ASTM C1421-15
(Test Method)Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
SIGNIFICANCE AND USE
5.1 Fracture toughness, KIc, is a measure of the resistance to crack extension in a brittle material. These test methods may be used for material development, material comparison, quality assessment, and characterization.
5.2 The pb and the vb fracture toughness values provide information on the fracture resistance of advanced ceramics containing large sharp cracks, while the sc fracture toughness value provides this information for small cracks comparable in size to natural fracture sources. Cracks of different sizes may be used for the sc method. If the fracture toughness values vary as a function of the crack size it can be expected that KIsc will differ from KIpb and KIvb. Table 1 tabulates advantages, disadvantages, and applicability of each method.
SCOPE
1.1 These test methods cover the fracture toughness, KIc, determination of advanced ceramics at ambient temperature. The methods determine KIpb (precracked beam test specimen), KIsc (surface crack in flexure), and KIvb (chevron-notched beam test specimen). The fracture toughness values are determined using beam test specimens with a sharp crack. The crack is either a straight-through crack formed via bridge flexure (pb), or a semi-elliptical surface crack formed via Knoop indentation (sc), or it is formed and propagated in a chevron notch (vb), as shown in Fig. 1.
Note 1: The figures on the right show the test specimen cross sections and crack types. Four-point loading may be used with all three methods. Three-point may be used with the pb and vb specimens.
Note 1: The terms bend(ing) and flexure are synonymous in these test methods.
1.2 These test methods are applicable to materials with either flat or with rising R-curves. Differences in test procedure and analysis may cause the values from each test method to be different. For many materials, such as the silicon nitride Standard Reference Material 2100, the three methods give identical results at room temperature in ambient air.
1.3 The fracture toughness values for a material can be functions of environment, test rate and temperature. These test methods give fracture toughness values for specific conditions of environment, test rate and temperature.
1.4 These test methods are intended primarily for use with advanced ceramics that are macroscopically homogeneous and microstructurally dense. Certain whisker- or particle-reinforced ceramics may also meet the macroscopic behavior assumptions. Single crystals may also be tested.
1.5 This standard begins with a main body that provides information on fracture toughness testing in general. It is followed by annexes and appendices with specific information for the particular test methods.
Main Body
Section
Scope
1
Referenced Documents
2
Terminology (including definitions, orientation and symbols)
3
Summary of Test Methods
4
Significance and Use
5
Interferences
6
Apparatus
7
Test Specimen Configurations, Dimensions and Preparations
8
General Procedures
9
Report (including reporting tables)
10
Precision and Bias
11
Keywords
12
Summary of Changes
Annexes
Test Fixture Geometries
Annex A1
Procedures and Special Requirements for Precracked Beam Method
Annex A2
Procedures and Special Requirements for Surface Crack in Flexure Method
Annex A3
Procedures and Special Requirements for Chevron Notch Flexure Method
Annex A4
Appendices
Precrack Characterization, Surface Crack in Flexure Method
Appendix X1
Complications in Interpreting Surface Crack in Flexure Precracks
Appendix X2
Alternative Precracking Procedure, Surface Crack in Flexure Method
Appendix X3
Chamfer Correction Factors, Surface Crack in Flexure Method Only
Appendix X4
Crack Orientation
Appendix X5
1.6 Values expressed in these test methods are in accordance with the...
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Designation: C1421 − 15
StandardTest Methods for
Determination of Fracture Toughness of Advanced Ceramics
1
at Ambient Temperature
This standard is issued under the fixed designation C1421; 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 1.5 This standard begins with a main body that provides
information on fracture toughness testing in general. It is
1.1 These test methods cover the fracture toughness, K ,
Ic
followed by annexes and appendices with specific information
determination of advanced ceramics at ambient temperature.
for the particular test methods.
The methods determine K (precracked beam test specimen),
Ipb
Main Body Section
K (surfacecrackinflexure),and K (chevron-notchedbeam
Isc Ivb
Scope 1
test specimen). The fracture toughness values are determined
Referenced Documents 2
using beam test specimens with a sharp crack. The crack is
Terminology (including definitions, orientation and symbols) 3
Summary of Test Methods 4
either a straight-through crack formed via bridge flexure (pb),
Significance and Use 5
orasemi-ellipticalsurfacecrackformedviaKnoopindentation
Interferences 6
(sc), or it is formed and propagated in a chevron notch (vb), as
Apparatus 7
Test Specimen Configurations, Dimensions and Preparations 8
shown in Fig. 1.
General Procedures 9
Report (including reporting tables) 10
NOTE 1—The terms bend(ing) and flexure are synonymous in these test
Precision and Bias 11
methods.
Keywords 12
1.2 These test methods are applicable to materials with Summary of Changes
Annexes
eitherflatorwithrisingR-curves.Differencesintestprocedure
Test Fixture Geometries Annex A1
and analysis may cause the values from each test method to be
Procedures and Special Requirements for Precracked Beam Annex A2
Method
different. For many materials, such as the silicon nitride
Procedures and Special Requirements for Surface Crack in Annex A3
Standard Reference Material 2100, the three methods give
Flexure Method
identical results at room temperature in ambient air.
Procedures and Special Requirements for Chevron Notch Flexure Annex A4
Method
1.3 The fracture toughness values for a material can be
Appendices
functions of environment, test rate and temperature. These test
Precrack Characterization, Surface Crack in Flexure Method Appendix
X1
methods give fracture toughness values for specific conditions
Complications in Interpreting Surface Crack in Flexure Precracks Appendix
of environment, test rate and temperature.
X2
Alternative Precracking Procedure, Surface Crack in Flexure Appendix
1.4 These test methods are intended primarily for use with
Method X3
advanced ceramics that are macroscopically homogeneous and
Chamfer Correction Factors, Surface Crack in Flexure Method Only Appendix
X4
microstructurally dense. Certain whisker- or particle-
Crack Orientation Appendix
reinforced ceramics may also meet the macroscopic behavior
X5
assumptions. Single crystals may also be tested.
1.6 Valuesexpressedinthesetestmethodsareinaccordance
with the International System of Units (SI) and Practice
1 IEEE/ASTM SI10.
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 .
1.7 The values stated in SI units are to be regarded as
Current edition approved July 1, 2015. Published September 2015. Originally
standard. No other units of measurement are included in this
approved in 1999. Last previous edition approved in 2010 as C1421–10. DOI:
10.1520/C1421-15. standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
C1421 − 15
NOTE 1—The figures on the right show the test specimen cross sections and crack types. Four-point loading may be used with all three methods.
Three-point may be used with the pb and vb specimens.
FIG. 1 The Three Test Methods
1.8 This standard does not purport to address all of the 3.1.4 slow crack growth (SCG)—sub critical crack growth
safety concerns, if any, associated with its use. It is the (extension)whichmayresultfrom,butisnotrestrictedto,such
responsibility of the user of this standard to establish appro- mechanisms as environmentally-assisted stress corrosion or
priate safety and health practices and determine the applica- diffusive crack growth.
bility of regulatory limitations prior to use.
-3/2
3.1.5 stress-intensity factor, K [FL ]—the magnitude of
the ideal-crack-tip stress field (stress field singularity) for a
2. Referenced Documents
particular mode in a homogeneous, linear-elastic bod
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM 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: C1421 − 10 C1421 − 15
Standard Test Methods for
Determination of Fracture Toughness of Advanced Ceramics
1
at Ambient Temperature
This standard is issued under the fixed designation C1421; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number 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 These test methods cover the fracture toughness, K , determination of advanced ceramics at ambient temperature. The
Ic
methods determine K (precracked beam test specimen), K (surface crack in flexure), and K (chevron-notched beam test
Ipb Isc Ivb
specimen). The fracture toughness values are determined using beam test specimens with a sharp crack. The crack is either a
straight-through crack formed via bridge flexure (pb), or a semi-elliptical surface crack formed via Knoop indentation (sc), or it
is formed and propagated in a chevron notch (vb), as shown in Fig. 1.
NOTE 1—The terms bend(ing) and flexure are synonymous in these test methods.
1.2 These test methods are applicable to materials with either flat or with rising R-curves. Differences in test procedure and
analysis may cause the values from each test method to be different. For many materials, such as the silicon nitride Standard
Reference Material 2100, the three methods give identical results at room temperature in ambient air.
1.3 The fracture toughness values for a material can be functions of environment, test rate and temperature. These test methods
give fracture toughness values for specific conditions of environment, test rate and temperature.
1.4 These test methods are intended primarily for use with advanced ceramics whichthat are macroscopically homogeneous.
homogeneous and microstructurally dense. Certain whisker- or particle-reinforced ceramics may also meet the macroscopic
behavior assumptions. Single crystals may also be tested.
1.5 This standard begins with a main body that provides information on fracture toughness testing in general. It is followed by
annexes and appendices with specific information for the particular test methods.
Main Body Section
Scope 1
Referenced Documents 2
Terminology (including definitions, orientation and symbols) 3
Summary of Test Methods 4
Significance and Use 5
Interferences 6
Apparatus 7
Test Specimen Configurations, Dimensions and Preparations 8
General Procedures 9
Report (including reporting tables) 10
Precision and Bias 11
Keywords 12
Summary of Changes
Annexes
Test Fixture Geometries Annex A1
Procedures and Special Requirements for Precracked Beam Annex A2
Method
Procedures and Special Requirements for Surface Crack in Annex A3
Flexure Method
Procedures and Special Requirements for Chevron Notch Flexure Annex A4
Method
Appendices
Precrack Characterization, Surface Crack in Flexure Method Appendix
X1
Complications in Interpreting Surface Crack in Flexure Precracks Appendix
X2
1
This test method is under the jurisdiction of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 .
Current edition approved Dec. 1, 2010July 1, 2015. Published January 2011September 2015. Originally approved in 1999. Last previous edition approved in 20092010
as C1421 – 09.C1421 – 10. DOI: 10.1520/C1421-10.10.1520/C1421-15.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
C1421 − 15
NOTE 1—The figures on the right show the test specimen cross sections and crack types. Four-point loading may be used with all three methods.
Three-point may be used with the pb and vb specimens.
FIG. 1 The Three Test Methods
Alternative Precracking Procedure, Surface Crack in Flexure Appendix
Method X3
Chamfer Correction Factors, Surface Crack in Flexure Method Only Appendix
X4
Crack Orientation Appendix
X5
1.6 Values expressed in these test methods are in accordance with the International System of Units (SI) and Practice
IEEE/ASTM SI 10.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 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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