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 revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2016 SAE InternationalAll rights reserved. No part of this publi
3、cation may 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: +1 724-776-4970 (out
4、side USA)Fax: 724-776-0790Email: CustomerServicesae.orgSAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/J3079/2_201607SURFACE VEHICLESTANDARDJ3079-2 JUL2016Issued 2016-07Low-preload Deflection Meas
5、urement for Brake Pads, Noise Shims, and Brake Pad AssembliesRATIONALEThis standard addresses brake pad deflection characteristics similar to SAE J2468 with the following refinements:x The brake system pressure range is from 30 kPa to 13000 kPax Test results are summarized both graphically and in ta
6、bular formatx Includes guidelines to improve the accuracy and repeatabilityx Includes a description of a test procedure for noise insulatorsThe deflection characteristics of friction materials, noise insulators, and disc brake pad assemblies are commonly used in caliper and brake system design as we
7、ll as for quality control during manufacturing. Pad deflection influences many design characteristics including brake fluid consumption, caliper stiffness and mass, caliper piston retraction, and park brake adjustment. The deflection also influences performance characteristics including brake pedal
8、travel, brake drag, park brake performance, and the propensity of the brake system to generate noise and roughness.1. SCOPEThis SAE Standard specifies a method for measuring the deflection of friction materials, noise insulators, and disc brake pad assemblies to be used in road vehicles with a Gross
9、 Vehicle Weight Rating below 4336 kg.This part of the SAE J3079 includes the test for deflection and creep at various pressures under ambient temperature conditions.This SAE test method differs from SAE J2468 and ISO 6310 in the preload and maximum load applied to the test sample when deflection is
10、measured. It also introduces additional measurements such as for deflection offset, hysteresis, and creep.SAE INTERNATIONAL J3079-2 JUL2016 Page 2 of 172. REFERENCES2.1 Applicable DocumentsThe following publications form a part of this specification to the extent specified herein. Unless otherwise i
11、ndicated, the latest issue of SAE publications shall apply.2.1.1 SAE PublicationsAvailable from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org.SAE J160 Swell, Growth, and Dimensional Stabil
12、ity of Friction Materials and Noise Insulators when Exposed to Elevated TemperaturesSAE J2468 Road Vehicles Brake Linings Compressibility Test Procedure 2.1.2 ISO Publications Copies of these documents are available online at http:/webstore.ansi.org/ISO 6310 Road Vehicles Brake Linings Compressive S
13、train Test Methods 2.1.3 EKB/VDA publications Available from German Association of the Automotive Industry (VDA),Behrenstrae 35, 10117 Berlin,Tel: +49 30 897842-0, www.vda.de/enEKB 1108 Compressibility Test for Anti-Noise Shims3. DEFINITIONSTable 1 Symbols and definitionsSymbol Definition UnitsAo Br
14、ake pad contact area with the rotormmAp Piston(s) hydraulic areammAs Sample or coupon contact area with heating platenmmci Inner chamfer of piston adaptormmcload Creepmco Outer chamfer of piston adaptormmdc Corrected deflectionmde Machine deflectionmdm Measured deflection mSAE INTERNATIONAL J3079-2
15、JUL2016 Page 3 of 17Table 1 Symbols and definitions (continued)do Deflection offsetmdz Zeroed deflectionmhcycle Hysteresis for the entire cycle%hload Hysteresis as a specific steps (equivalent hydraulic pressure or force) within the cycle mho External height of the piston simulator without the inter
16、face feature with the upper platenmmhi Internal depth of the piston simulator mmFTotal force applied to the sample during testing NPeqEquivalent Hydraulic Pressure kPataTotal assembly thickness mmtbBacking plate (or shoe table) thickness mmtfFriction material thickness mmri Inner radii of piston ada
17、ptormmro Outer radii of piston adaptormm3.1 CompressibilityCompressibility is the transient deflection or reduction in thickness of the test sampled due to compressive load. Deflection is measured in the direction of the applied load, perpendicular to the friction surface. Deflection or reduction in
18、 thickness is measured in micrometers (Pm).3.2 Corrected Deflection - dcMeasured deflection minus the machine deflection using Equation 1:dc = dm - de Eq. 13.3 Creep - cloadCreep is the tendency of the test sample to deform gradually while under clamp load. Creep is calculated using deflection data
