SIST EN ISO 15653:2011
Metallic materials - Method of test for the determination of quasistatic fracture toughness of welds (ISO 15653:2010)
Metallic materials - Method of test for the determination of quasistatic fracture toughness of welds (ISO 15653:2010)
This International Standard specifies methods for determining fracture toughness in terms of K (stress intensity factor), δ (crack tip opening displacement, CTOD) and J (experimental equivalent of the J-integral) for welds in metallic materials. This International Standard is complementary to ISO 12135, which covers all aspects of fracture toughness testing of parent metal and which needs to be used in conjunction with this document. This International Standard describes methods for determining point values of fracture toughness. It should not be considered a way of obtaining a valid R-curve (resistance-to-crack-extension curve). However, the specimen preparation methods described in this International Standard could be usefully employed when determining R-curves for welds. The methods use fatigue precracked specimens which have been notched, after welding, in a specific target area in the weld. Methods are described to evaluate the suitability of a weld for notch placement within the target area, which is either within the weld metal or within the weld heat-affected zone (HAZ), and then, where appropriate, to evaluate the effectiveness of the fatigue crack in sampling these areas.
Metallische Werkstoffe - Prüfverfahren zur Bestimmung der quasistatischen Bruchzähigkeit von Schweißverbindungen (ISO 15653:2010)
Diese Internationale Norm legt Verfahren zur Bestimmung von Bruchzähigkeiten mit K (Spannungsintensitätsfaktor), d (Rissspitzenöffnungsverschiebung, CTOD) und J (experimentelles Äquivalent für das J-Integral) für Schweißungen an metallischen Werkstoffen fest.
Dieses Verfahren ist ein Zusatz zu ISO 12135, die alle Aspekte der Bruchzähigkeitsprüfung von Grundwerkstoffen abdeckt und in Verbindung mit diesem Dokument verwendet werden muss. Diese Norm beschreibt Verfahren für die Bestimmung von Einzelwerten der Bruchzähigkeit. Sie darf nicht als Verfahren zur Erlangung einer R-Kurve für die Beständigkeit gegen die Rissausbreitung angesehen werden. Die in dieser Norm beschriebenen Vorbereitungsverfahren der Proben könnten jedoch bei der Bestimmung der R-Kurven von Schweißungen hilfreich eingesetzt werden. In diesem Verfahren werden Proben mit vorherigen Ermüdungsrissen verwendet, die nach dem Schweißen in einem festgelegten Zielbereich der Schweißnaht eingekerbt wurden. Es werden Verfahren beschrieben zur Bewertung der Eignung einer Schweißung für die Anbringung der Einkerbung in dem Zielbereich, der sich entweder im Schweißgut oder in der Wärmeeinflusszone (WEZ) der Schweißung befindet und dann, falls zutreffend, zur Bewertung der Wirksamkeit des Ermüdungsrisses durch Probenahme in diesen Bereichen.
Matériaux métalliques - Méthode d'essai pour la détermination de la ténacité quasistatique a la rupture des soudures (ISO 15653:2010)
L'ISO 15653:2009 spécifie des méthodes permettant de déterminer la ténacité à la rupture en termes de K (facteur d'intensité de contrainte), d (écartement à fond de fissure, CTOD) et J (équivalent expérimental de l'intégrale J) pour les soudures dans les matériaux métalliques.
L'ISO 15653:2009 complète l'ISO 12135, qui couvre tous les aspects des essais de ténacité à la rupture du métal de base et qui doit être utilisée conjointement avec le présent document. Elle décrit des méthodes de détermination des valeurs en point de la ténacité à la rupture. Elle ne doit pas être considérée comme une façon permettant d'obtenir une courbe R valide (courbe de résistance à la propagation de fissure). Cependant, les méthodes de préparation des éprouvettes décrites dans l'ISO 15653:2009 peuvent être employées utilement lors de la détermination des courbes R pour les soudures. Les méthodes utilisent des éprouvettes préfissurées par fatigue qui ont été entaillées, après soudage, dans une surface cible spécifique de la soudure. Les méthodes sont décrites pour évaluer l'adaptabilité d'une soudure au placement des entailles dans la surface cible qui se trouve soit dans la zone fondue soit dans la zone de soudure affectée thermiquement (ZAT) puis, en cas de besoin, pour évaluer l'efficacité de la fissuration par fatigue lors de l'échantillonnage de ces surfaces.
Kovinski materiali - Preskusna metoda za ugotavljanje kvazistatične lomne žilavosti zvarnih spojev (ISO 15653:2010)
Ta mednarodni standard določa metode za ugotavljanje lomne žilavosti v smislu vrednosti K (faktor intenzivnosti napetosti), δ (premik vrha odprtja razpoke, CTOD) in J (eksperimentalna enakovredna vrednost integrala J) za zvarne spoje v kovinskih materialih. Ta mednarodni standard dopolnjuje ISO 12135, ki zajema vse vidike preskušanja lomne žilavosti matične kovine in ki se mora uporabljati skupaj s tem dokumentom. Ta mednarodni standard opisuje metodo za ugotavljanje točkovnih vrednosti lomne žilavosti. Ne sme veljati za način pridobivanja veljavne krivulje R (krivulje upornosti proti širjenju razpoke). Metode za pripravo vzorca, opisane v tem mednarodnem standardu, se lahko koristno uporabijo pri določanju krivulj R za zvarne spoje. Pri metodah se uporabljajo vzorci z utrujenostno razpoko, po varjenju zarezani v določeno ciljno območje zvarnega spoja. Metode so opisane za vrednotenje primernosti zvarnega spoja za postavitev zareze v ciljnem območju, ki je bodisi v varilni kovini ali toplotno vplivanem območju vara (HAZ), nato pa se po potrebi ovrednoti tudi učinkovitost utrujenostne razpoke pri vzorčenju teh območij.
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Metallische Werkstoffe - Prüfverfahren zur Bestimmung der quasistatischen Bruchzähigkeit von Schweißverbindungen (ISO 15653:2010)Matériaux métalliques - Méthode d'essai pour la détermination de la ténacité quasistatique a la rupture des soudures (ISO 15653:2010)Metallic materials - Method of test for the determination of quasistatic fracture toughness of welds (ISO 15653:2010)25.160.40Varjeni spoji in variWelded jointsICS:Ta slovenski standard je istoveten z:EN ISO 15653:2010SIST EN ISO 15653:2011en,fr,de01-november-2011SIST EN ISO 15653:2011SLOVENSKI
STANDARD
SIST EN ISO 15653:2011
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 15653
April 2010 ICS 25.160.40 English Version
Metallic materials - Method of test for the determination of quasistatic fracture toughness of welds (ISO 15653:2010)
Matériaux métalliques - Méthode d'essai pour la détermination de la ténacité quasi statique à la rupture des soudures (ISO 15653:2010)
Metallische Werkstoffe - Prüfverfahren zur Bestimmung der quasistatischen Bruchzähigkeit von Schweißverbindungen (ISO 15653:2010) This European Standard was approved by CEN on 23 January 2010.
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 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 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 standards bodies of Austria, Belgium, Bulgaria, Croatia, 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.
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EN ISO 15653:2010 (E) 2 Contents Page Foreword .3 SIST EN ISO 15653:2011
EN ISO 15653:2010 (E) 3 Foreword This document (EN ISO 15653:2010) has been prepared by Technical Committee ISO/TC 164 "Mechanical testing of metals" in collaboration with Technical Committee CEN/TC 121 “Welding” the secretariat of which is held by DIN. 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 2010, and conflicting national standards shall be withdrawn at the latest by October 2010. 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, Croatia, 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 15653:2010 has been approved by CEN as a EN ISO 15653:2010 without any modification.
SIST EN ISO 15653:2011
SIST EN ISO 15653:2011
Reference numberISO 15653:2010(E)© ISO 2010
INTERNATIONAL STANDARD ISO15653First edition2010-04-15Metallic materials — Method of test for the determination of quasistatic fracture toughness of welds Matériaux métalliques — Méthode d'essai pour la détermination de la ténacité quasi statique à la rupture des soudures
SIST EN ISO 15653:2011
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SIST EN ISO 15653:2011
ISO 15653:2010(E) © ISO 2010 – All rights reserved iii Contents Page Foreword.iv 1 Scope.1 2 Normative references.1 3 Terms and definitions.1 4 Symbols and units.3 5 Principle.3 6 Choice of specimen design, specimen orientation and notch location.4 6.1 Classification of target area for notching.4 6.2 Specimen design.4 6.3 Specimen and crack plane orientation.4 7 Pre-machining metallography.8 7.1 Microstructural assessment of macrosections.8 7.2 Additional requirements for heat-affected zone tests.9 8 Machining.9 8.1 Tolerances on specimen dimensions.9 8.2 Notch placement for through-thickness notched specimens.10 8.3 Notch placement for surface-notched specimens.10 8.4 Notch machining.10 9 Specimen preparation.15 9.1 Fatigue precracking.15 9.2 Side grooving.15 10 Test apparatus, requirements and test procedure.15 11 Post-test metallography.15 11.1 General.15 11.2 Through-thickness notched specimens.16 11.3 Surface-notched specimens.16 11.4 Assessment of pop-in.16 12 Post-test analysis.19 12.1 Choice of tensile properties.19 12.2 KIc.20 12.3 δ and J.20 12.4 Qualification requirements.20 13 Test report.24 Annex A (informative)
Examples of notch locations.25 Annex B (informative)
Examples of pre-test and post-test metallography.27 Annex C (normative)
Residual-stress modification and precracking technique.29 Annex D (normative)
Assessment of pop-in.31 Annex E (informative)
Shallow-notched specimen testing.37 Bibliography.41
SIST EN ISO 15653:2011
ISO 15653:2010(E) iv © ISO 2010 – 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 15653 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee SC 4, Toughness testing — Fracture (F), Pendulum (P), Tear (T).
SIST EN ISO 15653:2011
INTERNATIONAL STANDARD ISO 15653:2010(E) © ISO 2010 – All rights reserved 1 Metallic materials — Method of test for the determination of quasistatic fracture toughness of welds 1 Scope This International Standard specifies methods for determining fracture toughness in terms of K (stress intensity factor), δ (crack tip opening displacement, CTOD) and J (experimental equivalent of the J-integral) for welds in metallic materials. This International Standard is complementary to ISO 12135, which covers all aspects of fracture toughness testing of parent metal and which needs to be used in conjunction with this document. This International Standard describes methods for determining point values of fracture toughness. It should not be considered a way of obtaining a valid R-curve (resistance-to-crack-extension curve). However, the specimen preparation methods described in this International Standard could be usefully employed when determining R-curves for welds. The methods use fatigue precracked specimens which have been notched, after welding, in a specific target area in the weld. Methods are described to evaluate the suitability of a weld for notch placement within the target area, which is either within the weld metal or within the weld heat-affected zone (HAZ), and then, where appropriate, to evaluate the effectiveness of the fatigue crack in sampling these areas. 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 3785, Metallic materials — Designation of test specimen axes in relation to product texture ISO 12135, Metallic materials — Unified method of test for the determination of quasistatic fracture toughness 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 12135 and the following apply. 3.1 stretch zone width SZW increase in crack length associated with crack tip blunting — i.e. prior to the onset of unstable crack extension, pop-in (see 3.3) or slow stable crack extension — and occurring in the same plane as the fatigue precrack 3.2 target area intended fatigue crack tip position within the weld metal or HAZ NOTE See 3.7 and 3.9. SIST EN ISO 15653:2011
ISO 15653:2010(E) 2 © ISO 2010 – All rights reserved 3.3 pop-in an abrupt discontinuity in the force versus displacement record, featured as a sudden increase in displacement and, generally, a sudden decrease in force, subsequent to which displacement and force increase to above their values at pop-in 3.4 local compression controlled compression applied to specimens in the thickness direction on the unnotched ligament prior to fatigue cracking using hardened steel platens NOTE See Annex C. 3.5 welding an operation in which two or more parts are united by means of heat, friction, pressure or all three of these, in such a way that there is continuity in the nature of the metal between these parts NOTE Filler metal, the melting temperature of which is of the same order as that of the parent metal, may or may not be used. 3.6 weld union of pieces of metal made by welding 3.7 weld metal all metal melted during the making of a weld and retained in the weld 3.8 parent metal base metal metal to be joined by welding 3.9 heat-affected zone HAZ zone in the parent metal that is metallurgically affected by the heat of welding 3.10 fusion line FL junction between the weld metal and the parent metal heat-affected zone 3.11 weld positional WP target position for the fatigue crack tip, defined with respect to a reference line NOTE See Figure A.1 for examples. 3.12 specific microstructure SM target microstructure for the fatigue crack tip NOTE See Figure A.2 for examples. SIST EN ISO 15653:2011
ISO 15653:2010(E) © ISO 2010 – All rights reserved 3 3.13 specimen blank specimen prepared from weld metal plus parent metal prior to notching 3.14 postweld heat treatment heat treatment applied after welding for the purpose of reducing residual stresses or modifying weld properties 4 Symbols and units For the purposes of this document, the symbols and units given in Table 1 apply in addition to those in ISO 12135. Table 1 — Symbols and units Symbol Unit Designation d1, d2 mm Lengths of microstructural features associated with pop-in. h mm Effective weld width, defined as shortest distance between fatigue crack tip and weld fusion line within the central 75 % of the thickness (see Figures 13 and 14). HV10
Vickers hardness using 10 kg force. N
Normal to welding direction. P
Parallel to welding direction. Q
Weld thickness direction. Rp0,2b MPa 0,2 % offset yield strength of parent metal at the temperature of the fracture test. Rp0,2w MPa 0,2 % offset yield strength of weld metal at the temperature of the fracture test. Rmb MPa Tensile strength of parent metal at the temperature of the fracture test. Rmw MPa Tensile strength of weld metal at the temperature of the fracture test. s1 mm Distance between crack tip and target area measured in the crack plane (see Figure 12). s2 mm Distance between crack tip and target area measured perpendicular to the crack plane (see Figure 12). V, V1, V2 mm Crack mouth opening displacement. X
Direction parallel to primary grain flow of parent metal. Y
Direction transverse to primary grain flow and to thickness of parent metal. Z
Direction through thickness of parent metal. ∆apop mm Maximum length of brittle crack extension (beyond SZW) (see 3.1) associated with pop-in. λ mm Length of specific microstructure measured in pre-test or post-test metallography (see Figure B.2). 5 Principle This International Standard specifies procedures for the determination of fracture toughness on notched-plus-fatigue-cracked specimens taken from welds. It pertains to situations where the crack tip is a) located in relation to a weld feature of interest, referred to as “weld positional” (WP); b) specifically located within a microstructure of interest, referred to as “specific microstructure” (SM). Metallographic examination of the weld is used to confirm that the target weld feature and/or microstructure is indeed present at the crack tip and in sufficient quantity for testing. SIST EN ISO 15653:2011
ISO 15653:2010(E) 4 © ISO 2010 – All rights reserved Specimen geometry and notch orientation are chosen, and a fatigue crack then extended from the specimen's notch tip into the target weld feature or microstructure by applying a controlled alternating force to the specimen. The purpose of the test is to determine weld fracture toughness in the absence of significant welding stresses. To achieve this and to produce a straight-fronted fatigue crack, modifications to the fatigue precracking procedure may be required. These modifications are usually necessary when testing as-welded or partially stress-relieved welds. The fracture toughness test is performed and evaluated in accordance with ISO 12135, but subject to additional requirements of this test method regarding post-test analysis (see 12.1, 12.2 and 12.3) and qualification (see 12.4). Post-test metallography is often required to make certain that the crack tip was located in the target weld feature and/or microstructure and to determine the significance of pop-ins. The sequence of operations is summarized in Figure 1. 