Evaluation of Dynamic J-R Curve by Using Normalization Method for Long Crack Extension

The test method for the reliability of this research dynamic J-R curve for long crack extension based on normalization method was introduced on this research. For nuclear power plant piping material made of ferritic steel, dynamic J-R curve is one of the important material properties used to evaluate the integrity for piping with the critical leakage crack size under seismic loading such as earthquake loading on leak before brake design (LBB). The measurement of dynamic J-R curve by compliance method is very difficult due to the fast loading speed. Normalization method of ASTM E1820 code A15 is therefore often used because of the merit that J-R curve can be obtained by only using load–displacement curve without measuring the crack extension length during the test. However, there is a restriction that physical crack extension should not exceed the lesser length of 4mm or 15% of the initial uncracked ligament. For J-T analysis on LBB design, long crack extension data on J-R curve are needed to simulate the crack stability of long cracked piping corresponding to leakage rate of 10gpm. In this paper, to overcome this problem at applying for the normalization method, two specimens were used where one is for short crack extension and the other is for long crack extension. Utilizing the two test data, dynamic J-R curve over the crack extension length range designated to ASME code was estimated.