19、that is zeroed prior to the 3rd loading cycle. Creep is calculated at discreet pressure levels by subtracting the zeroed deflection at the discreet pressure during the third loading cycle from the zeroed deflection 0.5 seconds prior to the end of the creep load condition. Use Equation 2.cload = dz l
20、oad 0.5 s prior to the end of the creep loading condition dz load during 3rd cycle apply Eq. 2SAE INTERNATIONAL J3079-2 JUL2016 Page 4 of 173.4 Deflection Offset - doDeflection offset is the corrected deflection value 0.5 seconds prior to the loading cycle. 3.5 Equivalent Hydraulic Pressure - peqPre
21、ssure calculated by dividing the apply force by the piston hydraulic area.3.6 Hysteresis per Cycle - hcycleHysteresis is the lag in deflection that occurs with the test sample during the unloading (release) condition compared to the loading (apply) condition. Hysteresis creates a loop in the deflect
22、ion versus load curve and depends on many parameters including the load application rate, dwell time, and material under test. Cycle hysteresis is calculated by comparing the stored energy to the total input energy during the apply cycle. See Figure 1; use Equations 3 through 5.Area a-b-c: total inp
23、ut energy during the apply cycleArea a-c-d-e: total energy stored within the hysteresis loopFigure 1 Deflections and forces to calculate cycle hysterisisD = ? Eq. 3 = ( 5 F( )( 5 + )/2 5 Eq. 4 = ( 5 F( )( 5 + )/2 5 Eq. 5SAE INTERNATIONAL J3079-2 JUL2016 Page 5 of 173.7 Hysteresis at Load - hloadHyst
24、eresis for a given load is defined as the difference between the deflection during the release step minus the deflection during the apply step. Use the zeroed deflection dz for this calculation. Use Equation 6; see Figure 2.F1, F2,F6: specific load steps or loads equivalent to specific hydraulic pre
25、ssure levelshload-p1, hload-p2,hload-p6: hysteresis for load steps 1-to-6Figure 2 Deflections and forces to calculate hysterisisD ? = F Eq. 63.8 Load CycleLoad cycle is the loading of the test sample that occurs after the preload. For this test procedure, the load cycle uses a constant rate to apply
26、 load during the apply and release conditions, with a constant load dwell time at the maximum and at the minimum loads.3.9 Measured Deflection - dmDeflection measured during the test.3.10 Machine Deflection - deDeflection measured during the third cycle of the machine deflection test.3.11 Piston Hyd
27、raulic Area - ApArea of the caliper bore used to convert the test systems actuator load to equivalent hydraulic pressure. This area is generally larger than the area calculated using the outside diameter of the piston simulator.3.12 Piston SimulatorPiston simulator is a device used to apply the load
28、 to the test sample replicating the interface of the caliper piston(s) from the caliper assembly.SAE INTERNATIONAL J3079-2 JUL2016 Page 6 of 173.13 PreloadPreload is the steady state load applied to the test sample prior to the load cycle. For this procedure, the preload was reduced compared to othe
29、r industry standard tests to more closely match how the test sample is preloaded in a brake caliper.3.14 Zeroed Deflection - dzCorrected deflection adjusted to 0.0 m during the pre-load condition 0.5 seconds prior to the loading cycle.Use Equation 7.dz = dc - do Eq. 74. EQUIPMENTTable 2 Minimum test
30、 system capabilities and specificationsParameterMinimum Requirement or CapabilityThe test facilities and equipment shall be in good working order and shall have a valid calibration labelCalibration recordsLoad capacity for hydraulic brake applications allows for 13,000 kPa equivalent hydraulic press
31、ure for a twin 51 mm piston simulator. Larger applications will need a larger actuator.53 kN minimumAnalog-to-digital converter for force measurement 16-bit minimumRate to apply the equivalent system pressure (1000 to 10 000) kPa/sControl of equivalent pressure at pre-load 5 kPaControl of equivalent
32、 pressure at target load 10 kPaRated accuracy for instrumentation controlling equivalent system pressure 5 kPaSignal noise for instrumentation controlling equivalent system pressure 5 kPaResolution of deflection measuring device 0.1 m Force exerted on piston simulator by the deflection measuring dev
33、ice 1 NFlatness and parallelism of steel plate 2 mTemperature control accuracy of heating platen 2 CSampling rate for force and deflection measurement 1 to 1000 HzSampling rate for temperature measurement 1 to 50 Hz minimum4.1 FacilitiesTest facility capable of maintaining test equipment and test ha
