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Experimental Validation of Full Toroidal Fatigue Life

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Presentation on theme: "Experimental Validation of Full Toroidal Fatigue Life"— Presentation transcript:

1 Experimental Validation of Full Toroidal Fatigue Life
Dr. Adrian Lee Torotrak (Development) Ltd.

2 Variator Durability Objectives Variables Investigated
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 ( CVT-21

3 Variator Test Rigs CVT-21 Research 100mm Variator Test Rig Base Frame
Hydraulic Power Pack Variator Gearbox Motor Drive Cooler Valve Block Control System Research 100mm Variator Test Rig CVT-21

4 100mm Variator Test Module
disk Centre rear disk Centre front Front disk Rear disk R2 roller F2 roller pressure Endload direction Rotational F1 F3 R1 R3 To motor Hy-vo chain CVT-21

5 Durability Testing Influence of Surface Roughness
Contact track Smooth roller (Ra<0.1) after 553 hrs Smooth disc (Ra<0.1) after 553 hrs Rough roller (Ra>0.13) after 264 hrs Rough disc (Ra>0.13) after 264 hrs CVT-21

6 Variator Durability Tests Influence of Surface Finish
Torotrak Durability Data 100mm Research Variator Rig 3.5 3 Model - 9th power law 2.5 Mean Hz contact Stress (GPa) 2 1.5 1 1.00 10.00 100.00 Stress Cycles (Disc) to failure (million) Model Koyo smooth surface Koyo rough surface Non brg man. Rough surface CVT-21

7 Importance of Manufacturing
Before Test After Test CVT-21

8 Variator Durability Tests Wear Volume
Roller smooth before test Ra = 0.07, Rsk = -1.67 Roller smooth after 634hrs running Ra = 0.08, Rsk = -1.67 Specific film thickness () = hmin / * where *2 = Rq12 + Rq22 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

9 Variator Durability Tests Failure Type & Position
Failed parts - Smooth parts tests 100mm Variator Test Rig Front disk/spall 13% Centre rear disk/spall 6% Rear disk/spall Roller R2/spall 30% Centre front disk/spall 12% Front disk/Cracked spline Roller F2/spall Failed parts - Rough parts tests 100mm Variator Test Rig Roller R2/spall 13% Variator/Micro-pitting 74% Roller F2/spall CVT-21

10 Variator Durability Tests Roller vs Disc Failure - Uneven Loading
CVT-21

11 Previous Durability Results
Torotrak Durability Data 100mm Research Variator Rig 1.00 10.00 100.00 Stress Cycles (Disc) to failure (million) Mean Hz contact Stress (GPa) 2002 Design Model Current Traction Fluid HTHL Disc/Rollers Model - 9th power law Surface Crack Sub-Surface Fatigue CVT-21

12 Variator Durability Tests Surface Initiated Fatigue Failure Cracks
Number of cracks and Mean Hz Contact pressure Contact track 100mm Research Variator Rig 10000 1000 100 Number of cracks in one variator No cracks 10 on rollers Cracks 1 1.6 1.8 2 2.2 2.4 2.6 2.8 Mean Hz contact stress (GPa) R19 smooth R19 rough R19 smooth, high speed & temp R19 smooth, high speed R15 smooth R12 smooth R12 rough R12 no S1 heat treatment rollers R12 normal SP rollers R12 carbonitrided rollers R12 smooth, high speed R25 smooth R25 rough R12 deep SP rollers CVT-21

13 Influence of Fluid on Durability
1000 750 Stress Cycles (millions) 500 250 A B C D E F G H I1 I2 Baseline Fluid Type CVT-21

14 Radical Fatigue Life Improvements
1 10 100 1000 10000 Stress Cycles (million) Mean Hz Contact Stress (Pa) Target Life 9th Power 2004 9th Power 2002 Completed Tests Suspended Tests 7 to 9 times improvement 2004 2002 CVT-21

15 Excellent High Power Durability
1 10 100 1000 10000 Stress Cycles (million) Mean Hz Contact Stress (Pa) Target Life Completed Tests (75kW typically) Suspended Tests (75kW typically) High Power (210kW typically) Test Suspended CVT-21

16 Variator Sizing CVT-21

17 Variator Durability Results
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 CVT-21

18 Conclusions 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 CVT-21

19 IVT fully competitive with 6AT
CVT-21


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