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 there
2、from, 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 2006 SAE International All rights reserved. No part of this publication m
3、ay 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.org J2468 REV. DEC2006 SURFACE VEHICLE STANDARD Issued 1999-04 Revised 2006-12 Superseding J2468 APR1999 (R) Road VehiclesBrake LiningsCompressibility Test Procedure RATIONALE Adjusted test pressures to be consistent wit
5、h US usage and practice. Allowed use of constant crosshead speed control equipment and constant loading rate equipment. FOREWORD The compressive response of a brake lining is an important design parameter when evaluating brake fluid volume displacement, brake pedal travel, or the propensity of a bra
6、ke system to generate roughness or noise. Brake lining compressibility is also useful for lining characterization and quality control. The purpose of this test procedure is to evaluate the compressibility of disc brake friction materials and brake pad assemblies. 1. SCOPE This SAE Standard specifies
7、 a method for testing and measuring the compressibility of friction materials and disc brake pad assemblies to be used in road vehicles. This SAE test method is consistent in intent with ISO 6310. 2. REFERENCES 2.1 Applicable Publications The following publications form a part of this specification
8、to the extent specified herein. Unless otherwise indicated, the latest version of SAE publications shall apply. 2.1.1 ISO Publications Available from ANSI, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org. ISO 611:1994 Road vehiclesBraking of automotive vehicles and thei
9、r trailersVocabulary ISO 6310:1998 Road vehiclesBrake liningsCompressibility test procedure 2.1.2 JIS Publications Available from JSA, 4-1-24 Akasaka Minato-ku, Tokyo 107-8440, Japan, Tel: +81-3-3583-8005, www.jsa.or.jp. JIS D 4413 Automotive PartsBrake Linings and Disc Brake PadsCompressibility Tes
10、t Procedure Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 Revised DEC2006 - 2 - 3. DEFINITIONS 3.1 Compressibility Compressibility is the absolute deflection, C, or reduction in thickness
11、 of the brake lining due to the compressive forces and temperatures given in this document. Compressibility is a measure of the brake lining assembly and is dependent upon assembly geometry. Deflection is measured in the direction of the application force, perpendicular to the friction surface. Samp
12、le deflection or reduction in thickness is measured in microns (m). Sample deflection or reduction in thickness is the recommended description of lining compressibility. 3.2 Compliance Rate of change of the deflection of the brake lining with change in compressive force, measured at a particular for
13、ce value is known as compliance, kx. Compliance is the instantaneous slope of the deflection-load curve measured during application of compressive force perpendicular to the friction surface. The units of compliance as defined here are m/N. 3.3 For other definitions relating to brake system componen
14、ts and design, see ISO 611. 3.4 This document allows for lining compressibility testing of two configurations; the sample types are described here: 3.4.1 Sample Type I Disc brake pad assembly (friction material and backing plate.) Sample Type I is commonly used for passenger car and light truck appl
15、ications. 3.4.2 Sample Type II Lining assembly coupon. A coupon may be sectioned from a large disc assembly, and the friction material may be removed from the backing plate if desired. It is recommended that coupon sample should be as large as possible to account for material inhomogeneity. Surfaces
16、 of specimen should be flat and parallel. 4. SYMBOLS AND UNITS See Table 1. TABLE 1 - SYMBOLS AND UNITS Parameter Symbol Equation Unit Initial thickness of friction material t0mm Initial thickness of assembly a0mm Displacement measurement d m Deflection of the test machine (without sample) dem Sampl
17、e contact area of friction material Ao cm2or m2Compressibility (or reduction of thickness under load) C = d dem Compliance at load x, (where L is load) Kx=xLLC=m/N Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license
18、from IHS-,-,-SAE J2468 Revised DEC2006 - 3 - 5. EQUIPMENT The test equipment should include: a. A compressibility test stand, uniaxial material testing load frame or a loading device that provides uniform loading over the surface of the test specimen. b. A loading cylinder to simulate a caliper pist
