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1、AEROSPACE RECOMMENDED PRACTICE ARP1974 Issued1986-03 Reaffirmed2007-08 Clamps, Support, Comparative Fatigue Strengths, Test Method 1.SCOPE: 1.1Scope: This recommended practice establishes vibration and transmissibility test procedures which compare the relative strengths of various loop and saddle t
2、ype support clamps. This procedure is intended for conducting fatigue testing which is standard throughout the aerospace industry thereby establishing a clamp strength comparison which can be used in an evaluation process. The testing required by this recommended practice ensures that clamps will me
3、et adequate fatigue requirements only. It does not infer qualification of the clamp installation techniques or its ability to meet in-service environments or operating conditions. Separate qualification testing should be performed to ensure satisfactory service of the installed clamp. 2.APPLICABLE D
4、OCUMENTS: 2.1Specifications and Standards: The following documents of the issue in effect on date of the start of testing form a part of this document to the extent specified herein. RATIONALE This document has been reaffirmed to comply with the SAE 5-Year Review policy. SAE Technical Standards Boar
5、d 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 therefrom, is the sole responsibili
6、ty 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 2007 SAE International All rights reserved. No part of this publication may be reproduced, stored in a
7、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) Fax: 724-776-0790 Email: Cust
8、omerServicesae.org SAE WEB ADDRESS: http:/www.sae.org Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE ARP1974 - 2 - 2.2Military S
9、pecifications: MIL-C-85052Clamp, Loop, Cushion, General Specification For MIL-C-85052/1Clamp, Loop, Tube, 17-7PH CRES, 275F, Fuel and Petroleum Based Hydraulic Fluid Resistant MIL-C-85052/2Clamp, Loop, Tube 17-7PH CRES, 275F, General Purpose MIL-C-85052/3Clamp, Loop, Tube 17-7PH CRES, 500F, General
10、Purpose MIL-C-85449Clamp Assembly, Saddle Type, Cushion, General Specification For MIL-C-85449/1Clamp Assembly, Saddle Type, Cushioned, NBR Rubber, 321 CRES, 275F, Fuel Resistant, General Purpose MIL-C-85449/2Clamp Assembly, Saddle Type, Cushioned, EPR Rubber, 321 CRES, 275F, General Purpose MIL-C-8
11、5449/3Clamp Assembly, Saddle Type, Cushioned, Silicone Fabric, Reinforced 321 CRES, 500F, General Purpose MIL-C-85449/4Clamp Assembly, Saddle-Type, Cushioned Teflon, 321 CRES, -320F to 450F, General Purpose 2.3Military Standards: MS21106Clamp, Loop, Cushioned, 1200F CRES MS21122Clamp, Loop, Cushione
12、d, Wedge, Polytetrafluoroethylene Type V, Class A and B MS21919Clamp, Loop Type, Cushioned, Support 2.4Federal Standards: QQ-T-580Tool Steel, Carbon and Carbon - Vanadium 2.5Aerospace Industries Association of America Standards: AN742Clamp, Plain Support, Loop-Type Aircraft NAS1713Clamp, Loop-Cushio
13、ned, Center Mount NAS1715Clamp, Loop-Cushioned NAS1716Clamp Assembly, Cushioned, Saddle Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-
14、,- SAE ARP1974 - 3 - 3.REQUIREMENTS: 3.1Fatigue Test Device: The test device should be capable of testing a wide variety of loop and saddle support clamps both cushioned and non-cushioned, metallic and non-metallic. The fatigue cycling shall be induced by means of vibration applied by a shaker in a
15、test set-up similar to those shown in Figure 1. The test device shall be capable of testing clamps up to a maximum of 5 inches in diameter. Multiple set-ups are permissible if the shaker has the required force range and the test fixture has the stiffness required to achieve the specified vibration s
16、pectrum for all of the clamps tested. The vibration device should be capable of automatic cycling and level control while maintaining sinusoidal loadings at constant acceleration of 2 g peak 10% through a frequency range of 20- 500Hz. The input forces shall be controlled through an accelerometer mou
17、nted on top of vibration fixture coupled directly to the shaker armature, while acceleration forces generated on the clamps shall be measured at a point adjacent to the clamp (see Figure 1). A recording method is required to plot forces (g) generated vs frequency (Hz). 3.2Vibration Test Specimens: T
18、he specimen to be tested using this procedure is classified as any type of loop or saddle support clamp that has the strength capability to ensure a reasonable probability of successfully completing the vibration tests. Clamps representative of those to be tested are shown in Figure 3 and as listed
19、below: AN742 MS21106 MS21122 MS21919 MIL-C-85052/1 MIL-C-85052/2 MIL-C-85052/3 MIL-C-85449/1 MIL-C-85449/2 MIL-C-85449/3 MIL-C-85449/4 NAS1713 NAS1715 NAS1716 3.3Test Mandrels and Test Weights: Test mandrels shall be tool steel drill rod in accordance with QQ-T-580 or equivalent and shall be as show
20、n in Figure 2. All dimensions shall be as shown in Table 1 with surface finishes of 125 microinches maximum unless otherwise specified. Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or n
21、etworking permitted without license from IHS -,-,- SAE ARP1974 - 4 - 3.4Vibration Test Fixture: The vibration test fixture shall be similar to that described by Figure 1 with mandrels and weights as specified in Table 1 and Figure 2. 4.PROCEDURE: 4.1Preparation for Test: 4.1.1Instrumentation, Accele
