Development of RefinedFriction 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

Friction Materials - Key Criteria

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

+……………………..

Federal-Mogul Approach to NVH

Friction Material(“Excitation”)

Brake System (“Response”)

Finite ElementModelling

Measurement of System on Noise Dynamometer

and/or Vehicle

Scanning Laser Vibrometer

Accelerometer DataAcquisition (LMS)

Noise vs Formulation (FMTL + Dev’t Centres)

Noise Measurement onDynamometer c/w knuckle

or full suspension

Core Development

ApplicationEngineering

Structured Dev’t of Quiet MaterialsTest Hardware Principal Test

Schedule(s)

Core Dev’t Noise dynamometer & standardcalliper/knuckle assembly

AK Noise

App’n Engineering

Level 1

Level 2/3

Troubleshooting

Noise dynamometer & appropriatecalliper/knuckle assembly

Schenck noise dynamometer & fullcorner assembly

“ “ “

LACT / AK noise matrix

“ “

Above + appropriateroutine to reproduceproblem condition

Final vehicleappraisal

Vehicle Customer critical test

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

NVH Problem Solving - Example 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:

mm/s Mod

0

10

20

30

40

50

60

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

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

High Speed (“Hot”) JudderS

peed

(K

m/h

)

Frequency (Hz)

DTV measurement systems and the F-M dual wavelength pyrometer may be used together to measure the effects of hot spotting

Temp (C)700

600

500

400

300

200

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

Summary

Performance, refinement, time & cost are often conflicting compromises

Structured approach required for problem identification & solution

More analytical work required