Wheel-Rail Interface Management

in

Heavy Haul

D R WelsbySenior Research Fellow

Wheel-Rail Interaction & Track Design

Institute of Railway Technology

20 May 2014

Brisbane, QLD.

Content• Overview of Operating Conditions

• Issues & Objectives

• Influencing Parameters

• Interface Management

• Interface Maintenance

Overview of Heavy Haul Operating Conditions• Definition of Heavy Haul (IHHA):

• Regularly operates trains ≥ 5000t gross mass

• Annual haulage of 20MGt over at least 150km

• Regularly carries axle loads ≥ 25t

• Australian Heavy Haul (examples):

• Pilbara Iron Ore: 36-40tal, 30-45,000Gt trains

• Queensland Coal: 26tal, 7-10,000Gt trains

• NSW Coal: 25-30tal, ~10,000Gt trains

Must Satisfy

at Least Two

Overview of Heavy Haul Operating Conditions• Track:

• Usually minimum head hardened rail, 60 or 68kg/m section

• CWR – limited use of aluminothermic welding over mob. flashbutt

• Heavy concrete sleepers

• Varying lubrication strategies (wayside – solid stick – none)

• Rollingstock:

• High adhesion AC locomotives

• Maximum speed ≤80km/h

• Wagon bogies usually 3-piece design (simple/cost effective)

• Includes passive, steering and non-steering types

Issues & Objectives• Issues of concern:

• High wheel and rail wear

• Rolling Contact Fatigue (RCF) preventing UT (shielding)

• RCF initiated defects (e.g. transverse defect)

• Vehicle hunting & instability

• Broken rails and derailment

(Wear) (Shielding) (Transverse Defect)

Issues & Objectives• Objectives:

• Reduce risk of rail break and derailment

• Limit RCF development, growth and associated defects

• Maintain surface condition suitable for effective UT inspection

• Limit wear and maximise rail and wheel life

• Maintain rails and wheels in the safest & most economical manner

• Maintain vehicle stability

No. 1 objective is

to prevent this !!

(Smith, 2009)

Influencing Parameters (RCF & Wear)• Contact stress

• Traction/adhesion & creepage

• Rail and wheel material

properties & behaviour

• Maintenance practices

(Magel, 2011)

Influencing Parameters• Contact stress:

• Simplified elliptical contact (Hertz)

• Highly dependent on contact

geometry

• Not directly proportional to axle

load

• In reality non-hertzian

(Rovira et. al., 2012)

(Innotrack, 2009)

• Contact stress:

• Non-hertzian contact more realistic

• Dynamic modeling software, such as Universal Mechanism, used to

analyse contact conditions

Contact patch Normal pressure distribution

-11

-6

-1

4

9

-50

510

0

500

1000

1500

p(x,y),

MPa

y, mm

x, mm

2 point contact (new)

Towards Conformal (worn)

Contact Evolution

Influencing Parameters• Traction/adhesion & creepage:

• At a macro level adhesion is defined as the “ratio

of tangential to normal traction” transmitted at

the wheel-rail interface (Fletcher & Lewis, 2012)

• At a micro level adhesion “depends on elastic

deformation of the rail and wheel surfaces at

their contact which produces partial slip

[creepage] with distinct sticking and slipping

regions” (Fletcher & Lewis, 2012)

• Directly affected by the friction characteristics

(interfacial layer)

(Olofsson & Lewis, 2006)

Influencing Parameters• Traction/adhesion & creepage (cont..):

• Three creep forces and creepages are generated:

• Longitudinal: velocity difference, yaw

• Lateral: lateral velocity, yaw, roll

• Spin (moment): contact angle, yaw

• Combined effect changes the stick/slip characteristics

(Vollebregt, 2013)

Influencing Parameters• Traction/adhesion & creepage (cont..):

• Impact:

• Wear ≈ energy dissipation ≈ Ʃ [creep forcei x creepi]

• RCF develops from high creep forces and resulting shearing action at

the surface. RCF damage increases with increasing surface shear

Position of Maximum Shear Stress

(Pointner, 2008)(FRA, 2011)

Influencing Parameters• Material properties & characteristics:

• Quality of manufacture:

• Avoid; inclusions, segregation & impurities

• Reduce; residual stresses in rolled section

• Modern techniques generally produce good quality steel

• Strength (yield / tensile):

• Shear strength resistance to RCF/deformation

• Fatigue strength fatigue life in bending

• Ductility:

• Ability to withstand the high plastic strains without fracture

• Can be measured through tensile testing (reduction of area) – indicative,

or through complex twin disk testing

Influencing Parameters• Material properties & characteristics (cont..):

• Work hardening:

• Desirable characteristic where the hardness of the surface material

increases due to strain

• Increases resistance to wear, deformation and development of RCF

• Often ~10mm deep into the head in heavy haul railways

• Toughness:

• Resist high impact loads & inhibit fatigue crack initiation

• Measured as the energy required to rupture per volume of material

Influencing Parameters• Material properties & characteristics (cont..):

• Wear resistance:

• Suitable hardness to reduce wear

• Can be considered in conjunction with lubrication

strategy

• Weldability:

• Suitable for flashbutt and aluminothermic welding

processes

• Aim to maintain a relatively uniform hardness

across joint

Influencing Parameters• Combined effects:

