ASTM C1421-01a

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Designation: C 1421 – 01a
Standard Test Methods for
Determination of Fracture Toughness of Advanced Ceramics
1
at Ambient Temperature
This standard is issued under the fixed designation C 1421; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope K , and K , for specific conditions of environment, test rate
Isc Ivb
and temperature. The fracture toughness values, K ,K , and
Ipb Isc
1.1 These test methods cover the fracture toughness deter-
K for a material can be functions of environment, test rate
Ivb
mination of K (precracked beam test specimen), K (surface
Ipb Isc
and temperature.
crack in flexure), and K (chevron-notched beam test speci-
Ivb
1.5 These test methods are intended primarily for use with
men) of advanced ceramics at ambient temperature. The
advanced ceramics which are macroscopically homogeneous.
fracture toughness values are determined using beam test
Certain whisker- or particle-reinforced ceramics may also meet
specimens with a sharp crack. The crack is either a straight-
the macroscopic behavior assumptions.
through crack (pb), or a semi-elliptical surface crack (sc), or it
1.6 These test methods are divided into three major parts
is propagated in a chevron notch (vb).
and related sub parts as shown below. The first major part is the
NOTE 1—The terms bend(ing) and flexure are synonymous in these test
main body and provides general information on the test
methods.
methods described, the applicability to materials comparison
1.2 These test methods determine fracture toughness values
and qualification, and requirements and recommendations for
based on a force and crack length measurement (pb, sc), or a
fracture toughness testing. The second major part is composed
force measurement and an inferred crack length (vb). In
of annexes that provide procedures, test specimen design,
general, the fracture toughness is determined from maximum
precracking, testing, and data analysis for each method. Annex
force. Applied force and displacement or an alternative (for
A1 describes suggested test fixtures, Annex A2 describes the
example, time) are recorded for the pb test specimen and vb
pb method, Annex A3 describes the sc method, and Annex A4
test specimen.
describes the vb method. The third major part consists of three
1.3 These test methods are applicable to materials with
appendices detailing issues related to the fractography and
either flat or with rising R-curves. The fracture toughness
precracking used for the sc method.
measured from stable crack extension may be different than
Main Body Section
Scope 1
that measured from unstable crack extension. This difference
Referenced Documents 2
may be more pronounced for materials exhibiting a rising
Terminology (including definitions, orientation and symbols) 3
R-curve.
Summary of Test Methods 4
Significance and Use 5
NOTE 2—One difference between the procedures in these test methods
Interferences 6
and test methods such as Test Method E 399, which measure fracture
Apparatus 7
toughness, K , by one set of specific operational procedures, is that Test Test Specimen Configurations, Dimensions and Preparations 8
Ic
General Procedures 9
Method E 399 focuses on the start of crack extension from a fatigue
Report (including reporting tables) 10
precrack for metallic materials. In these test methods the test methods for
Precision and Bias 11
advanced ceramics make use of either a sharp precrack formed via bridge
Annexes
flexure (pb) or via Knoop indent (sc) prior to the test, or a crack formed
Test Fixture Geometries A1
during the test (vb). Differences in test procedure and analysis may cause
Special Requirements for Precracked Beam Method A2
the values from each test method to be different. Therefore, fracture Special Requirements for Surface Crack in Flexure Method A3
Special Requirements for Chevron Notch Flexure Method A4
toughness values determined with these methods cannot be interchanged
Appendices
with K as defined in Test Method E 399 and may not be interchangeable
Ic
Precrack Characterization, Surface Crack in Flexure Method X1
with each other.
Complications in Interpreting Surface Crack in Flexure Precracks X2
Alternative Precracking Procedure, Surface Crack in Flexure X3
1.4 These test methods give fracture toughness values, K ,
Ipb
Method
1.7 Values expressed in these test methods are in accordance
1
This test method is under the jurisdiction of ASTM Committee C28 on
with the International System of Units (SI) and Practice E 380.
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on
Properties and Performance. 1.8 This st
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