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 2015 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/ARP5481AAEROSPACERECOMMENDED PRACTICEARP5481 REV. AIssued 2002-03Revised 2010-05Reaffirmed 20
5、15-08Superseding ARP5481Recommended Wheel Tie Bolt Preload ProcedureRATIONALEARP5481A has been reaffirmed to comply with the SAE five-year review policy.1. SCOPE This SAE Aerospace Recommended Practice (ARP) provides the recommended procedure for obtaining desired preloads in aircraft wheel tie bolt
6、s when mounting tires and assembling the wheel. It is generally referred to as the snug-angle bolted joint assembly procedure. It is also known as the “torque-turn” procedure in the heavy equipment ground vehicle industry. 1.1 Purpose The purpose of this document is to recommend a procedure that wil
7、l improve the accuracy of the desired pre-load in aircraft wheel tie bolts during installation. It promotes applying a specified angular degree of nut rotation instead of a specified nut torque, to establish bolted joint preload. The preload accuracy, thus achieved, will result in improved wheel and
8、 fastener performance in service. Fatigue life failures of wheel bolt bosses and their fasteners will be beneficially affected, as will crack propagation rates. Maintenance shops and operators who maintain and overhaul aircraft wheels are encouraged to follow this procedure in conjunction with the C
9、omponent Maintenance Manual (CMM) provided by the wheel and brake manufacturer. In case of a conflict between this document and the CMM, the CMM should be followed and the wheel manufacturer informed of the difference. It is recommended that the wheel designers and manufactures adopt this procedure,
10、 incorporate it in their maintenance manuals and recommend it to the maintenance shops and operators as a standard practice. It is also recommended that the wheel fastening systems be designed with the assumption that less precise methods could actually be employed in service. This will result in ro
11、bust designs, tolerant of a wider range of maintenance practices. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the i
12、ssue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obt
13、ained. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AMS2518 Thread Compound, Anti-Seize, Graphite-Petrolatum AS28431 Aerospace Signaling Torque Wrenche
14、s 2.1.2 U.S. Government Publications Available from the Document Automation and Production Service (DAPS), Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094, Tel: 215-697-6257, http:/assist.daps.dla.mil/quicksearch/. MIL-PRF-83483 Thread Compound, Anti-Seize, Molybdenum-Disulfide and Pet
15、rolatum 2.1.3 Other Publications Applicable Component Maintenance Manual (CMM) Applicable Technical Order (TO) 3. PROCEDURE The snug-angle procedure consists of a snugging torque followed by a final angle of nut rotation. It involves lubricating the fasteners, torquing the bolted joints all to a rel
16、atively low, snugging value and then rotating the nut of each bolted joint through a specified angle of rotation. 3.1 Anti-Seize Compound and Allowable Coating Thickness Apply anti-seize compound, preferably AMS2518 or MIL-PRF-83483, to the bolt and nut threads and to all interface or bearing surfac
17、es of the bolt, nut and both washers. Top and bottom surfaces of both washers must be coated. The anti-seize compound must be applied liberally. See Figure 1. Consideration should be given to compatibility of the anti-seize compound with the materials of the bolted joint, including the potential for
18、 corrosion, particularly since AMS2518 contains graphite. The clamped surfaces of the fasteners and the bolted members must be clean and free of any dirt or debris before applying the anti-seize compound. Consult the applicable CMM or TO for allowable coating thickness on the bolted members. Fastene
19、rs are typically plated and clamped parts are typically permitted a thin primer or thin coat of self priming paint only. Paint topcoat or any appreciable thickness of coating on any surface in a bolted joint needs to be carefully considered and is highly discouraged. Painted coatings can influence f
20、riction coefficient, may creep or wear away, and can lead to bolt breakage, loss of preload and/or other loose bolted joint problems. Do not heat the anti-seize compound to facilitate coverage. This causes separation of the constituents. AMS 2518 is especially prone to oil separation and should be m
21、ixed thoroughly prior to application. Do not thin the compound since this also promotes separation. SAE INTERNATIONAL ARP5481A 2 OF 4FIGURE 1 ANTI-SEIZE COMPOUND APPLICATION LOCATIONS 3.2 Snugging Torque The purpose of snugging torque is to make certain the clamped member surfaces are in contact wit
22、h a desired amount of minimum preload. This snugging torque is determined by the wheel manufacturer from bolt strain gauge or ultrasonic nondestructive test (NDT) data (refer to Section 6), and is listed in the wheel CMM or TO. Its magnitude is sized to accurately obtain the final preload. Make sure
23、 the snugging torque is the correct torque for the anti-seize compound being used, as some wheel manufacturers distinguish between the two compounds. Apply the snugging torque in a crisscross-tightening pattern or to two bolts at a time (automatic wrenching equipment), approximately 180 degrees apar
24、t. The nut must be rotating when the final snugging torque is applied. After the snugging torque is applied, the bolt assembly must be checked to assure the bolted joints are completely snugged. No additional torque tolerance beyond the capabilities of the equipment should be specified. The resultan
