© ISO 2017 Aerospace series — Hydraulic tubing joints and fittings — Planar flexure test Série aérospatiale — Joints et raccords des tuyauteries hydrauliques — Essai de flexion plane INTERNATIONAL STA[.]
INTERNATIONAL STANDARD ISO 9538 Second edition 2017-04 Aerospace series — Hydraulic tubing j oints and fittings — Planar flexure test Série aérospatiale — Joints et raccords des tuyauteries hydrauliques — Essai de flexion plane Reference number ISO 9538:2017(E) © ISO 2017 ISO 95 8: 01 7(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 9538:2017(E) Page Contents Foreword iv Introduction v Scope Normative references Terms and definitions Device for flexure test Flexure test specimens Stress determination Procedure 7.1 7.2 7.3 Instrumentation and strain gauges f f f 7.2.3 Determination of tube length Bending stress calibration of test specimen Frequency 7.2 Tes t 7.2 N atural requency requency o the s p ecimens Requirements Bibliography © ISO 2017 – All rights reserved iii ISO 9538:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and expressions related to formity assessment, as well as in formation about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso org/iso/foreword html This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 10, Aerospace fluid systems and components This second edition cancels and replaces the first edition (ISO 9538:1996), o f which it constitutes a minor revision The changes are as follows: — the publication dates o f ISO 7257 and ISO 7169 in the introduction were removed in order to reflect the most updated versions of those documents iv © ISO 2017 – All rights reserved ISO 9538:2017(E) Introduction T h i s c ument de s crib e s a pla na r flexu re te s t pro ce du re for hyd rau l ic tubi ng j oi nts and fitti ngs T he te s t pro ce du re c a n b e appl ie d as a n a lternative to the ro ta r y te s t pro ce dure s p e ci fie d i n I S O 7 T he qua l i fic ation te s t pro ce du re s for tub e fitti ngs are s p e ci fie d i n I S O 7169 O ther te s t me tho d s c an b e u s e d a s long as they develop the s ame re s u lts a s the pro ce dure s p e c i fie d i n this document © ISO 2017 – All rights reserved v ISO 9538:2017(E) I NTERNATI O NAL STANDARD Aerosp ace series — H ydraulic tub ing j oints and fittings — Planar flexure test Scope T h i s cu ment s p e ci fies a flexure te s t pro ce dure T h i s pro ce du re i s i ntende d for for re conne c table conduc ti ng flexu re te s ts on fitti ngs with h igh- s treng th hyd rau l ic tub e s made o f corro s ion-re s i s ti ng s te el, tita n iu m and a lu m i n iu m and p ermanent hyd rau l ic tub e j oi nts for u s e on com merci a l a nd m i l ita r y a i rcra ft f Normative re erences There are no normative references in this document Terms and definitions No term s and defi nition s a re l i s te d i n th i s c u ment ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia org/ — ISO Online browsing platform: available at http://www.iso org/obp D evice for flexure test The test device should be similar to that shown in Figure It shall consist of a vibrator, a manifold to re ceive at le a s t s i x te s t s p e ci men s , a nd a hyd rau l ic s upply un it c ap able o f s tantly ma i nta i ni ng the s tatic op erati ng pre s s u re du ri ng te s ti ng , i nclud i ng mon itors i nduci ng the shutdown o f the s ys tem i n the event of pressure drop © ISO 2017 – All rights reserved ISO 9538:2017(E) Key pressure supply pressure gauge test specimen Figure — Set-up o f test drive Three test specimens are attached to two opposite ends o f the mani fold, which is rigidly mounted on the vibrator A hose assembly establishes the connection with the hydraulic supply unit The vibrator shall allow for vibration frequencies up to 300 Hz Details of the set-up are shown in Figure 2 © ISO 2017 – All rights reserved ISO 9538:2017(E) Key stress cycle in the tube during vibration angle gauges for optical amplitude control pressure generation and monitoring in the test specimen acceleration cycle o f vibrator Figure — Details o f set-up Flexure test specimens The test specimens shall consist o f the tube fitting to be tested (for example straight union), the test tube and the fitting to seal the tube Stress determination The maximum permissible flexure fatigue stress o f the test tubing is determined for the combined stress level The combined stress, σ f, is composed o f the tensile stress, σ p , resulting from the internal pressure and the wall thickness o f the tube, and the bending stress, σb Strain gauges shall be used to demonstrate the bending stress, and the deflection can be checked during testing by means o f angle gauges A typical stress cycle is illustrated in Figure The bending stress, σb , is determined by the maximum permissible flexure fatigue stress o f the test tube and shall be specified for each application © ISO 2017 – All rights reserved ISO 9538:2017(E) Key maximum stress minimum stress σ σ σ p b f mean axial s tres s p ro duced by internal p res s ure s tres s caus ed by b ending co mb ined s tres s , σ p + σ b Figure — Typical test cycle Procedure 7.1 Instrumentation and strain gauges A strain gauge shall be mounted on each test specimen Figure Their location should be as follows T hey sha l l b e mounte d a s shown i n from a) For tub e s i z e s to D N 16: approxi mately m m the attach ment-p oi nt tub e to fitti ng b) For tub e s i z e s to DN and ab ove: approxi mately m m from the attach ment-p oi nt tub e to fitti ng Key strain gauge vibrator see 7.1 length giving natural frequency o f b etween 1 H z and H z Figure — Location o f gauges © ISO 2017 – All rights reserved ISO 95 8: 01 7(E) 7.2 Frequency 7.2.1 Test frequency I t i s re com mende d to p er form the te s t at approxi mately 10 H z 7.2.2 Natural frequency o f the specimens To m i n i m i z e the p ower i nput o f the vibrator u s e d , the natu l with i n the T he te s t fre quenc y fre quenc y fre quenc y sh a l l b e approxi mately 10 % to % b elow the natu l to prevent their resonance range from being reached 7.2.3 o f the s p e ci men s s hou ld b e range 10 H z to H z fre quenc y o f the s p e ci men s Determination o f tube length S crew the fu l ly a s s emble d tub e , fitte d with s trai n gauge s , i nto the he ader i n order to de term i ne the tub e leng th re qu i re d C on ne c t the s trai n gauge s , apply the nom i na l pre s s u re and vibrate the tub e T he tub e leng th sha l l b e adj u s te d u nti l the natu l fre quenc y o f the s p e ci men i s b e twe en 10 H z and H z 7.3 Bending stress calibration o f test specimen Clause 4) in order to produce the required moment After the tube bending setting is complete, introduce the Subm it the prep are d tub e to a s tatic lo ad (F ) corre s p ond i ng to the s p e c i fie d b end i ng s tre s s (s e e s p e ci fie d pre s s u re and re ad the s tre s s tra n s m itte d b y the s trai n gauge on a n o s c i l lo s cop e Start the vibrator and increase the vibration amplitude of the vibrator until the oscillograph shows the previou sly de term i ne d s tre s s va lue T he angle gauge a l lows the defle c tion(s) to be re ad for fu r ther control T he a ngle gauge s l l be mou nte d at the end c ap o f the te s t s p e ci men To control the defle c tion o f the te s t s p e ci men, a s u itable s trob o s cop e with variable fl as h fre quenc y sh a l l b e u s e d Requirements T he fle xu re te s t s p e ci men s sha l l with s ta nd 10 c ycle s Leakages and failures are not acceptable © ISO 2017 – All rights reserved ISO 9538:2017(E) Bibliography [1] [2] Aerospace — Separable tube fittings for fluid systems, for 24 degree cones, for pressures up to 000 psi or 21 000 kPa — Procurement specification, inch/metric ISO 7257, Aircraft — Hydraulic tubing joints and fittings — Rotary flexure test I S O 71 , © ISO 2017 – All rights reserved ISO 95 8: 01 7(E) ICS 49.080 Price based on pages © ISO 2017 – All rights reserved