SIST 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 (ISO 7539-9:2003)

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 under rising load or rising displacement. Tests conducted under constant load or constant displacement are dealt with in ISO 7539-6.

Korrosion von Metallen und Legierungen - Prüfung der Spannungsrisskorrosion - Teil 9: Vorbereitung und Anwendung von angerissenen Proben für die Prüfung mit zunehmender Kraft oder zunehmender Verformung (ISO 7539-9:2003)

1.1   Dieser Teil von ISO ISO 7539 behandelt Verfahren für die Gestaltung, Vorbereitung und Anwendung von angerissenen Proben zur Untersuchung der Beständigkeit von Metallen gegen Spannungsrisskorrosion mith Hilfe von Prüfungen, die mit zunehmender Kraft oder zunehmender Verformung durchgeführt werden. Prüfungen mit konstanter Kraft oder konstanter Verformung werden in ISO ISO 7539 6 behandelt.
In diesem Teil von ISO ISO 7539 werden mit der Benennung „Metall“ auch Legierungen erfasst.
1.2   Für die Bewertung dünner Produkte, z. B. Feinbleche oder Drähte, sind angerissene Proben nicht geeignet, weil die Notwendigkeit besteht, die Plastizität auf die Rissspitze zu beschränken; sie werden im Allgemeinen zur Bewertung dickerer Produkte angewendet, zu denen Grobbleche, Stangen und Schmiede¬stücke gehören. Sie können auch zur Bewertung von Schweißverbindungen angewendet werden.
1.3   Zur quantitativen Beanspruchung der angerissenen Proben darf eine Prüfeinrichtung angewendet werden, die an den Kraftangriffspunkten eine monoton zunehmende Kraft oder Verformung aufbringt.
1.4   Ein besonderer Vorteil angerissener Proben mit bekannter Geometrie, die bekannten Spannungen aus¬gesetzt werden, ist die Möglichkeit zur Ermittlung von Daten zur Abschätzung kritischer Fehlergrößen, bei deren Überschreitung das Auftreten von Spannungsrissen möglich ist. Mith Hilfe von angerissenen Proben ist es ferner möglich, die Ausbreitungsgeschwindigkeit von Spannungskorrosionsrissen zu bestimmen.
1.5   Der wichtigste Vorteil dieser Prüfung ist, dass der potentzielle Einfluss einer dynamischen Verformung auf den Grenzwert zur Auslösung von durch Spannungskorrosion erzeugten Rissen berücksichtigt wird.
1.6   Nach diesem Verfahren können bei einer ausreichend niedrigen Beanspruchungsgeschwindigkeit kleinere oder gleich große KISSC Werte rascher ermittelt werden als nach dem Verfahren mit konstanter Kraft oder Verformung.

Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 9: Préparation et utilisation des éprouvettes préfissurées pour essais sous charge croissante ou sous déplacement croissant (ISO 7539-9:2003)

L'ISO 7539-9:2003 couvre les procédures de définition, de préparation et d'utilisation d'éprouvettes préfissurées servant à évaluer la sensibilité d'un métal à la corrosion sous contrainte à l'aide d'essais sous charge croissante ou sous déplacement croissant. Le terme «métal» inclut également les alliages.
Comme il est nécessaire de maintenir la plasticité en fond de fissure, les éprouvettes préfissurées ne se prêtent pas à l'évaluation des produits minces tels que les tôles minces et les fils, et sont généralement utilisées pour des produits plus épais tels que les tôles fortes, les barres et les pièces forgées. Elles peuvent aussi être utilisées pour des pièces assemblées par soudage.
Les éprouvettes préfissurées présentent l'avantage de permettre l'acquisition de données dont on peut déduire les tailles critiques de défaut au-delà desquelles une fissuration par corrosion sous contrainte peut se produire au niveau de pièces de géométrie connue soumises à des efforts connus. Ces éprouvettes permettent également de déterminer la vitesse de propagation des fissures de corrosion sous contrainte.
L'essai a pour principal avantage de prendre en compte l'effet potentiel de la déformation dynamique sur la limite de fissuration par corrosion sous contrainte.

