ISO 22889:2007
Metallic materials — Method of test for the determination of resistance to stable crack extension using specimens of low constraint (Second Edition)

Standard No.

ISO 22889:2007

Release Date

2007

Published By

International Organization for Standardization (ISO)

Status

Withdraw

Replace By

ISO 22889:2013

Latest

ISO 22889:2013

Scope

This International Standard specifies methods for determining the resistance to stable crack extension in terms of crack opening displacement, δ5, and critical crack tip opening angle, ψc, 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 δ5 is relatively simple and well established. The δ5 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, δ5 R-curves for compact specimens show a strong specimen dependency on specimen width, whereas the δ5 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 δ5 applications. Both measures of crack extension resistance are suitable for structural assessment. The δ5 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 δ5 R-curve and the critical CTOA values.

ISO 22889:2007 Referenced Document

• ISO 12135:2002 Metallic materials - Unified method of test for the determination of quasistatic fracture toughness
• ISO 3785 Metallic materials — Designation of test specimen axes in relation to product texture*， 2023-05-01 Update
• ISO 7500-1 Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Calibration and verification of the force-measuring system*， 2018-02-01 Update
• ISO 9513 Metallic materials.Calibration of extensometer systems used in uniaxial testing; Technical Corrigendum 1*， 2013-05-01 Update

ISO 22889:2007 history

• 2013 ISO 22889:2013 Metallic materials.Method of test for the determination of resistance to stable crack extension using specimens of low constraint
• 2007 ISO 22889:2007 Metallic materials — Method of test for the determination of resistance to stable crack extension using specimens of low constraint (Second Edition)