【国外标准】 Standard Practice for Determination of Quasistatic Fracture Toughness of Welds

5.1 This test practice provides a recommended procedure for preparing fracture toughness specimens from welds to improve the likelihood of obtaining useful fracture toughness values.5.1.1 The subsequent fracture toughness values, that have significance and use as stated in the applicable ASTM test method, may allow for flaw tolerance assessments of welded structures. Flaw tolerance assessments require an understanding and compensation for the differences that may exist between laboratory test results and field conditions.5.1.2 The shallow-notched specimen testing procedures described in Annex E of ISO 15653 may be used by agreement between the parties involved as long as it is understood that Annex E is “Informative” and the result is a geometry dependent measurement of toughness that is not validated by the applicable test standard.1.1 This practice provides methods for preparing specimens from welds in metallic materials and interpreting subsequent test results when used in conjunction with standards Test Methods E1290 and E1820 for the determination of fracture toughness. The fatigue pre-cracking procedures included in this practice may also be used to aid in preparing straight pre-cracks for weld specimens in accordance with Test Method E1681.1.2 This practice draws heavily from ISO 15653: Metallic materials – Method of test for the determination of quasistatic fracture toughness of welds. All references to ISO 12135 in that test method should be replaced with the applicable ASTM Test Methods (E1820, E1290 or E1681).1.3 The recommended specimen is a single-edge bend [SE(B)] with width, W, equal to twice the specimen thickness, B. An alternate SE(B) specimen with W/B equal to one and a span, S, to W ratio of 4 may be used but may produce different toughness values. A compact tension [C(T)] specimen may be used if it can be demonstrated that the analysis of results properly accounts for weld-to-base metal strength mismatch effects on fracture toughness.1.4 The recommended limitation on weld-to-base metal yield strength ratio isUndermatching within this limitation leads to conservative estimates of fracture toughness, while overmatching may lead to an overestimation of the fracture toughness by up to 10%.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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.