1、_SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising theref
2、rom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2009 SAE International All rights reserved. No part of this publication ma
3、y be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA)
4、Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSURFACEVEHICLESTANDARDJ2725 JAN2009 Issued 2009-01Road VehiclesFriction MaterialsElastic Properties Measurements RATIONALENot applicable. FOREWORDThe elastic properties of friction materials are important design parame
5、ters because modulus variations may be significant in noise generation of braking systems. Variations in elastic properties as a result of processing and formulation are often a primary determinant of component performance. The purpose of this test procedure is to evaluate the elastic properties of
6、friction materials in brake pads. Data are provided in a format that is directly useful for modelinganalysis and simulation.TABLE OF CONTENTS 1. SCOPE 22. REFERENCES (SEE ALSO REFERENCES OF APPENDIX A) 22.1 Application Publications 23. DEFINITIONS . 33.1 Coordinate System Definition . 33.2 Ultrasoni
7、c Modes 33.3 Elastic Constants and Engineering Constants . 44. SYMBOLS AND UNITS 45. EQUIPMENT . 56. SAMPLE PREPARATION . 56.1 Rectangular Samples 66.2 45-degree Samples . 67. EQUIPMENT AND TEST RIG SPECIFICATION 78. CALIBRATION 79. TEST PROCEDURE (ELASITIC CONSTANTS) 8Copyright SAE International Pr
8、ovided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2725 Issued JAN2009 - 2 -10. RECOMMENDED INFORMATION TO INCLUDE IN ELASTIC CONSTANT REPORT 910.1 Sample Information . 910.2 Test Conditions and Hardware . 910.3 Raw Data 1010.4
9、 Averaged Data and Calculated Elastic and Engineering Constants 1111. TEST PROCEDURE (LOAD-DEPENDENCE AND VARIABILITY) 1112. RECOMMENDED INFORMATION TO INCLUDE IN LOAD DEPENDENCE REPORT 1213. NOTES 1313.1 Marginal Indicia . 13APPENDIX A THEORY: DETERMINATION OF ELASTIC PROPERTIES FROM ULTRASONICMEAS
10、UREMENTS 14A.1 INTRODUCTION. 14A.2 NOMENCLATURE, COORDINATE SYSTEM, AND GOVERNING RELATIONS . 14A.3 EXPERIMENTAL DETERMINATION OF ELASTIC CONSTANTS 19A.4 APPENDIX REFERENCES 22FIGURE 1 BRAKE PAD BASED COORDINATE SYSTEM . 3FIGURE 2 TYPICAL CUTTING DIAGRAM FOR BRAKE PAD 5FIGURE 3 DIRECTION OF ULTRASOU
11、ND FOR 45-DEGREE SAMPLE MEASUREMENTS -PROPAGATION IS NORMAL TO THE 45-DEGREE CUT SURFACE 6FIGURE 4 CUT RECTANGULAR AND 45-DEGREE SAMPLE 6FIGURE 5 CONFIGURATION FOR MEASURING THE TRANSIT TIME IN A STEEL CALIBRATIONTEST SAMPLE . 8FIGURE 6 RECTANGULAR SAMPLE MOUNTED IN COMPRESSION FIXTURE 9FIGURE 7 RAW
12、 ULTRASONIC AND TRANSIT TIME DATA 10FIGURE 8 LOAD DEPENDENCE OF ELASTIC CONSTANTS . 12FIGURE A1 COORDINATE DEFINITION . 14TABLE 1 SYMBOLS AND UNITS 4TABLE 2 SUMMARY DATA FOR ULTRASONIC MEASUREMENTS 11TABLE 3 LOAD DEPENDENCE OF VELOCITY AND ELASTIC CONSTANTS . 121. SCOPE This SAE Standard specifies a
13、 method for testing and measuring elastic constants in friction materials by precise ultrasonic velocity measurements.2. REFERENCES (SEE ALSO REFERENCES OF APPENDIX A) 2.1 Application Publications The following publications form a part of this specification to the extent specified herein. Results of
14、 Friction Materials Elastic Constant Round Robin Study, Donald E. Yuhas and Paul Sanders, 25thannual Brake Colloquium, Orlando FL October, 2007 SAE # 07BC-40 Non-linear Aspects of Friction Material Elastic Constants, Donald E. Yuhas, Jim Ding, and Srikanth VenKatesan, 24thannual Brake Colloquium, Da
15、llas TX October, 2006 SAE # 2006-01-3193 Elevated Temperature Measurements of Elastic Constants in Polymer Composites, Donald E. Yuhas and Bruce Isaacson, The 43rdInternational SAMPE Symposium May 31-June 4, 1998, Anaheim California Copyright SAE International Provided by IHS under license with SAEN
16、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2725 Issued JAN2009 - 3 -H.M. Ledbetter and D.T. Read, “Orthorhombic Elastic Constants of an NbTi/Cu composite Superconductor“, Jour. App. Phys, #5 May, 1977 Every A.G., “Determination of the Elastic Constants of
17、Anisotropic Solids”, NDT International Vol. 27, No. 1, p. 3, 1993 Disc Brake Squeal, Frank Chen, Chin An Tan, and Ronald L. Quaglia eds. Chapter 12 D.E. Yuhas and Marjorie P. Yuhas. Friction Material Elastic Constant Measurements ISBN 10 0-7680-1248-1 3. DEFINITIONS In this test, the elastic constan
18、ts of friction materials are determined by measuring both the longitudinal and shear wave speeds propagating at various directions in the friction material. It is important to record and maintain the relationship between the direction of ultrasonic propagation, wave polarization, and the principle a
19、xes of the friction material. From the measured ultrasonic velocities, and the symmetry of the friction material, the elastic constants as well as the Engineering constants i.e. Youngs moduli, Shear Moduli, and Poissons Ratios can be calculated. 3.1 Coordinate System Definition The coordinate geomet
20、ry referenced to the disk pad shape is shown in Figure 1. The same geometry is used for truck blocks and with a slight modification can be used for drum brakes. In all cases the “3” or z” axis is the thickness directionand the “1” or “x” direction is along the rotation axis. This coordinate definiti
21、on is used throughout the gathering of data and the subsequent analysis. Failure to adhere to the appropriate data collection protocol can lead to some unusual and potentially misleading results. FIGURE 1 - BRAKE PAD BASED COORDINATE SYSTEM In the coordinate system shown in Figure 1, the “3” axis is
22、 perpendicular to the friction surface, the “1” axis is along the long axis of the pad, and the “2” axis is parallel to the short axis of the pad. 3.2 Ultrasonic Modes Ultrasonic mechanical vibration in the frequency range from 0.1 to 100 MHz. Longitudinal or compressional wave ultrasonic wave mode
23、where the direction of wave propagation is parallel to the particle displacement or polarization of the wave. Shear wave ultrasonic wave mode where the direction of wave propagation is perpendicular to the particle displacement or polarization. Copyright SAE International Provided by IHS under licen
24、se with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2725 Issued JAN2009 - 4 -Using the above definitions and the coordinate system defined in Figure 1, we can define the following wave modes: V33 Longitudinal mode propagation along the “3” direction wit
25、h polarization along “3” V11 Longitudinal mode propagation along the “1” direction with polarization along “1” V22 Longitudinal mode propagation along the “2” direction with polarization along “2” V31 Shear mode propagating along the “3” direction polarized along the “1” direction V32 Shear mode pro
26、pagating along the “3” direction polarized along the “2” direction V21 Shear mode propagating along the “2” direction polarized along the “1” direction V12 Shear mode propagating along the “1” direction polarized along the “2” direction V45is a shear mode propagating along j k (the vector .707j - .7
27、07k) and polarized along j + k (the vector .707j +.707k). Here, j is the unit vector along the “2” (or 1) direction and k is the unit vector along the “3” direction. Using the same convention as used for the other modes along the principle axes, this mode would be designated as V.707y-.707z,.707y+.7
28、07z.3.3 Elastic Constants and Engineering Constants The equations relating the measured ultrasonic velocities to the material elastic constants and the engineering constants are derived in Appendix A. 4. SYMBOLS AND UNITS TABLE 1 - SYMBOLS AND UNITS Parameter Symbol Equation Unit Initial friction ma
29、terial thickness X1, X2, X3mm Longitudinal Transit timeTLmicroseconds Longitudinal offset TLomicroseconds Shear Transit time TSmicroseconds Shear offset TSomicroseconds Coupling Force Fckilograms Longitudinal velocity ViiXi/t mm/microsecond Shear Velocity Viji =/ j Xi/t mm/microsecond Density g/cc U
30、nique axis Longitudinal Modulus C33 V233GpaIn-plane Longitudinal ModulusC11= C22 (2GpaIn-plane Shear ModulusC66 (2GpaOut-of-plane Shear ModulusC44= C55 (2GpaFirst off-diagonal Elastic Constant C12c2-c=c661112GpaSecond off-diagonal Elastic Constant C13()()()4422334433224513222c- 20.52cccccc .25V s+=G
31、paCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2725 Issued JAN2009 - 5 -5. EQUIPMENT The test equipment should include: a. Ultrasonic pulser-receiver unit b. Waveform digitizer and display c.
32、 Coupling load test fixture d. 2 longitudinal wave ultrasonic sensors e. 2 shear wave ultrasonic sensors f. Micrometer g. Balance h. Ultrasonic couplant i. Propagation Timing Standard 6. SAMPLE PREPARATION For friction materials, the material symmetry is transversely isotropic with the unique axis a
33、long the materials thickness direction (axis “3” in Figure 1). We require a minimum of one rectangular sample oriented along the principle axes of the pad and one sample which has been sliced at a 45-degree angle relative to the “unique” axis of the pad. Figure 2 shows the brake pad cutting diagram.
34、 FIGURE 2 - TYPICAL CUTTING DIAGRAM FOR BRAKE PAD Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2725 Issued JAN2009 - 6 -6.1 Rectangular Samples The first step in sample preparation is to remo
35、ve the friction material from the steel backing using a band saw. The friction material is then sliced into a 20 mm wide segment parallel to the “2” direction. From this segment, small, 15 mm by 20 mm by 8 mm rectangular test specimens are cut. Note that material is discarded from areas near the inj
36、ection molding sites. Saw cut marks are removed using a belt-sander and efforts are made to produce rectangular test pieces with parallel surfaces. The longest sample dimension, (20 mm), corresponds to the longest dimension of the original pad (“1=x” direction in our defined coordinate system). The
37、smallest dimension (8 mm) always corresponds to the thickness dimension (“3=z” direction in our defined coordinate system). The parallelism is important for all samples and we generally want to control the variation to under 25 microns. The above shows recommended sizes for typical automotive disc b
38、rake pad. For larger truck blocks it may be desirable to increase the sample size in proportion by a factor of as much as 3 times. The thickness direction (“3” axis) is the controlling dimension. For drum brake segments, the same rectangular pieces are cut from the segment, however in this case the
39、slight curvature of the surface must be removed by sanding. This is particularly important for the concave surface.6.2 45-degree Samples A second sample type, a cut 45-degree relative to the thickness direction, is used to obtain the off-diagonal elements to the elastic constant matrix. This is show
40、n as Sample B in Figure 2. This Figure is somewhat misleading in that it suggests that Sample B, (45-degree Sample) has a large surface area for the face normal to the “3” axis. The 45-degree sample must be “thinner” than the thickness of the pad from which it came, i.e. thinner than the “3” directi
41、on thickness. Typical thickness is 6 mm. Measurements are made on this piece by propagation of waves perpendicularly to the 45-degree cut surface as indicated by the white arrow in Figure 3. This sample must be cut such that the 45-degree faces are parallel to one another and the ultrasound can prop
42、agate perpendicular to this cut surface reaching the other side before being reflected and refracted by a sidewall. FIGURE 3 - DIRECTION OF ULTRASOUND FOR 45-DEGREE SAMPLE MEASUREMENTS -PROPAGATION IS NORMAL TO THE 45-DEGREE CUT SURFACE Figure 3 shows a friction material in the 3-2 (or 3-1) plane wi
43、th a dark outline showing a 45-degree cut, which is appropriate for the transit time measurement. FIGURE 4 - CUT RECTANGULAR AND 45-DEGREE SAMPLE Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J
44、2725 Issued JAN2009 - 7 -Figure 4 shows a picture of a typical rectangular and 45-degree specimen. The thickness of this piece along the “3” axis is generally in the range from 6 mm to 10 mm. The 45-degree sample has been oriented so that it appears as it was in the pad prior to slicing. Its thickne
45、ss, measured normal to the 45-degree cut surfaces, is only 6 mm to 7.5 mm. All coordinate axis designations are referenced to the coordinate system shown in Figure 1. For all samples the parallelism should be accurate to 25 microns. The surface finish as obtained with 200 grit sandpaper. For the 45-
46、degree sample, the angular uncertainty is controlled primarily by the cutting fixture. It should be better than 5 degrees. 7. EQUIPMENT AND TEST RIG SPECIFICATION Ultrasonic pulser-receiver unit must have a frequency bandwidth of 90 MHz, be capable of shock excitation of transducer in the frequency
47、range from range of 1 to 10 MHz, and have a dynamic range of more than 90 dB. Waveform digitizer and display must have an acquisition speed greater than 50 MHz., ability to display of waveforms in real-time, have automatic peak detection, signal averaging, (50 times minimum) and automatic transit ti
48、me measurement capability. Timing precision of 10 nanoseconds is required. The coupling load test fixture must be capable of supplying and monitoring up to 1000 N (220 lb) of compressive load to the samples and of maintaining the polarization of the ultrasonic sensors to better than = 5 degrees. The precision of the load fixture should be 20 N (5 lb). For shear wave transducers, the direction of polarization is indicated on the sensors. The fixture must allow for rotation of each sensor (about the propagation direct
