EN ISO 7539-9-2008 en Corrosion of metals and alloys - Stress corrosion testing - Part 9 Preparation and use of pre-cracked specimens for tests under rising load or rising displace.pdf

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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 National foreword This British Standard is the UK implementation of EN ISO 7539-9:2008. It

2、 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 It supersedes BS ISO 7539-9:2003 which is withdrawn.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 alloys. A list of organizations represented on this committee can be obtained on request to its sec

3、retary. 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 immunity from legal obligations. BS EN ISO 7539-9:2008 This British Standard was published under the au

4、thority 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 as BS EN ISO 7539-9:2008 ISBN 978 0 580 60531 4EUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM ENISO

5、75399 April2008 ICS77.060 EnglishVersion CorrosionofmetalsandalloysStresscorrosiontestingPart 9:Preparationanduseofprecrackedspecimensfortestsunder risingloadorrisingdisplacement(ISO75399:2003) CorrosiondesmtauxetalliagesEssaisdecorrosion souscontraintePartie9:Prparationetutilisationdes prouvettespr

6、fissurespouressaissouscharge croissanteousousdplacementcroissant(ISO7539 9:2003) KorrosionvonMetallenundLegierungenPrfungder SpannungsrisskorrosionTeil9:Vorbereitungund AnwendungvonangerissenenProbenfrdiePrfungmit zunehmenderKraftoderzunehmenderVerformung(ISO 75399:2003) ThisEuropeanStandardwasappro

7、vedbyCENon21March2008. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEuropean Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcerningsuchnational standardsmaybeobtainedonapplicationtotheCENM

8、anagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytranslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCENManagementCentrehasthesamestatusasthe officialversions. CENmembersarethenationa

9、lstandardsbodiesofAustria,Belgium,Bulgaria,Cyprus,CzechRepublic,Denmark,Estonia,Finland, France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal, Romania,Slovakia,Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEAN COMMITTEE FO

10、R STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2008CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENISO75399:2008:EEN ISO 7539-9:2008 (E) Foreword The text of ISO 7539-9:

11、2003 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 he

12、ld 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

13、that 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

14、 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, Swi

15、tzerland 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 7539-9:2008ISO 7539-9:2003(E) ISO 2009 All rights reserved iiiContents Page 1 Scope 1 2 Normative references . 1 3 Terms and definition

16、s. 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 determining K ISCCfrom constant displacement rate tests 24 Annex B (informative) Determination of crack grow

17、th velocity. 25 Annex C (informative) Information on indirect methods for measuring crack length. 26 BS EN ISO 7539-9:2008This page deliberately set blankINTERNATIONAL STANDARD ISO 7539-9:2003(E) ISO 2009 All rights reserved 1Corrosion of metals and alloys Stress corrosion testing Part 9: Preparatio

18、n 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 un

19、der 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

20、 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 incr

21、easing 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 stress

22、es. 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

23、 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 appli

24、es. 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 testi

25、ng 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 7539-9:2008ISO 7539-9:2003(E) 2 ISO 2009 All rights reservedISO 7539-7: 2) , Corrosion of metals and alloys Stress corrosion test

26、ing 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 the purposes of this document, the terms and definitions given in ISO 7539-6 as well as the followi

27、ng 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-init stress intensity applied at the commencement of measurable crack growth 3.3 range of stress int

28、ensity 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 the loading point axis or away from the loading line 4 Principle 4.1 The use of pre-cracked specim

29、ens 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 defects can cause a susceptibility to stress corrosion cracking, which in some materials (e.g. titani

30、um) 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 a pre- cracked specimen or structure in terms of the plane strain-stress intensity. 4.2 The test in

31、volves 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 objective is to quantify the conditions under which environmentally-assisted crack extension can occur

32、 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 characteristic of the test is the low loading/displacement rate that is applied. 4.4 Because of the dynam

33、ic 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 are subjected to static loading only. 2) To be published. (Revision of ISO 7539-7:1989) BS EN ISO 753

34、9-9:2008ISO 7539-9:2003(E) ISO 2009 All rights reserved 34.5 The empirical data can be used for design 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-exist

35、ing defects may be present or that the amount of crack growth which would occur within the design life 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 w

36、ith crack depth, opening or shape because of variations in crack-tip chemistry and electrode potential 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 latt

37、er should be considered in both laboratory testing and application to more complex geometries. Gradients 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 condit

38、ions of loading. 5 Specimens 5.1 General 5.1.1 A wide range of standard specimen geometries of the type 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 susce

39、ptibility to stress corrosion cracking of the material to be tested and also on the objective of the 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

40、tip. Experience with fracture toughness testing has shown that for a valid K lcmeasurement, both the 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 adequ

41、ate constraint. From the view of fracture mechanics, a minimum thickness from which an invariant value 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 spec

42、imen dimensions needed to limit plastic deformation. However, in order to minimize the risk of inadequate 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

43、 KR BS EN ISO 7539-9:2008ISO 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 subst

44、ituted 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 l

45、arger 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 intensi

46、ty value obtained, K QSCC , is of relevance only to that specific application. Where it is required to determine stress corrosion crack growth behaviour as a function of stress intensity, the specimen size should be based on an estimate of the highest stress intensity at which crack growth rates are

47、 to be measured. 5.1.4 A wide choice of specimen geometries is available to suit the form of the test material, the experimental facilities available and the objectives of the test. Two basic types of specimen can be used a) those intended for being loaded by means of a tensile force; b) those inten

48、ded for being loaded by means of a bending force. This means that crack growth can be studied under either bend or tension loading conditions. The specimens can be used for either the determination of K ISCCby the initiation of a stress corrosion crack from a pre- existing fatigue crack using a series of specimens and for measurements of crack growth rates. Since the specimens are loaded duri