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Development of Refined Friction Materials

Development of Refined Friction Materials. Dr. Tim Hodges NVH Manager Federal-Mogul Friction Products Group. Overview. Key attributes of friction material NVH strategy Principal NVH concern areas squeal judder creep-groan Summary. Physical properties compressibility

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Development of Refined Friction Materials

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  1. Development of RefinedFriction Materials Dr. Tim Hodges NVH Manager Federal-Mogul Friction Products Group

  2. Overview • Key attributes of friction material • NVH strategy • Principal NVH concern areas • squeal • judder • creep-groan • Summary

  3. Physical properties compressibility thermal conductivity Performance nominal friction fade speed/temp/pressure sensitivity Wear Cost Environmental Refinement cold/thermal judder creep-groan squeal pedal feel +…………………….. Friction Materials - Key Criteria

  4. Noise Measurement on Dynamometer c/w knuckle or full suspension Noise vs Formulation (FMTL + Dev’t Centres) Scanning Laser Vibrometer Measurement of System on Noise Dynamometer and/or Vehicle Accelerometer Data Acquisition (LMS) Federal-Mogul Approach to NVH Friction Material (“Excitation”) Core Development Finite Element Modelling Application Engineering Brake System (“Response”)

  5. Structured Dev’t of Quiet Materials

  6. Noise Dynamometers • Must reproduce noise from vehicle testing • Full-suspension capability (front/rear axle) Other key features: • Climate control • LACT & matrix-type schedules • Standard objective assessment methods • Low background noise required for accurate assessment • Roller on some machines

  7. NVH Problem Solving - Example mm/s Mod 60 • 1.8 kHz noise problem • Modal analysis shows component frequencies not related to noise frequency • Laser vibrometer, noise dyno & vehicle used to provide solution • Laser identifies high vibration levels on leading edge inner pad • Solution - move inner pad clip by 1.5 mm • Subjective/objective results: 50 40 30 20 10 0

  8. Creep-groan • Creep-groan occurs at very low speeds, < 2rpm • Used for core development material screening • Very low speed, high torque capability, allows relation of  characteristics to vibration using full-size pads

  9. DTV Generation and Cold Judder • DTV generation subject to a wide range of factors (Driving style, Calliper characteristics, Friction material tribology & compressibility) • Need to “screen” good/bad materials • Key to control of test lies in pad/disc contact • In a vehicle contact refreshed with periodic brake app’s • Does not guarantee reproducible results even on dynamometer • Controlled Contact Device maintains and controls pad/disc contact in ‘off brakes’ situation • Compensates for wear • Does not require special caliper

  10. Temp (C) 700 600 500 400 300 200 High Speed (“Hot”) Judder Speed (Km/h) Frequency (Hz) DTV measurement systems and the F-M dual wavelength pyrometer may be used together to measure the effects of hot spotting

  11. Advanced NVH Modelling • Need to represent system components • We have good model-experiment correlation for system level modal analyses • We are continuing to develop our analytical modelling methods to give us a predictive capability

  12. Summary • Performance, refinement, time & cost are often conflicting compromises • Structured approach required for problem identification & solution • More analytical work required

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