Vibration Behaviour of a Disc Assembly with a Cracked Lacing Wire

Abstract

In this paper, mathematical descriptions of the static and dynamic behaviour of the bladed disc with the undamaged and damaged lacing wire are briefly explained. For a steam turbine disc with 70 axial blades coupled by the lacing wire, the centrifugal static analysis is performed. Then, the free and forced vibrations are computed to find differences in vibrations of the bladed disc with and without a failure in the lacing wire. The tip timing measurement is considered as an experimental tool for identifications of possible failures. According to the obtained FE results, a failure of the lacing wire in the rotating disc assembly can be identified by monitoring the centrifugal deformations of the blade tips, resonance frequencies and response amplitudes of the whole bladed disc. The dynamic behaviours of the failure-free disc and with cracked wire connection are compared to each other to outline differences in the known nodal diameter and dispersion curve definition.