【国外标准】 Standard Test Method for Determination of Crack-Tip-Opening Angle of Ferritic Steels Using DWTT-Type Specimens

1.1 This test method covers the determination of fracture propagation toughness in terms of the steady-state crack-tip-opening angle (CTOA) using the drop-weight tear test (DWTT)-type specimen. The method is applicable to ferritic steels that exhibit predominantly ductile fracture with at least 85 % shear area measured according to Test Method E436 - Standard Test Method for Drop-Weight Tear Tests of Ferritic Steels. This test method applies to ferritic steels with thicknesses between 6 mm and 20 mm. Annex A1 describes the method to test ferritic steels with thicknesses between 20 mm to 32 mm.1.2 In terms of apparatus, specimen design, and test methodology, this test method draws from Test Method E436 and API 5L3 - Recommended Practice for Conducting Drop-Weight Tear Tests on Line Pipe.1.3 The development of this test method has been driven by the need to design for fast ductile fracture arrest of axial running cracks in steel high-pressure gas pipelines (1). 2The purpose has been to develop a test to characterize fracture propagation resistance in a form suitable for use as a pipe mill test (2). The traditional Charpy test has been shown to be inadequate for modern high toughness pipe steels (1). This test method measures fracture propagation resistance in terms of crack-tip opening angle, and is used to characterize ferritic steels.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.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.