the line can be determined, and their detrimental effect on the fatigue life of wheels can be estimated. This means that the TCA can be used as a tool to assess the current track quality and determine the need for immediate and planned track maintenance. Using the instrumented wheelset on a Swedish passenger train, the 450 km line Stockholm—Gothenburg can be measured in both directions during an 8 h test campaign.

Dynamic Model of a Railway Wheelset for Corrugation Problem Analysis

In the present work a model of flexible shafts is adapted for modelling the railway wheelset. The dynamic properties of the solid are obtained from a solid finite element model of a real wheelset. The model adopts an Eulerian coordinate set for numerical efficiency. Results of the crossed-receptance and mobility functions are presented, where the excitation is the vertical wheel-rail contact force and the displacement (or velocity) is measured in the wheel-rail contact plane. These results let us know that the gyroscopic effect may contribute to define the wavelength-fixing mechanism in some corrugation problems, even if the train speed is low.

Dynamic interaction between train and railway turnout: full-scale field test and validation of simulation models

Results from an extensive field test performed in a UIC60-760-1:15 turnout on Svealandsbanan in Sweden are reported. Lateral and vertical wheel-rail contact forces were measured by a wheelset instrumented with strain gauges on the wheel discs. The test train with axle load 25 tonnes passed through the turnout in the main and diverging routes and in the facing and trailing moves. The influences of train speed and moving direction on the magnitude and the position of the maximum lateral contact force in the diverging route of the switch panel, and the influences of train speed, moving direction and route on the maximum vertical contact force in the crossing panel, are investigated. Measured contact forces are compared with calculated forces for a validation of two previously developed numerical models. The magnitude and position of the calculated maximum lateral contact forces are in good agreement with the corresponding measured values. Both measurements and numerical simulations show an increase in maximum lateral contact force with increasing train speed in both the facing and trailing moves. The facing move of the diverging route leads to the highest lateral contact forces in the switch panel. The maximum vertical contact force is not influenced significantly by whether the train is moving in the facing or trailing moves. However, the train route (main or diverging) has a large influence on the maximum vertical contact force at the crossing.

High-frequency vertical wheel–rail contact forces—Validation of a prediction model by field testing

The computer program DIFF, which is being developed at CHARMEC since the late 1980s, is used to simulate vertical vehicle–track interaction at high frequencies, from about 20 Hz to at least 2000 Hz. Measured results from two field test campaigns are used to validate the vehicle–track interaction model. The first test case involves impact loads from a wheel flat, while the other case studies the influence of a corrugated rail on dynamic vertical wheel–rail contact forces. Four vehicle models and two visco-elastic track models are compared. The track models are calibrated versus test data from laboratory and field tests. Input data on rail and wheel roughness are taken from field measurements. Good agreement between calculated and measured vertical contact forces is observed, both with respect to magnitude and frequency content, for most frequencies below 2000 Hz. The best agreement is obtained when using a vehicle model that accounts for both wheelsets in a bogie, instead of using a single wheelset model.

High-frequency vertical wheel–rail contact forces—Field measurements and influence of track irregularities

Field measurements of vertical wheel–rail contact forces in the frequency range 0–2000 Hz are reported. Instrumented wheels are employed together with a new method for signal processing including suppression of disturbing wheel resonances. Four different classes of rail irregularities are identified which all require consideration of high-frequency dynamics when evaluating wheel–rail contact forces. Ten stretches of Swedish track were selected for inspection and measurement of rail irregularities. The expected correlation between rail corrugation and measured dynamic forces is confirmed. It is found that high-frequency dynamics in the range 100–1250 Hz contributes significantly to contact forces which are important in the development of rolling contact fatigue. The present application is to high-speed trains on the Swedish track network with its mixed passenger and freight traffic. However, the method makes it possible to assess the level of high-frequency wheel–rail contact forces for all types of train traffic and could be used for a quantitative analysis of a complete railway network.

A method for setting wagon speed restrictions based\\\\ on wagon responses

This article presents a method to set wagon speed restrictions based on wagon body accelerations. For the specific locomotive, wagon conditions and track states, an individual wagon critical speed may be determined from its running stability. Furthermore, stability can be evaluated by a wheelset derailment index, which is determined by the ratio of lateral and vertical wheel–rail contact forces. Providing the information on the critical speed online has, without doubt, significant industrial application potentials. The research efforts in this article are focused on the estimation of wheel–rail contact forces using measured wagon body accelerations.

Out-of-round railway wheels—wheel-rail contact forces and track response derived from field tests and numerical simulations

The influence of different types of railway wheel out-of-roundness (OOR) on the vertical dynamic wheel-rail contact force and track response is investigated through extensive field tests and numerical simulations. The response from a freight train, provided with a number of different types of severe wheel tread damage, is studied. Two different axle loads are used in combination with different train speeds in the range 30-100km/h. The wheel defects are wheelflats, local spalls due to rolling contact fatigue cracking, long local defects and polygonal wheels (periodic OOR). The vertical wheel-rail contact force was measured using a strain gauge based wheel impact load detector. Strain gauges and accelerometers were positioned on rails and sleepers to measure the track response. Most of the magnitudes of measured impact forces were found to be lower than the current impact load limit that is used in Sweden to determine when a defective wheel should be removed for repair. Only the long local defect caused larger force magnitudes than the wheel removal criterion. Measured responses are used to calibrate and validate numerical models for simulation of train-track interaction. Results from one linear and one state-dependent track model are compared.