BS-ISO-22889-2007.pdf
BRITISH STANDARD BS ISO 22889:2007 Metallic materials Method of test for the determination of resistance to stable crack extension using specimens of low constraint ICS 77.040.10 ? Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- BS ISO 22889:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2008 © BSI 2008 ISBN 978 0 580 54886 4 National foreword This British Standard is the UK implementation of ISO 22889:2007. The UK participation in its preparation was entrusted by Technical Committee ISE/NFE/4, Mechanical testing of metals, to Subcommittee ISE/NFE/4/4, Toughness testing. 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 a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication DateComments Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- Reference number ISO 22889:2007(E) INTERNATIONAL STANDARD ISO 22889 First edition 2007-12-15 Metallic materials Method of test for the determination of resistance to stable crack extension using specimens of low constraint Matériaux métalliques Méthode d'essai pour la détermination de la résistance à la propagation stable de fissures au moyen d'éprouvettes à faible taux de triaxialité des contraintes BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- ii Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references. 2 3 Terms and definitions. 2 4 Symbols. 3 5 General requirements. 4 5.1 Introduction. 4 5.2 Test specimens. 4 5.3 Pre-test requirements. 6 5.4 Test apparatus 7 5.5 Test requirements. 8 5.6 Post-test crack measurements 9 6 Determination of 5 a resistance curve and CTOA 11 6.1 General. 11 6.2 Test procedure 11 6.3 R-curve plot. 12 6.4 Critical CTOA determination 13 7 Test report . 13 7.1 General. 13 7.2 Specimen, material and test environment . 14 7.3 Test data qualification 14 7.4 Qualification of the 5 R-Curve . 16 7.5 Qualification of c 16 Annex A (informative) Examples of test reports. 28 Annex B (informative) Apparatus for measurement of crack opening displacement, 5. 33 Annex C (informative) Determination of the crack tip opening angle, 35 Annex D (informative) Determination of point values of fracture toughness 45 Bibliography. 48 BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- iv 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 22889 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee SC 4, Toughness testing Fracture (F), Pendulum (P), Tear (T). BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- v Introduction ISO 12135 uses compact and bend specimens to determine specific (point) values of fracture toughness at the onset of either stable or unstable crack extension, and to quantify resistance to stable crack extension. These specimen types have near-square remaining ligaments to provide conditions of high constraint. If certain size requirements are met, then the values of the quantities KIc, 0,2BL and J0,2BL determined from these specimens are considered size insensitive, and regarded as lower-bound fracture toughness values. Although not explicitly stated, size insensitivity holds also for the crack extension resistance curve (R-curve). In engineering practice, however, there are cases which are not covered by the method of test in ISO 12135, for example where the component thickness is much less than that required for size-insensitive properties as determined using ISO 12135, the thickness of the available material does not enable fabrication of specimens meeting the criteria for size insensitivity, and the loading conditions in the structural component are characterized by tension rather than bending. In these cases, constraint in the structural component may be lower than that of the specimens specified by ISO 12135, thus leading to higher resistance to crack extension and higher load-carrying capability in the structural component than would have been forecast based on the test in ISO 12135. BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- blank Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 1 Metallic materials Method of test for the determination of resistance to stable crack extension using specimens of low constraint 1 Scope This International Standard specifies methods for determining the resistance to stable crack extension in terms of crack opening displacement, 5, and critical crack tip opening angle, c, for homogeneous metallic materials by the quasistatic loading of cracked specimens that exhibit low constraint to plastic deformation. Compact and middle-cracked tension specimens are notched, precracked by fatigue, and tested under slowly increasing displacement. This International Standard describes methods covering tests on specimens not satisfying requirements for size-insensitive fracture properties; namely, compact specimens and middle-cracked tension specimens in relatively thin gauges. Methods are given for determining the crack extension resistance curve (R-curve). Point values of fracture toughness for compact specimens are determined according to ISO 12135. Methods for determining point values of fracture toughness for the middle-cracked tension specimen are given in Annex D. Crack extension