An Experimental and Numerical Investigation of Damage Detection in a Mistuned Bladed Disc

Mistuning in repeating structures like bladed discs is caused by small variations in the individual blade properties that, results in the splitting of degenerate vibration modes and affects the dynamic behaviour of the system. As a result, it is complicated to highlight a small damage in the mistuned environment. This paper is focussed on the effect of mistuning on the dynamic characteristics of the bladed disc. An experimental rig is setup and a bladed disc having eight blades, rigidly attached to the base to represent a blisk, is selected for this study. The splitting of resonance frequency peaks in an FRF obtained for the mistuned structure is analysed experimentally and numerically. A very basic level of mistuning in any repeating structure usually comes from the manufacturing tolerance, so the effect of manufacturing tolerance-induced mistuning is also investigated in the paper. The possibility of utilising the Modal Assurance Criterion (MAC) for developing a damage detection strategy in mistuned bladed discs is also examined. Experimental and numerical results for the splitting of FRF peaks are then compared. Outlier detection analysis is utilised for detecting damage in the frequency domain.