1.1 This test method covers the determination of fracture toughness as characterized by the -integral. Three toughness properties are identified which vary with the amount of crack extension present at test termination:( ) instability without significant prior crack extension ( ); ( ) onset of stable crack extension ( JI ); ( ) stable crack growth resistance curve ( J-R ). A fourth quantity ( ) not currently interpretable as a toughness property may be measured at fracture instability following stable crack extension. The method applies specifically to geometries that contain notches and flaws that are sharpened with fatigue cracks. The recommended specimens are generally bend-type specimens that contain deep initial cracks. The loading rate is slow and environmentally assisted cracking is assumed to be negligible.

1.1.1 The recommended specimens are the pin-loaded compact (C(T)), the single, edge bend (SE(B)), and the pin- loaded disk-shaped compact (DC(T)) specimen. All specimens have in-plane dimensions of constant proportionality for all sizes.

1.1.2 Specimen dimensions are functions of the ratio of -integral to the material effective yield strength, thus the specimen design details must be based on known or estimates mechanical properties.

1.1.3 The objective of this test method is to set forth a method and to specify limitations for testing prescribed bend-type specimens that will result in -integral fracture toughness values of materials that will be geometry insensitive.

1.1.4 The single specimen elastic compliance method is detailed herein, but other techniques for measuring crack length are permissible if they equal or exceed the accuracy requirements of this test method. For example, a dc electric potential method is described in Annex A5.

1.1.5 A multiple specimen technique for JI measurement requiring five or more identically prepared specimens tested to different crack extensions and displacements is presented in Annex A4.

1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.3 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.