Experimental Four Points Bending Test on a Real Size Bimetallic Welded Pipe: European Project ADIMEW

In July 2003 EDF-R&D performed a 4 points bending test on a real size bimetallic welded pipe. This test (following the BIMET program) is a major part of the European project ADIMEW (Assessment of aged piping DIssimilar MEtal Welds integrity). The mock-up was representative of an Expansion line of the Pressurizers of French N4 Power Plants: it was a 16” pipe including a ferritic part (SA508 Class 3), an austenitic one (316L) and a weld with buttering (309L) and weld metal (308L). An outer circumferential 1/3-thickness defect had been introduced in the first layer of the buttering, parallel to the buttering/ferritic interface (at a distance of 2mm). The test was conducted under displacement control and the partial unloading method was used to control the defect initiation and propagation. Crack initiation occurred at a relatively low bending moment but a long stable propagation was to observe. This proves the ability of such junctions with large defects to overcome very high bending loads without any unstable crack growth. This paper will provide more detailed information about the testing conditions, all important experimental results and a discussion around them.