Experimental Validation of Full Toroidal Fatigue Life Dr. Adrian Lee Torotrak (Development) Ltd.
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Transcript of Experimental Validation of Full Toroidal Fatigue Life Dr. Adrian Lee Torotrak (Development) Ltd.
Experimental Validation of Full Experimental Validation of Full Toroidal Fatigue LifeToroidal Fatigue Life
Dr. Adrian Lee
Torotrak (Development) Ltd.
Variator DurabilityVariator Durability
CVT-21
Objectives Confirm current design S-N curve
Assess influence of surface roughness/finish
Investigate material importance
(KUJ7/Ovako)
Understand influence of different traction
fluids
Variables Investigated Surface finish
Contact stress (mean)
Variator speed (mainshaft rpm)
Shot peening
Roller temperature (degC)
Through hardened Material
Fluids
Over 120 variator module tests
undertaken
Variator Test RigsVariator Test Rigs
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Base Frame
Hydraulic Power Pack Variator Gearbox Motor
Drive
Cooler ValveBlock
Control System
Research 100mm Variator Test Rig
100mm Variator Test Module100mm Variator Test Module
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F1 F3
F2 roller R2 roller
R1 R3
To motor
Rotational
direction
Front disk Centre frontdisk Centre rear
disk Rear disk
Hy-vo chain
Endload
pressure
Durability Testing Durability Testing Influence of Surface RoughnessInfluence of Surface Roughness
Smooth roller (Ra<0.1) after 553 hrs Smooth disc (Ra<0.1) after 553 hrs
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Contact track
Contact track
Contact track
Rough roller (Ra>0.13) after 264 hrs Rough disc (Ra>0.13) after 264 hrs
Variator Durability TestsVariator Durability TestsInfluence of Surface FinishInfluence of Surface Finish
Torotrak Durability Data100mm Research Variator Rig
1
1.5
2
2.5
3
3.5
1.00 10.00 100.00 1000.00
Stress Cycles (Disc) to failure (million)
Me
an
Hz
co
nta
ct
Str
es
s
(GP
a)
Model Koyo smooth surface Koyo rough surface Non brg man. Rough surface
Model - 9th power law
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Importance of ManufacturingImportance of Manufacturing
Before Test After Test
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Variator Durability TestsVariator Durability TestsWear VolumeWear Volume
Roller smooth before test
Roller smooth after 634hrs running
Ra = 0.07, Rsk = -1.67
Ra = 0.08, Rsk = -1.67 Specific film thickness () = hmin / *
where *2 = Rq12 + Rq2
2
1<<3 some asperity contact, termed partial or mixed regime.
Tests with type A material & HT (k~ 2×10-9) indicate mixed / full-film EHL
Tests with type B material & HT (k ~ 2×10-11) indicates full-film EHL
CVT-21
Variator Durability TestsVariator Durability TestsFailure Type & PositionFailure Type & Position
Failed parts - Smooth parts tests
100mm Variator Test Rig
Front disk/spall
13%
Centre rear disk/spall6%
Rear disk/spall
13%
Roller R2/spall 30%
Centre front disk/spall
12%
Front disk/Cracked spline
13%
Roller F2/spall
13%
Failed parts - Rough parts tests
100mm Variator Test Rig
Roller R2/spall
13%
Variator/Micro-pitting
74%
Roller F2/spall
13%
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Variator Variator DurabilityDurability Tests TestsRoller vs Disc Failure - Uneven LoadingRoller vs Disc Failure - Uneven Loading
Variator life in terms of disk revolution based on 9th power model100mm Research Variator Rig
1.5
2.0
2.5
3.0
0.1 1 10 100 1000
Disk revolution to failure (million)
Me
an
Hz
co
nta
ct
str
es
s (
GP
a)
Disk in front cavity Disk in rear cavity F1 load percentage F2 load percentage F3 load percentage
R1 load percentage R2 load percentage R3 load percentage Disk model Roller model
12mm rol l er and di sk
15mm rol l er and di sk
19mm rol l er and di sk
25mm rol l er and di sk
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Previous Durability Results Previous Durability Results
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Torotrak Durability Data100mm Research Variator Rig
1.00 10.00 100.00 1000.00
Stress Cycles (Disc) to failure (million)
Mea
n H
z co
nta
ct S
tres
s (G
Pa)
2002 Design Model
Current Traction FluidHTHL Disc/Rollers
Model - 9th power law
Surface Crack
Sub-SurfaceFatigue
Variator Durability TestsVariator Durability TestsSurface Initiated Fatigue Failure CracksSurface Initiated Fatigue Failure Cracks
Contact track
Cracks
Number of cracks and Mean Hz Contact pressure100mm Research Variator Rig
1
10
100
1000
10000
1.6 1.8 2 2.2 2.4 2.6 2.8
Mean Hz contact stress (GPa)
Nu
mb
er o
f cr
acks
in
on
e va
riat
or
R19 smooth R19 roughR19 smooth, high speed & temp R19 smooth, high speedR15 smooth R12 smoothR12 rough R12 no S1 heat treatment rollersR12 normal SP rollers R12 carbonitrided rollersR12 smooth, high speed R25 smoothR25 rough R12 deep SP rollers
No crackson rollers
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Influence of Fluid on DurabilityInfluence of Fluid on Durability
0
250
500
750
1000S
tre
ss
Cy
cle
s (
mill
ion
s)
A B C D E F G H I1 I2 Baseline
Fluid Type
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1.50E+09
1.70E+09
1.90E+09
2.10E+09
2.30E+09
2.50E+09
2.70E+09
2.90E+09
1 10 100 1000 10000
Stress Cycles (million)
Mea
n H
z C
on
tact
Str
ess
(Pa)
Radical Fatigue Life ImprovementsRadical Fatigue Life Improvements
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2002Target Life
9th Power 2004
9th Power 2002
Completed Tests
Suspended Tests7 to 9 times improvement
2004
1.50E+09
1.70E+09
1.90E+09
2.10E+09
2.30E+09
2.50E+09
2.70E+09
2.90E+09
1 10 100 1000 10000
Stress Cycles (million)
Mea
n H
z C
on
tact
Str
ess
(Pa)
Excellent High Power DurabilityExcellent High Power Durability
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Target Life
Completed Tests (75kW typically)
Suspended Tests (75kW typically)
High Power (210kW typically)
Test Suspended
Variator SizingVariator Sizing
Start
Driveline Power
Engine Power
Engine Speed
Variator Ratio
Contact Mean HzStress
Contact LifeFraction
Variator Speed &Torque
Overall Tx Ratio
Finish
Contact Total LifeFraction
Manuf. DutyCycle
FDR and Txefficiency
EngineControl Line
ShuntArchitecture
VariatorDesign
TDL 9th PowerLaw
Miners’ Law
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Variator Durability ResultsVariator Durability Results
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Applying Series 3 SUV duty cycle, base durability curve equivalent to circa 50 % life fraction or circa 340,000 miles life
Durability extended - 9 times improvement to only 5% life used
Outcome - durability exceeds requirements hence downsize
0200
400600
-2000
0
20000
1
2
3
4x 10
-3
SpdTxOut (rad/s)
100 mm roller, New Fluid
TrqTxOut (Nm)
roll
er
life
fra
cti
on
(%
) Variator Ratio Band-0.45to -0.59
-0.59to -0.72
-0.72to -0.86
-0.86to -1.00
-1.00to -1.31
-1.31to -1.62
-1.62to -1.93
-1.93to -2.24
120mm Input Disc 49.3 15.2 6.2 5.1 15.6 4.6 0 0100mm Input Disc 29.4 6.6 1.7 1.7 4.4 2.3 0 0
120mm Output Disc 3.5 2.7 2.7 3.6 31.3 18.1 0.3 0.6100mm Output Disc 1 0.8 0.6 1.1 11.1 12.6 0.1 0.1
Total120mm Roller 13 5.5 3.1 3.2 16.6 7.5 0.1 0.2 50.1100mm Roller 7.7 2.2 0.8 1 5.4 4.8 0 0 22
ConclusionsConclusions
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• IVT size envelope same or smaller than 6AT
• Fatigue tests at high power and stress confirm traditional fatigue analysis applicable to the IVT
• Interaction between fluid and material has a significant influence on life
• SDT design tool enables rapid optimisation of the IVT layout
IVT fully competitive with 6ATIVT fully competitive with 6AT
IVT6-AT
CVT-21