This slip, which is known as creepage, creates longitudinal and lateral forces that help dictate wheelset steering. For a fast calculation of vehicletrack dynamics and wheel rail contact mechanics, wheel rail contact geometric gap is usually idealised in elliptic or nonelliptic form. Rail corrugation growth accounting for the flexibility and. The wheelrail contact is critical to the successful operation of a railway network. Parameters n and m for contact pressure were set in 10 and 8, respectively. The wheel rail contact is critical to the successful operation of a railway network. This makes it possible to estimate the contact patch analytically. Possible contamination at the wheelrail contact may further complicate the situation. Aug 28, 2012 the wheel profile output is utilized for asset optimization, condition based maintenance, wheel rail interface analysis including equivalent conicity and contact patch studies. Steel wheels on steel tracks have very small contact areas. Given that a train wheel is or at least should be a perfect circle, that the railhead itself has a curved profile in section and that metal doesnt deform like a pneumatic tyre, the contact patch per wheel must surely be much smaller. Experimental characterization of wheelrail contact patch. Considering the equivalence relationship given above, wheelrail contact with a negative yaw.
Energy loss at the contact patch is caused when wheelset movement is restrained during curving, causing relative slip at the wheelrail contact patch. The contact area and pressure distribution in a wheel rail contact is essential information required in any fatigue or wear calculations to determine design life, regrinding, and maintenance schedules. The contact patch size of solid materials is described by the equations of contact mechanics. Fastsim to fully model the rolling contact of the wheel over the rail. Apr 12, 2017 steel wheels on steel tracks have very small contact areas.
Contact patch transport technology from the ground up. Using the wheel load data shown in table 2 and the method of magel and kalousek 1996, contact. This leads to a redistribution of the contact stresses. An approximate analytical method is proposed for calculating the contact patch and pressure distribution in the wheelrail interface. What is the size of the contact surface of train wheels. Jun 16, 2019 the fourday wheelrail interaction conference brings together engineers the kind who run calculations, not locomotives from major railroads, transit agencies, suppliers, consulting firms, and research organizations to learn from each other and present their research and experiences in order to make railroading safer and more efficient. The work described in this paper has assessed the feasibility of measuring a dynamic wheelrail contact patch using an array of 64 ultrasonic elements mounted in the rail. The weight of the vehicle is translated through normal forces. Dynamic response of wheelrail interaction at rail weld in.
Contact conditions are more severe in the latter, which occurs mainly in curves. This gui program might be able to calculate the contact size and contact pressure on the contact patch by hertz theory. Failure of a wheelrail contact is usually by wear or fatigue of either component. The rolling contact patch could, especially, pose a challenge for the technology. Each element is individually pulsed in sequence to build up a linear crosssectional pressure profile measurement of the interface. Wheel rail contact calculator file exchange matlab central. Actively positioning the wheels and therefore the contact patch at the optimum point of the rail, along with active torque control, will practically. The contact area and pressure distribution in a wheelrail contact is essential information required in any fatigue or wear calculations to determine design life, regrinding, and maintenance schedules. The influence of these idealisations on contact solution has. Electromechanical design and development of the virginia. A driven wheel does not roll but actually turns faster than the corresponding locomotive movement and the difference between the two is known as the slip velocity. Rail load capacity constructed items general discussion. Feasibility study for an ultrasonic sensor for monitoring. As the contract stress exceed a certain limit, the metal at the near surface becomes slightly displaced in the direction of the tractive load and slip in the wheel rail contact patch.
The theory developed by hertz when he was a 24 year. Signal transmissibility of railcar bearing vibrations. Nonelliptic wheelrail contact modelling in vehicle. Investigation on wheelrail contact and damage behavior in.
Getting the right profile simon iwnicki, julian stow and adam bevan rail technology unit manchester metropolitan university the contact the contact patch between a wheel and a rail is typically the size of a 5p piece and its shape depends on the geometry of both bodies. Roller rig, wheelrail contact mechanics, rail vehicle dynamics, contact patch dynamics, wheel forces and moments a need exists for a new test rig design with advanced sensing technologies that will allow the railroad industry and regulatory agencies to better understand the wheelrail contact dynamics and mechanics, especially as it pertains. Clearly, the pressures at the key interface are very high, considerably in excess of the normal yield stress. Slip is the slip velocity compared to the vehicle velocity. The result is a map of the wheelrail contact stress as a vehicle moves through the turnout. For a fast calculation of vehicletrack dynamics and wheelrail contact mechanics, wheelrail contact geometric gap is usually idealised in elliptic or nonelliptic form.