34、rdware at (23 5) C and (50 10)% RH.4.2 Test StandA compressibility test stand with uniaxial load frame and loading device that provides loading of the test specimen similar to how it is loaded by the piston and rotor in a brake caliper assembly.4.3 Alignment SystemThe test stand must have self-align
35、ment capability to allow the piston simulator to align its contact surface to the specimen under test. The alignment system cannot cause extra compliance in the deflection measurement of the test specimen.SAE INTERNATIONAL J3079-2 JUL2016 Page 7 of 174.4 Deflection Measurement DeviceUse a device for
36、 measuring piston simulator deflection with a resolution of 0.1 Pm. Deflection measurement device shall exert less than 1.0 N of force during measurement.NOTE: Accuracy in a range of one-tenth of a micron requires attention to cleanliness and verification that plates, adaptors and test pieces do not
37、 contain burs and other contaminants.4.5 Test stand verificationVerify the control and measurement capability of the test stand:a. Verify the apply rate and deflection measurement using the standard and soft judge devices.b. Perform a gage repeatability and reproducibility study with at least 10 pre
38、selected test samples and at least three operators, with three repeats each.4.6 Piston simulator4.6.1 The piston simulator is a device that applies the load from the test stand to the test sample. Piston simulators shall be solid (not interchangeable with a separate carrier) and mount directly into
39、the loading device. Deflection shall be measured from the top of the piston simulator.NOTE 1: Multi-piece piston adaptors that slide into the top plate can be a source of variation due to orientation and the running clearance on the top plate sleeveNOTE 2: The piston simulator is a precision device.
40、 It must be protected during storage to avoid contact with other parts and it must be stored in an environmentally-controlled location. Conduct a visual Inspection prior to and post testing. Verify the surface topography at least annually using optical or laser holography methods. Verify flatness an
41、d parallelism to be within specification. If any part of the piston simulator shows surface damage (nicks, corrosion, or excessive material deposits), it should be reworked, re-qualified, or replaced.4.6.2 Piston simulator shall be representative of production caliper piston position and geometry at
42、 the pad backing plate/piston interface. The inner diameter (ID), outer diameter (OD), and flatness of the piston area that contacts the brake pad should be used to determining the piston adaptor dimensions, including chamfers or small radii machined into the piston edge. See Figures 3 and 4 for ill
43、ustrations.NOTE: The OD of the piston adaptor is not the same as the caliper piston diameter and should not be used to determine the piston hydraulic area.Figure 3 Basic geometry for single piston simulator SAE INTERNATIONAL J3079-2 JUL2016 Page 8 of 17(A) (B) (C) (D)Figure 4 Basic profiles for pist
44、on simulator interface (a) double chamfer, (b) inner chamfer and external radii, (c) inner radii and external chamfer, and (d) double radii 4.7 Steel PlateA 15 mm thick steel plate made of the same material as the heating platen is required. Length, width, surface finish, and flatness of steel plate
45、 shall allow full surface contact between the steel plate and piston simulator and between the steel plate and heating platen. The steel plate is intended to reduce the potential for damaging the heating platen during piston simulator baseline deflection measurements. Maintain and verify the flatnes
46、s and parallelism to be within 2 m.NOTE 1: The steel plate is a precision device. It must be protected during storage to avoid contact with other parts and must be stored in an environmentally-controlled location. Conduct a visual Inspection prior to testing. The surface topography should be verifie
47、d annually using optical or laser holography. Verify flatness and parallelism to be within specification. If any part of this device shows surface damage (nicks, corrosion, or excessive material deposits), it should be reworked and re-qualified, or replaced.NOTE 2: A poor quality steel block (high s
48、urface roughness or lack of flatness) can cause extra deflection during the machine baseline measurement. This additional deflection can lower the compensated results for the test sample by 2-5 microns.4.8 Sample LocatorA fixture shall be used to locate the test sample relative to the piston simulator to duplicate the alignment in the brake caliper.The locating device shall have (0.5-to-1.0) mm clearance from the test samp
