ASTM C1421-16
Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature

Standard No.

ASTM C1421-16

Release Date

2016

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM C1421-18

Latest

ASTM C1421-18

Scope

5.1 Fracture toughness, K_Ic, 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 K_Isc will differ from K_Ipb and K_Ivb. Table 1 tabulates advantages, disadvantages, and applicability of each method.

1.1 These test methods cover the fracture toughness, K_Ic, determination of advanced ceramics at ambient temperature. The methods determine K_Ipb (precracked beam test specimen), K_Isc (surface crack in flexure), and K_Ivb (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.

ASTM C1421-16 Referenced Document

• ASTM C1161 Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
• ASTM C1322 Standard Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics
• ASTM E112 Standard Test Methods for Determining Average Grain Size
• ASTM E177 Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• ASTM E1823 Standard Terminology Relating to Fatigue and Fracture Testing
• ASTM E337 Standard Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
• ASTM E4 Standard Practices for Force Verification of Testing Machines
• ASTM E691 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E740 Standard Practice for Fracture Testing with Surface-Crack Tension Specimens
• IEEE/ASTM SI 10 American National Standard for Metric Practice

ASTM C1421-16 history

• 2018 ASTM C1421-18 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2016 ASTM C1421-16 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2015 ASTM C1421-15 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2010 ASTM C1421-10 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2009 ASTM C1421-09 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2001 ASTM C1421-01b(2007) Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2001 ASTM C1421-01b Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
• 2001 ASTM C1421-01a Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperatures
• 2001 ASTM C1421-99 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperatures