# Modeling of the wheel/rail coupling

The wheel/rail-coupling is a very important coupling for a railroad vehicle, especially in lateral direction. Between the wheel-flanges and rails we have a clearance between 6-10 [mm], which is about the same as we have in secondary and primary suspension (at least on tangent track). Therefore the wheel- and rail- profiles has a great influence on the lateral behavior of the railway vehicle.
In vertical direction however the contact point is very stiff, why the vertical comfort not is affected much, but it is important when calculating the vertical wheel rail forces.

 Coupl Creep_tanel_springs_1 Reference manual

The most accurate model. No precalculated wheel/rail geometry functions are needed. "Coupl creep_tanel_springs_1" uses the wheel and rail profiles directly. On top of the rail a mesh of brushes are located, all brushes are normal to the rail surface and all have flexibilities in compression- and tangential- directions. The compression flexibility solves the vertical problem, the wheel profile is pressed towards the rail profile until the enough vertical force is generated. The shape of the contact surface is determined by the shape and the positions of the wheel- and the rail- profiles. The contact pressure distribution calculated in the vertical problem, are later used for calculating the tangential creep forces.

 Example : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Coupl Creep_fasim_1 Reference manual

Wheel-rail forces are calculated by J.J.Kalkers routine FASIM. The normal problem is solved by a contact spring knwr between wheel and rail, normal to the contact surface. In order to speed up calculations "coupl creep_fasim_1" uses precalculated wheel/rail-geometry functions calculated by preprocessor kpf,

 Example : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Coupl Creep_lookuptable_1 Reference manual

Wheel-rail forces are calculated by interpolation in a four dimensional lookup table. The four dimensions are: absolute creep, direction of creep, spin and shape of contact ellipse. The normal problem is solved by a contact spring knwr between wheel and rail, normal to the contact surface. In order to speed up calculations "coupl creep_lookuptable_1" uses precalculated wheel/rail-geometry functions calculated by preprocessor kpf,

 Example #1 : Input data code to be copied into your rail vehicle model. Example #2 : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.

 Func Wr_coupl_pe0 Reference manual

Convenience function which connects a wheelset to a vehicle following track-piece similar to wr_coupl_pe3. Function wr_coupl_pe0 handles speeds down to zero velocity, by gradually switching to Coulomb friction.

 Example #1 : Input data code to be copied into your rail vehicle model. Example #2 : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Func Wr_coupl_pe1 Reference manual

 Func Wr_coupl_pe2 Reference manual

 Func Wr_coupl_pe3 Reference manual

Convenience function which connects a wheelset to a vehicle following track-piece. Creates up to three simultaneous contact surfaces similar to "coupl creep_lookuptable_1" on each wheel. The contact couplings are named cp1, cp2 and cp3. Using the convenience function wr_coupl_pe3 is faster and requires less input data compared to creating the wheel/rail-couplings manually with coupl creep_lookuptable_1.

 Example #1 : Input data code to be copied into your rail vehicle model. Example #2 : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Func Wr_coupl_pe4 Reference manual

Convenience function which connects a wheelset to a vehicle following track-piece similar to wr_coupl_pe3. Function wr_coupl_pe4 handles varying rail profiles along the track.

 Example : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Func Wr_coupl_pr3 Reference manual

Convenience function which connects a wheelset to a vehicle following track-piece. Creates up to three simultaneous contact surfaces similar to "coupl creep_fasim_1" on each wheel. The contact couplings are named cp1, cp2 and cp3.

 Example : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.
 Func Wr_coupl_pra3 Reference manual

Convenience function which connects a wheelset to a vehicle following track-piece similar to wr_coupl_pr3. Function wr_coupl_pra3 calculates the wear according to Archard's Wear Law for each strip in the contact point.

 Example : A model of three wheels subjected to pure creepages in longitudinal, lateral and spin direction.