1、BRITISH STANDARD BS EN ISO 7539-5:1995 Incorporating Amendment No.1 Corrosion of metals and alloys Stresscorrosion testing Part 5: Preparation and use of C-ring specimens The European Standard EN7539-5:1995 has the status of a BritishStandardBSENISO7539-5:1995 This BritishStandard, having been prepa
2、red under the directionof the Iron and Steel Standards Policy Committee andthe Non-ferrous Metals Standards Policy Committee, waspublished under the authorityof the Board ofBSIandcomes into effect on 31July1990 BSI 04-2000 The following BSI references relate to the work on this standard: Committee r
3、eference ISM/NFM/8 Draft for comment88/36889 DC ISBN 0 580 18795 0 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) and Non-ferrous Metals Standards Policy Committee (NFM/-) to Technical Com
4、mittee ISM/NFM/8, upon which the following bodies were represented: Aluminium Federation British Gas plc British Steel Industry Department of Trade and Industry (National Physical Laboratory) Department of Transport (Transport and Road Research Laboratory) Electricity Supply Industry in England and
5、Wales Institution of Corrosion Science and Technology Institution of Structural Engineers Society of Chemical Industry UnitedKingdom Atomic Energy Authority Welding Institute Amendments issued since publication Amd. No. Date Comments 8716 October 1995 Indicated by a sideline in the marginBSENISO7539
6、-5:1995 BSI 04-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN ISO7539-5 3 Publications referred to Inside back coverBSENISO7539-5:1995 ii BSI 04-2000 National foreword This Part of BS EN ISO7539 has been prepared under the direction of the E
7、ngineering Sector Board. It is identical with ISO7539-5:1989 Corrosion of metals and alloys Stress corrosion testing Part5: Preparation and use of C-ring specimens, published by the International Organization for Standardization (ISO). BS EN ISO7539 comprises the following parts: Part 1: General gui
8、dance on testing procedures; Part 2: Preparation and use of bent-beam specimens; Part 3: Preparation and use of U-bend specimens; Part 4: Preparation and use of uniaxially loaded tension specimens; Part 5: Preparation and use of C-ring specimens; Part 6: Preparation and use of pre-cracked specimens;
9、 Part 7: Slow strain rate testing. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-
10、references International Standard Corresponding BritishStandard ISO 7539-1:1987 BS EN ISO7539 Corrosion of metals and alloys Stress corrosion testing Part1:1995 General guidance on testing procedures (Identical) ISO 7539-6:1989 Part6:1995 Preparation and use of pre-cracked specimens (Identical) Summ
11、ary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN ISO title page, pages2 to12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment tab
12、le on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO7539-5 May 1995 ICS 77.060 Descriptors: Metals, alloys, tests, corrosion tests, stress corrosion tests, test specimens English version Corrosion of metals and alloys Stress corrosion testing Part5: Preparation and u
13、se of C-ring specimens (ISO7539-5:1989) Corrosion des mtaux et alliages Essais de corrosion sous contrainte Partie5: Prparation et utilisation des prouvettes en forme danneau en C (ISO7539-5:1989) Korrosion der Metalle und Legierungen Prfung der Spannungsrikorrosion Teil5: Vorbereitung und Anwendung
14、 von C-ring-Prben (ISO7539-5:1989) This European Standard was approved by CEN on1995-04-08. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date
15、lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. The European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the res
16、ponsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norw
17、ay, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1995 All rights of reproduction and communication in any form and by any means
18、 reserved in all countries to CEN and its members Ref. No. EN ISO7539-5:1995 EENISO7539-5:1995 BSI 04-2000 2 Foreword This European Standard has been taken over by the Technical Committee CEN/TC262, Protection of metallic materials against corrosion, from the work of ISO/TC156, Corrosion of metals a
19、nd alloys, of the International Organization for Standardization (ISO). 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 November1995, and conflicting national standards shall be withdrawn at the l
20、atest by November1995. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland
21、, UnitedKingdom. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Principle 3 5 Specimens 3 6 Procedure 7 7 Assessment of results 8 8 Test report 8 Annex A (normative) Formula for calculating stressing of C-ring specimens 10 Figure 1 Sampling procedure for testing proced
22、ures 4 Figure 2 Example of C-ring specimen 5 Figure 3 Methods of stressing C-rings 7 Figure 4 Suitable jig for the placement of a wedge opening insert 8 Figure 5 Protection against crevice corrosion and galvanic effects 9 Figure A.1 Correction factor for curved beams 11 Table A.1 Deflection %D for a
23、 C-ring of nominal19mm outside diameter and1,50mm wall thickness of alloy with a modulus of elasticity of100000MN/m 2for stressing to500MN/m 2 10ENISO7539-5:1995 BSI 04-2000 3 1 Scope 1.1 This part of ISO7539 covers procedures for designing, preparing, stressing, exposing and inspecting C-ring test
24、specimens for investigating the susceptibility of a metal to stress corrosion. Analysis of the state and distribution of stress in the C-ring is presented. The term “metal” as used in this part of ISO7539 includes alloys. 1.2 The C-ring is a versatile, economical specimen for determining the suscept
25、ibility to stress corrosion cracking of all types of metals in a wide variety of product forms including parts joined by welding. It is particularly suitable for tests of tube, rod and plate (see Figure 1). Notched specimens may also be used (see5.3.8). 1.3 C-ring specimens may be stressed to predet
26、ermined levels, using simple equipment for application of either constant load or constant strain. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO7539. At the time of publication, the editions indicate
27、d were valid. All standards are subject to revision, and parties to agreements based on this part of ISO7539 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
28、 Standards. ISO 7539-1:1987, Corrosion of metals and alloys Stress corrosion testing Part1: General guidance on testing procedures. ISO 7539-6:1989, Corrosion of metals and alloys Stress corrosion testing Part6: Preparation and use of pre-cracked specimens. 3 Definitions For the purposes of this par
