1、BRITISH STANDARD BS EN ISO 11782-2:2008 Corrosion of metals and alloys Corrosion fatigue testing Part 2: Crack propagation testing using precracked specimens ICS 77.060 BS EN ISO 11782-2:2008 This British Standard was published under the authority of the Standards Board and comes into effect on 15 O
2、ctober 1998 BSI 2008 ISBN 978 0 580 60536 9 National foreword This British Standard is the UK implementation of EN ISO 11782-2:2008. It is identical with ISO 11782-2:1998. It supersedes BS ISO 11782-2:1998 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committ
3、ee ISE/NFE/8, Corrosion of metals and 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
4、 a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication Date Comments 31 July 2008 This corrigendum renumbers BS ISO 11782-2:1998 as BS EN ISO 11782-2:2008EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 11782-2 April 2008 ICS 77.060
5、English Version Corrosion of metals and alloys - Corrosion fatigue testing - Part 2: Crack propagation testing using precracked specimens (ISO 11782-2:1998) Corrosion des mtaux et alliages - Essais de fatigue- corrosion - Partie 2: Essais damorce de rupture sur des prouvettes prfissures (ISO 11782-2
6、:1998) Korrosion von Metallen und Legierungen - Prfung der Schwingungskorrosion - Teil 2: Rissausbreitungsprfung an angerissenen Proben (ISO 11782-2:1998) This European Standard was approved by CEN on 21 March 2008. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stip
7、ulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard
8、 exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standa
9、rds bodies of 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, Switzerland and United King
10、dom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 11782-2:2008:
11、 EForeword The text of ISO 11782-2:1998 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 11782-2:2008 by Technical Committee CEN/TC 262 “Metallic and other inorganic coat
12、ings” the secretariat of which is held 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. At
13、tention is drawn to the possibility 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
14、of the following countries are bound 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, Sl
15、ovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 11782-2:1998 has been approved by CEN as a EN ISO 11782-2:2008 without any modification. BS EN ISO 11782-2:2008 BSI 2008iii Contents Page 1 Scope 1 2 Normative reference 1 3 Definitions 1 4 Test 2
16、 4.1 Principle of corrosion fatigue crack propagation testing 2 4.2 Specimens for corrosion fatigue crack propagation testing 3 5 Apparatus 4 6 Fatigue precracking 5 7 Test conditions 6 8 Test procedure 7 9 Test report 9 Annex A (informative) Information on methods for measuring crack lengths 10 Fig
17、ure 1 Fracture plane identification 21 Figure 2 Corrosion fatigue crack propagation rate as a function oftherangeofthe stress intensity factor 23 Figure 3 Three-point single edge notch bend specimen (SENB3) 24 Figure 4 Four-point single edge notch bend specimen (SENB4) 24 Figure 5 Compact tension sp
18、ecimen (CT) 25 Figure 6 Centre-cracked tension specimen (CCT) 26 Figure 7 Permitted notch geometry 27 Table 1 Toleranced dimensions of specimens 12 Table 2 Stress intensity factor function values for SENB3 specimens 13 Table 3 Stress intensity factor function values forSENB4 specimens 15 Table 4 Str
19、ess intensity factor function values for CT specimens 17 Table 5 Stress intensity function values for CCT specimens 19 Descriptors: Metal products, metals, alloys, corrosion, tests, corrosion tests, fatigue tests, crack propagation. BS EN ISO 11782-2:2008 BSI 2008 Introduction 1blank1 Introduction C
20、rack propagation testing employs precracked specimens to provide information on the threshold conditions and on rates of corrosion fatigue crack growth. These data can be used in the design and evaluation of engineering structures where corrosion fatigue crack growth can dominate component life. Bec
21、ause of the need to maintain elastically constrained conditions at the crack tip, the precracked specimens used for crack propagation tests are not suitable for the evaluation of thin products such as sheet or wire and are generally used for thicker products including plate, bar and forgings. They c
22、an also be used for parts joined by welding. The results of corrosion fatigue testing are suitable for direct application only when the service conditions exactly parallel the test conditions especially with regard to material, environmental and stressing considerations. 1 Scope 1.1 This part of ISO
23、11782 describes the fracture mechanics method of determining the crack growth rates of pre-existing cracks under cyclic loading in a controlled environment and the measurement of the threshold stress intensity factor range for crack growth below which the rate of crack advance falls below some defin
24、ed limit agreed between parties. 1.2 This part of ISO11782 provides guidance and instruction on corrosion fatigue testing of metals and alloys in aqueous or gaseous environments. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provis
25、ions of this part of ISO11782. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO11782 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated belo
26、w. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 7539-1:1987, Corrosion of metals and alloys Stress corrosion testing Part 1: General guidance on testing procedures. 3 Definitions For the purposes of this part of ISO11782, the following definitions apply.
