1、BSI Standards PublicationBS ISO 29221:2014Plastics Determination ofmode I plane-strain crack-arresttoughnessBS ISO 29221:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 29221:2014.The UK participation in its preparation was entrusted to TechnicalCommittee
2、PRI/21, Testing of plastics.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. Users are responsible for its correctapplication. The British Standards Institution 201
3、4. Published by BSI StandardsLimited 2014ISBN 978 0 580 67823 3ICS 83.080.01Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 January 2014.Amendments issued since
4、 publicationDate Text affectedBS ISO 29221:2014 ISO 2014Plastics Determination of mode I plane-strain crack-arrest toughnessPlastiques Dtermination de la tnacit darrt de fissure en dformation planeINTERNATIONAL STANDARDISO29221First edition2014-01-15Reference numberISO 29221:2014(E)BS ISO 29221:2014
5、ISO 29221:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All 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 posting on the i
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7、w.iso.orgPublished in SwitzerlandBS ISO 29221:2014ISO 29221:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 25 Apparatus . 25.1 General . 25.2 Loading arrangement 25.3 Displacement gauge 46 Test s
8、pecimen 56.1 General . 56.2 Dimensions . 56.3 Starter notch . 67 Procedure. 77.1 Measurements of specimen dimensions. 77.2 Conditioning 77.3 Loading 77.4 Displacement measurement 87.5 Arrested crack length (aa) measurement 87.6 Number of tests 98 Calculation and validation of results 108.1 Calculati
9、on of Kand KQa.108.2 Validity requirement . 109 Precision 1110 Test report 1110.1 Test details . 1110.2 Calculations . 1210.3 Validity requirements (see Table 1) 1210.4 Photographic record of fracture surface and descriptive comments (optional) .12Annex A (informative) Determination of the initial c
10、rack length, ao, when using the chevron notch .13Annex B (informative) Procedure for measuring the arrested crack length (ao) .15Annex C (informative) Fracture surface acceptability.16Annex D (informative) Comment on precision statement .17Bibliography .18BS ISO 29221:2014ISO 29221:2014(E)ForewordIS
11、O (the International 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 co
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16、itute an endorsement.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 com
17、mittee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical properties.iv ISO 2014 All rights reservedBS ISO 29221:2014ISO 29221:2014(E)IntroductionThere has been much interest in a better understanding of the fracture behaviour of polymeric materials and, as a consequ
18、ence, several International Standard methods for evaluating the fracture properties have been developed. In the light of the fact that these standard methods provide critical information on fracture prevention of structures and products made from polymeric materials, as well as give directions for t
19、he research and development of materials, any additional test methods of importance to fracture need to be added to the list. In line with such importance, in particular, a test method for evaluating the resistance to rapid crack propagation in terms of a materials ability to arrest the fast-running
20、 crack would be of interest for polymers.1-410-1214The value of the stress intensity factor, K, during the short time interval in which a fast-running crack arrests is a measure of the ability of materials to arrest such a crack. The values of the stress intensity factor of this kind, which are dete
21、rmined using the dynamic methods of analysis, provide a value for the crack-arrest fracture toughness, KA. To ease complexity arising from the dynamic effects, static methods of analysis, which are much less complex, can often be used to determine the stress intensity factor at a short time (1 ms to
22、 2 ms) after crack arrest. The estimate of the crack-arrest fracture toughness obtained in this fashion is termed Kaand the difference between KAand Kacan be made small by minimizing the macroscopic dynamic effects during the test.5-8For cracks propagating under the conditions of crack-front plane-s
23、train, in situations where the dynamic effects are also known to be small, Kladeterminations using laboratory-sized specimens have been used successfully to estimate whether, and at what point, a crack arrests in a structure.9-11Depending upon the component design, the loading compliance, and the cr
24、ack-jump length, a dynamic analysis of a fast-running crack propagation event can be necessary in order to predict whether crack arrest will occur and the arrest position. In such cases, values of Kla,determined by this International Standard can be used to identify those values of K below which the
25、 crack speed is zero. More details on the use of dynamic analyses can be found in Reference 8.This International Standard describes a method for mode I plane-strain crack-arrest toughness measurement for polymers. ISO 2014 All rights reserved vBS ISO 29221:2014BS ISO 29221:2014Plastics Determination
26、 of mode I plane-strain crack-arrest toughness1 ScopeThis International Standard specifies a method for the determination of the plane-strain crack-arrest fracture toughness, Kla, of polymeric materials by using a side-grooved, crack-line-wedge-loaded compact tension specimen to obtain a rapid crack
27、 run-arrest segment of flat-tensile separation with a satisfactory crack front. This International Standard employs a static fracture analysis determination of the stress intensity factor at a short time after crack arrest. The estimate is denoted as Kaand when certain size requirements are met, the
28、 test result provides an estimate, termed as Kla, of the plane-strain crack-arrest toughness of the polymer. The specimen size requirements provide for in-plane dimensions large enough to allow the specimen to be modelled by linear elastic analysis. If the specimen does not exhibit rapid crack propa
29、gation and arrest, Kacannot be determined.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. For undated references, the latest edition of the