29、t of ISO7539, the definitions given in ISO7539-1 are applicable. 4 Principle 4.1 The test consists of subjecting a specimen to constant load or to constant strain with a view to determining stress corrosion susceptibility by reference to one or more of the parameters enumerated in clause7. 4.2 Corro
30、sive environments may cause a deterioration of the properties of stressed materials beyond those observed with the same combination of environment and material when the latter is not subjected to stress. This enhanced deterioration may be expressed in a number of different ways for the purpose of as
31、sessing stress corrosion susceptibility. 4.3 The commonest form of deterioration due to stress corrosion involves the initiation and growth of cracks, one or more of which may eventually lead to total failure of a specimen if the test is conducted for an appropriate time. 4.4 Wide variations in test
32、 results may be obtained for a given metal and environment even when testing nominally identical specimens and the replication of tests is frequently necessary. If specimens are prepared to different sizes or orientations or are subjected to different stressing procedures, test results may be even m
33、ore variable. 4.5 The time required for cracks to appear after exposure of stressed specimens to the test environment or the threshold stress below which cracks do not appear can be used as a measure of the stress corrosion resistance of the material in the test environment at the stress level emplo
34、yed. 5 Specimens 5.1 Specimen design 5.1.1 The size of C-rings may be varied over a wide range, but C-rings with an outside diameter less than15mm are not recommended because of increased difficulties in machining and decreased precision in stressing. The dimensions of the ring can affect the stress
35、 state, and these considerations are discussed in5.2. Figure 2 is a drawing showing typical dimensions for the manufacture of a C-ring. 5.1.2 In testing thick sections that have a directional grain structure, it is essential that the C-ring should be orientated in the section so that the direction o
36、f the principal stress is normal to the plane of minimum resistance to stress corrosion cracking. If the ring is not so orientated it will tend to crack off-centre at a location where the stress is unknown and lower than the calculated stress (see5.3.3). Appropriate instructions should therefore be
37、given to workshop personnel. C-ring specimens may be used as notched or fatigue pre-cracked specimens, the stress states of which are considered in5.3.8 for notched specimens and in ISO7539-6 for pre-cracked specimens.ENISO7539-5:1995 4 BSI 04-2000 Figure 1 Sampling procedure for testing various pro
38、ductsENISO7539-5:1995 BSI 04-2000 5 5.2 Stress considerations 5.2.1 The stress of principal interest in the C-ring specimen is the circumferential stress. This is not uniform: there is a gradient through the thickness, varying from a maximum in tension on one surface to a maximum in compression on t
39、he opposite surface. The stress varies also around the circumference of the C-ring from zero at each bolt hole to a maximum at the centre of the arc opposite the stressing bolt. The stress calculated according to Annex A is present only along a line across the ring at the middle of the arc. Thus, if
40、 the stress is determined by measuring the strain on the tension surface of the C-ring, the strain gauge should be positioned at the middle of the arc in order to indicate the maximum strain. The stress varies across the width of the ring to an extent which depends on the width-to-thickness and diam
41、eter-to-thickness ratios. In general, if loaded as shown in Figure 3 a) and Figure 3 b), the tensile stress on the outer surface is greater at the edges than at the centre, while if loaded as shown in Figure 3c), the tensile stress on the inner surface is less at the edges than at the centre. 5.2.2
42、Another characteristic of the stress system in the C-rings is the presence of biaxial stresses; that is, transverse as well as circumferential stresses are developed. The transverse axial stress varies from a maximum at the mid-width to zero at the edges, and has the same sign as the circumferential
43、 stress. In general, the transverse stress decreases with decreasing width-to-thickness and increasing diameter-to-thickness ratios. 5.2.3 In the case of the notched C-ring a triaxial stress state is present adjacent to the root of the notch. In addition, the circumferential stress at the root of th
44、e notch will be greater than the nominal stress and generally may be expected to be in the plastic range. 5.2.4 When C-rings are machined from products that contain appreciable residual stress or are subjected to heat treatment involving quenching after being machined, internal stresses may be prese
45、nt. These may introduce errors in the calculated stress. It is necessary to measure the tubing diameter before and after the axial cut is made and to use these measurements to calculate the residual stresses in the tube. 5.2.5 The possibility of relaxation during the exposure period should be consid
46、ered, especially when specimens are exposed at elevated temperatures. Relaxation can be estimated if creep data are available for both the ring and the stressing bolt. Figure 2 Example of C-ring specimenENISO7539-5:1995 6 BSI 04-2000 NOTEIf the ring and bolt have different coefficients of thermal ex
47、pansion, the applied stress may be significantly changed when testing at elevated temperatures. Also, if plastic insulators are used to avoid galvanic corrosion, the possibility of stress relaxation should be anticipated. 5.3 Stressing methods 5.3.1 C-ring specimens are usually loaded under constant
48、 displacement conditions with tensile stress produced on the exterior of the ring by tightening a bolt centred on the diameter of the ring see Figure 3 a). 5.3.2 C-rings can alternatively be stressed in the reverse direction by spreading the ring and creatinga tensile stress on the inside surface as
49、 in Figure 3c) or, preferably, by the use of a wedge opening technique to displace the arms of the C-rings as in Figure 4. In the latter case the necessary displacement is provided by inserting an accurately machined wedge of the same material as the C-ring, so avoiding galvanic effects. A suitable jig for inserting the wedge is shown in Figure 4. 5.3.3 The C-ring test can be modified for approximately constant load conditions by the use of a suitably calibrated spring placed on the loading bolt see Figure 3b). 5
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