For rolling contact and the same thermal material properties in wheel and rail, the rfect heat wj transferredq. Most of the noise and vibration comes from larger irregularities, and measurements have revealed a peak at a wavelength of about 6 cm, corresponding to regular bumps in the rail surface known as corrugations. Roller rig, wheel rail contact mechanics, rail vehicle dynamics, contact patch dynamics, wheel forces and moments a need exists for a new test rig design with advanced sensing technologies that will allow the railroad industry and regulatory agencies to better understand the wheel rail contact dynamics and mechanics, especially as it pertains. The roller is five times larger than the scaled wheel to keep the contact patch distortion that is inevitable with a roller rig to a minimum. Tread braking of railway wheels wheel and block temperatures. The contact patch, which is 1015 mm long, bridges across small irregularities so they dont inject pulses into the wheel. Wheel rail contact stresses the wheel rail contact patch is normally about the size of the u. As wheelset yaw motion is inevitable in vehicle system dynamics, this motion will affect the wheel rail normal contact behaviour. It is mainly related to the hardness of the material in terms of youngs modulus. The contact patch is the width of the wheel that contacts the ground when youre riding.
Wheelrail contact behaviors in the switch have been studied with a number of laboratory experiments and numerical procedures. The contact is small and supports large loads, therefore. An evaluation of ultrasonic arrays for the static and. Effects of profile wear on wheelrail contact conditions. Abstracta modified kikpiotrowski mkp model is proposed in this paper for an accurate and robust calculation of wheelrail normal contact problem. Rolling contact fatigue of rails the stress concentration feature which causes initiation of rcf cracks is the contact between the wheel and the rail.
Conditions under the contact patch are always severe and the yield stress of the rail steel is always exceeded, on at least a microscale, due to the surface roughness of the wheel and the rail. The solutions of the normal contact problem in terms of the shape and area of the contact patch and the corresponding pressure distribution within the contact region are obtained by the method proposed in sect. Jan 12, 2016 the solutions of the normal contact problem in terms of the shape and area of the contact patch and the corresponding pressure distribution within the contact region are obtained by the method proposed in sect. The wheelrail contact patch is normally about the size of the u. The fourday wheelrail interaction conference brings together engineers the kind who run calculations, not locomotives from major railroads. They have very little rolling resistance around x less than a car tire so can carry heavy p. The shape of the wheelrail contact patch satisfies 4 x p y, y w. The rolling contact between the wheel and rail was solved in. A comparison is made to the kikpiotrowski model in terms of contact patch and pressure as well. Feb 02, 2009 given that a train wheel is or at least should be a perfect circle, that the railhead itself has a curved profile in section and that metal doesnt deform like a pneumatic tyre, the contact patch per wheel must surely be much smaller. The rolling contact between the wheel and rail was solved in the time domain by the penalty method. The program also calculates normal force versus creepage comparing both johnson and vermeulen theory and kalkers theory. The deformation of the surfaces in contact is approximated using the separation between them. Also parameters phi1 and phi2 for johnson and kalker methods were set in 0.
The timedomain vehicletrack interaction model comprises a flexible rotating wheel set model, a cyclic track model based on a substructuring. Ultrasonic railwheel contact investigation a recent development is in the monitoring of railwheel contacts and their pressure distribution using ultrasonics. Join a select group of researchers, suppliers and railway practitioners in sharing the latest information on wheelrail, vehicletrack interaction at wri eu 19 in vienna, austria, 2931 october, 2019, the hilton vienna danube waterfront. Understanding the wheelrail interface part one the. The presented method is able to consider the relationship between the elastic deformation of a line and the normal pressure distribution within the contact patch. Pdf distribution of contact pressure in wheelrail contact area. Contact occurs mainly at the wheel tread rail head and wheel flange rail gauge corner. Using the wheel load data shown in table 2 and the method of magel and kalousek 1996, contact stresses for a 36inch wheel and a 38inch. There is an amount of deformation where the wheel meets the rail.
When a wheel rolls freely along the rail the contact patch is in what is known as a stick condition. Nonelliptic wheelrail contact modelling in vehicle dynamics. The wheel contact faces have a little taper, and the rail head is crowned. Jan 04, 2014 energy loss at the contact patch is caused when wheelset movement is restrained during curving, causing relative slip at the wheelrail contact patch. The vt roller rig is comprised of a wheel and a roller in a vertical configuration that simulate the singlewheelrail interaction in onefourth scale. When the contact patch is located at the transition regions of flange bearing part, the process of wheelload transition is accomplished by the ramps of bearing flangeway, and the wheel drops with the height decrease of bearing flangeway s5s6. The wheelscan system provides immediate feedback on the wheel wear and wheel profile of every axles of each train that passes wayside measurement system. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheelrail contacts. An evaluation of ultrasonic arrays for the static and dynamic. The contact model between wheel and rail is approximated to be elliptical, which is shown to be accurate for the described purpose. A single contact patch between the wheel and the rail is typically the size of a small coin. The hardness of both materials dictates how large this contact patch is due to the immense pressure between the two objects. For instance, kassa and nielsen 5,6 used the commercial multibody system mbs software, gensys, to model the dynamic interaction between the railway vehicle and turnout. In practice, singlepoint contact is also regarded as one of the effective measures to reduce the wheelrail wear and to provide satisfactory dynamic performance of the vehicletrack system.