27、3.1 corrosion fatigue process involving conjoint corrosion and alternating straining of the metal, often leading to cracking NOTECorrosion fatigue may occur when a metal is subjected to cyclic straining in a corrosive environment. 3.2 force, P force applied to the specimen considered positive when i
28、ts direction is such as to cause the crack faces to move apart 3.3 maximum force, P max algebraic maximum value of force during a loading cycle 3.4 minimum force, P min algebraic minimum value of force during a loading cycle 3.5 force range, %P difference between the algebraic maximum and minimum va
29、lues of the force 3.6 stress intensity factor, K l function of applied load, crack length and specimen geometry having dimensions of stress (length) 1/2which uniquely defines the elastic stress field intensification at the tip of a crack subjected to opening mode displacements (mode I) NOTEIt has be
30、en found that stress intensity factors, calculated assuming that specimens respond purely elastically, correlate the behaviour of real cracked bodies provided that the size of the zone of plasticity at the crack tip is small compared to the crack length and the length of the uncracked ligament. In t
31、his standard, mode I is assumed and the subscript l is implied everywhere. 3.7 maximum stress intensity factor, K max , in fatigue highest algebraic value of the stress intensity factor in a cycle corresponding to the maximum load 3.8 minimum stress intensity factor, K min , in fatigue lowest algebr
32、aic value of the stress intensity factor in a cycle NOTEThis value corresponds to the minimum load when the stress ratio, R, is greater than zero and is set equal to zero when R is less than or equal to zero. BS EN ISO 11782-2:2008 BSI 20082 3.9 range of stress intensity factor, %K, in fatigue algeb
33、raic difference between the maximum and minimum stress intensity factors in a cycle: %K = K max K min 3.10 threshold stress intensity factor range, %K th , in fatigue value of the stress intensity factor range below which the rate of crack advance becomes insignificant for the application 3.11 stres
34、s ratio, R, in fatigue loading algebraic ratio of the minimum and maximum force in a cycle 3.12 cycle smallest segment of the load- or stress-time function which is repeated periodically. The terms fatigue cycle, load cycle and stress cycle are also commonly used 3.13 fatigue crack growth rate, da/d
35、N rate of crack extension caused by fatigue loading and expressed in terms of crack extension per cycle 3.14 stress intensity factor coefficient, Y factor derived from the stress analysis for a particular specimen geometry which relates the stress intensity factor for a given crack length to the loa
36、d and specimen dimensions 3.15 plane strain fracture toughness, K lc the critical value of K at which the first significant environmentally independent extension of the crack occurs under the influence of rising stress intensity under conditions of high constraint to plastic deformation 3.16 specime
37、n orientation the fracture plane of the specimen identified in terms of firstly the direction of stressing and secondly the direction of crack growth expressed with respect to three reference axes. These are identified by the letters X, Y and Z where 3.17 crack length, a effective crack length measu
38、red from the crack tip to either the mouth of the notch or the loading point axis depending on the specimen geometry 3.18 specimen width, W effective width of the specimen measured from the back face to either the face containing the notch or the loading plane depending on the specimen geometry 3.19
39、 waveform shape of the peak-to-peak variation of load as a function of time 3.20 cyclic frequency number of cycles per unit time, usually expressed in terms of cycles per second (Hz) 4 Test 4.1 Principle of corrosion fatigue crack propagation testing A fatigue pre-crack is induced in a notched speci
40、men by cyclic loading. As the crack grows the loading conditions are adjusted until the values of %K andR are appropriate for the subsequent determination of%K thor crack growth rates and the crack is of sufficient length for the influence of the notch to be negligible. Corrosion fatigue crack propa
41、gation tests are then conducted using cyclic loading under environmental and stressing conditions relevant to the particular application. During the test, crack length is monitored as a function of elapsed cycles. These data are subjected to numerical analysis so that the rate of crack growth, da/dN
42、, can be expressed as a function of the stress intensity factor range, %K. R P min P max - K min K max - = = Z is coincident with the main working force employed during manufacture of the material (short-transverse axis); X is coincident with the direction of grain flow (longitudinal axis); Y is nor
43、mal to the X and Z axes (see Figure 1). BS EN ISO 11782-2:2008 BSI 20083 Crack growth rates presented in terms of %K are generally independent of the geometry of the specimen used. The principle of similitude allows the comparison of data obtained from a variety of specimen types and allows da/dN ve
44、rsus %K data to be used in the design and evaluation of engineering structures provided that appropriate mechanical, chemical and electrochemical test conditions are employed. An important deviation from the principle of similitude can occur in relation to short cracks because of crack-tip chemistry
45、 differences, microstructurally sensitive growth and crack tip shielding considerations. The threshold stress intensity factor range for corrosion fatigue, %K thmay be higher or lower than the threshold in air depending on the particular metal/environment conditions. It may be determined by a contro
46、lled reduction in load range (see 6.3) until the rate of growth becomes insignificant for the specific application. Practically, from a measurement perspective it is necessary to assign a value to this (see8.5). NOTEBoth crack growth rate measurements and threshold stress intensity factor range dete
47、rminations can be markedly affected by residual stresses. Thermal stress relief should, therefore, be considered prior to testing, but if this is not acceptable, the possibility of an effect should be recognized in the interpretation of the results. In particular, the presence of residual stresses c
48、an lead to an apparent dependence of %K thon specimen thickness. Thickness effects can also arise in principle in relation to hydrogen charging and also where through-thickness transport of fluid occurs in flowing aqueous solutions. In the latter case it should be recognized that solution transport
49、via the crack sides in the through-thickness direction is an artifact of the fracture mechanics specimen and may not be representative of cracking in service. Results of corrosion fatigue crack growth rate tests for many metals have shown that the relationship between da/dN and %K can differ significantly from the three-stage relationship usually observed for tests in air, as shown in Figure 2. The
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