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

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Presentation on theme: "Experimental Validation of Full Toroidal Fatigue Life Dr. Adrian Lee Torotrak (Development) Ltd."— Presentation transcript:

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

2 Variator 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

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

4 100mm Variator Test Module CVT-21 F1F3 F2 roller R2 roller R1R3 To motor Rotational direction Front disk Centre front diskCentre rear disk Rear disk Hy-vo chain Endload pressure

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

6 Variator Durability Tests Influence of Surface Finish Torotrak Durability Data 100mm Research Variator Rig 1 1.5 2 2.5 3 3.5 1.0010.00100.001000.00 Stress Cycles (Disc) to failure (million) Mean Hz contact Stress (GPa) ModelKoyo smooth surfaceKoyo rough surfaceNon brg man. Rough surface Model - 9th power law CVT-21

7 Importance of Manufacturing Before TestAfter Test CVT-21

8 Variator Durability Tests Wear 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 ( ) = h min / * where * 2 = R q1 2 + R q2 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

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 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% CVT-21

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

11 Previous Durability Results CVT-21 Torotrak Durability Data 100mm Research Variator Rig 1.0010.00100.001000.00 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

12 Variator Durability Tests Surface Initiated Fatigue Failure Cracks Contact track Cracks Number of cracks and Mean Hz Contact pressure 100mm Research Variator Rig 1 10 100 1000 10000 1.61.822.22.42.62.8 Mean Hz contact stress (GPa) Number of cracks in one variator R19 smoothR19 rough R19 smooth, high speed & tempR19 smooth, high speed R15 smoothR12 smooth R12 roughR12 no S1 heat treatment rollers R12 normal SP rollersR12 carbonitrided rollers R12 smooth, high speedR25 smooth R25 roughR12 deep SP rollers No cracks on rollers CVT-21

13 Influence of Fluid on Durability 0 250 500 750 1000 Stress Cycles (millions) ABCDEFGHI1I2Baseline Fluid Type CVT-21

14 1.50E+09 1.70E+09 1.90E+09 2.10E+09 2.30E+09 2.50E+09 2.70E+09 2.90E+09 110100100010000 Stress Cycles (million) Mean Hz Contact Stress (Pa) Radical Fatigue Life Improvements CVT-21 2002 Target Life 9 th Power 2004 9 th Power 2002 Completed Tests Suspended Tests 7 to 9 times improvement 2004

15 1.50E+09 1.70E+09 1.90E+09 2.10E+09 2.30E+09 2.50E+09 2.70E+09 2.90E+09 110100100010000 Stress Cycles (million) Mean Hz Contact Stress (Pa) Excellent High Power Durability CVT-21 Target Life Completed Tests (75kW typically) Suspended Tests (75kW typically) High Power (210kW typically) Test Suspended

16 Variator Sizing CVT-21

17 Variator Durability Results CVT-21 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

18 Conclusions CVT-21 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

19 IVT fully competitive with 6AT IVT6-AT CVT-21


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