BS ISO 18489-2015 Polyethylene (PE) materials for piping systems Determination of resistance to slow crack growth under cyclic loading Cracked Round Bar test method《管道系统用聚乙烯 (PE) 材.pdf

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1、BSI Standards PublicationBS ISO 18489:2015Polyethylene (PE) materialsfor piping systems Determination of resistance toslow crack growth under cyclicloading Cracked Round Bartest methodBS ISO 18489:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 18489:2015.

2、The UK participation in its preparation was entrusted to TechnicalCommittee PRI/88/4, Test Methods - Plastic Piping.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract.

3、 Users are responsible for its correctapplication. The British Standards Institution 2015. Published by BSI StandardsLimited 2015ISBN 978 0 580 84899 5ICS 23.040.20; 23.040.45Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the

4、 authority of theStandards Policy and Strategy Committee on 30 September 2015.Amendments issued since publicationDate Text affectedBS ISO 18489:2015 ISO 2015Polyethylene (PE) materials for piping systems Determination of resistance to slow crack growth under cyclic loading Cracked Round Bar test met

5、hodMatriaux polythylne (PE) pour systmes de tuyauterie Dtermination de la rsistance la propagation lente de fissures sous un chargement cyclique Mthode dessai de la barre ronde fissureINTERNATIONAL STANDARDISO18489First edition2015-09-01Reference numberISO 18489:2015(E)BS ISO 18489:2015ISO 18489:201

6、5(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or pos

7、ting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 2

8、2 749 09 47copyrightiso.orgwww.iso.orgBS ISO 18489:2015ISO 18489:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 35 Apparatus . 35.1 Test machine . 35.1.1 Loading system 35.1.2 Load-cycle frequency . 45.1.3 Grips 45.1.4 Temperature chamber 45

9、.2 Microscope . 45.3 Notching apparatus . 46 Test specimen 46.1 Specimen geometry and dimensions . 46.2 Test specimen preparation . 56.3 Specimen notching 56.4 Specimen conditioning . 67 Test procedure 67.1 Measurement of specimen dimensions . 67.2 Specimen mounting 67.3 Test atmosphere 67.4 Calcula

10、tion of test load . 67.5 Load application 77.6 Notch depth measurement . 78 Data treatment . 79 Test report . 9Annex A (informative) Comparison of different test specimen diameters 10Bibliography .11 ISO 2015 All rights reserved iiiContents PageBS ISO 18489:2015ISO 18489:2015(E)ForewordISO (the Inte

11、rnational Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has

12、 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 of electrotechnical s

13、tandardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in acco

14、rdance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Detail

15、s of any patent rights identified during the development of 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 information given for the convenience of users and does not constitute an endo

16、rsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee respon

17、sible for this document is ISO/TC 138, Plastics pipes, fittings and valves for the transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic materials and their accessories Test methods and basic specifications .iv ISO 2015 All rights reservedBS ISO 18489:20

18、15ISO 18489:2015(E)IntroductionKnowledge about the resistance to long-term failure mechanisms as a result of crack initiation and slow crack growth (SCG) is important for the ranking and pre-selection of thermoplastic materials, especially for long-term applications such as pipes and fittings made o

19、f polyethylene. Several tests to determine the relevant failure mechanisms are available today where elevated temperatures and also the combination with stress cracking liquids are used to decrease the time frame for testing.However, developments in modern raw materials have led to a significant inc

20、rease of resistance of polyethylene to crack initiation and SCG so that testing with available methods exceeds practical time frames. Therefore, new acceleration methods, preferably at application relevant temperatures and without additional time reducing liquids, are required.This test method achie

21、ves a significant decrease of testing time even at ambient temperatures of 23 C. This is more relevant to the temperature range of many applications and testing at this temperature does not change the structural status of the polymer. Acceleration of material testing is achieved by the specimen geom

