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 2012 SAE International All rights reserved. No part of this pub
3、lication 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
4、(outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2928_201207SURFACEVEHICLERECOMMENDEDPRACTICEJ2928 JUL2012 Issued 2012-07Brake Rotor
5、 Thermal Cracking Procedure for Vehicles Below 4 540 kg GVWR RATIONALEThis recommended practice provides a standard laboratory method and performance criteria to assess brake rotors for crack initiation and crack propagation during high-energy brake applications. The SAE Task Force acknowledges the
6、developments and best practices from different European working groups and regulatory entities as the backbone of this recommended practice. TABLE OF CONTENTS 1. SCOPE 21.1 Purpose . 22. REFERENCES 22.1 SAE Publications . 22.2 ECE Publications 23. DEFINITIONS . 34. ROTOR CHARACTERIZATION . 45. TEST
7、CYCLES 46. TEST EQUIPMENT . 57. TEST CONDITIONS AND SAMPLE PREPARATION 68. TEST INERTIA 79. TEST PROCEDURE AND CONDITIONS 710. TEST REPORT . 911. NOTES 10SAE J2928 Issued JUL2012 Page 2 of 13 APPENDIX A CRACK FAILURE DEFINITIONS . 11APPENDIX B TEST REPORT PHOTOGRAPHS 13FIGURE 1 TYPICAL BRAKE APPLICA
8、TION TIME STAMPS . 5FIGURE 2 THERMOCOUPLE LOCATION FOR VENTED ROTORS . 6FIGURE 3 THERMOCOUPLE LOCATION FOR SOLID ROTORS . 6FIGURE A1 EXAMPLE OF SURFACE CRACK . 11FIGURE A2 EXAMPLE OF INITIAL CRACK 11FIGURE A3 EXAMPLE OF THROUGH CRACK 12 FIGURE A4 CRACK DESCRIPTION 12FIGURE B1 OUTBOARD ROTOR FACE . 1
9、3 FIGURE B2 INBOARD ROTOR FACE . 13FIGURE B3 MOST SEVERE CRACK SECTOR . 13 FIGURE B4 SIDE VIEW OF THE MOST SEVERE CRACK . 13 TABLE 1 ROTOR CRACK TEST SEQUENCE 8TABLE 2 INSPECTION LOG FOR CRACKS AND PAD REPLACEMENT . 81. SCOPE This recommended practice is derived from common test sequences used withi
10、n the industry. This procedure applies to all on-road passenger cars and light trucks up to 4 540 kg of GVWR. This recommended practice does not address other aspects such as performance, NVH, and durability. Test results from this recommended practice should be combined with other measurements and
11、dynamometer tests (or vehicle-level tests), and acceptance criteria to validate a given design or configuration.1.1 Purpose This recommended practice establishes a minimum evaluation procedure for brake rotor thermal cracking. 2. REFERENCES 2.1 SAE Publications Available from SAE International, 400
12、Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J2784 FMVSS Inertia Dynamometer Test Procedure for vehicles below 4 540 kg GVWR SAE J2789 Inertia Calculation for Single-Ended Inertia Dynamometer Testing 2.2 ECE P
13、ublications Available at www.unece.org/trans/main/wp29/meeting_docs_grrf.html?expandable=0&subexpandable=99 under: Working Documents. ECE-TRANS-WP29-GRRF-2011-09e Replacement brake linings - Proposal for amendment to Regulation No. 90 SAE J2928 Issued JUL2012 Page 3 of 13 3. DEFINITIONS 3.1 APPARENT
14、 FRICTION FOR DISC BRAKES Per Equation 1: ()effPThresholdrAppT=2105(Eq. 1) where: = apparent friction for disc brakes. unitless T= output torque. Nm p= brake pressure. kPa Thresholdp= minimum pressure required to start developing braking torque. Unless otherwise indicated by the requestor, use 100 k
15、Pa for service-only brake corners and 300 kPa for integral parking brake corners. kPa PA= total piston area acting on one side of the caliper for disc brakes. mm2effr= radial distance from centerline of the piston to the axis of rotation for disc brakes, unless other dimensions are provided by the r
16、equestor. mm 3.2 DECELERATION-CONTROLLED BRAKE APPLICATION Inertia dynamometer control algorithm that adjusts brake pressure in real time to maintain a constant torque output calculated from the instantaneous deceleration specified in the test procedure. 3.3 PRESSURE-CONTROLLED BRAKE APPLICATION Ine
17、rtia-dynamometer control algorithm that maintains a constant input pressure to the brake independent of the torque output.3.4 GROSS VEHICLE WEIGHT RATING- GVWR Maximum vehicle weight indicated by the manufacturer. kg 3.5 INITIAL BRAKE TEMPERATURE - IBT Rotor temperature at the start of the brake app
18、lication C3.6 TIRE DYNAMIC ROLLING RADIUS Equivalent tire radius that will generate the Revolutions Per Mile (RPM) published by the tire manufacturer for the specific tire size per Equation 2. Use the tire dynamic rolling radius to calculate the dynamometer rotational speed for a given linear vehicl
