ASTM E561-98

1.1 This practice covers the determination of resistance to fracturing of metallic materials by R-curves using either the center-cracked tension panel M(T), the compact specimen C(T), or the crack-line-wedge-loaded specimen C(W), to deliver applied stress intensity factor, K, to the material. An -curve is a continuous record of toughness development in terms of KR plotted against crack extension in the material as a crack is driven under a continuously increased stress intensity factor, .

1.2 Materials that can be tested for -curve development are not limited by strength, thickness, or toughness, so long as specimens are of sufficient size to remain predominantly elastic throughout the duration of the test.

1.3 Specimens of standard proportions are required, but size is variable, to be adjusted for yield strength and toughness of the materials.

1.4 Only three of the many possible specimen types that could be used to develop -curves are covered in this practice.

1.5 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.