In order to ensure the integrity of the structure, the material should have excellent toughness. Especially, in the case of the nuclear piping materials applied to leak before break (LBB) design, high toughness materials are mainly used to meet excellent fracture toughness criteria and the integrity should be verified through the static J-R curve testing using compliance method, one of the measurements of fracture toughness. Also, measured value and estimated value for the crack extension length during the test should have matched each other within certain tolerance. However, in the case of materials with high toughness, the rotation of the specimen becomes larger because the test is performed until the crack open displacement (COD) is relatively large to ensure sufficient crack propagation. In this case, it is not easy to satisfy these conditions due to the rotational effect of the specimen. Even though ASTM E1820 suggests a method for correcting the crack length due to the rotational effect of these specimens, it has been found that there are many differences for highly tough materials. To solve this problem, we newly proposed the crack length correction formula considering the rotation effect. As a result of analyzing the data of the J-R curve testing with the proposed method, it is confirmed that the accuracy of crack extension length is improved compared to the existing method. The proposed method well explains the variation of crack extension length due to rotation and is suitable as a correction equation for rotation of compact tension specimen.


Improved Method for Fracture Toughness Testing Using Compliance Method for High Toughness Materials

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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