Korozija kovin in zlitin - Preskušanje napetostne korozije - 9. del: Priprava in uporaba preskušancev z umetno razpoko za preskuse pri naraščajoči obremenitvi ali naraščajoči deformaciji (ISO 7539-9:2003)

General Information

• Status: Withdrawn
• Publication Date: 03-Jun-2008
• Withdrawal Date: 14-Sep-2021
• ICS: 77.060 - Corrosion of metals
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 15-Sep-2021
• Due Date: 08-Oct-2021
• Completion Date: 15-Sep-2021
• Ref Project: 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 (ISO 7539-9:2003)

Relations

• Replaced By: SIST EN ISO 7539-9:2021 - 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 (ISO 7539-9:2021)
• Effective Date: 01-Sep-2021

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.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 (ISO 7539-9:2003)Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 9: Préparation et utilisation des éprouvettes préfissurées pour essais sous charge croissante ou sous déplacement croissant (ISO 7539-9:2003)Korrosion von Metallen und Legierungen - Prüfung der Spannungsrisskorrosion - Teil 9: Vorbereitung und Anwendung von angerissenen Proben für die Prüfung mit zunehmender Kraft oder zunehmender Verformung (ISO 7539-9:2003)77.060Korozija kovinCorrosion of metalsICS:SIST EN ISO 7539-9:2008enTa slovenski standard je istoveten z:EN ISO 7539-9:200801-julij-2008SIST EN ISO 7539-9:2008SLOVENSKI
STANDARD







EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 7539-9April 2008ICS 77.060 English VersionCorrosion of metals and alloys - Stress corrosion testing - Part9: Preparation and use of pre-cracked specimens for tests underrising load or rising displacement (ISO 7539-9:2003)Corrosion des métaux et alliages - Essais de corrosionsous contrainte - Partie 9: Préparation et utilisation deséprouvettes préfissurées pour essais sous chargecroissante ou sous déplacement croissant (ISO 7539-9:2003)Korrosion von Metallen und Legierungen - Prüfung derSpannungsrisskorrosion - Teil 9: Vorbereitung undAnwendung von angerissenen Proben für die Prüfung mitzunehmender Kraft oder zunehmender Verformung (ISO7539-9:2003)This European Standard was approved by CEN on 21 March 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards 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 Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2008 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 7539-9:2008: E



EN ISO 7539-9:2008 (E) 2 Contents Page Foreword.3



EN ISO 7539-9:2008 (E) 3 Foreword The text of ISO 7539-9:2003 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 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. Attention 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 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, Slovakia, Slovenia, Spain, Sweden, Switzerland 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.







Reference numberISO 7539-9:2003(E)© ISO 2003
INTERNATIONAL STANDARD ISO7539-9First edition2003-04-01Corrosion of metals and alloys — Stress corrosion testing —
Part 9: Preparation and use of pre-cracked specimens for tests under rising load or rising displacement Corrosion des métaux et alliages — Essais de corrosion sous contrainte —
Partie 9: Préparation et utilisation des éprouvettes préfissurées pour essais sous charge croissante ou sous déplacement croissant



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ii © ISO 2003 — All rights reserved



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved iii Contents Page Foreword.iv 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 determining KISCC from 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



ISO 7539-9:2003(E) iv © ISO 2003 — All rights reserved Foreword ISO (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 committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 7539-9 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys. ISO 7539 consists of the following parts, under the general title Corrosion of metals and alloys — Stress corrosion testing: =Part 1: General guidance 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 for tests under constant load or constant displacement =Part 7: Slow strain rate testing =Part 8: Preparation and use of specimens to evaluate weldments =Part 9: Preparation and use of pre-cracked specimens for tests under rising load or rising displacement



INTERNATIONAL STANDARD ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 1 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
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 under 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 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 increasing 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 stresses. 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 KISCC determined 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 applies. 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 testing —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)



ISO 7539-9:2003(E) 2 © ISO 2003 — All rights reserved ISO 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 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 VLL deflection at the loading point access measured over a fixed period 3.2 stress intensity factor at crack initiation KI-init stress intensity applied at the commencement of measurable crack growth 3.3 range of stress intensity factor ∆Kf, 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 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 defects 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 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 objective is to quantify the conditions under which environmentally-assisted crack extension can occur in terms of the threshold stress intensity for stress corrosion cracking, KISCC, 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 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 are subjected to static loading only.
2) To be published. (Revision of ISO 7539-7:1989)



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 3 4.5 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-existing 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 with 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 latter 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 KISCC is 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 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 susceptibility 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 tip. Experience with fracture toughness testing has shown that for a valid Klc measurement, both the crack length, a, and the thickness, B, shall be not less than 2Icp0,22,5K R and that, where possible, larger specimens where both a and B are at least 2Icp0,24K R shall be used to ensure adequate constraint. From the view of fracture mechanics, a minimum thickness from which an invariant value of KISCC is 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 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 2Ip0,22,5K R



ISO 7539-9:2003(E) 4 © ISO 2003 — All rights reserved and preferably shall be not less than 2Ip0,24K R where KI is 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 substituted for KI in the first of these expressions. 5.1.3 If the specimens are to be used for the determination of KISCC, the initial specimen size shall be based on an estimate of the KISCC of the material (in the first instance, it being better to over-estimate the KISCC value and therefore use a larger 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, KQSCC, 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 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 intended 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 KISCC by 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 during exposure to the test environment, the risk of unnecessary incubation periods is avoided. 5.1.5 Crack length measurements can be readily made with a number of continuous monitoring methods such as the electrical resistance technique. 5.1.6 Bend specimens can in principle be tested in relatively simple cantilever beam equipment but specimens subjected to tension loading require a tensile test machine. 5.2 Specimen design 5.2.1 The specimens can be subjected to either tension or bend loading. Depending on the design, tension loaded specimens can experience stresses at the crack tip which are predominantly tensile (as in remote tension types such as the centre-cracked plate) or contain a significant bend component (as in crackline loaded types such as compact tension specimens). The presence of significant bending stress at the crack tip can adversely affect the crack path stability during stress corrosion testing and can facilitate crack branching in certain materials. Bend specimens can be loaded in 3-point, 4-point or cantilever bend fixtures. 5.2.2 The occurrence of crackline bending with an associated tendency for crack growth out of plane can be curbed by the use of side grooves. 5.2.3 A number of specimen geometries have specific advantages, which have caused them to be frequently used for rising load/displacement stress corrosion testing. These include: a) compact tension (CTS) specimens, which minimize the material requirement; b) cantilever bend specimens, which are easy to machine and inexpensive to test;



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 5 c) C-shaped specimens, which can be machined from thick walled cylinders in order to study the radial propagation of longitudinally oriented cracks. Details of standard specimen designs for each of these types of specimen are given in Figures 1 to 3. 5.2.4 If required, e.g. if fatigue crack initiation and/or propagation is difficult to control satisfactorily, a chevron notch configuration as shown in Figure 4 may be used. If required, its included angle may be increased from 90° to 120°. 5.2.5 Where it is necessary to measure crack opening displacements, knife edges for the location of displacement gauges can be machined into the mouth of the notch, as shown in Figure 5a). Alternatively, separate knife edges can either be screwed or glued on to the specimen at opposite sides of the notch, as shown in Figure 5b). Details of a suitable tapered beam displacement gauge are given in Figure 6. 5.3 Stress intensity factor considerations 5.3.1 It can be shown, using elastic theory, that the stress intensity, KI, acting at the tip of a crack in specimens or structures of various geometries can be expressed by relationships of the form IKQaσ=×× where Q is a dimensionless geometrical constant; σ is the applied stress in MPa; a is the crack length in metres. 5.3.2 The solutions for KI for specimens of particular geometry and loading method can be established by means of finite element stress analysis, or by either experimental or theoretical determinations of specimen compliance. 5.3.3 Kl values can be calculated by means of a dimensionless stress intensity coefficient, Y, related to crack length expressed in terms of a/W through relationship of the form IYPKBW= for compact tension and C-shaped specimens, where W is the width of the specimen in metres and P the applied load. 5.3.4 Where it is necessary to use side-grooved specimens in order to curb crack branching tendencies, etc., shallow side grooves (usually 5 % of the specimen thickness on both sides) can be used. Either semi-circular or 60° V-grooves can be used, but it should be noted that even with semi-circular side grooves of up to 50 % of the specimen thickness, it is not always possible to maintain the crack in the desired plane of extension. Where side grooves are used, the effect of the reduced thickness, Bn, due to the grooves on the stress intensity can be taken into account by replacing B withnBBin the above expression. However, the influence of side grooving on the stress intensity factor is far from established and correction factors should be treated with caution, particularly if deep side grooves are used. 5.3.5 Solutions for Y for specimens with geometries which are often used for stress corrosion testing are given in Figures 7 to 9.



ISO 7539-9:2003(E) 6 © ISO 2003 — All rights reserved Dimensions in millimetres
Width = W Thickness, B = 0,5 W Notch width, N = 0,065 W maximum (if W > 25 mm) or 1,5 mm maximum (if W u 25 mm) Effective notch length, l = 0,25 W to 0,45 W Effective crack length, a = 0,45 W to 0,55 W Figure 1 — Proportional dimensions and tolerances for cantilever bend test pieces



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 7 Dimensions in millimetres
Net width = W Total width, C = 1,25 W minimum Thickness, B = 0,5 W Half height, H = 0,6 W Hole diameter, D = 0,25 W Half distance between hole outer edges, F = 1,6 D Notch width, N = 0,065 W maximum Effective notch length, l = 0,25 W to 0,40 W Effective crack length, a = 0,45 W to 0,55 W Figure 2 — Proportional dimensions and tolerances for compact tension test pieces



