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ASTM E 1921 : 2009 : REV A

Superseded
Superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

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superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

Standard Test Method for Determination of Reference Temperature, To, for Ferritic Steels in the Transition Range
Available format(s)

Hardcopy , PDF

Superseded date

11-11-2014

Language(s)

English

Published date

15-02-2009

1.1 This test method covers the determination of a reference temperature, To, which characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at elastic, or elastic-plastic KJc instabilities, or both. The specific types of ferritic steels (3.2.1) covered are those with yield strengths ranging from 275 to 825 MPa (40 to 120 ksi) and weld metals, after stress-relief annealing, that have 10 % or less strength mismatch relative to that of the base metal.

1.2 The specimens covered are fatigue precracked single-edge notched bend bars, SE(B), and standard or disk-shaped compact tension specimens, C(T) or DC(T). A range of specimen sizes with proportional dimensions is recommended. The dimension on which the proportionality is based is specimen thickness.

1.3 Median KJc values tend to vary with the specimen type at a given test temperature, presumably due to constraint differences among the allowable test specimens in 1.2. The degree of KJc variability among specimen types is analytically predicted to be a function of the material flow properties (1) and decreases with increasing strain hardening capacity for a given yield strength material. This KJc dependency ultimately leads to discrepancies in calculated To values as a function of specimen type for the same material. To values obtained from C(T) specimens are expected to be higher than To values obtained from SE(B) specimens. Best estimate comparisons of several materials indicate that the average difference between C(T) and SE(B)-derived To values is approximately 10°C (2). C(T) and SE(B) To differences up to 15°C have also been recorded (3). However, comparisons of individual, small datasets may not necessarily reveal this average trend. Datasets which contain both C(T) and SE(B) specimens may generate To results which fall between the To values calculated using solely C(T) or SE(B) specimens. It is therefore strongly recommended that the specimen type be reported along with the derived To value in all reporting, analysis, and discussion of results. This recommended reporting is in addition to the requirements in 11.1.1.

1.4 Requirements are set on specimen size and the number of replicate tests that are needed to establish acceptable characterization of KJc data populations.

1.5 To is dependent on loading rate. To is evaluated for a quasi-static loading rate range with 0.1< dK/dt < 2 MPam/s. Slowly loaded specimens (dK/dt < 0.1 MPam) can be analyzed if environmental effects are known to be negligible. Provision is also made for higher loading rates (dK/dt > 2 MPam/s).

1.6 The statistical effects of specimen size on KJc in the transition range are treated using weakest-link theory (4) applied to a three-parameter Weibull distribution of fracture toughness values. A limit on KJc values, relative to the specimen size, is specified to ensure high constraint conditions along the crack front at fracture. For some materials, particularly those with low strain hardening, this limit may not be sufficient to ensure that a single-parameter (KJc) adequately describes the crack-front deformation state (5).

1.7 Statistical methods are employed to predict the transition toughness curve and specified tolerance bounds for 1T specimens of the material tested. The standard deviation of the data distribution is a function of Weibull slope and median KJc. The procedure for applying this information to the establishment of transition temperature shift determinations and the establishment of tolerance limits is prescribed.

1.8 The fracture toughness evaluation of nonuniform material is not amenable to the statistical analysis methods employed in this standard. Materials must have macroscopically uniform tensile and toughness properties. For example, multipass weldments can create heat-affected and brittle zones with localized properties that are quite different from either the bulk material or weld. Thick section steel also often exhibits some variation in properties near the surfaces. Metallography and initial screening may be necessary to verify the applicability of these and similarly graded materials. Particular notice should be given to the 2% and 98% tolerance bounds on KJc presented in 9.3. Data falling outside these bounds may indicate nonuniform material properties.

1.9 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.

Committee
E 08
DocumentType
Test Method
Pages
22
PublisherName
American Society for Testing and Materials
Status
Superseded
SupersededBy

ASTM E 399 : 2017 Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness K<inf>Ic</inf > of Metallic Materials
ASTM E 1823 : 2013 Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 636 : 2014 : EDT 1 Standard Guide for Conducting Supplemental Surveillance Tests for Nuclear Power Reactor Vessels
ASTM E 185 : 2016 Standard Practice for Design of Surveillance Programs for Light-Water Moderated Nuclear Power Reactor Vessels
ASTM E 1253 : 2013 Standard Guide for Reconstitution of Irradiated Charpy-Sized Specimens
ASTM E 2215 : 2019 Standard Practice for Evaluation of Surveillance Capsules from Light-Water Moderated Nuclear Power Reactor Vessels
ASTM E 2899 : 2015 Standard Test Method for Measurement of Initiation Toughness in Surface Cracks Under Tension and Bending

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