PowerPoint Presentation
Ryan G. Kernes, Amogh A. Shurpali, J. Riley Edwards, Marcus S.
Dersch, David A. Lange, and Christopher P.L. BarkanInternational
Concrete Crosstie & Fastening System SymposiumUrbana, IL6-8
June 2012
Investigation of the Mechanics of Rail Seat Deterioration (RSD)
and Methods to Improve the Abrasion Resistance of Concrete
SleepersSlide #Investigating Rail Seat DeteriorationPart of larger
tie and fastener research program sponsored by
FRA1OutlineObjectivesRail seat deterioration (RSD) backgroundLarge
scale abrasion testEvaluation of frictional propertiesSmall scale
abrasion resistance testResultsConclusions and future work
Slide #Investigating Rail Seat
Deterioration2ObjectivesUnderstand the mechanics of the most
critical failure modesInvestigate parameters that affect abrasion
mechanismCharacterize frictional forces between rail seat and rail
padPropose methods of mitigating the critical failure modesQuantify
abrasion resistance of various concrete mix designs, curing
conditions, and surface treatments
Slide #Investigating Rail Seat DeteriorationThrough industry
surveys and focused discussions with industry expertsUnderstand
mechanics by experimentation or modeling
3Rail Seat Deterioration (RSD)Degradation of concrete material
under rail and padIncreases maintenance costs Shortens service life
of the concrete crosstieLeads to track geometry defects
Feasible mechanisms:AbrasionCrushingFreeze-thaw
damageHydro-abrasive erosionHydraulic pressure cracking
Slide #Investigating Rail Seat DeteriorationTrack geometry
defects could result in an unstable rail condition4Abrasion
Mechanism of RSDAbrasion is a progressive failure mechanism that
occurs when:Frictional forces act between two surfaces in
contactRelative movement occurs between the surfacesHarder surface
cuts or ploughs into softer surface
Progression of abrasion at the rail seatCyclic motion of rail
base induces shear forcesShear forces overcome static frictionPad
slips relative to concreteStrain is imparted on concrete matrix
Abrasion involves 3-body wear: two interacting surfaces (rail
pad and rail seat) and abrasive slurry (water and fines)
Slide #Investigating Rail Seat DeteriorationNot an intrinsic
property but a system property. Therefore, pads, environmental
characteristics, must be investigated.
In order to investigate this complex phenomena, we have
developed a laboratory setup at the University of Illinois.5Large
Scale Abrasion Resistance Test Experimental Setup
Vertical ActuatorHorizontal ActuatorAbrasion PadConcrete
SpecimenSlide #Investigating Rail Seat DeteriorationHorizontally
mounted actuator produces displacements of a pad relative to a
fixed concrete specimen A static normal force is applied with a
vertically mounted actuatorObjectives:Isolate abrasion
mechanismMaintain representative contact mechanicsUnderstand effect
of variables on abrasion rateLoad magnitude, displacement, load
rate, water, sandEstablish most abrasive parameters to evaluate
rail seat materials and surface treatmentsTest Setup:Nominal
pressure: up to 900 psiDisplacements: 1/16 1/86 x 6 concrete
specimens, f(c) > 7000 psi4 x 3 stock pad materials, Nylon 6/6
(unreinforced), Polyurethane (95 Shore A)Contaminates: laboratory
sand, water
6Large Scale Abrasion Resistance Test ResultsConsistently able
to cause deterioration of concrete due to abrasionConcrete
deterioration initiates near pad edges and propagates inwardHeat
build up in pad materials at local contact points leads to
softening and adhesion to concrete surfaceDifficulty in correlating
severity of abrasion to input variablesContact angle and pressure
distributionHeterogeneity of concrete surface
Slide #Investigating Rail Seat DeteriorationDue to the
difficulties in correlating abrasion severity, we decided to shift
gears with the testing protocol.
Due to physical setup of the testing equipment where we can
constantly monitor both lateral and vertical loads throughout the
test, we are able to gain information related to the friction at
the contact interface. So why is friction important?
7Experimental Evaluation of FrictionMagnitude of static
frictional force is directly related to the normal force between
the two bodies by the coefficient of friction ()Experimental
frictional coefficient measured during test calculated by: =
||/where F is the force required to initiate lateral sliding under
vertical normal load P400 loading cycles to simulate single unit
train pass5,000 pound normal vertical load (420 psi), 1/8 lateral
displacement, 3 cycles/second, no abrasive fines or water added
Slide #Investigating Rail Seat DeteriorationBecause friction is
not understood, we devised an experimental protocol to measure the
friction at the pad rail seat contact interface.
Pads allowed to cool to original temperature in between
tests.8
Mean Coefficient of Friction per Loading CyclePolyurethaneNylon
6/6Slide #Investigating Rail Seat DeteriorationEach line on graph
represents an average of 4 repetitions of a single pad on a
concrete specimen.Overall trendsDiff in Poly vs Nylon 6/6 based,
changes based on modulus and thermal effectsNylon 6/6 experimental
modulus is about 44 KSIPoly experimental modulus is about 30
KSI
Overall trend of decreasing COF due to contact films
9
Effect of Environmental Conditions on Nylon 6/6
Slide #Investigating Rail Seat DeteriorationAverage of 16
trials
10Effect of Environmental Conditions on Concrete Abrasion
Polished surface with no sandAbrasion initiated with sandSlide
#Investigating Rail Seat Deterioration
Effect of Increasing Normal Load on Nylon 6/65 kips 3 kips 10
kips Slide #Investigating Rail Seat DeteriorationAverage of 8
trials at 3 and 10 kips5 kip data is average of 44 trials12Small
Scale Abrasion Resistance Test (SSART): Test SetupIn general,
similar to other standard abrasion testsConsists of powered
rotating steel wheel with 3 lapping rings Lapping rings permitted
to rotate about their own axisVertical load applied using the dead
weightsAbrasive sand and water dispensed during testing
Slide #Investigating Rail Seat DeteriorationLap 12 in; Rings 6
in. by 1.5 inch (depth) ; dead weight 4.5 lb
Hanging words (more than one)
Ottawa sand standard for testing13Test ProtocolEach test can
evaluate 3 specimens Multiple tests are run to evaluate more than 3
specimensSpecimen dimensions: 4 inch (diameter),1 inch
(thickness)Duration: 120 minutes Wear depth measurements taken
every 20 minutesSpeed: 60 revolutions per minuteAbrasive fine:
Ottawa 20-30 sand
BeforeAfter
Slide #Investigating Rail Seat Deterioration20-30: Passing
through 841 microns retained on 596 micronsAverage wear depth:
2.5-6.0 mm/test Average weight loss: 75-100 gm/test.
14Test VariablesAdmixturesSilica fume: 5%,10%Fly ash: 15%,
30%
Curing ConditionMoistSubmergedOven dryAir
Surface TreatmentUV epoxyPolyurethaneGrindingFiber Reinforced
Concrete (FRC) PolyurethaneSteel
Slide #Investigating Rail Seat DeteriorationLapping machine not
a representative test, thats the reason for large scale which
is15Effect of Mineral Admixtures
Slide #Investigating Rail Seat DeteriorationCompressive strength
1-2 specimensART: 3 ASTM 231 Pressure method
Generated results that are in agreement with the prevalent
literature related to fly ash and silica fume. This gives us
confidence moving forward in evaluating other mixes that have not
been tested before.
16Effect of Fiber Reinforcement
Slide #Investigating Rail Seat DeteriorationCompressive strength
1-2 specimensART: 3 ASTM 231 Pressure method
17Effect of Curing Conditions
Slide #Investigating Rail Seat DeteriorationComparison of
Techniques to Increase Abrasion Resistance
Slide #Investigating Rail Seat DeteriorationAdditional Tests
Conducted Objective: to obtain specimens batched by industry
concrete crosstie suppliersSilica fume and epoxy coated specimens
testedSaw-cut surface of control specimens considered analogous to
ground surface and tested
GrindingEpoxy coatingSlide #Investigating Rail Seat
DeteriorationSaw cut (Sustersic et al 1991)20Effect of Surface
Treatments
Slide #Investigating Rail Seat DeteriorationConclusions Large
scale testing:Confirmation of abrasion as a feasible RSD
mechanismFrictional coefficient is affected by temperature, water,
sand, normal forceSSART:Successfully compared 13 approaches to
improving abrasion resistance of rail seat through material
improvementsImprove abrasion resistance of concrete with:Optimal
amounts of fly ashProper curing conditionAddition of steel
fibersGrinding cement paste
Slide #Investigating Rail Seat Deterioration22Future
WorkDetermining the optimal frictional properties at each interface
of multi-layer rail pads (top, bottom, and between layers)
could:Reduce movement at critical interfacesInfluence load path and
location of slipDelay the onset of abrasive wear and extend rail
seat lifeExtend to other fastening system componentsSSART:Perform
image analysis to characterize the role of coarse aggregate in
abrasion resistance Study the effect of air entrainment and quality
of aggregates on abrasion resistance of rail seatUse of Statistical
Analysis Software (SAS) to model abrasive wear of concrete
specimensOptimize concrete mix design and surface treatments to
mitigate abrasion
Slide #Investigating Rail Seat
Deterioration23AcknowledgementsFunding for this research has been
provided byAssociation of American Railroads Technology Scanning
ProgramNEXTRANS Region V Transportation CenterEisenhower Graduate
FellowshipFor providing direction, advice, and resources:Amsted
Rail - Amsted RPS: Jose Mediavilla, Dave Bowman, Brent Wilson, BNSF
Railway: John Bosshart, Tom Brueske, Hank LeesAREMA Committee 30:
Winfred Boesterling, Pelle Duong, Kevin Hicks, Tim Johns, Steve
Mattson, Jim Parsley, Michael Steidl, Fabian Weber, John ZemanTTCI:
Dave Davis, Richard ReiffPandrol Track Systems: Bob Coats, Scott
TrippleUIUC: Tim Prunkard, Mauricio Gutierrez, Don Marrow, Darold
MarrowFor assisting with the research and lab work:Josh Brickman,
Ryan Feeney, Kris Gustafson, Steven Jastrzebski, Andrew Kimmle,
Calvin Nutt, Chris Rapp, Amogh Shurpali, Emily Van Dam, Michael
Wnek
Slide #Investigating Rail Seat DeteriorationQuestionsRyan
KernesResearch EngineerRail Transportation and Engineering Center -
RailTECemail: [email protected]
Amogh A. ShurpaliGraduate Research AssistantRail Transportation
and Engineering Center - RailTECemail: [email protected]
Slide #Investigating Rail Seat Deterioration25