22、etry and the cyclic loading regime to result in completion of testing in a relatively short time.2,3,4 ISO 2015 All rights reserved vBS ISO 18489:2015BS ISO 18489:2015Polyethylene (PE) materials for piping systems Determination of resistance to slow crack growth under cyclic loading Cracked Round Ba

23、r test method1 ScopeThis International Standard specifies a method to determine the resistance to slow crack growth (SCG) of polyethylene materials, pipes, and fittings. The test is applicable to samples taken from compression moulded sheet or extruded pipes and injection moulded fittings of suitabl

24、e thickness.This International Standard provides a method that is suitable for an accelerated fracture-mechanics characterization at ambient temperatures of 23 C of different polyethylene grades, especially for PE 80 and PE 100 types for pipe applications.NOTE This test method could be adapted for o

25、ther thermoplastics materials by developing the procedure using different test parameters.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. F

26、or undated references, the latest edition of the referenced document (including any amendments) applies.ISO 291, Plastics Standard atmospheres for conditioning and testingISO 2818, Plastics Preparation of test specimens by machining3 Terms and definitionsFor the purposes of this document, the follow

27、ing terms and definitions apply.3.1crack lengthadepth of the crack at any time during a test measured from the specimen surface to the crack tipNote 1 to entry: It is expressed in millimetres (mm).3.2cycleNsmallest segment of a load-time or stress-time function which is repeated periodically3.3failu

28、re cycle numberNftotal number of cycles (3.2) from the beginning until failure of the test specimen3.4frequencyfnumber of cycles (3.2) within one secondNote 1 to entry: It is expressed in hertz (Hz).INTERNATIONAL STANDARD ISO 18489:2015(E) ISO 2015 All rights reserved 1BS ISO 18489:2015ISO 18489:201

29、5(E)3.5initial crack lengthainimeasured depth of the crack from the specimen surface through the crack tip at the beginning of the testNote 1 to entry: It is expressed in millimetres (mm).3.6initial ligament diameterDiniinner diameter of the cylindrical specimen after notchingNote 1 to entry: It is

30、expressed in millimetres (mm).Note 2 to entry: It is calculated byDDainiini=23.7load ratioRratio of the minimum to the maximum load (3.9) in one cycle (3.2)Note 1 to entry: It is calculated byRFF=minmax3.8load rangeFdifference between the maximum and minimum load (3.10), in Newtons (N), in one cycle

31、 (3.2)3.9maximum loadFmaxhighest value of the applied load, in Newtons (N), in one cycle (3.2)3.10minimum loadFminlowest value of the applied load, in Newtons (N), in one cycle (3.2)3.11notch distanceLminminimum distance from notch to clamping systemNote 1 to entry: It is expressed in millimetres (m

32、m).3.12target initial crack lengthaini*target depth of the crack from the specimen surface through the crack tip after notchingNote 1 to entry: It is expressed in millimetres (mm).2 ISO 2015 All rights reservedBS ISO 18489:2015ISO 18489:2015(E)3.13target initial ligament diameterDini*target inner di

33、ameter of the cylindrical specimen after notchingNote 1 to entry: It is expressed in millimetres (mm).3.14target stress range0*target difference between the maximum and minimum stress at the beginning of the testNote 1 to entry: It is expressed in megapascals (MPa).3.15specimen diameterDdiameter of

34、the cylindrical specimenNote 1 to entry: It is expressed in millimetres (mm).3.16specimen lengthLtotal length of the test specimenNote 1 to entry: It is expressed in millimetres (mm).3.17stress range0applied difference between the maximum and minimum stress after notching at the beginning of the tes

35、tNote 1 to entry: It is expressed in megapascals (MPa).3.18waveformshape of the load-time curve within a single cycle (3.2)4 PrincipleA cyclic tensile test with constant load range is imposed on a cylindrical specimen under suitable test conditions within the stress range where SCG is achieved. A ci

