An Approach on Bladed-Disc Tuning

High cycle fatigue of rotating components, produced as the system is driven near to resonant conditions, is undesirable and is one of the major design concerns in engineering today. Structurally, it is imperative to tune the excited vibration mode out of the operating speed range to avoid large amplitude vibrations. It has been demonstrated that for a single blade with distinct eigenvalues, it is possible to tune the eigenvalue of choice out of the operating speed range while maintaining little change to other natural frequencies through structural perturbations. These perturbations usually come in the form of a redistribution of the stiffness and/or mass [1]. The focus of this paper is to extend this approach to the tuning of two adjacent excited frequencies of a bladed-disc by first reducing the inter-blade coupling through stiffening the disc structure followed by “individual” blade tuning. Due to the complexity of the bladed disc structure, results from direct finite element analyses are used based upon analytical eigen-perturbed expressions to investigate the dynamic inter-blade behavior of an impeller. A good correlation between analysis and laser vibrometry test measurements is obtained.