ASTM C1421-01b

    Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature

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    1. Scope

    1.1 These test methods cover the fracture toughness determination of KIpb (precracked beam specimen), KIsc (surface crack in flexure), and KIvb (chevron-notched beam specimen) of advanced ceramics at ambient temperature. The fracture toughness values are determined using beam test specimens with a sharp crack. The crack is either a straight-through crack (pb), or a semi-elliptical surface crack (sc), or it is propagated in a chevron notch (vb).

    Note 1—The terms bend(ing) and flexure are synonymous in these test methods.

    1.2 These test methods determine fracture toughness values based on a force and crack length measurement (pb,sc), or a force measurement and an inferred crack length (vb). In general, the fracture toughness is determined from maximum force. Applied force and displacement or an alternative (for example, time) are recorded for the pb specimen and vb specimen.

    1.3 These test methods are applicable to materials with either flat or with rising R-curves. The fracture toughness measured from stable crack extension may be different than that measured from unstable crack extension. This difference may be more pronounced for materials exhibiting a rising R-curve.

    Note 2—One difference between the procedures in these test methods and test methods such as Test Method E 399, which measure fracture toughness, KIc, by one set of specific operational procedures, is that Test Method E 399 focuses on the start of the crack extension from a fatigue precrack for metallic materials. In these test methods the test methods for advanced ceramics make use of either a sharp precrack formed via bridge loading (pb) or via Knoop indent (sc) prior to the test, or a crack formed during the test (vb). Differences in test procedure and analysis may cause the values from each test method to be different. Therefore, fracture toughness values determined with these methods cannot be interchanged with KIc as defined in Test Method E 399 and may not be interchangeable with each other.

    1.4 These test methods give fracture toughness values, KIpb, KIsc, KIvb, for specific conditions of environment, test rate and temperature. The fracture toughness values, KIpb, KIsc, and KIvb for a material can be functions of environment, test rate and temperature.

    1.5 These test methods are intended primarily for use with advanced ceramics which are macroscopically homogeneous. Certain whisker- or particle-reinforced ceramics may also meet the macroscopic behavior assumptions.

    1.6 These test methods are divided into three major parts and related sub parts as shown below. The first major part is the main body and provides general information on the test methods described, the applicability to materials comparison and qualification, and requirements and recommendations for fracture toughness testing. The second major part is composed of annexes that provide procedures, test specimen design, precracking, testing, and data analysis for each method. Annex A1 describes suggested test fixtures, Annex A2 describes the pb method, Annex A3 describes the sc method, and Annex A4 describes the vb method. The third major part consists of three appendices detailing issues related to the fractography and precracking used for the sc method.

    Main BodySection
    Referenced Documents2
    Terminology (including definitions, orientation and symbols)3
    Summary of Test Methods4
    Significance and Use5
    Test Specimen Configurations, Dimensions and Preparations8
    General Procedures9
    Report (including reporting tables)10
    Precision and Bias11
    Test Fixture GeometriesA1
    Special Requirements for Precracked Beam MethodA2
    Special Requirements for Surface Crack in Flexure MethodA3
    Special Requirements for Chevron Notch Flexure MethodA4
    Precrack Characterization, Surface Crack in Flexure MethodX1
    Complications in Interpreting Surface Crack in Flexure Precracks X2
    Alternative Precracking Procedure, Surface Crack in Flexure MethodX3

    1.7 Values expressed in these test methods are in accordance with the International System of Units (SI) and Practice E 380.

    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.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    C1161 Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature

    C1322 Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics

    E4 Practices for Force Verification of Testing Machines

    E112 Test Methods for Determining Average Grain Size

    E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

    E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

    E740/E740M Practice for Fracture Testing with Surface-Crack Tension Specimens

    E1823 Terminology Relating to Fatigue and Fracture Testing

    Reference Material

    NIST SRM 2100 Fracture Toughness of Ceramics Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070,

    ICS Code

    ICS Number Code 81.060.30 (Advanced ceramics)

    UNSPSC Code

    UNSPSC Code

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/C1421-01B

    Citation Format

    ASTM C1421-01b, Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature, ASTM International, West Conshohocken, PA, 2001,

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