simpack how-to-model-axle-bogie

How to model a two axle bogie

1. General

The basic component of all wheel/rail models is a bogie. This guide shows, how to set-up a basic bogie structure. It gives an overview about the topology of bogie models and should be a fundamental model for your further work. The model can be further extended for use in various different applications.

2. Additional Features

During the model set-up it will also be shown, how to define substitution variables and apply them to the model. It’s a very efficient method, which allows modifications to be easily made to complicated structures.

3. Creating an Example Model

3.1. Concept

The model is a simple model to allow you to understand the topology and the concepts in SIMPACK. First a short substitution variable set is to be defined, to aid an efficient model set-up and further modifications to the model. Two identical wheelsets will then be defined in different positions and a bogie frame using the pre-defined substitution variables. Finally a simplified primary suspension will be set-up; using component force elements between the wheels and the bogie frame. To prepare the solver, there will be a number of globals such as wheel/rail profiles and velocity, which are to be defined.

3.2 Modelling

3.2.1

Create a new model. Then switch, as usual, the gravity to the positive z direction (Menu Globals/gravity) and adjust the view to …Wheel/Rail Perspective View“.

3.2.2

Define the following substitution variables to help an efficient model set-up.

Under the icon above, define new substitution variables as shown in the screenshot below.

$_WS_BASE = 2.5000000000E+00 $_SUSP_BASE_LAT = 2.0000000000E+00 $_PRIM_SUSP_X = $_WS_BASE/2 $_PRIM_SUSP_Y = $_SUSP_BASE_LAT/2 $_PRIM_SUSP_Z = -5.0000000000E-01 $_NEG_PRIM_SUSP_X = -1*$_PRIM_SUSP_X $_NEG_PRIM_SUSP_Y = -1*$_PRIM_SUSP_Y

3.2.3

Rename $B_Body1 to $B_WS1 and enter the data for the body definition as shown in the figure below.

3.2.4

Modify the …3D Geometry“ and replace the Cuboid by a Cylinder with the following data;

Diameter: 0,18m

Length: 2,00m

3.2.5

Modify the wheelset joint as shown in the figure below ( Joint Type 07, No. of DOF = 6 ) and enter the menu …Generate/Update Wheel-Rail Elements of Joint“.

3.2.6

In the window below, please note that the bodies for the rails can be changed as well as the bodies for the left and right wheel. Click on OK!

3.2.7

Define the track under the menu globals/track and accept the default settings with OK!

3.2.8

Define a new body “$B_WS2” and repeat the instructions from 3 to 7. In the Joint definition window type 2.5 m for the arc length!

3.2.9

Create new markers in the Body definition window for the wheelsets left and right side using the defined substitution variables!

3.2.10

Define a new body, called $B_BF with the following parameters.

3.2.11

Define the joint of the bogie frame (Joint type 7, 6DOF) and set the arc length to 1.25 m.

3.2.12

Define new markers on the bogie frame using the substitution variables!

3.2.13

Define also 4 new Force elements for the primary suspension with the following parameters.

Force type: 05 Spring-damper parallel cmp

From Marker of the primary suspension is always located at the Bogie_frame and not at the rotating wheelset. (SIMPACK uses the from marker as reference for the calculations)

To Marker is on the wheelset.

Force Parameters:

Cx: 100000000N/m

Cy: 100000000N/m

Cz: 5000000N/m

Dx,Dy,Dz: 20000Ns/m

3.2.14

Finally define some global settings! In the menu Globals/Vehicle Globals define the velocity for the model and click on …apply as defaults“ Leave all other settings as default and close the window. In the menu views/view setup switch on moved view. Select in the menu calculation assemble system and save the model!

3.2.15

Close the Model Setup window and define the solver settings in the Main window! In the Menu Calculation/Time Integration/Configure set end time of the simulation to 5 seconds save the settings and exit the window. Click on the icon below to perform the time integration + measurements!

3.2.16

In the post-processing general plots look at, for example, the force element output values.

3.2.17

Nominal Force Calculation

With the icon above or in the calculation menu in the main window you can open the nominal force calculation block, looks like below.

Pick in the window on selection of force parameters and pick in the new window; “Init with all possible forces”. Than close the window and pick perform. After the calculation save the results and reload your model.

3.2.18

By nominal force calculation you reached with your system an equilibrium state, so it′s possible to carry out eigenvalue calculations.

Also in the menu calculation you could find eigenvalues or start the block directly using the icon above. Just pick on perform, save the results and reload the model. In the model setup window; menu Animation/Model Shapes you can open a window like below. Choose on of the eigenvalues, set the scaling and start the animation.

4. Application

This model is a simple representation of a bogie used to analyse dynamic behaviour. Bogie models of this kind have been used in the eighties and early nineties for investigating stability and curving behaviour of railway vehicles. This type of model requires the real primary suspension design to be reduced to a compact force element with resulting stiffness and damping coefficients in the x, y, and z directions. Kinematically non-linear effects caused by axle boxes with trailing arms, for example, are not considered with this model. Additionally, each design modification, e.g. a different bushing of a trailing arm, requires a recalculation of the contact spring parameters.

Today, with the state of the art SIMPACK Wheel/Rail, more advanced and versatile models can be achieved. Bogies with a higher level of detail are covered in the SIMPACK Wheel/Rail training.