1.1 This test method covers the determination of JIc , which can be used as an engineering estimate of fracture toughness near the initiation of slow stable crack growth for metallic materials. It applies specifically to geometries that contain notches and flaws and that are sharpened with fatigue cracks. The recommended specimens are generally bend type that contain deep initial cracks. The loading rate is slow and environmentally assisted cracking is assumed to be negligible.

1.1.1 The recommended three-point bend specimen [ SE ( )] is a single edge-cracked beam having an initial normalized crack length, ao/W , of 0.5 to 0.75. Overall span-to-width ratio, S/W is set at 4.

1.1.2 The recommended compact specimen is the standard compact specimen [ ( )] that is pin-loaded in tension. The specimen configuration has fixed planar dimensional proportionality with an initial normalized crack length, ao/W of 0.5 to 0.75.

1.1.3 Specimen dimension requirements are based upon the ratio of J-integral to material effective yield strength. Therefore, in specimen design, it is helpful to have a general idea of the expected results in advance.

1.1.4 Specimen configurations other than those recommended in this test method may involve different validity requirements than those presently specified in this method.

1.2 Values stated in SI units are to be regarded as the standard. Inch-pound values are given in parentheses for information only.

1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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.