NESC-1 SPINNING CYLINDER EXPERIMENT. EDF PRE-TEST FRACTURE ANALYSIS EVALUATION

摘要

The NESC project (Network for the Evaluation of SteelrnComponents) has been started in Europe with fundings fromrnEuropean Community (EC) and Health and Safety Executive (HSE,rnUK). This project contains several aspects of the structuralrnintegrity assessment procedure and more specifically nonrndestructive examination, fracture mechanics and materialsrncharacterization. A first test is being planned at the AEArnTechnology Laboratories (Risley, UK) on the Spinning Cylinderrntest facility. The experiment will be conducted on a large scalerncladded cylinder containing surface and subclad cracks exposed to arnpressurised thermal shock transient (PTS). The main purpose of therntest is to obtain the cleavage initiation in base metal.rnWithin the framework of this project, a preliminary pre-testrnstructural analysis evaluation has been conducted by Electricité dernFrance (EDF) including several three dimensional elastic andrnelastic-plastic computations. Two cylinder geometries have beenrnstudied, the first one with a 40 mm deep semi-elliptical subcladrnflaw, the second with a 70 mm deep semi-elliptical subclad flaw inrna thicker vessel.rnHigher values of the stress intensity factor are obtained in bothrngeometries in the elastic-plastic computations due to the yieldingrnof the cladding during the thermal transient. The comparisonsrnbetween the stress intensity factors and the expected base metalrntoughness show that cleavage initiation must occur preferably in base metal near the interface with cladding. The comparisonrnbetween both geometries show also that the thicker vessel with arndeeper semi-elliptical subclad flaw (70 mm deep) is morernfavourable to cleavage initiation near the base metal - claddingrninterface.