19、on configuration or other brake application mechanism. c. A compression platen. d. A device to measure applied compression force to an accuracy of 1% full scale load of test machine. e. A gauge for measuring the deflection of the sample to an accuracy of 0.001 mm. This gauge should be positioned eit
20、her on the loading cylinder or the platen and in contact with the ram as near to its center line as possible. f. A recording device or computer to log the measured load and/or pressures, displacements, temperatures as function of time. g. A heating device to raise the temperature of the platen to a
21、specified temperature and a thermocouple to monitor that temperature. h. A thermocouple or device to measure the temperature of the test sample. i. A micrometer. 6. TEST RIG SPECIFICATION 6.1 Loading 6.1.1 For hydraulic disc brakes, the maximum force required is that which corresponds to the service
22、 maximum vehicle system line pressure or 100 bar simulated line pressure. The recommended loading rate is that which achieves 15 mm/min when testing in crosshead speed control, or 80 bar/s (4 MPa/s) simulated line pressure if testing in constant loading rate control. The testing machine must have se
23、lf-aligning capability or parallelism between the platen and ram loading face must be maintained. 6.1.2 For air operated disc brakes, the maximum force required shall correspond to 80 bars (8 Mpa) unit pressure on the friction surface, also called as face pressure. 6.2 Elevated Temperature Capabilit
24、y 400 C. 6.3 Loading Configurations 6.3.1 Sample Type I, Disc Brake Pad Assembly See Figure 1. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 Revised DEC2006 - 4 - FIGURE 1 - SAMPLE TYPE 1
25、: BRAKE LINING ASSEMBLY A fixture representing a piston is introduced between the ram and the friction material pad such that the loading surface has the same form and location as the actual contact surface of the piston in which the pad will be used in service. If the intended brake system has a du
26、al piston caliper, a dual piston-shaped loading fixture should be used. 6.3.2 Sample Type II, Friction material Coupon Sample See Figure 2. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 R
27、evised DEC2006 - 5 - FIGURE 2 - SAMPLE TYPE II: FRICTION MATERIAL COUPON Coupons should be tested with a parallel metal adapter plate, of larger dimensions than the coupon, to uniformally distribute the load over the coupon surface. (A fixture simulating a piston is not recommended for this sample t
28、ype.) 6.4 Compensation of Deflection of the Test Machine During compression testing, a test machine will also deflect. This deflection has to be compensated for (manually or automatically) in the determination of the net displacement of the friction material sample. The deflection of the test device
29、, de, is measured by loading the ram with the piston fixture in place on the base platen without a sample installed and then recording displacement at the test pressures. Compressibility or deflection of the sample is then C = d - de. 7. SAMPLING AND PREPARATION OF SAMPLES 7.1 It is recommended that
30、 a minimum of five samples be measured at room temperature, and three samples at elevated temperature. 7.2 The flatness and surface roughness of the samples should be that of normal production. 7.3 When testing to measure friction material properties, it is recommended that backing materials, such a
31、s anti-noise shims or rubber coatings, be removed prior to testing and this information should be reported. When testing to evaluate the full disc brake pad assembly, backing materials may be left on. 7.4 For accurate measurements, parts should be stabilized at 23 5 C and 50 10% relative humidity be
32、fore testing. Record and report environmental test conditions. 8. TEST PROCEDURE 8.1 Ensure that test stand is properly calibrated. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 Revised D
33、EC2006 - 6 - 8.2 Measure the thickness of Sample Type I at 5 points as in Figure 3 with a micrometer. Calculate the mean value a0, of the assembly thickness. (If the pad sample contains a slot, then take the center measurement just adjacent to the slot.) Measure the thickness of Sample Type II at 5
34、points similarly distributed. FIGURE 3 - RECOMMENDED THICKNESS MEASUREMENT POSITIONS FOR SAMPLE TYPE I (IF LINING HAS A CENTER SLOT, SHIFT CENTER POSITION MEASUREMENT TO APPROXIMATELY 3 mm FROM THE SLOT.) 8.2.1 If the compressive strain of the friction material is required, then the friction materia
35、l thickness, t0, independent of the backing plate, must be determined. 8.3 Measure and record nominal sample contact area, Ao. 8.4 Place the sample on the platen at room temperature (23 C 5 C) with its friction surface against the surface of the platen with the ram and piston fixture correctly locat
36、ed. Careful centering of the sample beneath the loading (piston) fixture is important for repeatability of results. 8.5 Test Sequence The room temperature test sequence is illustrated in Figure 4 and is described as follows: 8.5.1 Room Temperature Test 8.5.1.1 Pre-load to the force value that corres
37、ponds to 5 bar (0.5 MPa) hydraulic system pressure or pneumatic face pressure and hold for no more than 5 s. 8.5.1.2 Zero the displacement gage while the sample is held at pre-load. 8.5.1.3 Perform three loading and unloading cycles starting from the pre-load. A cycle consists of increasing to the m
38、aximum pressure at the rate specified in Table 2, then unloading at the same rate to the pre-load value. The recommended maximum force is that which yields a system pressure as stated in Table 2 for the listed time period. An alternative maximum pressure or time can be used for specific applications
39、. If deviating from the specified values, note maximum pressure and hold time on test report. TABLE 2 - TEST CYCLE CONDITIONS Brake Input Mechanism Application Rate Maximum Pressure Maximum Pressure Hold Time Hydraulic 15 mm/min or 80 bar/s 100 bar (10 MPa) simulated input pressure 1 second Air 3.0
40、0.5 MPa/s 8.0 MPa unit face pressure 1 second Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 Revised DEC2006 - 7 - For testing sample Type II, the maximum load should be the same fraction
41、of the system maximum that corresponds to the fraction of the sample area with respect to the full pad contact area. (For example, if a 10 cm2small sample is cut from a 60 cm2pad, then to achieve the same pressure at the contact area, the maximum load value should be 1/6th that of the full pad test.
42、) If deviating from this prescribed maximum condition, note conditions on test report. Room Temperature Compressibility Test Loading Pattern01020304050607080901000 1 2 3 4 5 6 7 8 9 10 11 12 13 14Time, secondsSimulated LinePressure,BarFIGURE 4 - ROOM TEMPERATURE COMPRESSIBILITY TEST SEQUENCE 8.5.1.4
43、 Measure displacement and load during the loading cycles. If computer data acquisition is available, it is recommended that continuous displacement versus pressure (and load) be recorded. Displacement should be recorded and reported at the maximum pressure on the first cycle and last cycle, and in a
44、ddition on the last cycle, readings should be recorded at several points while the pressure increases. 8.5.2 Hot Test The hot test is conducted at 400 C or the maximum anticipated operating temperature. 8.5.2.1 Remove sample from the heating plate. Preheat the heating plate to a stabilized surface t
45、emperature of 400 C 10 C. 8.5.2.2 Place the same sample on the heating plate and apply pre-load of 5 bar (0.5 MPa). 8.5.2.3 Zero the displacement gauge. 8.5.2.4 Maintain the pre-load for 10 min 30 s. Record changes in displacement during this preheat, pre-load period. 8.5.2.5 Re-zero the displacemen
46、t gauge. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE J2468 Revised DEC2006 - 8 - 8.5.2.6 Perform two loading-unloading cycles. Use same loading parameters as used for room temperature cycles
47、described in 8.5.1.3. Following hot testing, cool equipment to ambient temperature. 9. REPORT The test report should include information regarding the samples tested, test conditions used, and compressibility values determined. There may be an agreement among parties regarding which measure(s) of co
48、mpressibility should be reported. Any deviations from recommended practice should be reported. 9.1 Recommended Information to Include in Report 9.1.1 Sample Information a. Manufacturer, identification of brake lining, material batch reference b. Type of sample used (Type I or II) c. Sample dimensions, including surface area d. Conditions of samples, e.g., noise insulators removed, or backing plate removed e. Number of samples tested at room temperature; number of samples tested at elevated temp
