ASTM E561-98

Standard Practice for R-Curve Determination

SCOPE
1.1 This practice covers the determination of resistance to fracturing of metallic materials by R-curves using either the center-cracked tension panel M(T), the compact specimen C(T), or the crack-line-wedge-loaded specimen C(W), to deliver applied stress intensity factor, K, to the material. An -curve is a continuous record of toughness development in terms of KR plotted against crack extension in the material as a crack is driven under a continuously increased stress intensity factor, .  
1.2 Materials that can be tested for -curve development are not limited by strength, thickness, or toughness, so long as specimens are of sufficient size to remain predominantly elastic throughout the duration of the test.  
1.3 Specimens of standard proportions are required, but size is variable, to be adjusted for yield strength and toughness of the materials.  
1.4 Only three of the many possible specimen types that could be used to develop -curves are covered in this practice.  
1.5 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.

General Information

• Status: Historical
• Publication Date: 09-Dec-1998
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: E08 - Fatigue and Fracture
• Drafting Committee: E08.07 - Fracture Mechanics

Relations

• Replaced By: ASTM E561-05 - Standard Test Method for <bdit>K-R</bdit> Curve Determination
• Effective Date: 01-Jun-2005
• Referred By: ASTM B645-21 - Standard Practice for Linear-Elastic Plane-Strain Fracture Toughness Testing of Aluminum Alloys
• Effective Date: 10-Dec-1998
• Referred By: ASTM E1823-23 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 10-Dec-1998
• Referred By: ASTM D7779-20 - Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature
• Effective Date: 10-Dec-1998
• Referred By: ASTM B909-21a - Standard Guide for Plane Strain Fracture Toughness Testing of Non-Stress Relieved Aluminum Products
• Effective Date: 10-Dec-1998
• Referred By: ASTM E647-23a - Standard Test Method for Measurement of Fatigue Crack Growth Rates
• Effective Date: 10-Dec-1998
• Referred By: ASTM E2472-12(2018)e2 - Standard Test Method for Determination of Resistance to Stable Crack Extension under Low-Constraint Conditions
• Effective Date: 10-Dec-1998
• Referred By: ASTM B646-19 - Standard Practice for Fracture Toughness Testing of Aluminum Alloys
• Effective Date: 10-Dec-1998
• Referred By: ASTM E740/E740M-03(2016) - Standard Practice for Fracture Testing with Surface-Crack Tension Specimens
• Effective Date: 10-Dec-1998

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E561–98
Standard Practice for
1
R-Curve Determination
This standard is issued under the fixed designation E561; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 crack size, a (L)—a lineal measure of a principal
planar dimension of a crack. This measure is commonly used
1.1 This practice covers the determination of resistance to
in the calculation of quantities descriptive of the stress and
fracturing of metallic materials by R-curves using either the
displacement fields, and is often also termed crack length.
center-cracked tension panel M(T), the compact specimen
3.1.1.1 Discussion—In practice, the value of a is obtained
C(T), or the crack-line-wedge-loaded specimen C(W), to
from procedures for measurement of physical crack size, a ,
deliver applied stress intensity factor, K, to the material. An p
original crack size, a , and effective crack size, a , as appro-
o e
R-curve is a continuous record of toughness development in
priate to the situation being considered.
terms of K plotted against crack extension in the material as a
R
3.1.2 physical crack size, a (L)—the distance from a
p
crack is driven under a continuously increased stress intensity
reference position to the observed crack front. This distance
factor, K.
mayrepresentanaveragefromseveralmeasurementsalongthe
1.2 Materialsthatcanbetestedfor R-curvedevelopmentare
crack front. The reference position depends on the specimen
not limited by strength, thickness, or toughness, so long as
form, and it is normally taken to be either the boundary, or a
specimensareofsufficientsizetoremainpredominantlyelastic
plane containing either the load line or the centerline of a
throughout the duration of the test.
specimen or plate.
1.3 Specimensofstandardproportionsarerequired,butsize
3.1.3 original crack size, a (L)—the physical crack size at
o
is variable, to be adjusted for yield strength and toughness of
the start of testing.
the materials.
3.1.4 effective crack size, a (L)—the physical crack size
e
1.4 Only three of the many possible specimen types that
augmented for the effects of crack-tip plastic deformation.
could be used to develop R-curves are covered in this practice.
3.1.4.1 Discussion—Sometimes the effective crack size, a ,
e
1.5 This standard does not purport to address all of the
is calculated from a measured value of a physical crack size,
safety concerns, if any, associated with its use. It is the
a , plus a calculated value of a plastic-zone adjustment, r .A
p Y
responsibility of the user of this standard to establish appro-
preferred method for calculation of a compares compliance
priate safety and health practices and determine the applica- e
from the secant of a load-deflection trace with the elastic
bility of regulatory limitations prior to use.
compliance from a calibration of the specimen.
2. Referenced Documents
3.1.5 plastic-zone adjustment, r (L)—an addition to the
Y
physicalcracksizetoaccountforplastic,crack-tipdeformation
2.1 ASTM Standards:
effects on the linear-elastic stress field.
E399 Test Method for Plane-Strain Fracture Toughness of
2
3.1.5.1 Discussion—Commonlytheplastic-zoneadjustment
Metallic Materials
2
is given by:
E616 Terminology Relating to Fracture Testing
2
E647 Test Method for Measurement of Fatigue Crack
1 K
2
r 5 ,forplane2stressmode1,and
Growth Rates Y 2
2p
s
Y
2
3. Terminology a K
r 5 ,forplane2strainmodeI,
Y
2
2p
s
3.1 Definitions: Y
1 1
where a . ⁄3 to ⁄4 and s is the effective yield strength.
Y
In this practice, plane-stress mode 1 is assumed.
1
This practice is under the jurisdiction ofASTM Committee E-8 on Fatigue and
3.1.6 crack extension, Da (L)—an increase in crack size.
Fracture and is the direct responsibility of Subcommittee E08.07 on Linear–Elastic
3.1.6.1 Discussion—For example, Da or Da is the differ-
Fracture. p e
CurrenteditionapprovedDecember10,1998.PublishedMarch1999.Originally ence between the crack size, either a (physical crack size) or
p
published as a proposed recommended practice in 1974. Last previous edition
a (effective crack size), and a (original crack size).
e o
E561–94.
2
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

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E561
−3/2
3.1.7 stress–intensity factor, K, K,K,K (FL )—the
1 2 3
magnitude of the ideal-crack-tip stress field (a stress-field
singularity) for a particular mode in a homogeneous, linear-
elastic body.
3.1.7.1 Discussion—Values of K for modes 1, 2, and 3 are
given by:
1/2
l
...