# Users Manual for Program PRE_CONTACT

Introduction
Wheel profile input data
Rail profile input data
Input data commands

## Introduction

Calculates the distances between the surfaces of wheel and rail. Contact pressure distribution in contact point can also be calculated.

## Wheel profile input data

The wheel profile is described in Y- and Z- coordinates. Positive direction for the Y-coordinate is toward the center of the track for both wheels. Positive direction for the Z-coordinate is downwards. The origin of the Y-coordinates should be at the radius where the wheel diameter of the wheel is measured, this diameter is sometimes also called "The Nominal Running Circle".

For standard gauge tracks, the following is valid:
Lateral semi-spacing between the wheels = 680 mm
Lateral distance between inside of the wheel and "The Nominal Running Circle" = 70 mm
Lateral semi-spacing between "The Nominal Running Circles" = 750 mm

Example of an input data file describing a wheel profile:

```
-40.01 -1.302       Data starts on the tread, as far from the flange
-39.55 -1.269       as possible.
-39.08 -1.236
-38.53 -1.202
-38.09 -1.169
-37.50 -1.136       The Y-coordinate in the first column with
positive direction towards the flange.
.     .
.     .          The Z-coordinate in the second column,
.     .          with positive direction away from the wheel
-2.05 -0.061       center.
-1.52 -0.047       The origins lateral position is on standard gauge
-1.04 -0.032       defined to be 70 mm from the inside surface of the wheel
-0.56 -0.016
0.00  0.004  < The lateral position of the origin = "The Nominal Running Circle"
0.54  0.017
1.01  0.035
1.55  0.054
2.08  0.074

.     .
.     .          Data stops as far up on the flange as possible.
.     .          The larger part of the wheel and rail profiles
that are given, the larger will the contact point
53.05 27.832       functions the program creates be. The functions
53.54 27.906       created by PRE_CONTACT will span a slightly
54.05 27.958       smaller domain than the input profile data.
54.52 27.990
55.03 28.000

```

## Rail profile input data

The rail profile is described in Y- and Z- coordinates. Positive direction for the Y-coordinate is toward the center of the track for both rails. Positive direction for the Z-coordinate is downwards. The origin of the Y-coordinates should be located at the same lateral spacing as for the wheelset ("The Nominal Running Circle"), if the lateral spacing between the two rails are correct. If the rails are worn in a way so the gauge has been changed, the location of the origin of the coordinate system of the rail should move the same distance, because gauge deviation should be considered as a track alignment irregularity. Therefore is the origin of the rail profile is defined relative to the gauge measuring point. The gauge measuring point of the rail is defined as follows: the gauge measuring points are the two points on right and left rail located in a vertical interval between top of rail and 14 mm below top of rail which are closest to each other.

For standard gauge tracks, the following is valid:
Lateral semi-spacing between the gauge measuring points = 717.5 mm
Lateral distance between the gauge measuring point and origin = 32.5 mm
Lateral semi-spacing between "The Nominal Running Circles" = 750 mm

Example of an input data file describing a rail profile:

```
-20.01      0.21457
-19.55      0.16290
-19.08      0.11441   Data start on the rail head, as far from
-18.54      0.06908   track center line as possible.
-18.09      0.02691
-17.54     -0.01211
-17.07     -0.04796   The Y-coordinate in the first column, with
-16.56     -0.08068   positive direction toward track center line.

.         .        The Z-coordinate in the second column, with
.         .        positive direction downward.
.         .

-2.05     -0.07264
-1.56     -0.05574
-1.09     -0.03799
-0.58     -0.01941
0.00      0.00195   < Origin
0.56      0.02025
1.01      0.04133
1.55      0.06325
2.07      0.08601

.         .
.         .
.         .
The data series stops as far down on the rail edge as
30.08      7.69060   possible. Normally data should be present all the way
30.565     8.40925   to the gauge measuring point, i.e. 32.5 mm from origin.
31.05      9.24991   The normal case is that the rail profile is curved in
31.535    10.27144   a way yielding the profile line to be vertical at the
32.011    11.61505   gauge measuring point. This means that no more data of
32.51     13.98782   the rail can be treated.

