Fracture Analysis of Multiple Cracks in a Spinning Cylinder Experiment

This paper presents finite-element analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The NESC was organized as an international forum to exchange information on procedures for structural integrity assessment, to collaborate on specific projects, and to promote the harmonization of international standards. The objective of the NESC-1 project is to focus on a complete procedure for assessing the structural integrity of aged reactor pressure vessels. Current plans for the testing program call for two large cracks to be installed in the NESC-1 cylinder separated by 90 deg. Three-dimensional finite-element analyses were carried out to determine: 1) the extent of interaction between multiple cracks in the cylinder; and 2) the predicted effects of using an initial cylinder temperature of 295°C and coolant temperature of 5°C in the experiment. The cylinder was modeled with innersurface through-clad cracks having a depth of 74 mm and aspect ratio of 2:1. The cylinder specimen was subjected to centrifugal loading followed by a thermal shock and analyzed with a thermo-elastic-plastic material model. The analytical results indicate that the stress-intensity factor changes less than 0.2 percent between a model with one crack and a model with four cracks evenly spaced around the circumference. Cleavage initiation is likely to be achieved for initial and coolant temperatures of 295 and 5°C, respectively.