Ceramics Division Characterization of Fracture Origins

$characterization of fracture$

Origin Size

The third attribute of a fracture origin is its size.

According to C 1322, the origin size need not be measured precisely. This characterization is intended to describe the general nature of the origins (e.g. a 20 µm pore versus a 1 µm pore).

A fully-quantitative size characterization is recommended for some applications (e.g. fracture mechanics analysis, design, or nondestructive evaluation). See C 1322 section 7.2.4.

Origin size measurement is highly recommended as a means to ensure that the correct features have been identified as the fracture origin. For example, if the fracture origins are 20 µm pores, but fracture mechanics estimates suggest the flaws should be 200 µm in size, then the fractographic interpretation should be reconsidered.

If the origin is in the volume:

for an equiaxed origin, measure the approximate diameter.
for an elongated origin, measure the approximate minor (2a) and major axis (2c) lengths.

If the origin is at the surface:

measure the origin depth (a) and the width (2c).

If fracture mechanics data are available for the particular material, the size of the fracture origin or the stress at fracture may be estimated:

From the material's fracture toughness or fracture surface energy
From the fracture mirror size
From the number of fragments or crack branches

See C 1322 for further details, or:

G. D. Quinn and J. J. Swab, "Fractography and Estimates of Fracture Origin Size from Fracture Mechanics," Ceram. Eng. and Sci. Proc., 17 [3] (1996) pp. 51 -58.

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Date created: 08 February 2001
Last updated: 30 June 2008

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