ISO 7539-9:2003(E) 8 © ISO 2003 — All rights reserved Dimensions in millimetres
Net width = W Thickness B = 0,50 W ± 0,01 W Axis of holes to tangent to inner radius, X = 0,50 W ± 0,005 W Notch width, N = 1,5 mm minimum (0,1 W maximum) Notch width, I = 0,3 W Axis of holes to face of specimen, Z = 0,25 W ± 0,01 W Axis of holes toouter surface, T = 0,25 W ± 0,01 W Diameter of holes, D = 0,25 W ± 0,005 W NOTE All surfaces should be perpendicular and parallel, as applicable, to within 0,002 W TIR and “E” surfaces perpendicular to “Y” surfaces to within 0,02 W TIR: Figure 3 — Proportional dimensions and tolerances for C-shaped test pieces



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 9 Dimensions in millimetres
a Mill with 60° cutter, notch root radius 0,3 maximum for all test piece sizes. Figure 4 — Chevron notch



ISO 7539-9:2003(E) 10 © ISO 2003 — All rights reserved
a)
Integral type
b)
Screw-on type NOTE Provided adequate strength can be assured, the above knife edges may be fixed using adhesive. Figure 5 — Knife edges for location of displacement gauges



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 11 Dimensions in millimetres
a)
Displacement gauge mounted on a test piece
b)
Dimensions of beams



ISO 7539-9:2003(E) 12 © ISO 2003 — All rights reserved
c)
Bridge measurement circuit a This dimension should be 3,8 × the minimum initial gauge length b Beam thickness taper 0,5 to 0,8 NOTE Strain gauges and materials should be selected to suit the test environment. Figure 6 — Details of tapered beam displacement gauge
IYPKBW= where 316,21131aYWaW=−+−in the case where S = 1,5 W NOTE This expression was originally derived from the combined techniques of stress analysis and compliance and although its inaccuracy and validity limits are not well-defined, it has been used over the range 0,20,6aWuu. For greatest confidence, it is recommended that an emprical compliance be used. Figure 7 — Stress intensity solution for cantilever bend specimen



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 13
IYPKBW= where 22340,8864,6413,3214,725,631aaaaaWYWWWWaW+=+−+−− NOTE The inaccuracy of this expression is considered to be no greater than ± 0,5 % over the range 0,21,0aWuu. Figure 8 — Stress intensity solution for compact tension specimen



ISO 7539-9:2003(E) 14 © ISO 2003 — All rights reserved
IYPKBW= where 35791218,23106,2397,7582,0369,111,540,510,2211raaaaaXaaYWWWWWWWWr=−+−×++×+−− NOTE The inaccuracy of this expression is considered to be no greater than 1 % over the range 0,450,55aWuu. However, it can be used over the wider range 0,30,7aWuuwhen 00,7XWuuand 1201rruuin which case the accuracy is believed to be no greater than 2 %. Figure 9 — Stress intensity solution for C-shaped specimen 5.4 Specimen preparation 5.4.1 Residual stresses can have an influence on stress corrosion cracking. The effect can be significant when test specimens are removed from material in which complete stress relief is impractical, such as weldments, as-quenched materials and complex forged or extruded shapes. Residual stresses superimposed on the applied stress can cause the localized crack-tip stress intensity factor to be different from that computed solely from externally applied loads. The presence of significant residual stress, often in the form of irregular crack growth, namely excessive crack front curvature or out-of-plane crack growth, generally indicates that residual stresses are affecting behaviour. Measurement of residual stress is desirable. 5.4.2 Specimens of the required orientation (see Figure 10) shall, where possible, be machined in the fully heat-treated condition. For specimens in material that cannot easily be completely machined in the fully heat-treated condition, the final heat treatment may be given prior to the notching and finishing operations provided that at least 0,5 mm per face is removed from the thickness at this finish machining stage. However, heat treatment may be carried out on fully machined specimens in cases in which heat treatment will not result in detrimental surface conditions, residual stress, quench cracking or distortion.



ISO 7539-9:2003(E) © ISO 2003 — All rights reserved 15 5.4.3 After machining, the specimens shall be fully degreased in order to ensure that no contamination of the crack tip occurs during subsequent fatigue pre-cracking or stress corrosion testing. In cases where it is necessary to attach electrodes to the specimen by soldering or brazing for crack monitoring by means of electrical resistance measurements, the specimens shall be fully degreased following this operation prior to pre-cracking in order to remove traces of remnan
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