1. Scope
1.1 This test method covers the determination of fracture toughness
(KIc and optionally KIsi) of metallic
materials under predominantly linear-elastic, plane-strain conditions using
fatigue precracked specimens having a thickness of 1.6 mm (0.063 in.) or
greater2 subjected to
slowly, or in special (elective) cases rapidly, increasing crack-displacement
force. Details of test apparatus, specimen configuration, and experimental
procedure are given in the annexes. Two procedures are outlined for using the
experimental data to calculate fracture toughness values:
1.1.1 The KIc test procedure is described in the
main body of this test standard and is a mandatory part of the testing and
results reporting procedure for this test method. The KIc
test procedure is based on crack growth of up to 2 % percent of the specimen
width. This can lead to a specimen size dependent rising fracture toughness
resistance curve, with larger specimens producing higher fracture toughness
results.
1.1.2 The KIsi test procedure is
described in Appendix X1 and is an optional part of this test method. The
KIsi test procedure is based on a fixed
amount of crack extension of 0.5 mm, and as a result, KIsi
is less sensitive to specimen size than KIc.
This less size-sensitive fracture toughness, KIsi, is called size-insensitive throughout this test method.
Appendix X1
contains an optional procedure for reinterpreting the force-displacement
test record recorded as part of this test method to calculate the additional
fracture toughness value, KIsi.
NOTE 1— Plane-strain fracture toughness tests of materials thinner than 1.6 mm (0.063 in.) that are sufficiently brittle (see 7.1) can be made using other types of specimens (1).3 There is no standard test method for such thin materials.