• Best represented in terms of „Shakedown‟ theory (concept of first yield

and residual stress effects)

a. Fully elastic = No deformation occurs

b. Elastic shakedown = elastic limit is

reached in the first few load cycles, but

the steady state is entirely elastic (load

carrying capacity increased)

c. Plastic shakedown = steady state strain

cycle consists of a closed cycle of

plastic deformation

d. Ratchetting: Incremental collapse(Johnson, 2000)

Influencing Parameters• Combined effects (cont..):

• Shakedown diagram used to help predict

the onset of RCF

• Shakedown ratio P0/ky = Maximum

contact pressure / Shear strength of the

material

• Traction coefficient = Adhesion (macro)

• Lower bound not applicable to rail steels

• ~0.3 adhesion transition point

Interface Management

Effective

Management

Traction/

Adhesion

Contact

Stresses

Material

Characteristics

Maintenance

Practices

Interface Management• Contact stress:

• Implement and maintain appropriate wheel and rail profiles

• Work within wheel and rail wear limits

• Implement and monitor appropriate profiling practices and quality

Wear RCFOptimum

?

“Magic Wear Rate”(Magel et. al., 2004)

Interface Management• Traction/adhesion and creepage:

• Consider friction management (lubrication, friction modifiers)

• Maintain good track geometry

• Maintain appropriate wheel and rail profiles

• Consider vehicle curving performance (design / maintenance)

• Consider environmental conditions (high/low rainfall, leaf debris etc.)

www.dipostel.fr www.lbfoster.com

> Steering in curves

< RCF & wear

< Stability in tgt

< Steering in curves

> RCF & wear

> Stability in tgt

Interface Management• Rail material:

• Generally minimum head hardened rail grade for heavy haul

• Current move towards premium (hypereutectoid) grades in the

Pilbara – why?:

Higher load carrying capacity

Harder material = less wear and

longer service life

Shallower crack propagation

Lower maintenance requirement

Interface Management• Rail material (simplistic e.g.):

• 30t axle load moderate curve

• SC rail – ratchetting, surface and

subsurface damage

• Std. HH – Elastic shakedown to

stable condition

• Prem. HH – Fully elastic (no

deformation/damage)

Interface Management• Rail material:

• Estimated rail life

Interface Management• Rail material:

• However, harder rails are sensitive to:

• High adhesion/creepage effects

• Rail profile anomalies (not meeting target profile)

• Metal removal during grinding

• Ground surface finish

• Due to the low ductility of premium rail material its ability to

accommodate profile anomalies by plastic deformation is less than

that of HH rail

• Care is therefore needed to maintain high grinding quality and

sufficient metal removal to control damage

Interface Maintenance• Rail grinding:

• Clean-up fatigued material

• Control crack growth

• Install and maintain correct profile

• Maintain appropriate surface finish

• Ultrasonic testing:

• Frequent inspection to improve defect detection and reduce risk of

rail break and possible derailment

• Wheel profiling:

• Remove hollow wheels responsible for rail damage

• Prevent instability and track/vehicle damage

Thank You

Federal Railroad Association (2011), Rolling contact fatigue a comprehensive review, Report No. DOT/FRA/ORD-11/24, November.

Innotrack (2009), D4.3.4 – Calculation of contact stresses, Integrated Project No. TIP5-CT-2006-031415, International Union of Railways (UIC),

Paris;15 February.

International Heavy Haul Association (2013), accessed 15 May 2013, http://www.ihha.net/.

Johnson, K.L. (2000), „Plastic deformation in rolling contact‟, in Jacobson, B and Kalker, J (ed.), Rolling contact phenomena, Springer-Verlag

Wien/New York, Udine, pp. 164-201.

Jönsson, P. (2007), Dynamic performance of freight wagons and their influence on cost for track deterioration, Presentation at Elmia Nordic Rail

Conference, Jönköping, Sweden; Oct. 9-11.

Magel, E., Sroba, P., Sawley, K. & Kalousek, J. (2004), Control of rolling contact fatigue of rails, Proc. 2004 Annual AREMA Conference, Nashville,

TN; Sept. 19-22.

Magel, E. (2011), Rolling contact fatigue: A comprehensive review, Federal Railroad Administration, Washington DC.

Olofsson, U & Lewis, R. (2006), Tribology of the wheel-rail contact, in Iwnicki, S. (ed.), Handbook of railway vehicle dynamics, CRC Press; Boca

Raton FL.

Pointner, P. (2008), „Impact of wear and rolling contact fatigue on rails – A pragmatic approach‟, ZEVrail Glasers Annalen, vol. 132, pp 304-312.

Rovira, A., Roda, A., Lewis, R. & Marshall, M.B. (2012), Application of fastsim within variable coefficient of friction using twin disc experimental

measures, Wear 274-275, pp. 109-126.

Smith, L. (2009), Derailed iron ore train, Australian Broadcasting Corporation, accessed 22 April 2013, http://www.abc.net.au/news/2009-01-

30/derailed-iron-ore-train/278956

Vollebregt, E. (2013), The frictional contact problem Part 1 the creep phenomenon, Notes on Introductory CONTACT Course, WRI2013, Chicago IL;

6-7 May.

Welsby, D. R. & Zheng, D. (2008), „A fast algorithm for rail subsurface stress calculation due to wheel/rail contact load‟, Proc. Conference on

Railway Engineering 2008, Railway Technical Society of Australasia, Perth, pp. 61-72.

Welsby, D. R. (2009), Characteristics & performance of hypereutectoid rail steels, Presented at the Railway Technical Society of Australasia AGM,

Melbourne, 19 August.

References: