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Tutorial

BoBo-vehicle

  1. Introduction
  2. Download the example
  3. Examine directory "intro_tutor_3_bobo_pe3"
  4. View the vehicle in program GPLOT
  5. View the vehicle in program RUNF_INFO
  6. Make a simulation on tangent track without track irregularities
  7. Perform a modal analysis of the vehicle
  8. Perform a modal analysis taking car-body structural flexibility into account
  9. Make a simulation on tangent track at 340[km/h].
  10. Find the non-linear critical speed of the vehicle.
  11. Make a simulation through a curve, without track irregularities.
  12. Make a simulation through a curve, with track irregularities and in-line post processing.
  13. Estimate average wear over a longer track section.   Method #1
  14. Estimate average wear over a longer track section.   Method #2
  15. Modeling of wheel flange lubrication
  16. Modeling of rail lubrication
  17. Modeling of individually rotating wheels
  18. Passenger vehicle
  19. A vehicle model with faults

Introduction

An example of a complete railway vehicle. Explanation of the input data model can be found in "Description of a rail road vehicle model". Which can be found under Rail Road applications.

Bo'Bo' is the denotation of the axle arrangement classification according to UIC (also known as German classification). For further information please see: Wikipedia. The denotation Bo'Bo' means there are two bogies under the unit and each bogie has two powered axles individually driven by traction motors. This axle arrangment is today the most common arrangement in modern locomotives.

The connection between wheels and rails can be modeled in many different ways. In this tutorial func wr_coupl_pe3 has been used.

The steps taken in this tutorial follows the steps suggested under Debugging a vehicle model. These steps are also good to follow in order to get acquainted with the model.


Download the example


Examine the directory "intro_tutor_3_bobo_pe3"


View the vehicle in program GPLOT

Program GPLOT is a graphic program showing a three dimensional view of the vehicle.
Start program GPLOT with the file runf/tang_ideal.tsimf by:

In the GPLOT-window the mouse buttons are defined as:

If you zoom in to a bogie you can see that all couplings have a hot-spot. If you press the hot-spot with mouse button #1 you will get information of that specific coupling. Below is a close up of the first bogie of the vehicle:

README_files/gplot_view.gif

Close the GPLOT-window, before continuing with the next section.


Examine the vehicle in program RUNF_INFO

Program RUNF_INFO is a program which lists how masses and couplings in the model are linked together. Program RUNF_INFO is controlled by an input data file which is described in the RUNF_INFO users manual.

Close all windows except the genfile-window, before proceeding to next task.


Make a simulation on tangent track without track irregularities.

This simulation is used to check the vehicle behaves well on tangent track. Checks all masses are connected and all forces are in balance. From the genfile window perform the simulation by:


Here you can see the wheels have penetrated the rails because of the flexibility in the contact points.
(It is the very big scale factor that makes it possible to detect this deformation)


Perform a modal analysis of the vehicle

Another type analysis that is also very good to start with when debugging and getting acquainted with the model, is modal analysis.

Program MODAL calculates all possible modes of vibration in the model. Number of modes are as many as the number of equations in the model. A low damped mechanical system of one degree of freedom has two complex conjugated eigenvalues. A high damped mechanical system of one degree of freedom has two real eigenvalues, both eigenvalues are negative. A self oscillating mechanical system is a system where the real part of the eigenvalue is positive.
Before the modal analysis starts, program MODAL linearizes the nonlinear equations by an amplitude defined in command modal_param.
Make a modal analysis of the vehicle:

Show animation of the lower sway mode of the BoBo-vehicle: □



Exercise:

Find the following mode shapes in the vehicle:

Lower sway: _________________________________________________
Upper sway: _________________________________________________
Body bounce: _________________________________________________
Body pitch: _________________________________________________
Body yaw: _________________________________________________
1:st bogie kinematic mode: _________________________________________________
2:d bogie kinematic mode: _________________________________________________
Bogie longitudinal vibration: _________________________________________________

Answers

Close the GPLOT-window, before continuing with the next section.



Perform a modal analysis taking car-body structural flexibility into account

Results from a modal analysis in a FEM-program of a car-body at free-free conditions are stored in the subdirectory patranr. This example shows how to take car-body structural flexibility into account:

Show animation of the first bending mode of the car-body: □

If you open the Deform->draw_deform popup menu. You will see that you have got 6 more eigenvalues, compared to the previous case modalRigid. These new equations arise from the three flexible modes added by program NPICK.


Exercise:

Find the following mode shapes in the vehicle:

Lower sway: _________________________________________________
Upper sway: _________________________________________________
Body bounce: _________________________________________________
Body pitch: _________________________________________________
Body yaw: _________________________________________________
1:st bogie kinematic mode: _________________________________________________
2:d bogie kinematic mode: _________________________________________________
Car-body bending mode in phase with bogies: _________________________________________________
Car-body bending mode out of phase with bogies: _________________________________________________
Car-body torsion mode: _________________________________________________
Car-body 2:d bending mode: _________________________________________________

Answers

Please close the GPLOT-window, before continuing with the next section.


Make a simulation on tangent track at 340[km/h].


Find the non-linear critical speed of the vehicle.


Make a simulation through a curve, without track irregularities.


Make a simulation through a curve, with track irregularities and in-line post processing.


Estimate average wear over a longer track section.   Method #1

The simplest method to estimate the wear on wheels and rails, is to calculate the quasi-static portion of the dissipated energy in the contact points. Track irregularities also contribute to wear, but the main portion of the wear is quasi-static due to the curve geometry. To perform this task use program OPTI to initiate several simulations, one simulation for each curve radius.

First create an input data file for program TSIM:


Estimate average wear over a longer track section.   Method #2

This method requires more calculation, but gives more and better results. In this method all steps in the wear loop are performed with the octave script wear_loop.m. The script makes the following calculations in each step:

With this method it is possible to see if the wear will lead to thicker or thinner flanges.


To execute this example:


Modeling of wheel flange lubrication.


Modeling of rail lubrication.


Modeling of individually rotating wheels.

Critical speed:

As you can see, for this vehicle the critical speed is higher ~824km/h. The critical speed depends on the moment of inertia of the wheels. If the speed is high enough, the moment of inertia of the wheels starts to make the wheelset to behave like a rigid wheelset.



Make a simulation through a curve, without track irregularities:


Passenger vehicle.

The above vehicle model describes a quite heavy motor-car approximately. If you want to study a lighter passenger-car without motors, please use runf/tang_ideal_pass.tsimf as Master file.


A vehicle model with faults.

A vehicle model contains many input data, and errors in input data can happen. Therefore it is important to check the model before the real calculations starts. At Debugging a vehicle model you can find some simple checks. Please read Debugging a vehicle model and try to find potential errors in file runf/tang_ideal_err.tsimf.