resistance is determined using either the multiple-specimen or single-specimen method. The multiple-specimen method requires that each of several nominally identical specimens be loaded to a specified level of displacement. The extent of ductile crack extension is marked and the specimens are then broken open to allow measurement of crack extension. Single-specimen methods based on either unloading compliance or potential drop techniques can be used to measure crack extension, provided they meet specified accuracy requirements. Recommendations for single-specimen techniques are described in ISO 12135. Using either technique, the objective is to determine a sufficient number of data points to adequately describe the crack extension resistance behaviour of a material. The measurement of 5 is relatively simple and well established. The 5 results are expressed in terms of a resistance curve, which has been shown to be unique within specified limits of crack extension. Beyond those limits, 5 R-curves for compact specimens show a strong specimen dependency on specimen width, whereas the 5 R-curves for middle-cracked tension specimens show a weak dependency. CTOA is more difficult to determine experimentally. The critical CTOA is expressed in terms of a constant value achieved after a certain amount of crack extension. The CTOA concept has been shown to apply to very large amounts of crack extension and can be applied beyond the current limits of 5 applications. Both measures of crack extension resistance are suitable for structural assessment. The 5 concept is well established and can be applied to structural integrity problems by means of simple crack driving force formulae from existing assessment procedures. The CTOA concept is generally more accurate. Its structural application requires numerical methods, i.e. finite element analysis. Investigations have shown a very close relation between the concept of constant CTOA and a unique R-curve for both compact and middle-cracked tension specimens up to maximum load. Further study is required to establish analytical or numerical relationships between the 5 R-curve and the critical CTOA values. BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 2 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 7500-1, Metallic materials Verification of static uniaxial testing machines Part 1: Tension/compression testing machines Verification and calibration of the force-measuring system ISO 9513, Metallic materials Calibration of extensometers used in uniaxial testing ISO 12135:2002, Metallic materials Unified method of test for the determination of quasistatic fracture toughness 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 crack opening displacement COD 5 relative displacement of the crack surfaces normal to the original (undeformed) crack plane at the tip of the fatigue precrack, as measured on the specimens side surface over an initial gauge length of 5 mm 3.2 crack tip opening angle CTOA relative angle of the crack surfaces measured (or calculated) at 1 mm from the current crack tip 3.3 stable crack extension a crack extension that, in displacement control, occurs only when the applied displacement is increased 3.4 crack extension resistance curve R-curve variation in 5 with stable crack extension a 3.5 critical crack tip opening angle c steady-state value of crack tip opening angle at 1 mm from the current crack tip NOTE This value is insensitive to the in-plane dimensions specified in this method; however, it may be thickness dependent. BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 3 4 Symbols For the purposes of this International Standard, the following symbols and units apply. For all parameters, the temperature is assumed to be the test temperature unless otherwise noted. Symbol Unit Designation a mm crack length af mm final crack length (a0 + af) am mm length of machined crack starter notch a0 mm initial crack length a mm stable crack extension amin mm crack extension beyond which c is nearly constant amax mm crack extension limit for 5 or c controlled crack extension af mm final stable crack extension B mm specimen thickness E MPa Youngs modulus of elasticity F kN applied force Ff kN maximum fatigue precracking force Rp0,2 MPa 0,2 % offset yield strength perpendicular to crack plane at the test temperature Rm MPa tensile strength perpendicular to crack plane at the test temperature degrees crack path deviation W mm width of compact specimen, half width of middle-cracked tension specimen W a mm uncracked ligament length W a0 mm initial uncracked ligament length W af mm final uncracked ligament length degrees crack tip opening angle (CTOA) c degrees critical crack tip opening angle (critical CTOA) Poissons ratio 5 mm crack opening displacement over a 5 mm gauge length at tip of fatigue precrack NOTE This is not a complete list of parameters. Only the main parameters are given here; other parameters are referred to and defined in the text. BS ISO 22889:2007 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:27:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 4 5 General requirements 5.1 In
