ASTM E2472 - 12e1

    Standard Test Method for Determination of Resistance to Stable Crack Extension under Low-Constraint Conditions

    Active Standard ASTM E2472 | Developed by Subcommittee: E08.07

    Book of Standards Volume: 03.01


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    Significance and Use

    5.1 This test method characterizes a metallic material’s resistance to stable crack extension in terms of crack-tip-opening angle (CTOA), ψ and/or crack-opening displacement (COD), δ5 under the laboratory or application environment of interest. This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint and that are tested under slowly increasing displacement.

    5.2 When conducting fracture tests, the user must consider the influence that the loading rate and laboratory environment may have on the fracture parameters. The user should perform a literature review to determine if loading rate effects have been observed previously in the material at the specific temperature and environment being tested. The user should document specific information pertaining to their material, loading rates, temperature, and environment (relative humidity) for each test.

    5.3 The results of this characterization include the determination of a critical, lower-limiting value, of CTOA (ψ c) or a resistance curve of δ5, a measure of crack-opening displacement against crack extension, or both.

    5.4 The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens.

    5.5 Materials that can be evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-thickness (a/B) ratio or ligament-to-thickness (b/B) ratio are equal to or greater than 4, which ensures relatively low and similar global crack-front constraint for both the C(T) and M(T) specimens (2, 3).

    5.6 The values of CTOA and COD (δ5) determined by this test method may serve the following purposes:

    5.6.1 In research and development, CTOA (ψc) or COD (δ5), or both, testing can show the effects of certain parameters on the resistance to stable crack extension of metallic materials significant to service performance. These parameters include, but are not limited to, material thickness, material composition, thermo-mechanical processing, welding, and thermal stress relief.

    5.6.2 For specifications of acceptance and manufacturing quality control of base materials.

    5.6.3 For inspection and flaw assessment criteria, when used in conjunction with fracture mechanics analyses. Awareness of differences that may exist between laboratory test and field conditions is required to make proper flaw assessment.

    5.6.4 The critical CTOA (ψc) has been used with the elastic-plastic finite-element method to accurately predict structural response and force carrying capacity of simple and complex cracked structural components, see Appendix X1.

    5.6.5 The δ5 parameter has been related to the J-integral by means of the Engineering Treatment Model (ETM) (10) and provides an engineering approach to predict the structural response and force carrying capacity of cracked structural components.

    5.6.6 The K-R curve method (Practice E561) is similar to the δ5-resistance curve, in that, the concept has been applied to both C(T) and M(T) specimens (under low-constraint conditions) and the K-R curve concept has been used successfully in industry (11). However, the δ5 parameter has been related to the J-integral and the parameter incorporates the material non-linear effects in its measurement. Comparisons have also been made among various fracture criteria on fracture of C(T), M(T) and a structurally configured crack configuration (12) that were made of several different materials (two aluminum alloys and a very ductile steel), and the K-R curve concept was found to have limited application, in comparison to the critical CTOAc (ψ c) concept.

    1. Scope

    1.1 This standard covers the determination of the resistance to stable crack extension in metallic materials in terms of the critical crack-tip-opening angle (CTOA), ψc and/or the crack-opening displacement (COD), δ5 resistance curve (1).2 This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-size-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4) and that are tested under slowly increasing remote applied displacement. The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens. The fracture resistance determined in accordance with this standard is measured as ψc (critical CTOA value) and/or δ 5 (critical COD resistance curve) as a function of crack extension. Both fracture resistance parameters are characterized using either a single-specimen or multiple-specimen procedures. These fracture quantities are determined under the opening mode (Mode I) of loading. Influences of environment and rapid loading rates are not covered in this standard, but the user must be aware of the effects that the loading rate and laboratory environment may have on the fracture behavior of the material.

    1.2 Materials that are evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-thickness (a/B) ratio and the ligament-to-thickness (b/B) ratio are greater than or equal to 4, which ensures relatively low and similar global crack-front constraint for both the C(T) and M(T) specimens (2, 3).

    1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

    1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E4 Practices for Force Verification of Testing Machines

    E8/E8M Test Methods for Tension Testing of Metallic Materials

    E399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness K Ic of Metallic Materials

    E561 Test Method for K-R Curve Determination

    E647 Test Method for Measurement of Fatigue Crack Growth Rates

    E1290 Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement

    E1820 Test Method for Measurement of Fracture Toughness

    E1823 Terminology Relating to Fatigue and Fracture Testing

    E2309 Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines

    ISO Standards

    ISO12135 Metallic Materials--Unified Method of Test for the Determination of Quasistatic Fracture Toughness

    ISO22889:2007 Metallic Materials--Method of Test for the Determination of Resistance to Stable Crack Extension Using Specimens of Low Constraint


    ICS Code

    ICS Number Code 77.040.10 (Mechanical testing of metals)

    UNSPSC Code

    UNSPSC Code


    DOI: 10.1520/E2472-12E01

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