ASTM C1421-18
(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.
1.6 Values expressed in these test methods are in accordance with the International System of Units (SI) and 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1421 − 18
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
Main Body Section
Scope 1
1.1 These test methods cover the fracture toughness, K ,
Ic Referenced Documents 2
determination of advanced ceramics at ambient temperature. Terminology (including definitions, orientation and symbols) 3
Summary of Test Methods 4
The methods determine K (precracked beam test specimen),
Ipb
Significance and Use 5
K (surfacecrackinflexure),and K (chevron-notchedbeam
Isc Ivb Interferences 6
test specimen). The fracture toughness values are determined Apparatus 7
Test Specimen Configurations, Dimensions and Preparations 8
using beam test specimens with a sharp crack. The crack is
General Procedures 9
either a straight-through crack formed via bridge flexure (pb),
Report (including reporting tables) 10
Precision and Bias 11
orasemi-ellipticalsurfacecrackformedviaKnoopindentation
Keywords 12
(sc), or it is formed and propagated in a chevron notch (vb), as
Annexes
shown in Fig. 1.
Test Fixture Geometries Annex A1
Procedures and Special Requirements for Precracked Beam Annex A2
NOTE 1—The terms bend(ing) and flexure are synonymous in these test
Method
methods.
Procedures and Special Requirements for Surface Crack in Annex A3
Flexure Method
1.2 These test methods are applicable to materials with
Procedures and Special Requirements for Chevron Notch Annex A4
eitherflatorwithrisingR-curves.Differencesintestprocedure
Flexure Method
Appendixes
and analysis may cause the values from each test method to be
Precrack Characterization, Surface Crack in Flexure Method Appendix X1
different. For many materials, such as the silicon nitride
Complications in Interpreting Surface Crack in Flexure Appendix X2
Standard Reference Material 2100, the three methods give
Precracks
Alternative Precracking Procedure, Surface Crack in Flexure Appendix X3
identical results at room temperature in ambient air.
Method
1.3 The fracture toughness values for a material can be Chamfer Correction Factors, Surface Crack in Flexure Appendix X4
Method Only
functionsofenvironment,testrate,andtemperature.Thesetest
Crack Orientation Appendix X5
methods give fracture toughness values for specific conditions
1.6 Valuesexpressedinthesetestmethodsareinaccordance
of environment, test rate, and temperature.
with the International System of Units (SI) and IEEE/ASTM
1.4 These test methods are intended primarily for use with
SI10.
advanced ceramics that are macroscopically homogeneous and
1.7 The values stated in SI units are to be regarded as
microstructurally dense. Certain whisker- or particle-
standard. No other units of measurement are included in this
reinforced ceramics may also meet the macroscopic behavior
standard.
assumptions. Single crystals may also be tested.
1.8 This standard does not purport to address all of the
1.5 This standard begins with a main body that provides
safety concerns, if any, associated with its use. It is the
information on fracture toughness testing in general. It is
responsibility of the user of this standard to establish appro-
followed by annexes and appendixes with specific information
priate safety, health, and environmental practices and deter-
for the particular test methods.
mine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accor-
1
dance with internationally recognized principles on standard-
These test methods are under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on
ization established in the Decision on Principles for the
Mechanical Properties and Performance.
Development of International Standards, Guides and Recom-
Current edition approved Jan. 1, 2018. Published January 2018. Originally
mendations issued by the World Trade Organization Technical
approved in 1999. Last previous edition approved in 2016 as C1421–16. DOI:
10.1520/C1421-18. Barriers to Trade (TBT) Committee.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
1
---------------------- Page: 1 ----------------------
C1421 − 18
NOTE 1—The figures on the right show the test specimen cross sections and crack types. Four-point loading may be u
...
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 − 16 C1421 − 18
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 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 appendicesappendixes 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 Precracked Beam Annex A2
Method
Procedures and Special Requirements for Surface Crack in Annex A3
Flexure Method
Procedures and Special Requirements for Surface Crack in Annex A3
Flexure Method
Procedures and Special Requirements for Chevron Notch Annex A4
Flexure Method
1
ThisThese test method ismethods are under the jurisdiction of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01
on Mechanical Properties and Performance.
Current edition approved Jan. 1, 2016Jan. 1, 2018. Published March 2016January 2018. Originally approved in 1999. Last previous edition approved in 20152016 as
C1421 – 15.C1421 – 16. DOI: 10.1520/C1421-16.10.1520/C1421-18.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
C1421 − 18
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
Procedures and Special Requirements for Chevron Notch Annex A4
Flexure Method
Appendices
Appendixes
Precrack Characterization, Surface Crack in Flexure Method Appendix X1
Complications in Interpreting Surface Crack in Flexure Appendix X2
Precracks
Complications in Interpreting Surface Crack in Flexure Appendix X2
Precracks
Alternative Precracking Procedure, Surface Crack in Flexure Appendix X3
Method
Alternative Precracking Procedure, Surface Crack in Flexure Appendix X3
Method
Chamfer Correction Factors, Surface Crack in Flexure Appendix X4
Method Only
Chamfer Correction Factors, Surface Crack in Flexure Appendix X4
Method Only
Crack Orientation Appendix X5
Crack Orientation Appendix
...
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