Contact Benchmark Version2

Yann

Description

A Wheel-Rail Contact Benchmark thDiscussion Document – Version 2 ( 7 April 2006 ) 1. Introduction The Rail Technology Unit at Manchester Metropolitan University (MMU) is planning to coordinate a benchmark of the wheel-rail contact models currently used in railway vehicle simulations. The aim of the benchmark is to allow an informed choice when selecting a contact model for a particular modelling situation. This document is a revised proposal following initial discussions. After further discussion the aim is to propose a detailed Contact Benchmark which and to use this to evaluate the different tools used to model rail-wheel contact. 2. Background Computer models are used to predict the behaviour of railway vehicles in an ever widening variety of applications. A key aspect of railway vehicle modelling is the interaction between the wheels and rails. A wide range of contact models exist to define the wheel-rail interaction, and to achieve acceptable computational times all of these models make simplifying assumptions. As a result each model has a limit to its validity and restrictions to its application. The effects of these simplifications are not always apparent to the end user, and due to the widening scope of railway simulations the possibility arises that contact models are used beyond the extent of their initial validation. 3. Aim To allow an informed choice of wheel-rail contact model for railway simulations. 4. Objectives ...

Informations

• Publié par: Phyon
• Nombre de lectures: 20
• Langue: English

Extrait

A Wheel-Rail Contact Benchmark - Discussion Document – Version 2

7

th

April 2006

Page

1 of

4

A Wheel-Rail Contact Benchmark

Discussion Document – Version 2 ( 7

th

April 2006 )

1. Introduction

The Rail Technology Unit at Manchester Metropolitan University (MMU) is planning to

coordinate a benchmark of the wheel-rail contact models currently used in railway vehicle

simulations. The aim of the benchmark is to allow an informed choice when selecting a

contact model for a particular modelling situation. This document is a revised proposal

following initial discussions. After further discussion the aim is to propose a detailed

Contact Benchmark which and to use this to evaluate the different tools used to model rail-

wheel contact.

2. Background

Computer models are used to predict the behaviour of railway vehicles in an ever widening

variety of applications. A key aspect of railway vehicle modelling is the interaction between

the wheels and rails. A wide range of contact models exist to define the wheel-rail

interaction, and to achieve acceptable computational times all of these models make

simplifying assumptions. As a result each model has a limit to its validity and restrictions to

its application.

The effects of these simplifications are not always apparent to the end user, and due to the

widening scope of railway simulations the possibility arises that contact models are used

beyond the extent of their initial validation.

3. Aim

To allow an informed choice of wheel-rail contact model for railway simulations.

4. Objectives

4.1. To investigate the difference between predicted

o

Contact size, shape and position

o

Normal stress distribution

o

Tangential stress distribution

o

Creep forces

by different contact models

4.2. To investigate the effects of different wheel-rail contact models on

dynamic vehicle simulation

The effects of the contact models on the dynamic behaviour of a

vehicle simulation will be evaluated and their capabilities in handling

straight, transitional, curve and switch track sections assessed.

4.3. Validation

The outputs from Objective 1 could be validated against tests on a

purpose built laboratory rig.

A Wheel-Rail Contact Benchmark - Discussion Document – Version 2

7

th

April 2006

Page

2 of

4

5. Simulation Cases

To satisfy the objectives above, two distinct simulation cases are proposed:

A) Prescribed wheelset simulation

B) Dynamic vehicle simulation

5.1. Simulation Case A – Prescribed wheelset simulation

This case aims to provide comparable data from different contact models for clearly

defined contact conditions. Real wheel and rail profiles will be used, with dictated

lateral displacement, yaw angle, roll angle, wheel load, velocity and friction

coefficient. The simulated contact size/shape/position, stress distribution, creep

forces generated and computational time will be compared. Combinations of wheel

attitude and position could be selected to challenge the contact models.

To try to include all the various aspects of interest it is suggested that Case A be split

into two sub-cases:

o

Normal contact

o

Tangential contact

Case A-1 Normal Contact

Purpose – To consider only the geometrical and normal parts of the contact model

with a static wheelset.

Inputs:

Wheel profiles

Rail profiles

Wheel rolling radius

Gauge width

Flange-back spacing

Vertical load

Variables:

Lateral displacement

Yaw angle

Outputs:

Contact position or point of highest normal pressure

Contact patch area

Contact patch shape

Normal stress

Contact angle

Effective conicity using UIC method

Roll angle of wheelset

Computational time to return contact data

A Wheel-Rail Contact Benchmark - Discussion Document – Version 2

7

th

April 2006

Page

3 of

4

Case A-2 Tangential Contact

Purpose – to use the contact patch data output from Case A-1 to simulate a wheelset

moving along a track with given forward velocity, lateral displacement and yaw angle.

Inputs:

Wheel profiles

Rail profiles

Wheel rolling radius

Gauge

Flange-back spacing

Vertical load

Variables:

Lateral displacement

Yaw angle

Velocity

Outputs:

Creepages

Creepforces

Energy dissipation in the contact patch

Tangential stress

Computational time

5.2. Simulation Case B –Dynamic vehicle simulation

This case aims to evaluate the effects of the contact model on the simulation of the

dynamic behaviour of a representative vehicle. It is proposed that Benchmark

vehicle 1 from the Manchester Benchmarks is used. This vehicle is a general

passenger coach with two bogies and a simple primary suspension.

It is based on

the ERRI B176 benchmark vehicle, without yaw dampers, and with the following

major simplifications:-

Simple primary suspension;

Symmetric vehicle;

Non-inclined dampers with simple damping rates.

Full details of this benchmark vehicle are given in Vehicle System Dynamics Vol 30

Numbers 3-4 pp 295-313 September 1998. The information is also available on the

MMU Web site at

www.railtechnologyunit.com

. The sections of track used will

include straight track, transitions, curves and switches. The resulting wheelset path,

normal forces, creep forces and contact size/shape/position will be compared.

Evaluation of derailment, curving and stability could also be carried out.

A Wheel-Rail Contact Benchmark - Discussion Document – Version 2

7

th

April 2006

Page

4 of

4

6. Validation

The comments made during the discussion so far all indicate that validation of the

benchmark tests would be important and would allow the results to be put into some sort

of context, however the difficulties in comparing computer models to field measurements

are also recognised. This discussion will need to continue for the moment until there is an

agreed proposal for a method(s) of validation.

7. Summary

Table 1 summarises the inputs and outputs for the simulation cases.

Please send comments or points for discussion on this proposal to:

Simon Iwnicki

[e-mail]

or

Phil Shackleton

[e-mail]

Input

C

a

s

e

A

-

1

C

a

s

e

A

-

2

C

a

s

e

B

Wheel/Rail Profiles

3

3

3

Wheel Load

3

3

Lateral displacement

3

3

Attitude/Yaw

3

3

Velocity

3

3

Friction Coefficient

3

3

3

Track Geometry

3

Output

Contact size/shape/position

3

3

Normal Stress Distribution

3

Tangential Stress Distribution

3

Creep Forces

3

3

Wheelset Path

3

Normal Forces

3

3

Derailment Quotient

3

Stability

3

Computational Time

3

3

3