Bench-Top Screening of Wet Clutch Materials. SJ Shaffer, Ph.D. Bruker-TSOM

Transcription

1 Bench-Top Screening of Wet Clutch Materials SJ Shaffer, Ph.D. Bruker-TSOM

2 Acknowledgements Collaboration, data and images from full-scale clutch tests provided by: Tom Freshly Group Leader - Wet Friction Development LuK, USA LLC Wooster, OH, USA Additional bench-top data and constructive suggestions provided by: Dr. Udo Volz Bruker Nano Applications Karlsruhe, Germany Lab assistance, technical discussions, and constructive suggestions: Steve Papanicolaou Bruker, TSOM San Jose, CA 8/19/2016 Bruker Confidential 2

3 Outline Motivation and Background for Clutch Testing and Material Screening Past and Current Test Methods Developing the Bench-top Test Conditions Identifying the Key Variables for friction testing Sample & Rig Configuration Examples Clutch Materials ATF Chemistry Run-in Effect 8/19/2016 3

4 Motivation and Background 8/19/2016 4

5 Motivation Why test clutch Material? Smooth wet clutch performance is directly tied to friction behavior (1,2) Harshness, vibration and noise (HVN) is strongly correlated with the Velocity Dependence of the coefficient of friction (COF) Increasing COF with decreasing velocity ( negative slope ) promotes stick-slip (1,2) 1. A. Crowther, N. Zhang, D.K. Liu, J.K. Jeyakumaran, Analysis and simulation of clutch engagement judder and stick-slip in automotive powertrain systems, Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering December 1, 2004 vol. 218 no EJ Berger, Friction modeling for dynamic system simulation, Appl. Mech. Rev 55(6), (Oct 16, 2002) 8/19/2016 5

6 Motivation Why test clutch Material? Recently, increasing interest and demand for higher torque capacities at reduced sizes of automatic transmissions Lower weight = better fuel economy Modeling of clutch behavior is an important development tool in reduced weight new clutch designs COF data are critical for modeling efforts 8/19/2016 6

7 Motivation Why test clutch Material? Many possible new materials combinations and processing parameters exist to obtain desired torque capacity and durability Fibers, friction modifiers, abrasives, fillers, binder, counter-surface COF data are typically obtained from tests on full scale clutch test machines Time and resource consuming, costly Desire to get accurate COF data economically for modeling efforts 8/19/2016 7

8 Past and Current Test Methods 8/19/2016 8

9 Historical Clutch Material Testing Early Days Design changes were evolutionary and empirical Build and test clutches on vehicles In the lab, prior to 1967 Test fully assembled clutches using SAE #1 Friction Test Machine Friction test conducted under steady state conditions In 1967, SAE #2 Friction Test Machine was introduced (3) Varying conditions designed to simulate in-service clutch conditions 3. G.R. Smith, W.D. Ross, P.L. Silbert, W.B Herndon, Putting Automatic Transmission Clutch Researchers on Speaking Terms, SAE Technical Paper , Society of Automotive Engineers, doi:10:4271/ /19/2016 9

10 SAE No.2 Friction test machine and Samples Typical sample size 133mm/99mm 1.9 m Clutch disc photo courtesy of Par Marklund, Doctoral Thesis, Wet Clutch Tribological performance optimization methods Lulea Univ of Technology /19/

