Optimization of the TriboconditioningProcessfor Low Friction Surfaces

Transcription

1 Int. workshop Super-lubricity in the automotive real world, May 5 th 2015, Sao Paolo, Brazil Optimization of the TriboconditioningProcessfor Low Friction Surfaces ZlateDimkovski

2 Outline A studyon Triboconditioningprocess on a valvetraincomponents Introduction Process/Friction Tests Surface Analysis Conclusions Triboconditionedliner surfaces 2

3 Introduction: Valve Train Mechanical losses 3

4 Pin-roller contact 4

5 Tool sample F Wear width increases Ring sample Triboconditioning as a cost-effective process n WS 2 Tool sample Ring sample asperities flatten 5

6 Process tests on tribometer Test variables: Load-F (180 & 360N) Speed-n (600 & 1200 rpm) Surface finish (Ground & Honed) Time: ~6 min Test outputs: Coef. of friction El. resistance Block-on-ring module F Tool Ring n 6

7 Friction (start-stop) tests Test variables: Load: F=3N Speed: n=0-714rpm Surface finish (Ground & Honed) 3 repetitions (3 diff. ring samples) Test outputs: Coef. of friction (COF) El. Resistance (R) Block sample Width=3mm F=3N n Ring sample Width=6mm Block-on-ring module 7

8 Start-stop tests: Testing sequence (5min total test time)

9 Analyzed interval COF & R (resistence) Signals Rotational Speed V2= rev/s (0-714rpm) 9

10 Functional friction (start-stop) tests 0,12 COF Ground 0,12 COF Honed 0,11 0,1087 0,11 0,1084 0,1034 0,1033 0,10 0,10 0,0950 0,09 0,088 0,0867 0,09 0,08 0,076 0,08 0,07 0,07 0,06 0,06 360/ / / / / / / /1200 Load (N)/Speed(rpm) Load (N)/Speed(rpm) 10

11 3D roughness parameters Honed Ground Load/Speed Sq S10z Shv Sha Spk Sk Sk reduct. N/rpm µm µm µm³ µm² µm µm % 180/360 Before 0,145 0,813 7,5 791,2 0,110 0, /360 After 0,088 0,829 6,6 918,3 0,074 0,206 43,8 180/1200 Before 0,149 0,846 5,9 650,0 0,115 0, /1200 After 0,098 0,914 7,1 771,2 0,082 0, /600 Before 0,141 0,782 8,3 910,1 0,107 0, /600 After 0,109 1,039 8,2 779,7 0,083 0, /1200 Before 0,154 0,856 10,7 1101,4 0,135 0, /1200 After 0,127 1,019 4,6 476,7 0,117 0, /360 Before 0,084 0,785 3,9 306,9 0,061 0, /360 After 0,076 0,877 5,9 619,7 0,056 0, /1200 Before 0,102 0,897 3,8 263,0 0,093 0, /1200 After 0,075 1,064 6,6 769,4 0,059 0, /600 Before 0,081 0,725 4,2 337,3 0,054 0, /600 After 0,079 0,897 4,4 526,9 0,073 0,121? 360/1200 Before 0,083 0,757 4,2 331,9 0,058 0, /1200 After 0,096 Zlate 1,021 Dimkovski, Halmstad 4,5 University 401,9 0,107 0,179 42,0 33,3 16,9 26,9 39,5 34,4 8,3 11

12 Multi-scale analysis: Morphological decomposition for 180N/600rpm Ground Honed (Before-After)/Before*100 (Before-After)/Before*100 12

13 Morphological decomposition for 180N/600rpm Ground Honed 4 measurements/ring Roughness Waviness Roughness Waviness Zoom on Roughness Scales Zoom on Roughness Scales 13

14 Morphological decomposition (Averages of 3 samples) Increase/decrease percentage over all the scales Sqchange [%] (Sq before Sq after)/sq before* N/600rpm Ground Honed 360N/600rpm Scales Scales Ground Honed N/1200rpm Ground Honed 360N/1200rpm Scales Ground Honed Scales

15 Conclusions (Valvetrainsurfaces) The lowest friction showed the ground surface treated by low load/low speed process parameters Contrary to the ground rings, the longer wavelengths of the honed surfaces increase during triboconditioning The ground (rougher) surface before treatment better than the honed (smooth) one due to the better reduction of the waviness & core roughness 15

16 Cylinder liner surfaces 16

17 Power Lossesin IC Engines (Richardson D. E. 2000) Focus: Cylinder Liner Twin Land Oil Control Ring 17

18 TriboconditionedLiner Surfaces Coated Uncoated ISO Height Parameters Sa µm Sz µm Ssk Sku EUR 15178N Functional Parameters Sk µm Spk µm Svk µm Sr % Sr % SMOOTHER PLATEAUS ISO Height Parameters Sa µm Sz µm Ssk Sku EUR 15178N Functional Parameters Sk µm Spk µm Svk µm Sr % Sr % 18

19 Truck ring-liner tribotests Testing parameters: 10mm wide liner samples: 2 Load: 8N Speeds: 0.5Hz, 1Hz, 2Hz & 5Hz Stroke: 24mm Nominal contact pressure: 1.42 MPa Liner samples half-coated, half-uncoated New (TLOCR) Twin Land Oil Control Rings: 2 Viscous engine oil: 20W50 Room temperature Time: 10min 19

20 Setup Force sensor Stiffer suspension in tangential direction 20

21 0.5Hz Sample 1 COATED Sample 2 21

22 1Hz Sample 1 COATED Sample 2 22

23 2Hz Sample 1 COATED Sample 2 23

24 5Hz Sample 1 COATED Sample 2 24

25 ObviousFrictionReductionin Boundary& Mixed LubricationRegime Speed: 1Hz COATED 25

26 Conclusions/Futurework (Liner Surfaces) Conclusions Triboconditioned surfaces reducefriction(morein boundary/mixed regime). Coating/Surface topography contribution? Future work Novel stratified/honed/textured surfaces in production Coated(plasma/DLC) surfaces with low viscosity oils Better models/simulations/tribotests 26

27 References 1. DimkovskiZ. et al, 2014, Int. Conference on Metrology and Properties of Engineering Surface, Charlotte, USA 2. ZhmudB., 2011, Tribology and Lubrication Technology, 67,42 3. ZhmudB., TomanikE. and Xavier F.-A., 2014, Lubrication Science, 26,277 27

28 Acknowledgements Vinnova, Swedish Energy Foundation Volvo Groups Truck Technologies Volvo Cars AppliedNano Surfaces GnuttiCarlo Sweden Scania Digitalsurf, France 28

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