```

## Input data commands

Summary of all commands:

 BCP_KPF = Approx size of the semi-axis b DXMESH = Long. distance between points in generated mesh. DYMESH = Lat. distance between points in generated mesh. EH = Modulus of elasticity of the wheel material ER = Modulus of elasticity of the rail material FNHR = Contact force normal to the wheel-rail contact surface. IDENT = Three ident lines written to output lists and plots. INTP_STEP_X = Interpolation steps in longitudinal direction INTP_STEP_Y = Interpolation steps in lateral direction MU = Coefficient of friction between wheel and rail NUX = Longitudinal creepage NUY = Lateral creepage NXMESH = Size of mesh in longitudinal direction NYMESH = Size of mesh in lateral direction NYH = Poisson's ratio of the wheel material NYR = Poisson's ratio of the rail material POSW_KPF = Center of contact point for left wheel lateral direction. POSR_KPF = Center of contact point for left rail lateral direction. PHIPOS = Roll angle of left wheel relative to left rail PSIPOS = Yaw angle of left wheel relative to left rail R0 = Defines the nominal radius of the wheels on the wheelset. RLFILE = Input data file separate for the left rail profile. SPIN = Spin creepage WLFILE = Input data file separate for the left wheel profile. YPOS = Lateral position of the wheel relative to rail left

Below follows a description of all input commands in alphabetical order and their default values:

BCP_KPF
Approx size of the semi-axis b
Declared= Real*4    Default= 0.

DXMESH
Long. distance between points in generated mesh.
Declared= Real*4    Default= 2.e11

DYMESH
Lat. distance between points in generated mesh.
Declared= Real*4    Default= 2.e11

EH
Modulus of elasticity of the wheel material.
Declared= Real*4    Default= 2.e11

ER
Modulus of elasticity of the rail material.
Declared= Real*4    Default= 2.e11

FNHR
Contact force normal to the wheel-rail contact surface.
Declared= Real*4    Default= 70.e3

IDENT1, IDENT2, IDENT3
Three ident lines that are written to the output list and to plots.
Declared= Character*80    Default= '  ' (Space)

INTP_STEP_X
Interpolation steps in longitudinal direction.
Declared= Real*4    Default= 0.1 [mm]

INTP_STEP_Y
Interpolation steps in lateral direction.
Declared= Real*4    Default= 0.1 [mm]

MU
Coefficient of friction between wheel and rail.
Declared= Real*4    Default= 0.5

NUX
Longitudinal creepage.
Declared= Real*4    Default= 0.

NUY
Lateral creepage.
Declared= Real*4    Default= 0.

NXMESH
Size of mesh in longitudinal direction.
Declared= Real*4    Default= 31

NYMESH
Size of mesh in lateral direction.
Declared= Real*4    Default= 31

NYH
Poisson's ratio of the wheel material.
Declared= Real*4    Default= 0.28

NYR
Poisson's ratio of the rail material.
Declared= Real*4    Default= 0.28

POSW_KPF
Center of contact point for left wheel lateral direction. If more than one contact area are possible.
Declared= Real*4    Default= 0.

POSR_KPF
Center of contact point for left rail lateral direction. If more than one contact area are possible.
Declared= Real*4    Default= 0.

PHIPOS
Roll angle of left wheel relative to left rail
Declared= Real*4    Default= 0.

PSIPOS
Yaw angle of left wheel relative to left rail
Declared= Real*4    Default= 0.

R0
Defines the nominal radius of the wheels on the wheelset.
The nominal radius of the wheels is the radius measured on the nominal running circle of the wheels. The nominal running circle is described in more detail under Wheel profile input data.
Declared= Real*4    Default= 0.5

RLFILE
The input data file for the left rail profile. If RLFILE not is defined, RFIL will be used.
Lines in RLFILE beginning with the # character are treated as comments.
Declared= Character*132    Default= RFIL

SPIN
Spin creepage.
Declared= Real*4    Default= 0.

WLFILE
The input data file for the left wheel profile. If WLFILE not is defined, HFIL will be used.
Lines in WLFILE beginning with the # character are treated as comments.