22、rometers: A control accelerometer (input) should be mounted to the top of the vibration fixture as close to a clamp mounting bolt of the fixture as possible. A monitoring accelerometer (output) should be mounted as shown in Figure 1. The output accelerometer should be monitored and recorded as frequ
23、ency vs g force generated. 4.1.2Failure Criteria: When tested in accordance with this ARP no clamp shall exhibit any evidence of cushion separation or their deterioration (when applicable). There shall be no cracking or separation of metal components. The Transmissibility Ratio (TR) shall be recorde
24、d at the start of testing and at the time of failure. 4.1.3Environment: Unless otherwise specified all testing shall be done at room temperature (60 F - 90 F). 4.2Vibration Fatigue Testing: The clamps to be tested shall be mounted as shown in Figure 1 using mandrels as specified in Figure 2 and Tabl
25、e 1. The clamps shall be installed flat on a mounting block using 10-32UNF-3A bolts (160 KSI or higher strength) with a rounded or chamfered edge washer against the clamp foot to avoid chaffing of the clamp. The bolt size may be changed where a clamp requires a size other than specified. This test a
26、ssembly shall then be mounted to a shaker table. A resonance search shall be performed at a constant sine wave vibration of 2 g peak 10% acceleration (in the vibration axis, see Figure 1) from 50 to 500 CPS using a logarithmic sweep rate of approximately 5 minutes per cycle, where a cycle shall cons
27、ist of a sweep from 50 Hz to 500 Hz to 50 Hz. One complete cycle shall be performed. Both Accelerometer signals shall be continuously recorded. Each resonant frequency peak shall be monitored and recorded and the transmissibility ratio (TR) shall be calculated for each resonance peak, and shall also
28、 be recorded. The clamps shall then be dwelled at the most severe resonance peak for 30 minutes at a constant sine wave vibration of 10 g peak 10% acceleration. TR CLAMP OUTPUT RESPONSE ACCELERATION TESTINPUT CONTROL ACCELERATION = () () Copyright SAE International Provided by IHS under license with
29、 SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE ARP1974 - 5 - 4.2 (Continued): Following the test, the clamp shall be inspected for evidence of failure as defined in 4.1.2. If no evidence of
30、failure is found continue testing at the most severe resonant peak at a constant sine wave vibration of 10 g peak 10% acceleration until failure occurs. Record the total time to fail the clamp. 4.4Test Report: The testing agency shall furnish a certified test report, showing quantitative results whi
31、ch shall include but not be limited to plots of input and response acceleration (g) versus frequency (Hz) and photographs of the test set ups for the vibration and transmissibility tests. The report shall designate the part number of the clamp tested. 5.BACKGROUND AND PHILOSOPHY OF VIBRATION TESTING
32、: 5.1Background: The requirements for vibration testing are based on MIL-C-85052 which requires vibration testing of a three clamp set-up with long mandrels and heavy test fixturing. This test method resulted in the need for larger more costly vibration equipment which in many cases were not readily
33、 available to the clamp manufacturers. The test requirements herein are such that the test set-ups are more compact, lighter in weight and therefore reduce the size of the shaker which results in more readily obtainable vibration equipment. 5.2Vibration Test Philosophy: Vibration testing has been us
34、ed successfully as a means of comparing the relative fatigue life of clamp installations. Previous test analysis has been compared with actual service data and has confirmed conclusions derived from test programs. 6.EQUIPMENT: 6.1Vibration Equipment: If vibration test equipment is not available at t
35、he clamp manufacturers plant, the vibration testing can be subcontracted to an independent testing laboratory. PREPARED BY SAE SUBCOMMITTEE G3-E, AEROSPACE TUBING INSTALLATION OF SAE COMMITTEE G-3, AEROSPACE COUPLINGS, FITTINGS, HOSE AND TUBING ASSEMBLIES Copyright SAE International Provided by IHS
36、under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE ARP1974 - 6 - FIGURE 1 - Loading Schematic for Fatigue Testing Tube Clamps Single Clamp Method Copyright SAE International Pr
37、ovided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE ARP1974 - 7 - FIGURE 2 - Mandrel Configurations TABLE 1 - Mandrel Dimensions NOMINAL CLAMP SIZE (.062 INCR.) DA
38、SH NUMBERS TUBE DIAMETER MANDREL DIAMETER +.005 -.000 LENGTH + .010 - .000 APPROX. WT. EACH END LBS (REF) -4 .250 .4001.5 .05 -6 .375 .003 .5251.0 .06 -8 .500 .6501.25 .12 -10 .625 .8251.50 .23 -12 .750 .004 .9501.75 .34 -161.0001.2002.00 .64 -201.2501.4502.50 1.17 -241.5001.7502.50 1.70 -281.7502.0
39、001.25 1.11 -322.000 .0052.2501.50 1.68 -362.2502.5001.50 2.08 -402.5002.7501.50 2.52 -442.7503.0001.50 3.00 -483.0003.2501.75 4.10 -523.2503.6501.75 5.20 -563.500 .0063.8501.75 5.76 -644.0004.3501.75 7.36 -724.5004.8502.0010.50 -805.0005.3502.0012.72 Copyright SAE International Provided by IHS unde
40、r license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE ARP1974 - 8 - FIGURE 3 - Representative Clamps Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:43:35 MSTNo reproduction or networking permitted without license from IHS -,-,-