This is why trains grip because the pressure being exerted on the rail is so high. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. What is the size of the contact surface of train wheels and. Effects of profile wear on wheelrail contact conditions and. The timedomain vehicletrack interaction model comprises a flexible rotating wheel set model, a cyclic track model based on a. As we reach the bottom corner of the head we reach the upper fishing surface. A phased array transducer in a specially machined rail provides contact patch information from fullsize railwheel contacts. These two idealisations deviate from the actual one if the lateral combined curvature within the contact patch is not constant or the yaw angle of wheelset exists. The contact pressure distribution in the rolling direction is assumed to be.
Numerical investigation into the effect of geometric gap. The rail steel can be assumed to have a shear yield strength of k70 ksi. Users can choose between the krausepoll and the more detailed archard wear laws. Back for more wheelrail interaction trains magazine. A robust nonhertzian contact method for wheelrail normal. Automated the wheelscan system provides immediate feedback on the wheel wear and wheel profile of every axles of each train that passes wayside measurement system. The profiles of wheel and rail were, respectively, modelled as lma and cn60, and the track cant of 1. The contact patch between a wheel and a rail is typically the size of a 5p piece and its shape depends on the geometry of both bodies. The objective of the project was to investigate the transmissibility of the wheel bearing vibration signals through the complicated path from the defective bearing to the rail. Heres a quick summary of what weve learned over the years skateboard and longboard wheels are made from the petrochemical called polyurethane.
Rail wear the amount of material removed from the wheel or rail after the simulated run is estimated by using the contact patch positionssizes and contact forcescreepages. The perfect wheel rail contact means that the wheel and rail surfaces in the contact patch instantly assume a common temperature at contact. Pdf a rail mounted ultrasonic sensor for contact patch. Analysis of wheelroller contact and comparison with the. A novel method to model wheelrail normal contact in vehicle. Interestingly, much the same happens when the driver applies the brakes of a railway train. The majority of railway tracks have sufficiently large radii to enable a combination of wheel coning and superelevation to mitigate the differences in. Both mechanisms depend on the state of stress which in turn depends on size and location of the contact patch. The wheel profile output is utilized for asset optimization, condition based maintenance, wheel rail interface analysis including equivalent conicity and contact patch studies. Senior director inspection services and technology. A simplified model for solving wheelrail nonhertzian normal.
The contact patch between wheel and rail is an incredibly highly stressed and vital area of the rail. The wheel rail interface anatomy and key terminology the contact patch and contact pressures creepage and traction forces part 2 vehicle steering and curving forces wear and rolling contact fatigue part 3 the third body layer, tractioncreepageand friction management. Contact conditions are more severe in the latter, which occurs mainly in. Possible contamination at the wheel rail contact may further complicate the situation. However, ignoring the influence of the profile curvature on the wheel rail normal contact could cause worse estimations of the shape of the wheel rail contact patch and the contact pressure 22,27. Every year, some of the brightest people in the railroad and transit worlds gather to discuss the dimesized contact patch between wheels and rails. Lets assume a circular contact patch, with a radius of 0. What area of a typical commuter train wheel is in contact. Clearly, the pressures at the key interface are very high, considerably in excess of the normal yield stress of the material. Mar 21, 2006 the contact area and pressure distribution in a wheel rail contact is essential information required in any fatigue or wear calculations to determine design life, regrinding, and maintenance schedules. A novel method to model wheelrail normal contact in. What is the contact area between a train wheel and the rail.
I am guessing it isnt more than a few square millimetres per wheel. With more choice than ever before out there, and myths all over the internet, the world of wheels is a little confusing. The contact patch of a railroad wheel is much smaller than for pneumatic rubber tires. In this work, a simulation tool is developed to analyse the growth of rail corrugation consisting of several models connected in a feedback loop in order to account for both the shortterm dynamic vehicletrack interaction and the longterm damage. Aug 24, 2015 on curved track, the contact patch on the outside wheel shifts laterally towards its larger radius and the inside wheel towards the smaller radius, balance depending upon curvature severity. A simplified model for solving wheelrail nonhertzian. Assessing the effects of coupler force and train speed on. The theory developed by hertz when he was a 24 year old research assistant. Contact occurs mainly at the wheel treadrail head and wheel flangerail gauge corner.
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