The ASTM standard method for the measurement of fracture toughness, E 1820 [
], covers procedures and guidelines for the determination of this material property in metallic materials using the parameters
. The fracture toughness may be measured as a point value, or as a complete fracture toughness resistance curve. In the latter option a
-based resistance curve may be obtained from a single specimen fracture test, in which the crack length is measured from compliance changes, and later verified by optical measurements. The single specimen
curve construction procedure defined in E1820 involves several steps, which go from obtaining and plotting the raw
data, to calculating an interim value of
, to finally qualifying
, a size-independent value of fracture toughness.