11 Individual Effect Studies Pin-on-Disk and comparison studies (4-6) Specific properties of oils and paper (7,8) Modeling studies - dynamic effects, judder, shudder and chatter (9-11) 4. P. Marklund, R. Larsson, Wet Clutch Friction Characteristics Obtained for Simplified Pin-on-Disc Test, Tribology International, V41 (9-10), (2008), NordTrib 2006, pp A. Senatore, V. D Agostino, R. Di Giuda, V. Petrone, Experimental Investigation and Neural Network Prediction of Brakes and Clutch Friction Material Behaviour Considering the Sliding Acceleration Influence, Tribology International, v44(10), (2011), pp W. Ost, P. De Baets, J. Degrieck, The Tribological Behaviour of Paper Friction Plates for Wet Clutch Application Investigated on SAE#II and Pin-on-Disk Test Rigs, Wear, V.249(5-6), (2001), pp W. Scott and P. Suntiwattana, Effect of Oil Additives on the Performance of a Wet Friction Clutch Material, Wear, v , pt. 2, (1995) pp T. Matsumoto, The Influence of Paper-Based Friction Material Porosity on the Performance of a Wet Clutch, SAE paper , doi: / Y. Fuji, T. Snyder, R.Waldecker, W. Tobler, L. Davis, M. Scherzer, D. Zander, Dynamic Characterization of Wet Friction Component under Realistic Transmission Shift Condition, SAE Technical Paper , 2006, doi: / D. Centea, H. Rahnejat, MT Menday. The influence of the interface coefficient of friction upon the propensity to judder in automotive clutches. Proc IMechE Part D: J Autom Eng 1999; v245: P. Maucher, Clutch chatter. In: Proceedings of the 4th international symposium on torsional vibrations in the drive train, Baden- Baden; /19/

12 So why a bench-top screening test? The answer is multifold, but simple: Friction data are used in modeling Many things affect friction behavior Materials, porosity, cure parameters, counterface material and roughness Easy and economical to make a small batch (single sheets) of new clutch materials Fast and easy down-selection process for full-scale SAE #2 tests and in-service vehicle tests* Bottom line: Cost effective, less material intensive, less time consuming, * - Not trying to replace full scale, component level test machine, just make those tests more efficient. 8/19/

13 Developing the Bench-top Test Conditions 8/19/

14 Defining the Tribotest Turning the Tribosystem into a Tribotest What are the important parameters? Materials Contact Geometry Loading Motion Environment 8/19/

15 Materials and Contact Geometry Bench-top Test Sample to be of same material of interest: Prototype wet clutch papers. Contact Geometry: Flat ring on flat counterface, scaled down Focus on influence of the materials 145 mm Dia. 29 mm Dia. 8/19/

16 Size Effect Concerns (Macro geometry excluded) Minimum Contact Size Non-Homogenous Nature (Material and Geometry Features) R a =9.09mm R a =12.88mm R a =3.11mm 8/19/

17 Loading, Motion and Environment (From Specific OEM Test) Test calls for 3 Pressures of 0.8 MPa, 2 MPa and 3 MPa 3 MPa on Bench-top Sample = 750N Load Test calls for 14 Speed Slip Steps from m/sec to 1.7 m/sec Equivalent Linear Velocity on Bench-top Sample for 1.7 m/sec = 1,237 RPM Test calls for 3 Temperatures of 40 C, 90 C and 120 C. Higher Temperatures can be achieved on Bench-top system (limit depends only on lubricant) Flooded Lubrication Condition Only ml of fluid are required for each Bench-top test 8/19/

18 Test Sequences (to mimic OEM-specific test) Additional Sequences: Up-and-Down Velocity Ramp Tests at Constant Pressure Breakaway Friction Reverse loading direction (high to low pressure) Total of over 300 test conditions! 8/19/

19 Loading and Motion Example: Speed-Slip Test Achieve and hold each successive velocity. Return to zero velocity after each step. Apply fixed load at given velocity, hold for 3-seconds. Unload after each step. (COF data point captured at 2.9 seconds) 8/19/

20 Loading and Motion Example: Velocity Ramp 5-Sec hold Constant Load 20-Sec ramp up 20-Sec ramp down 8/19/

21 Sample & Rig Configuration 8/19/

22 Upper & Lower Clutch Sample Pair Upper Sample Lower Sample 29 mm diameter x 5 mm width 40 mm diameter 8/19/

23 Bench-Top System - Samples Upper Sample Holder (Self-Aligning) Clutch Material ATF Supply Port Clutch Material Sample Reaction Plate Material Samples 8/19/

24 Bench Top System - Overview UMT-TL (TriboLab) 775 mm UMT-TL Base Unit 8/19/

25 Bench Top System Details 1 Load Cell (0-2 kn) 4-Spring Suspension Torque Sensor ( N m) Insulating Lid Heater Chamber (RT-400 C) Rotary Stage ( rpm) 8/19/2016

26 Bench Top System Details 2 Fluid Thermocouple ATF Supply Upper Sample Holder, Self- Aligning Gimbal, ATF supply channel Liquid bowl, holds lower Sample Heating Chamber/Rotary Drive ATF Return 8/19/

27 Bench Top System Lubricant-Reflow Between Steps (Video) 8/19/

28 Bench Top System ATF Feed (Video) 8/19/

29 Examples 8/19/

30 14 Speed Step Test 4 Materials Standard ATF 120 C 30

31 Results: Slip-Speed Step Tests: Clutch Materials A & B 8/19/

32 Results: Slip-Speed Step Tests: Clutch Materials C & D 8/19/

33 Speed Ramp Test Material C Standard ATF 40 C 33

34 Results: Speed-Ramp Test Full-Scale SAE #2 Tests Velocity Ramp Sub-Scale Bench-Top Tests Velocity Ramp 8/19/

35 Results: Speed-Ramp Test Full-Scale SAE #2 Tests Velocity Ramp Note dynamic effects in both full-scale and benchtop tests Sub-Scale Bench-Top Tests Velocity Ramp 8/19/

36 Results: Speed-Ramp Test Full-Scale SAE #2 Tests Velocity Ramp Sub-Scale Bench-Top Tests Velocity Ramp Note breakaway friction in both full-scale and benchtop tests 8/19/

37 Fluid Chemistry Effect Neat vs. Fully Formulated 8/19/

38 Results: Slip-Speed Step Tests: Effect of ATF Chemistry Fully Formulated ATF Neat ATF Base Fluid 8/19/

39 Run-in Effect 8/19/

40 Coefficient of Friction COF-T Results: Run-in at low contact pressure, 20 C Sample FD No. 2 / No / Run-In MPa 20 C 0,24 0,22 0,2 0,18 0,16 Run-in effect File 1 Run 0 File 2 Run 4 File 3 Run 2 File 4 Run 1 File 5 Run 3 0,14 0, Speed (rpm)

41 Coefficient of Friction COF-T Results: Run-in at medium contact pressure, 20 C Sample FD No. 2 / No / Run-In 1.94 MPa 20 C 0,24 0,22 0,2 0,18 0,16 Run-in effect File 1 Run 0 File 2 Run 1 File 3 Run 2 File 4 Run 4 File 5 Run 3 0,14 0, Speed (rpm)

42 Coefficient of Friction COF-T Results: Run-in at high contact pressure, 20 C Sample No MPa 20 C FD / No. 2 / 2.96 MPa 0,24 0,22 0,2 0,18 0,16 0,14 Run-in effect File 1 Run 0 File 2 Run 3 File 3 Run 1 File 4 Run 2 File 5 Run 4 0, Speed (rpm)

43 Coefficient of Friction COF-T Results: After Run-in, all contact pressures, 20 C Sample FD No. 2 / No. 32 / Loads Run-In: Run 420 C 0,24 0,22 0,2 0,18 0,16 After Run-in File Mpa File Mpa File Mpa 0,14 0, Speed (rpm)

44 Bench-top screening of wet clutch materials: Wrap-up 8/19/

45 Concluding Remarks for Wet-Clutch Material Screening Agreement with full scale tests were very good in: Relative rankings Curve shape Magnitude of COF for each material Effect of chemistry Observation of Phenomena was possible: Dynamic effects Breakaway friction Run-in Test cycle time is reduced and resources are minimized in bench-top test Changing of clutch materials and fluids is simplified Minimal disposal of Fluid (only ml used) 8/19/

46 Penultimate slide Please complete the survey questions which will be sent subsequently Please write to with additional questions or requests for information Please put UMT Clutch-Material Screening in the Subject Line 8/19/

47 Copyright Bruker Corporation. All rights reserved.