6 Choice of specimen design, specimen orientation and notch location 6.1 Classification of target area for notching A specimen selected for weld positional (WP) testing is intended to test a defined weld region with respect to a reference position (e.g. the weld metal centreline). A specimen selected for specific microstructure (SM) testing is intended to sample a specific microstructure along the whole or part of the crack front length within the central 75 % of the specimen thickness. NOTE Some examples of WP and SM notch locations are given in Annex A. WP weld metal centreline notch locations sampling predominantly grain-refined regions may give misleading (overly high) values of fracture toughness for misaligned two-pass and parallel multi-pass welds. For these welds, it is recommended that the SM notch locations shown in Figures A.2 iv) and A.2 v), respectively, be used. 6.2 Specimen design Specimen design shall be of compact or single-edge-notched bend configuration as defined in ISO 12135 and may be plain-sided or side-grooved. Bend specimens notched into the plate thickness (see Figures 2, 3 and 4, parent metal specimens XY and YX and weld metal specimens NP and PN) are referred to as through-thickness notched specimens, whilst those notched into the planar surface of the plate (see Figures 2, 3 and 4, parent metal specimens XZ and YZ and weld metal specimens NQ and PQ) are referred to as surface-notched specimens. NOTE Tolerances on weld specimen dimensions are less stringent than those for testing parent metal (see 8.1). Test specimens shall have the dimension B or W (see Figure 5) equal to the full thickness of the parent metal adjacent to the weld to be tested (excluding weld overfill). Testing of sub-sized (i.e. B or W < full thickness in directions Q for weld and Z for parent metal in Figures 2, 3 and 4) and/or side-grooved specimens is permitted, but shall be properly identified as such in the test report. Results from sub-sized and/or side-grooved specimens may differ from those from full-thickness specimens owing to size effects and/or different microstructural regions being tested. 6.3 Specimen and crack plane orientation Specimen and crack plane orientation relative to the weld and parent metal working directions shall be defined using the identification system described in Figures 2, 3 and 4. SIST EN ISO 15653:2011
ISO 15653:2010(E) © ISO 2010 – All rights reserved 5
Figure 1 — Flow chart for testing SIST EN ISO 15653:2011
ISO 15653:2010(E) 6 © ISO 2010 – All rights reserved
a)
Parent metal
b)
Weld metal Key 1 rolling direction N = normal to weld direction P = parallel to weld direction Q = weld thickness direction First letter in designation: the direction normal to the crack plane. Second letter in designation: the expected direction of crack propagation. See ISO 3785 for the definitions of X, Y and Z. Specimen orientations NP and PN shall be referred to as through-thickness notched, whilst specimen orientations NQ and PQ shall be referred to as surface-notched. Figure 2 — Crack plane orientation code for fracture toughness specimens of parent metal and weld metal SIST EN ISO 15653:2011
ISO 15653:2010(E) © ISO 2010 – All rights reserved 7
a)
Typical butt weld
b)
Cruciform joint Key 1 HAZ 2 weld 3 weld specimen orientation NP/XY 4 weld specimen orientation NP/YX 5 through-crack NP/ZX or NP/ZY X = rolling direction Q = weld thickness direction For tests of the HAZ, where the rolling direction of the parent metal may affect resistance to crack extension, the weld and parent metal orientations may be combined to give both the weld direction and the parent metal rolling direction as shown in this figure and Figure 4. Figure 3 — Crack plane orientation code for fracture toughness specimens for testing the HAZ of a typical butt weld and cruciform joint SIST EN ISO 15653:2011
ISO 15653:2010(E) 8 © ISO 2010 – All rights reserved
a)
Typical butt weld
b)
Angled cruciform joint Key 1 rolling direction For tests of the HAZ, where the rolling direction of the parent metal may affect resistance to crack extension, the weld and parent metal orientations may be combined to give both the weld direction and the parent metal rolling direction as shown in this figure and Figure 3. Figure 4 — Crack plane orientation code for fracture toughness specimens for testing the HAZ at an angle, α, to the parent metal rolling direction for a typical butt weld and angled cruciform joint 7 Pre-machining metallography 7.1 Microstructural assessment of macrosections When the notch target area is defined as SM, either separate macrosections or the ends of the welds shall be prepared with the plane of the section perpendicular to the welding direction. These transverse weld sections shall bound the length of weld to be tested to ensure that the target microstructure is present at the expected crack tip position and in sufficient quantity for testing. The macrosections shall be polished, etched and examined at a magnification suitable to identify the target area prior to specimen manufacture. Where separate macrosections are prepared, their positions along the weld shall be recorded. Examination of the macrosections shall be used to establish that a) in a through-thickness notched specimen, the intended crack tip is likely to reside in the target area within the central 75 % of the thickness; b) in a surface-notched specimen, the intended crack tip is no more than 0,5 mm from the target area. SIST EN ISO 15653:2011
ISO 15653:2010(E) © ISO 2010 – All rights reserved 9 If the desired microstructure is not present, there is insufficient quantity to test, or the crack tip position tolerances cannot be achieved, the weld shall be rejected as unsuitable for testing to the SM criteria. In this case, a new target area may be selected or a new weld prepared. If the bend specimen is to be employed and the specific microstructure is available in sufficient quantity to test, but the crack tip position tolerances cannot be achieved, the shallow-notched specimen testing procedures described in Annex E may be used by agreement between the parties involved. Owing to the lower crack tip constraint associated with a shallow notch, the fracture toughness value determined from a shallow-notched specimen (0,10 u ao/W u 0,45) (ao = initial crack length, W = specimen thickness) may be higher than that obtained from a standard notched specimen (0,45 u ao/W u 0,70) for the same crack tip microstructure. The significance of this potential difference shall be considered when a shallow-notched specimen is to be used. 7.2 Additional requirements for heat-affected zone tests When the target area is SM in the HAZ, microstructural examinations additional to those in 7.1 shall be conducted on the polished and etched macrosection to determine whether or not the target microstructure is within the central 75 % of the thickness and in sufficient quantity for a successful test. The measured positions and lengths of the target microstructure may optionally be presented in map form (an example is shown in Annex B). If such a map is drawn, it shall include the full macrosection thickness, showing the positions of the target microstructure. The percentage of target microstructure shall be calculated over the central 75 % of the specimen thickness. Where surface-notched specimens are selected, the macrosection shall be used to confirm that the target microstructure is present within the range 0,45 u ao/W u 0,70. If it is considered unlikely that the fatigue crack tip is placed in accordance with the SM acceptance criteria, then consideration shall be given to revising the target area, preparing a new weld or using a shallow-notched specimen as described in 7.1. 8 Machining 8.1 Tolerances on specimen dimensions Specimen blanks shall be machined from the product so that the target area identified for testing can be successfully notched. Blanks shall be machined to the dimensional tolerances defined here prior to notching. Compact specimens shall meet the dimensional requirements of ISO 12135. Standard bend specimens shall conform to Figure 5. Shallow-notched bend specimens (see 7.1, 7.2 and Annex E) shall likewise conform to Figure 5 except that the relative crack length shall be in the range 0,10 u ao/W u 0,45. NOTE 1 The dimensional tolerances in Figure 5 for the standard single-edge-notched bend specimen are intentionally less stringent than those of ISO 12135 in order to minimize alteration of the original weld product. Weld misalignment, weld distortion and specimen blank curvature (for blanks removed from pipe sections) shall conform to the requirements of Figure 6. The straightness requirement of 2,5 % of W on specimen blank sides applies to pipe curvatures (expressed as the ratio of pipe radius to weld thickness) W 10. Welded joints not meeting the specified straightness/misalignment requirements shall be straightened by local bending prior to notching. The points of straightening-force application shall be located at a minimum distance B from the region to be notched. It is essential that the region to be notched is not deformed by straightening operations. A method for straightening specimen blanks from distorted or curved sections is illustrated in Figure 7. When it is not possible to straighten a specimen bla
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