Tham khảo tài liệu 'nuclear power control, reliability and human factors part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Evaluation of Dynamic J-R Curve for Leak Before Break Design of Nuclear Reactor Coolant Piping System 199 conventional fitting method for tearing modulus curve. However analytical approach has uncertainty basically by fitting. In this paper to evaluate reliable Tmat curve at long crack extension region experimentally we have researched the method for measurement of dynamic J-R curve with crack extension as long as possible. Fig. 9. Graphical illustration of J T method Fig. 10. The illustration diagram for estimation of crack instability point for J T method Dynamic J-R curve testing for long crack extension To obtain the effective J-R curve under the condition of long crack extension two specimens were used where one is for short crack extension and the other is for long crack extension. By using two test data the dynamic J-R curve was evaluated over the crack extension length range according to ASTM code. Table 1 shows test matrix for reactor coolant piping base metal for Shin-Wolsung. 200 Nuclear Power - Control Reliability and Human Factors Item Material Pipe size Inner Dia. Number of test Short crack extension Long crack extension Main Loop Piping Hot Leg SA508 Gr. 1a 42 in. 1 1 Cold Leg SA508 Gr. 1a 30 in. 1 1 Elbow SA516 Gr. 70 1 1 Table 4. Dynamic J-R test conditions for short and long crack extension conditions The load - displacement curve for each piping material is shown in Fig 11. In the dynamic JR curves obtained by normalization method for hot leg pipe and elbow materials dynamic J-R curves were similar regardless of crack extension length whereas for cold leg piping material J-R curve for short crack extension length was lower than that for long crack extension length as shown in . To analyze the reason for the difference between short and long crack extension for cold leg pipe normalized load-displacement curve is described in Fig. 13. Normalized load-displacement curve PN - v pl curve shows different shape between two tests with different