30、 referenced document (including any amendments) applies.ISO 527-1, Plastics Determination of tensile properties Part 1: General principlesISO 16012, Plastics Determination of linear dimensions of test specimensISO 18872, Plastics Determination of tensile properties at high strain rates3 Terms and de
31、finitionsFor the purposes of this document, the following terms and definitions apply.3.1conditional value of the plane-strain crack-arrest fracture toughnessKQaconditional value of Kla, calculated from the test result and subject to the validity criteria specified for the side-grooved, crack-line-w
32、edge-loaded specimen usedNote 1 to entry: The calculation of KQais based upon the measurements of both the arrested crack length and of the crack-mouth opening displacement prior to the initiation of a fast-running crack and shortly after crack arrest.Note 2 to entry: It is expressed as Nm3/2.3.2cra
33、ck-arrest fracture toughnessKavalue of the stress intensity factor, K, shortly after crack arrestNote 1 to entry: The in-plane specimen dimensions shall be large enough for adequate enclosure of the crack-tip plastic zone by a linear-elastic stress field.Note 2 to entry: It is expressed as Nm3/2.INT
34、ERNATIONAL STANDARD ISO 29221:2014(E) ISO 2014 All rights reserved 1BS ISO 29221:2014ISO 29221:2014(E)3.3plane-strain crack-arrest fracture toughnessKlavalue of the crack-arrest fracture toughness, Ka, for a crack that arrests under the conditions of crack-front plane-strainNote 1 to entry: The requ
35、irements for attaining the conditions of crack-front plane-strain are specified in the procedures of this International Standard.Note 2 to entry: It is expressed as Nm3/2.3.4stress intensity factor at crack initiationKovalue of K at the onset of rapid fracturingNote 1 to entry: Only a nominal estima
36、te of the initial driving force is needed. For this reason, Kois calculated based on the initial crack (or notch) length and the crack-mouth opening displacement at the initiation of a fast-running crack.Note 2 to entry: It is expressed as Nm3/2.4 PrincipleThis International Standard estimates the v
37、alue of the stress intensity factor, K, at which a fast-running crack arrests. In this test method, a wedge is forced into a split pin, which applies an opening force across the crack starter notch in a modified compact specimen, causing a crack run-arrest segment of crack extension. The rapid run-a
38、rrest event suggests the need for a dynamic analysis of test results. However, experimental observations indicate that, for this test method, an adjusted static analysis of test results provides a useful estimate of the value of the stress intensity factor at the time of crack arrest.1-2The calculat
39、ion of nominal stress intensity at initiation, K,is based on the measurements of the initial notch length and the crack-mouth opening displacement at initiation. The value of Kais based on the measurements of the arrested crack length and the crack-mouth opening displacements prior to initiation and
40、 shortly after crack arrest.5 Apparatus5.1 GeneralThe procedure involves testing the modified compact specimens that have been notched by machining. To minimize the introduction of additional energy into the specimen during the crack run-arrest event, the loading system shall have a low compliance c
41、ompared with the test specimen. For this reason, a wedge and split-pin assembly is used to apply a load on the crack line. This loading arrangement does not permit easy measurement of the opening loads. Consequently, the opening displacement measurement, in conjunction with crack size and compliance
42、 calibrations, is used for calculating Kand Ka.5.2 Loading arrangementA typical loading arrangement is shown in Figure 1. The specimen is placed on a support block whose thickness should be adequate to allow the completion of the test without interference between the wedge and the lower crosshead of
43、 the testing machine. The support block should contain a hole that is aligned with the specimen hole, and whose diameter should be between 1,05 and 1,15 times the diameter of the hole in the specimen. The load that forces the wedge into the split pin is transmitted through a load cell.The surfaces o
44、f the wedge, split pin, support block, and specimen hole should be lubricated if necessary. The lubricant used shall not affect the polymer being tested. It can be also helpful to have the sliding surfaces of the wedge, the split pin, and the support block matte-finished (grit-blasted), so as to pre
45、vent 2 ISO 2014 All rights reservedBS ISO 29221:2014ISO 29221:2014(E)possible galling. A low-taper-angle wedge and split-pin arrangement is used. The split pin shall be long enough to contact the full specimen thickness, and the radius should be large enough to avoid plastic indentations of the test
46、 specimen. In all cases, it is recommended that the diameter of the split pin shall be 0,10 mm less than the diameter of the specimen hole. The wedge shall be long enough to develop the maximum expected opening displacement and any air or oil-hardening tool steel is suitable for making the wedge and
47、 split pins. Hardness in the range from Rc45 to Rc55 has been used successfully. The dimensions of a wedge and split-pin assembly suitable for use with a 25 mm diameter loading hole are shown in Figure 2. The dimensions should be scaled when other hole diameters are used.KeyP load1 wedge2 split pin
48、or bushing3 test specimen4 support blockFigure 1 Schematic illustration of the wedge-loading system Specimen assembly: a) pictorial view, b) standard arrangement, and c) arrangement in case high friction between the support block and specimen exists ISO 2014 All rights reserved 3BS ISO 29221:2014ISO
49、 29221:2014(E)Dimensions in millimetresFigure 2 Suggested geometry and dimensions of wedge and split-pin assemblyNOTE The dimensions given are suitable for use with a 25 mm diameter loading hole in 25-mm to 50-mm thick test specimens.5.3 Displacement gaugeA displacement gauge is used to measure the crack-mouth opening displacement at L = 0,25 W measured from the load-line, which is the centre line of the wedge loading hole, with distance L away from the specimen edge (Figure 3). Accuracy to within 2