19、e speed. mm whereRPMRR=23446091(Eq. 2) RR = tire dynamic rolling radius mm RPM = tire manufacturer specification for revolutions per mile. Typically shown for the tire size on the manufacturers website3.7 PRESSURE LIMIT Maximum allowable pressure during a brake application SAE J2928 Issued JUL2012 P
20、age 4 of 13 3.8 MAXIMUM VEHICLE SPEED VmaxHighest speed attainable by accelerating at a maximum rate from a standstill to a distance of 3.2 km on a level surface, with the vehicle at LLVW for vehicles per FMVSS 135 or at GVWR for vehicles per FMVSS 105. For electric vehicles, the speed attainable is
21、 determined with the propulsion batteries at a state of charge of not less than 95% at the beginning of the run. km/h 3.9 ROTOR GOOSENECK On integral rotor designs, a cast or machined groove at the transition from the inboard braking surface to the cylindrical (or conical) portion of the rotor that
22、connects to the wheel hub/bearing unit. 4. ROTOR CHARACTERIZATION 4.1 Record and report features that characterize the rotor such as: 4.1.1 Rotor mass 4.1.2 Vane count and configuration (straight radial vanes, straight slanted vanes, curved slanted vanes, multiple straight slanted vanes, rung shaped
23、 blades, or pillars) 4.1.3 Cross-drills or slots 4.1.4 Surface treatment or coating 4.1.5 Rotor thickness variation measured 10 mm from the outside diameter 4.1.6 Cheek thickness variation measured every 90 on both friction surfaces (for vented rotors only) 4.1.7 Mounted lateral run-out measured 10
24、mm from the outside diameter on the outboard cheek 4.1.8 Friction surface finish Rameasured every 90 on both friction surfaces for non-coated rotors 4.1.9 Hardness of friction surface measured every 90 on both friction surfaces 4.1.10 Basic material description 4.1.11 Rotor design/type (standard ven
25、ted, inverted, standard solid, solid drum-in-hat, vented drum-in-hat, or solid single flange rotor)5. TEST CYCLES 5.1 Dynamic Brake Application Figure 1 illustrates the main time-stamps used to characterize the brake application. SAE J2928 Issued JUL2012 Page 5 of 13 FIGURE 1 - TYPICAL BRAKE APPLICA
26、TION TIME STAMPS 5.1.1 Time t0Brake application initiation. At this time, the pressure starts to rise. 5.1.2 Time t1Time at level reached. At this time, the brake reaches its target level for torque or pressure control. At time t1, the calculation of average by time and the average by distance begin
27、s. 5.1.3 Time t2Time at the end of averages. At time t2the inertia-dynamometer data acquisition system terminates the calculation of average by time and average by distance. Time t2is the end of the stable portion of the brake application. t2is defined as the time at which speed is 0.5 km/h above th
28、e release speed (t3).5.1.4 Time t3Time at release speed. At time t3, the inertia-dynamometer servo controller releases the brake (specified in 8.1.3).5.1.5 Time t4Time at brake pressure and torque lost. At time t4, pressure and torque are below the minimum thresholds. The inertia-dynamometer conside
29、rs the braking event complete. 6. TEST EQUIPMENT 6.1 Single ended brake inertia-dynamometer capable of performing deceleration and pressure controlled brake applications.6.2 Enclosure or cage to safely contain any debris or broken test components during testing SAE J2928 Issued JUL2012 Page 6 of 13
30、6.3 Automatic data collection system capable of recording the following channels at 100 Hz minimum sample rate 6.3.1 Brake equivalent linear speed. km/h 6.3.2 Brake input pressure. kPa 6.3.3 Brake output torque. Nm6.4 Automatic data collection system capable of recording brake rotor temperature at 5
31、0 Hz minimum sample rate. C7. TEST CONDITIONS AND SAMPLE PREPARATION 7.1 For disc brakes, the assembled rotor lateral run-out shall not exceed 50 microns when measured on the outboard surface and 10 mm from the outside diameter when coupled to the dynamometer shaft. 7.2 Use a new rotor as received a
32、nd new brake pads for each test 7.3 Additional pads sets may be required. This will depend on individual brake platforms 7.4 Cooling air shall remain enabled per item 9.5 and 9.6 during the entire test sequence 7.5 Use OEM (or OES) friction material. If the OEM (or OES) friction material is not avai
33、lable alternatives are permitted in agreement with the requestor. Include the actual friction material edge code used for the test on the final test report.7.6 Temperature measurement 7.6.1 For vented rotors use a welded thermocouple on the outboard brake cheek between fins (black dot on Figure 2).
34、An alternative method is to use a rubbing thermocouple on the outboard rotor face located at the effective radius (black square on Figure 2).FIGURE 2 - THERMOCOUPLE LOCATION FOR VENTED ROTORS 7.6.2 For solid rotors use a welded thermocouple in the relief groove (black triangle on Figure 3). An alter
35、native method is to use a rubbing thermocouple on the outboard brake cheek (black square on Figure 3). FIGURE 3 - THERMOCOUPLE LOCATION FOR SOLID ROTORS SAE J2928 Issued JUL2012 Page 7 of 13 8. TEST INERTIA Calculate the test inertia according to the default values indicated on Tables 1 and 2 of SAE
36、 J2789 for deceleration 0.65 g, with the vehicle loaded at GVWR. 9. TEST PROCEDURE AND CONDITIONS 9.1 Test sequence per table 1 9.2 Use a release speed of 0.5 km/h for all brake applications 9.3 Pressure ramp rate 20 000 kPa/s 9.4 Cooling air speed of 50 km/h measured approximately 200 mm from the r
37、otor outside diameter in front of the incoming cooling air. Unless otherwise specified by the test requestor, direct the cooling air on the opposite side of the caliper.NOTE: Monitor final rotor temperature. After final rotor temperature stabilizes, cast iron or steel rotors achieve typical temperat
38、ures of approximately (500-600) C. Rotor temperatures above this range may cause premature failure or damage to other brake components. 9.5 Control cooling air temperature to (25 10) C 9.6 Control deceleration levels within 10% of the set-point. 9.7 Cycle time is controlled from the start of the fir
39、st brake application of the cycle to the start of the second brake application during the same cycle. 9.8 In the event the brake corner does not achieve target deceleration, perform the following sequence:9.8.1 Increase maximum brake pressure above 14 000 kPa, as long as the new pressure is not abov
40、e brake corner maximum operating pressure 9.8.2 Continue testing as-is, with the understanding the deceleration levels will not be achieved and add the corresponding note on the final test report 9.8.3 Change the friction material to a different type or formulation (edge-code). In the case when the
41、friction material is changed, a new test series is required using new rotors in agreement with the test requestor. 9.9 Unless otherwise indicated by the test requestor, replace with friction material of the same edge-code when one of the following items applies. When replacing the friction material,
42、 conduct 50 burnish stops per step 1 on Table 1: 9.9.1 The minimum usable thickness is 3 mm or less at the thinnest position 9.9.2 The friction material exhibits structural damage (example: a loss of 10% of more of the working area) 9.9.3 Detachment of friction from the backing plate 9.9.4 Permanent
43、 and significant deflection of the backing plate9.9.5 Cracks across the friction material thickness 9.10 At each Inspection check for rotor cracks, record length of longest crack, verify pad life (minimum thickness), and conduct a visual inspection of the brake corner per item 9.10 and update the in
44、spection log per Table 2. Crack classification and structural failure criteria are indicated in Appendix A. SAE J2928 Issued JUL2012 Page 8 of 13 TABLE 1 - ROTOR CRACK TEST SEQUENCE Step Description Braking Speed km/h Brake ApplicationControl (IBT, Cycle Time) Decelerationlevel m/s2Number of Stops p
45、er Cycle Number of Cycles 1 Burnish 80 IBT= 100 C 3 200 12Rotor Crack Sequence (1-25) 160 IBT=100 C first, then 70 s 5 2 253 Planned Inspection Perform inspection per 9.104 Rotor Crack Sequence (26-50) 160 IBT=100 C first, then 70 s 5 2 255 Planned Inspection Perform inspection per 9.106 Rotor Crack
46、 Sequence (51-70) 160 IBT=100 C first, then 70 s 5 2 207 Planned Inspection Perform inspection per 9.108 Rotor Crack Sequence (71-80) 160 IBT=100 C first, then 70 s 5 2 109 Planned Inspection Perform inspection per 9.1010 Rotor Crack Sequence (81-90) 160 IBT=100 C first, then 70 s 5 2 1011 Planned I
47、nspection Perform inspection per 9.1012 Rotor Crack Sequence (91-100) 160 IBT=100 C first, then 70 s 5 2 1013 Planned Inspection Perform inspection per 9.1014 Rotor Crack Sequence (101-110) 160 IBT=100 C first, then 70 s 5 2 1015 Planned Inspection Perform inspection per 9.1016 Rotor Crack Sequence
48、(111-120) 160 IBT=100 C first, then 70 s 5 2 1017 Planned Inspection Perform inspection per 9.1018 Rotor Crack Sequence (121-130) 160 IBT=100 C first, then 70 s 5 2 1019 Planned Inspection Perform inspection per 9.1020 Rotor Crack Sequence (131-140) 160 IBT=100 C first, then 70 s 5 2 1021 Planned In
49、spection Perform inspection per 9.1022 Rotor Crack Sequence (141-150) 160 IBT=100 C first, then 70 s 5 2 1023 Final inspection Perform inspection per 9.10 and take final measurements including photographs TABLE 2 - INSPECTION LOG FOR CRACKS AND PAD REPLACEMENT Step Cycles Padreplacementsyes/no Crack/failure classification A1, A2, A3, A4 Crack type Length of longest cr