25、t tolerance range of the torque actually applied depends on the quality of the tools used by the assembler, which should be suitable for the use intended. These tools may include torque wrenches or automatic wrenching equipment. Consideration should be given to the accuracy of the equipment when ope
26、rating at the relatively low torque levels of the snug angle tightening method. Typical torque tolerances for automated and manual torque wrenches are 5% of the maximum capacity of the tool. Note that this will be greater than 5% of the snugging torque value applied to the fasteners. Use of a proper
27、 torque wrench, such as per AS28431, is recommended. A proper torque wrench is defined as one that is not of an impact type and where the required torque falls within 20-80% of the full capacity of the wrench. CAUTION: The use of impact (pulse) tools is not recommended. These devices should not be u
28、sed unless specifically addressed by the wheel manufacturer, or referenced in the CMM or TO instructions. The resulting final preload is dependent on the initial preload obtained by the snugging torque. Wide variance in the initial preload due to the snugging torque results in a corresponding varian
29、ce in the final preload. Consistency of bolted joint procedures during assembly contributes to a properly bolted assembly. SAE INTERNATIONAL ARP5481A 3 OF 43.3 Final Preload Final preload in a bolted joint is achieved by rotating the nut through a specified angle. The magnitude of the final angle of
30、 nut rotation beyond snugging is determined by the wheel manufacturer from bolt strain gauge or ultrasonic NDT data (refer to Section 6), and is listed in the wheel CMM or TO. Apply the final angle of rotation in a crisscross-tightening pattern or to two bolts at a time (automatic wrenching equipmen
31、t), approximately 180 degrees apart. Final bolted joint preload must be obtained by rotating the nut a specified amount, or specified degrees of rotation, starting from the location resulting from the snugging torque. Angle measuring devices or automatic equipment with this capability are highly rec
32、ommended. Restrain the bolt head while turning the nut. Torque may be monitored during this procedure and compared against upper and lower allowables when supplied by the wheel manufacturer. Automatic equipment typically makes use of a socket tree to prevent bolt head rotation while the tool control
33、s the snugging torque and final angle of rotation of the nut. An angle tolerance may, or may not be specified. This tolerance depends on how the angle is measured. Although not recommended, even crude measurements or visual approximations will result in more accurate preloads than are possible with
34、the most accurate applications of bolted joint preload by the torque method. This is due to the relatively large range in friction coefficients and mechanical inefficiencies inherent in fastener systems. It is recommended that each nut be marked after final preload is achieved to ensure that none ar
35、e missed. 4. FASTENING SYSTEM ASSESSMENT By monitoring the torque when obtaining the final preload, and comparing against the wheel manufacturers allowable range or against an experience base, it is possible to determine the condition of the fasteners and the care with which the assembly procedure w
36、as followed. If the torque is too high, it may indicate excessive thread wear, bolt grip length is too long, cross-threaded condition, blind hole bottoming, excessive wear/repair of the bolt boss, incorrect fastener material or insufficient application of anti-seize compound. If it is too low, it co
37、uld indicate worn out nuts, soft bolt material, stripped threads, yielding or cracked fasteners, incorrect fastener material, non-snugged bolted joint, heat affected fastening system or warped interface. 5. PRELOAD ACCURACY The snug-angle tightening method compensates for variables such as friction
38、and mechanical inefficiencies and results in more accurate and consistent preload than torque methods. For this snug-angle method, preload variations are typically within 15%. Accuracy and consistency in bolted joint preload are the primary benefits of the snug-angle tightening method. This leads to
39、 longer life and reduced maintenance of the fasteners and the clamped parts. By comparison, using bolt torque to obtain final preload typically results in variations of 25% or more. This variation can have significant impact on fastener and wheel fatigue life. Employing poor technique when using tor
40、que to obtain final preload can result in excessive preload variations, as much as six to one. This could then proportionally affect fastener and wheel performance resulting in premature failure. 6. PRELOAD VERIFICATION It is possible to monitor the preload in the assembled bolted joint. Custom ultr
41、asonic NDT equipment used with prepared bolts enables bolted assemblies to be monitored prior to their use or disassembly. Prepared bolts have their threaded ends ground flat and square and reference transducer signals are established for the specific bolt per the material, length, diameter and head
42、 configuration. Actual readings are then compared against the reference baseline to monitor bolted joint integrity. 7. NOTES A change bar (|) located in the left margin is for the convenience of the user in locating areas where technical revisions, not editorial changes, have been made to the previo
43、us issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document, including technical revisions. Change bars and (R) are not used in original publications, nor in documents that contain editorial changes only. PREPARED BY SAE COMMITTEE A-5, AEROSPACE LANDING GEAR SYSTEMS SAE INTERNATIONAL ARP5481A 4 OF 4
