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Transcript of Darrien Welsby - Institute of Railway Technology - Monash University - Wheel rail interface...
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: