ASTM B771-11e1

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.

General Information

• Status: Historical
• Publication Date: 30-Sep-2011
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.06 - Cemented Carbides

Relations

• Replaces: ASTM B771-11 - Standard Test Method for Short Rod Fracture Toughness of Cemented Carbides
• Effective Date: 01-Oct-2011

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
´1
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
ε NOTE—This Test Method was changed editorially in 2012.
1. Scope where:
r = distance directly forward from the crack tip to a
1.1 Thistestmethodcoversthedeterminationofthefracture
location where the significant stress σ is calculated,
y
toughness of cemented carbides (K ) by testing slotted short
IcSR
and
rod or short bar specimens.
σ = principal stress normal to the crack plane.
y
1.2 The values stated in SI units are to be regarded as
3.2 Abbreviations: fracture toughness of cemented carbide,
−3/2
standard. The values given in parentheses are for information
K ,(dimensional units FL )—the material-toughness
IcSR
only.
property measured in terms of the stress-intensity factor K by
l
the operational procedure specified in this test method.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 This test method involves the application of an opening
priate safety and health practices and determine the applica-
load to the mouth of the short rod or short bar specimen which
bility of regulatory limitations prior to use.
contains a chevron-shaped slot. Load versus displacement
across the slot at the specimen mouth is recorded autographi-
2. Referenced Documents
cally.As the load is increased, a crack initiates at the point of
2 thechevronslotandslowlyadvanceslongitudinally,tendingto
2.1 ASTM Standards:
split the specimen in half. The load goes through a smooth
E399Test Method for Linear-Elastic Plane-Strain Fracture
maximum when the width of the crack front is about one third
Toughness K of Metallic Materials
Ic
of the specimen diameter (short rod) or breadth (short bar).
Thereafter, the load decreases with further crack growth. Two
3. Terminology Definitions
unloading-reloading cycles are performed during the test to
−3/2
measure the effects of any macroscopic residual stresses in the
3.1 stress intensity factor, K,(dimensional units FL )—
l
specimen. The fracture toughness is calculated from the
the magnitude of the ideal-crack-tip stress field for mode 1 in
maximumloadinthetestandaresidualstressparameterwhich
a linear-elastic body.
is evaluated from the unloading-reloading cycles on the test
NOTE 1—Values of K for mode l are given by:
record.
@ = # 5. Significance and Use
K 5limit σ 2πr (1)
l y
5.1 The property K determined by this test method is
IcSR
r→0
believedtocharacterizetheresistanceofacementedcarbideto
fracture in a neutral environment in the presence of a sharp
crack under severe tensile constraint, such that the state of
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal stress near the crack front approaches tri-tensile plane strain,
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
and the crack-tip plastic region is small compared with the
tee B09.06 on Cemented Carbides.
cracksizeandspecimendimensionsintheconstraintdirection.
Current edition approved Oct. 1, 2011. Published February 2012. Originally
AK valueisbelievedtorepresentalowerlimitingvalueof
approved in 1987. Last previous edition approved in 2011 as B771–11. DOI:
IcSR
10.1520/B0771-11E01.
fracture toughness. This value may be used to estimate the
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
relation between failure stress and defect size when the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
conditions of high constraint described above would be ex-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. pected. Background information concerning the basis for
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B771 − 11
Standard Dimensions
Standard Dimensions
Short Rod
Short Bar
(mm) (in.)
(mm) (in.)
B = 12.700 ± 0.025 0.500 ± 0.001
B = 12.700 ± 0.025 0.500 ± 0.001
W = 19.050 ± 0.075 0.750 ± 0.003
H = 11.050 ± 0.025 0.435 ± 0.001
τ = 0.381 ± 0.025 0.015 ± 0.001
W = 19.050 ± 0.075 0.750 ± 0.003
For Curved Slot Option
τ = 0.381± 0.025 0.015 ± 0.001
a = 6.350± 0.075 0.250 ± 0.003
o
For Curved Slot Option
θ = 58.0° ± 0.5°
a = 6.350± 0.075 0.250 ± 0.003
o
R = 62.23 ± 1.27 02.45 ± 0.05
θ = 58.0° ± 0.5°
F
...