Combining experimental data and numerical processing for failure probability evaluation of Coil Retaining Rings

Turbogenerator coil retaining rings (CRRs) are shrunk fitted onto the rotor over the coils, in order to restrain them against the centrifugal force. They are typically subjected to low cycle fatigue (LCF), with a cycle being completed at every machine switch-on and switch-off. The object of this paper is to show a computationally efficient methodology, based on the AMV, to determine the failure probability of a CRR. Its estimation is based on the experimental evaluation of material static, cyclic and fatigue properties and on the knowledge of the entity of cyclic loads. The determined value, in the order of 10-11 at the last stage of the machine life, is compatible with reference values for structures under fatigue in the aeronautical field.