A Study on the Normalized Load Function for J-R Curve Testing Using Normalization Method Available to Purchase

The purpose of this study is to suggest a more appropriate normalized load G-function for normalization method of J-R curve testing in the ASTM 1820 standard. For leak before break (LBB) design of reactor coolant piping system, J-R curve testing is required to verify the crack stability integration using J-T analysis. The normalization method of J-R curve testing is an excellent candidate testing method for dynamic J-R curve testing. In the normalization function, the load value is normalized by the G-function based on the plastic η factor. The normalized load function, G-function is important because the resultant J-R curve depends on the normalized function type used. However, for existing J-R curve calculation using the G-function in ASME standards, there exists a mismatch of estimated J integral values between the two different J-integral calculation approaches: the standard method in ASTM 1820, and the approach based on a J-integral physical concept with energy release rate. This problem is caused by the G-function type. To set up a more appropriate G-function, finite element (FE) analysis has been performed for compact tension specimens with various a/W and strain hardening index n. Also, application of the newly proposed G-function to J-R curve estimation is discussed.