Switch design optimisation - Multiconsult

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Switch design optimisation: Optimisation of track gauge and track stiffness

Baneseminaret 2015, Multiconsult, 28 January 2015

Elias Kassa

Professor, Phd

Department of Civil and Transport Engineering, NTNU

Trondheim, Norway

E-mail: [email protected]

mailto:[email protected]

2

Outline of presentation

1. Background

2. Train-turnout interaction

3. Track gauge optimisation

4. Track stiffness optimisation

5. Conclusions

3

Background

• Turnouts are composed of a

switch panel, a crossing

panel, and a closure panel

• The maintenance cost is high

in comparison with plain line

• The demand for a novel

turnout design is very high

Facing move Trailing move

4

Common Damage Mechanisms

Fracture Wear Rail Head Cracks Plastic deformation (lipping)

5

Common Damage Mechanisms

Some remedies to reduce maintenance costs are:

1. reducing turnout population (# turnouts)

2. using more durable and advanced materials

3. adopting a preventative maintenance strategy instead of

corrective maintenance

4. optimizing the geometry (layout), support stiffness

(structure) and rail profiles

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Rail profile optimisation [not part of this presentation]

• The rail cross-section varies in the switch and crossing panels

01

23

45

67

89

10

switch rail

Switch rail

stock rail

7

TRAIN-TURNOUT INTERACTION • Track models

• Track receptance

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Train-turnout interaction models

Three models

• Vehicle model

• Track model

• Contact model

Vehicle model Wheel/rail contact

model Track model

vvvvvvvv QFqKqCqM

ttttttt FqKqCqM

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Train-turnout interaction

• The MBS code SIMPACK is used to

model the train-track interaction:

– freight vehicle model, with two Y25

bogies

– track model with time-varying stiffness

and damping values

• The track model is for the standard

turnout type UIC60-760-1:15 (curve

radius 760 m and turnout angle 1:15)

II

IV

Simulation of dynamics

simulation

F v

a) Plasticity

calculation

b) Wear

calculation

III

b

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Wheel-rail contact

• Accurately solving the wheel-rail

contact detection at S&C is the first step

towards the optimisation exercise

Challenges

0 0.02 0.04 0.06 0.08 0.1

-0.02

-0.015

-0.01

-0.005

0

0 0.02 0.04 0.06 0.08 0.1-0.05

-0.045

-0.04

-0.035

-0.03

-0.025

-0.02

-0.015

-0.01

-0.005

0

S6300 and6600

• Simpack uses rail profile interpolation based on

arc length along the profile curve. Requires

very closely measured (sampled) profiles

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Track model

• The track model is based on a simple

moving mass-spring-damper system, with

few degrees-of-freedom, that is coupled to

each wheelset

• This is a common method in MBS software

to account for the track dynamics

– It is sufficient for studies of vehicle ride

dynamics

– It doesn’t accurately predict impact loads in

switches and crossings

kbv

kby

cby

cbv

mt, J

cbv kbv

3 degrees-of-freedom

kbv

kpz kby

cby

cpz

cbv

mt, J

cbv kbv

mr mr

kpz cpz


12

)

)

)

)

Applied wheel load

(q)

Rail pad

rail

Ballast

sleep.

Ballast

sleep.

Ballast

sleep.

Ballast

sleep.

Track model

• This modelling approach is useful in parameter studies and

optimisation exercise as several simulation can be run in short time

• The frequency range of the model can be increased by extending the

track model with few more degrees-of-freedom

kz3

kz23

kz3

kz23

kz12 kz12

ky12 ky12

ky2

cy12 cy12

cy2

cz12 cz12

cz23 cz23

cz3 cz3

m1 m1

m3 m3

m2, J


kbv

kpz kby

cby

cpz

cbv

mt, J

cbv kbv

mr mr

kpz cpz

Track receptance

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TRACK GAUGE OPTIMISATION

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Track gauge optimisation

• When a vehicle is running through a

switch panel, significant lateral

wheelset displacement develop

– leading to severe flange contact in

the curved switch rail

– sometimes leading to flange contact

in the straight switch rail

Lateral wheelset

displacement,

diverging route

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contact point trajectories

contact point jump

• There is an artificial gauge widening on the side of the switch rail (the wheel tries to follow the stock rail)

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• There is a short transition with a

two point contact situation for the

through route

• In the diverging route, the contact

with the switch rail starts earlier and

there is a long transition for the load

transfer

• The severe flange contact result in

an increase in wear of the switch

rails and on some occasions rolling

contact fatigue problems

through route

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• The aim is to relieve the flange contact with

the switch rail at the early stage by steering

the wheel towards the other rail

• A continuous gauge variation (dynamic

gauge widening) is applied at the switch

entry to balance the artificial gauge increase

contact point trajectories

contact point jump

Evaluate the performance of the optimum design with other load cases

Identify design parameters (maximum gauge widening is the critical parameter)

for facing move

Identify optimal design

for trailing move

• The optimal solutions for the

nominal case is validated by

running a wider set of

simulation cases both in the

facing and trailing moves

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Optimisation process

The geometry of the gauge variation is

represented parametrically by:

1. Length L1 where radius is Rc

2. Rout (curvature after the jump)

3. LTotal (total length of gauge increase)

• The influence of Rout and LTotal is not

significant as their effect comes after

the contact point jump

• The variable L1 is directly related to the

maximum amplitude of the gauge

increase d

• The optimal design is obtained by

varying the values of d and five levels

are evaluated: d = {8 mm, 12 mm, 16

mm, 18 mm and 20 mm}

RC

L1

LJump

ROut

LTotal

RC

Jump to

straight

Contact on

diverging rail SWITCH RAIL

STOCK RAIL d

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Track gauge optimisation Results

Facing move

• The wheelset displacement is

reduced to 1.3 - 2 mm, when

using dynamic gauge widening

• The 18 mm and 20 mm gauge

amplitudes lead to a larger

displacement (-6 mm) to the

reverse side

• There is a reduction in wear

index with gauge widening

• Increasing the gauge beyond

18 mm amplitude gives an

adverse effect

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Track gauge optimisation Results

Trailing move

• Gauge widening designs with

12 mm and 16 mm amplitudes are

examined in trailing move to identify

the optimal design

• The 12 mm gauge widening amplitude

leads to a significant improvement in

the wear index

• The wear index for the 16 mm gauge

widening is rather increased both in the

1st and 2nd contacts

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Evaluation of the optimum design

• The performance of the optimal design

is assessed by several load cases with

respect to wear and RCF indices

• The load cases are based on 18

measured wheel profiles and 100

realizations generated using one

Karhunen-Loève expansion

• Deterministic analyses were performed

for each realization to determine the

distribution of the response

100 realizations of wheel profile

contact point location

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Evaluation of the optimum design

• The peak wear index value of

207 N for the nominal case has

reduced to 133 N

• The location of the peak value

has shifted forward

• RCF index exceeded the limit at

several locations for the nominal

case compared to the gauge

optimised geometry

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TRACK STIFFNESS OPTIMISATION

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Advanced track design

Steel - Concrete Two Layered Track

(Corus) [source: INNOTRACK]

• offer a more consistent support

• offer a bridging support

• Track stiffness and track inertia

varies along the turnout

vertical track stiffness along

the turnout

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Track stiffness optimisation

• Measured track receptances at

three locations in the switch at 4.5

m, 9.1 m and 21.85 m from the

front of turnout are used to extract

input data to the track model

• The stiffness in the upper spring-

damper elements of the moving

7-dof track model represents the

combined rail and rail pad

stiffness (kp)

• The remaining flexibility (the

structure underneath the rail pad)

is represented by the lower

spring-damper elements (kb)

kbv

kpz kby

cby

cpz

cbv

mt, J

cbv kbv

mr mr

kpz cpz


Track receptance at location 1

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• There is a 70% change in the

value of kp from location 1 to 3

• There is an 80% increase in the

value of kb

• The aim is to optimise the vertical

track stiffness in the switch panel

• A simple procedure is followed

based on varying the measured

track data parameters

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• Two alternative stiffness kp

variation are developed

• This change is expected to be

gained by adjusting the rail pad

stiffness along the turnout

• In kp_v1, the value of kp is

– increased by 30% at location 1

– not changed at location 2

– reduced by 15% at location 3

• The overall increase in the kp value

is 11%

• In kp_v2, the value of kp is

– increased by 28% at location 1



• This limits the stiffness increase to about 8%

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• The lower spring-damper element

stiffness (kb) is also adjusted

• The value of kb is increased by

20% at location 1, reduced by

10% at location 2 and reduced by

20% at location 3

• The overall change in the value of kb

has reduced to 15%

• This change is expected to be gained

by adjusting under sleeper pads and

ballast mats along the turnout

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Results

• A slight reduction in wear index

is obtained when only kp is

adjusted

• Varying only kb reduces the wear

index at the second contact point

by almost a half

• The peak wear index is reduced

by 50% at the first contact point

and by 80% at the second

contact point when using a

combined kp and kb optimised

values

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Conclusions

• Several gauge widening amplitudes have been analysed

• Larger gauge amplitudes lead to larger displacements to the other side

of the track which cause additional lateral excitation

• The geometry with 12 mm gauge widening amplitude resulted in an

improved performance, both in the facing and trailing moves for the

through route

• The main benefits are very significant reduction of wear and RCF

indices at all times along the switch panel, and therefore improved

behaviour in terms of wear and rolling contact fatigue

• Also, the optimised geometry showed more consistency in the results

when using different wheel profiles

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Conclusions

• With gauge optimisation the contact points near the gauge

corner move towards the rail head and this relieves the flange

contact

• Reducing the stiffness variation along the switch panel seems to

improve the performance of the turnout

• There has been demonstration tests in Sweden with different rail

pad stiffness to validate the technique

Documents

Switch design optimisation - Multiconsult