36、rcumferential notch is machined in the centre of the test specimen to enable crack initiation and SCG to final failure of the specimen. The number of cycles until final failure, Nf, is recorded as a function of the stress range, 0, at the initial crack length, aini. The specimen geometry ensures qui

37、ck crack initiation and short testing times due to the high constraint and low plastics deformations along the crack tip.NOTE Crack initiation can be monitored by the use of extensometers if required.25 Apparatus5.1 Test machine5.1.1 Loading systemThe loading system shall be capable of imposing and

38、recording a cyclic load varied by time between accurately defined limits (load control mode) with a specific waveform. Servo-hydraulically driven test ISO 2015 All rights reserved 3BS ISO 18489:2015ISO 18489:2015(E)machines with electronic control are generally suitable for this purpose. However, me

39、chanically driven machines may also be used if they meet the requirements.The cyclic load shall follow a sinusoidal waveform which is characterized by the maximum load, Fmax, and the load ratio, R. The maximum and minimum loading values shall be constant during the entire test with an accuracy of 1

40、%.5.1.2 Load-cycle frequencyThe load-cycle frequency (test frequency), f, shall not exceed 10 Hz with an accuracy of 1 %. The hysteretic heating at a frequency of 10 Hz usually causes no significant influence on Nf.2If extraordinary hysteretic heating at the crack tip is suspected, the frequency sha

41、ll be reduced to 5 Hz or 1 Hz with an accuracy of 1 %.5.1.3 GripsThe machine shall be equipped with grips suitable to clamp cylindrical specimens. It shall be ensured that the load distribution is in alignment with the specimen axis.5.1.4 Temperature chamberFor testing at temperatures other than (23

42、 2) C, the test machine shall be equipped with a suitable chamber that contains the environment and ensures complete immersion of the specimen. The chamber shall be constructed of materials which do not affect the environment and which are not affected by it. The temperature of the environment shall

43、 be controlled in order to maintain the test specimens within 2 C of the specified temperature.5.2 MicroscopeA microscope or an equivalent device shall be used to measure the initial crack length after the finished cyclic tests with an accuracy of 0,01 mm.5.3 Notching apparatusThe device used shall

44、be capable of producing a razor-sharp notch of accurately defined depth at the circumference of the cylindrical specimen. The notch tip radius produced shall be less than 10 m. Usually, razor blades meet this requirement. A conventional lathe in combination with a razor blade tool may be suitable fo

45、r this purpose. Bending of the razor blade shall be avoided and notching perpendicular to the specimen axis shall be ensured.6 Test specimen6.1 Specimen geometry and dimensionsThe specimen configuration of the cracked round bar (CRB) specimen is shown in Figure 1. A cylindrical bar of length, L, and

46、 diameter, D, is prepared with a circumferential razor-sharp notch with a depth of aini* (target initial crack length) in the middle of the specimen resulting in a target initial ligament diameter, Dini*.Preferred specimen dimensions are L of 80 mm to 100 mm and D of 14 mm. The initial crack shall b

47、e perpendicular to the specimen axis with a target crack length of aini* of (1,50 +0,15/-0,0) mm. To avoid clamping effects at the crack tip, the notch distance, Lmin, shall be at least 20 mm from the grips. To support specimen clamping, the specimen may be manufactured with, for example, M 14 1,0 m

48、etric fine thread.NOTE Alternative dimensions can be used, but results are to be compared by the stress intensity factor range instead of the stress range (see Annex A),4 ISO 2015 All rights reservedBS ISO 18489:2015ISO 18489:2015(E)KeyL specimen lengthLminminimum distance between notch and clamping

49、 systemaini* target initial crack lengthDini* target initial ligament diameterD specimen diameter1 razor-sharp notchFigure 1 Principal configuration of CRB test specimen with optional metric fine thread6.2 Test specimen preparationThe test specimens can be machined from compression moulded sheets or from pipe or fittings. Conditions for compression moulding of test specimens are given in Table 1. The use of different moulding conditions may affect the results. The specimens shall be machined in