1、BRITISH STANDARD BS EN ISO 7539-9:2008 Corrosion of metals and alloys Stress corrosion testing Part 9: Preparation and use of pre-cracked specimens for tests under rising load or rising displacement ICS 77.060 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy
2、, (c) BSINational foreword This British Standard is the UK implementation of EN ISO 7539-9:2008. It is identical with ISO 7539-9:2003. It supersedes BS ISO 7539-9:2003 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee ISE/NFE/8, Corrosion of metals amd
3、alloys. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immu
4、nity from legal obligations. BS EN ISO 7539-9:2008 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 2 May 2003 BSI 2009 Amendments/corrigenda issued since publication Date Comments 31 October 2009 This corrigendum renumbers BS ISO 7539-9:2003
5、as BS EN ISO 7539-9:2008 ISBN 978 0 580 60531 4 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM ENISO75399 April2008 ICS77.060 EnglishVersion CorrosionofmetalsandalloysStresscorrosiontestingPart 9:Prepa
6、rationanduseofprecrackedspecimensfortestsunder risingloadorrisingdisplacement(ISO75399:2003) CorrosiondesmtauxetalliagesEssaisdecorrosion souscontraintePartie9:Prparationetutilisationdes prouvettesprfissurespouressaissouscharge croissanteousousdplacementcroissant(ISO7539 9:2003) KorrosionvonMetallen
7、undLegierungenPrfungder SpannungsrisskorrosionTeil9:Vorbereitungund AnwendungvonangerissenenProbenfrdiePrfungmit zunehmenderKraftoderzunehmenderVerformung(ISO 75399:2003) ThisEuropeanStandardwasapprovedbyCENon21March2008. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatet
8、heconditionsforgivingthisEuropean Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcerningsuchnational standardsmaybeobtainedonapplicationtotheCENManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,Ger
9、man).Aversioninanyotherlanguagemadebytranslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCENManagementCentrehasthesamestatusasthe officialversions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Bulgaria,Cyprus,CzechRepublic,Denmark,Estonia,Finland, France,Germa
10、ny,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal, Romania,Slovakia,Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG ManagementCentre:rued
11、eStassart,36B1050Brussels 2008CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENISO75399:2008:E Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIEN ISO 7539-9:2008 (E) Foreword The text of ISO 7539-9:2
12、003 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and alloys” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 7539-9:2008 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of which is hel
13、d by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2008, and conflicting national standards shall be withdrawn at the latest by October 2008. Attention is drawn to the possibility t
14、hat some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound
15、to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Swit
16、zerland and the United Kingdom. Endorsement notice The text of ISO 7539-9:2003 has been approved by CEN as a EN ISO 7539-9:2008 without any modification. BS EN ISO 7539-9:2008 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIISO 7539-9:2003(E) ISO 20
17、09 All rights reserved iiiContents Page 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 2 4 Principle . 2 5 Specimens . 3 6 Initiation and propagation of fatigue cracks 16 7 Procedure. 18 8 Test report 23 Annex A (informative) Determination of a suitable displacement rate for determini
18、ng K ISCCfrom constant displacement rate tests 24 Annex B (informative) Determination of crack growth velocity. 25 Annex C (informative) Information on indirect methods for measuring crack length. 26 BS EN ISO 7539-9:2008 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncon
19、trolled Copy, (c) BSIThis page deliberately set blank Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIINTERNATIONAL STANDARD ISO 7539-9:2003(E) ISO 2009 All rights reserved 1Corrosion of metals and alloys Stress corrosion testing Part 9: Preparation
20、 and use of pre-cracked specimens for tests under rising load or rising displacement 1 Scope 1.1 This part of ISO 7539 covers procedures for designing, preparing and using pre-cracked specimens for investigating the susceptibility of metal to stress corrosion cracking by means of tests conducted und
21、er rising load or rising displacement. Tests conducted under constant load or constant displacement are dealt with in ISO 7539-6. The term “metal” as used in this part of ISO 7539 includes alloys. 1.2 Because of the need to confine plasticity to the crack tip, pre-cracked specimens are not suitable
22、for the evaluation of thin products such as sheet or wire and are generally used for thicker products including plate, bar and forgings. They can also be used for parts joined by welding. 1.3 Pre-cracked specimens may be stressed quantitatively with equipment for application of a monotonically incre
23、asing load or displacement at the loading points. 1.4 A particular advantage of pre-cracked specimens is that they allow data to be acquired from which critical defect sizes, above which stress corrosion cracking may occur, can be estimated for components of known geometry subjected to known stresse
24、s. They also enable rates of stress corrosion crack propagation to be determined. 1.5 A principal advantage of the test is that it takes into account the potential impact of dynamic straining on the threshold for stress corrosion cracking. 1.6 At sufficiently low loading rates, the K ISCCdetermined
25、by this method can be less than or equal to that obtained by constant load or displacement methods and can be determined more rapidly. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applie
26、s. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 7539-1:1987, Corrosion of metals and alloys Stress corrosion testing Part 1: General guidance on testing procedures ISO 7539-6: 1) , Corrosion of metals and alloys Stress corrosion testin
27、g Part 6: Preparation and use of pre-cracked specimens for tests under constant load or constant displacement 1) To be published. (Revision of ISO 7539-6:1989) BS EN ISO 7539-9:2008 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIISO 7539-9:2003(E)
