Fracture Analysis of Welded Type 304 Stainless Steel Pipe

Abstract : An experimental investigation was performed to determine the fracture resistance of 4 in. diameter circumferentially welded type 304 stainless pipe at 550 F (288 C). Two crack geometries were investigated. These were a circumferential through wall crack (simple) and circumferential through wall crack superimposed on a 360 degree radial crack on the inside diameter of the pipe (complex). Test results were analyzed using J-integral and limit load techniques. Additionally, J-integral resistance curve tests were performed on large plan size compact tension specimens for comparison with the pipe specimen results. Results of the J-integral analysis indicate that J-initiation for pipes containing simple cracks was approximately 1120 kJ/sq m (6400 in-lb/sq in) and a factor of four decrease in J-initiation was noted for pipes containing the complex crack. Good agreement was shown at J-initiation between pipe specimens containing the simple crack geometry and compact tension specimens. The accuracy of the limit load analysis was variable for pipes containing the simple crack geometry with the average predicted limit load calculated using the ASME Code flow stress being 8.7% higher than that actually attained in the tests. The calculated limit loads based on the ASME Code flow stress were conservative for the complex crack cases.