ASTM B771-11
(Test Method)Standard Test Method for Short Rod Fracture Toughness of Cemented Carbides
Standard Test Method for Short Rod Fracture Toughness of Cemented Carbides
SIGNIFICANCE AND USE
The property KIcSR determined by this test method is believed to characterize the resistance of a cemented carbide to fracture in a neutral environment in the presence of a sharp crack under severe tensile constraint, such that the state of stress near the crack front approaches tri-tensile plane strain, and the crack-tip plastic region is small compared with the crack size and specimen dimensions in the constraint direction. A KIcSR value is believed to represent a lower limiting value of fracture toughness. This value may be used to estimate the relation between failure stress and defect size when the conditions of high constraint described above would be expected. Background information concerning the basis for development of this test method in terms of linear elastic fracture mechanics may be found in Refs (1-4).
This test method can serve the following purposes:
To establish, in quantitative terms significant to service performance, the effects of fabrication variables on the fracture toughness of new or existing materials, and
To establish the suitability of a material for a specific application for which the stress conditions are prescribed and for which maximum flaw sizes can be established with confidence.
SCOPE
1.1 This test method covers the determination of the fracture toughness of cemented carbides (KIcSR) by testing slotted short rod or short bar specimens.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 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.
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Designation: B771 – 11
Standard Test Method for
1
Short Rod Fracture Toughness of Cemented Carbides
This standard is issued under the fixed designation B771; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 Thistestmethodcoversthedeterminationofthefracture 4.1 This test method involves the application of an opening
toughness of cemented carbides (K ) by testing slotted short load to the mouth of the short rod or short bar specimen which
IcSR
rod or short bar specimens. contains a chevron-shaped slot. Load versus displacement
1.2 The values stated in SI units are to be regarded as across the slot at the specimen mouth is recorded autographi-
standard. The values given in parentheses are for information cally.As the load is increased, a crack initiates at the point of
only. thechevronslotandslowlyadvanceslongitudinally,tendingto
1.3 This standard does not purport to address all of the split the specimen in half. The load goes through a smooth
safety concerns, if any, associated with its use. It is the maximum when the width of the crack front is about one third
responsibility of the user of this standard to establish appro- of the specimen diameter (short rod) or breadth (short bar).
priate safety and health practices and determine the applica- Thereafter, the load decreases with further crack growth. Two
bility of regulatory limitations prior to use. unloading-reloading cycles are performed during the test to
measure the effects of any macroscopic residual stresses in the
2. Referenced Documents
specimen. The fracture toughness is calculated from the
2
2.1 ASTM Standards:
maximumloadinthetestandaresidualstressparameterwhich
E399 Test Method for Linear-Elastic Plane-Strain Fracture is evaluated from the unloading-reloading cycles on the test
Toughness K of Metallic Materials
record.
Ic
3. Terminology Definitions 5. Significance and Use
−3/2
3.1 stress intensity factor, K,(dimensional units FL )—
5.1 The property K determined by this test method is
l
IcSR
the magnitude of the ideal-crack-tip stress field for mode 1 in believedtocharacterizetheresistanceofacementedcarbideto
a linear-elastic body.
fracture in a neutral environment in the presence of a sharp
crack under severe tensile constraint, such that the state of
NOTE 1—Values of K for mode l are given by:
stress near the crack front approaches tri-tensile plane strain,
K 5limit [s 2pr#
=
l y
and the crack-tip plastic region is small compared with the
r→0 (1)
cracksizeandspecimendimensionsintheconstraintdirection.
AK value is believed to represent a lower limiting value of
IcSR
where:
fracture toughness. This value may be used to estimate the
r = distance directly forward from the crack tip to a
relation between failure stress and defect size when the
location where the significant stress s is calculated,
y
conditions of high constraint described above would be ex-
and
pected. Background information concerning the basis for
s = principal stress normal to the crack plane.
y
development of this test method in terms of linear elastic
3.2 Abbreviations:fracture toughness of cemented carbide,
3
−3/2
fracture mechanics may be found in Refs (1-4).
K ,(dimensional units FL )—the material-toughness
IcSR
5.2 This test method can serve the following purposes:
property measured in terms of the stress-intensity factor K by
l
5.2.1 To establish, in quantitative terms significant to ser-
the operational procedure specified in this test method.
vice performance, the effects of fabrication variables on the
fracture toughness of new or existing materials, and
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
5.2.2 To establish the suitability of a material for a specific
Powders and Metal Powder Products and is the direct responsibility of Subcom-
application for which the stress conditions are prescribed and
mittee B09.06 on Cemented Carbides.
Current edition approved Oct. 1, 2011. Published October 2011. Originally for which maximum flaw sizes can be established with
approved in 1987. Last previous edition approved in 2006 as B771–87 (2006).
confidence.
DOI: 10.1520/B0771-11.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the ASTM website. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United State
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:B771–87(Reapproved2006) Designation: B771 – 11
Standard Test Method for
1
Short Rod Fracture Toughness of Cemented Carbides
This standard is issued under the fixed designation B771; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Thistestmethodcoversthedeterminationofthefracturetoughnessofcementedcarbides(K )bytestingslottedshortrod
IcSR
or short bar specimens.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.3 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
2
2.1 ASTM Standards:
E399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness K of Metallic Materials
Ic
3. Terminology Definitions
−3/2
3.1 stress intensity factor, K,(dimensional units FL )—the magnitude of the ideal-crack-tip stress field for mode 1 in a
l
linear-elastic body.
NOTE 1—Values of K for mode l are given by:
K 5limit [s =2pr #
l y
r→0
(1)
where:
r = distance directly forward from the crack tip to a location where the significant stress s is calculated, and
y
s = principal stress normal to the crack plane.
y
−3/2
3.2 Abbreviations:fracture toughness of cemented carbide, K ,(dimensional units FL )—the material-toughness property
IcSR
measured in terms of the stress-intensity factor K by the operational procedure specified in this test method.
l
4. Summary of Test Method
4.1 This test method involves the application of an opening load to the mouth of the short rod or short bar specimen which
contains a chevron-shaped slot. Load versus displacement across the slot at the specimen mouth is recorded autographically. As
the load is increased, a crack initiates at the point of the chevron slot and slowly advances longitudinally, tending to split the
specimen in half.The load goes through a smooth maximum when the width of the crack front is about one third of the specimen
diameter (short rod) or breadth (short bar). Thereafter, the load decreases with further crack growth. Two unloading-reloading
cycles are performed during the test to measure the effects of any macroscopic residual stresses in the specimen. The fracture
toughness is calculated from the maximum load in the test and a residual stress parameter which is evaluated from the
unloading-reloading cycles on the test record.
5. Significance and Use
5.1 ThepropertyK determinedbythistestmethodisbelievedtocharacterizetheresistanceofacementedcarbidetofracture
IcSR
inaneutralenvironmentinthepresenceofasharpcrackunderseveretensileconstraint,suchthatthestateofstressnearthecrack
front approaches tri-tensile plane strain, and the crack-tip plastic region is small compared with the crack size and specimen
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee
B09.06 on Cemented Carbides.
Current edition approved AprilOct. 1, 2006.2011. Published April 2006.October 2011. Originally approved in 1987. Last previous edition approved in 20012006 as
B771–87 (2001).(2006). DOI: 10.1520/B0771-87R06.10.1520/B0771-11.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
B771 – 11
dimensions in the constraint direction. A K value is believed to represent a lower limiting value of fracture toughness. This
IcSR
value may be used to estimate the relation between failure stress and defect size when the conditions of high constraint described
above would be expected. Background information concerning the basis for development of this test method in terms of linear
3
elastic fracture mechanics may be found in Refs (1-4).
5.2 This test method can serve the following purposes:
5.2.1 To establish, in quantitative terms significant to ser
...
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