28、2 ISO 2009 All rights reservedISO 7539-7: 2) , Corrosion of metals and alloys Stress corrosion testing Part 7: Slow strain rate testing ISO 11782-2:1998, Corrosion of metals and alloys Corrosion fatigue testing Part 2: Crack propagation testing using precracked specimens 3 Terms and definitions For
29、the purposes of this document, the terms and definitions given in ISO 7539-6 as well as the following apply. 3.1 rate of change of crack opening displacement at loading plane V LLdeflection at the loading point access measured over a fixed period 3.2 stress intensity factor at crack initiation K I-i
30、nit stress intensity applied at the commencement of measurable crack growth 3.3 range of stress intensity factor K f , in fatigue algebraic difference between the maximum and minimum stress intensity factors in a cycle 3.4 displacement rate dq/dt rate of increase of the deflection either measured at
31、 the loading point axis or away from the loading line 4 Principle 4.1 The use of pre-cracked specimens acknowledges the difficulty of ensuring that crack-like defects, introduced during either manufacture or subsequent service, are totally absent from structures. Furthermore, the presence of such de
32、fects can cause a susceptibility to stress corrosion cracking, which in some materials (e.g. titanium) may not be evident from tests on smooth specimens under constant load. The principles of linear elastic fracture mechanics can be used to quantify the stress situation existing at the crack tip in
33、a pre- cracked specimen or structure in terms of the plane strain-stress intensity. 4.2 The test involves subjecting a specimen, in which a crack has been developed from a machined notch by fatigue, to an increasing load or displacement during exposure to a chemically aggressive environment. The obj
34、ective is to quantify the conditions under which environmentally-assisted crack extension can occur in terms of the threshold stress intensity for stress corrosion cracking, K ISCC , and the kinetics of crack propagation. 4.3 Tests may be conducted in tension or in bending. The most important charac
35、teristic of the test is the low loading/displacement rate that is applied. 4.4 Because of the dynamic straining which is associated with this method, the data obtained may differ from those obtained for pre-cracked specimens with the same combination of environment and material when the specimens ar
36、e subjected to static loading only. 2) To be published. (Revision of ISO 7539-7:1989) BS EN ISO 7539-9:2008 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Uncontrolled Copy, (c) BSIISO 7539-9:2003(E) ISO 2009 All rights reserved 34.5 The empirical data can be used for desig
37、n or life prediction purposes in order to ensure either that the stresses within large structures are insufficient to promote the initiation of environmentally-assisted cracking at whatever pre-existing defects may be present or that the amount of crack growth which would occur within the design lif
38、e or inspection periods can be tolerated without the risk of unstable failure. 4.6 Stress corrosion cracking is influenced by both mechanical and electrochemical driving forces. The latter can vary with crack depth, opening or shape because of variations in crack-tip chemistry and electrode potentia
39、l and may not be uniquely described by the fracture mechanics stress intensity factor. 4.7 The mechanical driving force includes both applied and residual stresses. The possible influence of the latter should be considered in both laboratory testing and application to more complex geometries. Gradie
40、nts in residual stress in a specimen may result in non-uniform crack growth along the crack front. 4.8 K ISCCis a function of the environment, which should simulate that in service, and of the conditions of loading. 5 Specimens 5.1 General 5.1.1 A wide range of standard specimen geometries of the ty
41、pe used in fracture toughness tests may be used. Those most commonly used are described in ISO 7539-6. The particular type of specimen used will be dependent upon the form, the strength and the susceptibility to stress corrosion cracking of the material to be tested and also on the objective of the
42、test. 5.1.2 A basic requirement is that the dimensions be sufficient to maintain predominantly triaxial (plane strain) conditions in which plastic deformation is limited in the vicinity of the crack tip. Experience with fracture toughness testing has shown that for a valid K lcmeasurement, both the
43、crack length, a, and the thickness, B, shall be not less than 2 Ic p0,2 2, 5 KR and that, where possible, larger specimens where both a and B are at least 2 Ic p0,2 4 KR shall be used to ensure adequate constraint. From the view of fracture mechanics, a minimum thickness from which an invariant valu
44、e of K ISCCis obtained cannot currently be specified. The presence of an aggressive environment during stress corrosion may reduce the extent of plasticity associated with fracture and hence the specimen dimensions needed to limit plastic deformation. However, in order to minimize the risk of inadeq
45、uate constraint, it is recommended that similar criteria to those employed during fracture toughness testing used regarding specimen dimensions, i.e. both a and B shall be not less than 2 I p0,2 2, 5 KR BS EN ISO 7539-9:2008 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 23/12/2009 06:42, Un
46、controlled Copy, (c) BSIISO 7539-9:2003(E) 4 ISO 2009 All rights reservedand preferably shall be not less than 2 I p0,2 4 KR where K Iis the stress intensity to be applied during testing, in MPa/m. As a test for its validity, the threshold stress intensity value eventually determined shall be substi
47、tuted for K Iin the first of these expressions. 5.1.3 If the specimens are to be used for the determination of K ISCC , the initial specimen size shall be based on an estimate of the K ISCCof the material (in the first instance, it being better to over-estimate the K ISCCvalue and therefore use a la
48、rger specimen than may eventually be found necessary). Where the service application involves the use of material of insufficient thickness to satisfy the conditions for validity, it is permissible to test specimens of similar thickness, provided that it is clearly stated that the threshold intensity value obtained, K QSCC , is of relevance only to that specific application. Where it is required to determine stress corrosion crack
