Forced Response Analysis of a Mistuned Blisk Using Noncyclic Reduced-Order Models

Abstract

The importance of mistuning analysis lies on understanding the distribution of the vibrational energy around the blisk. The large vibration amplitudes of individual blades inherent in mistuned blisks reduces the high cycle fatigue margin significantly. It is therefore important to perform mistuning analyses at a high accuracy while keeping the computational cost at an acceptable level. Because numerous analyses with large amount of degrees of freedom models are commonly performed, it is frequent to employ reduced-order models such as to reduce the computational effort. In this paper, a unique way to address the reduced-order model is presented, where each blisk sector is attached as individual substructures with the free-interface approach known as Craig–Chang. This implementation is compared against a fixed-interface approach known as Craig–Bampton in terms of accuracy for disk- and blade-dominated modes. Neither of these approaches applies cyclic symmetry, making them more accurate in the presence of mistuning when the harmonic patterns are destroyed. Results show the high benefits of using the free-interface approach for a mistuned forced response analysis.