Effect of Geometrical Mistuning on Modal Characteristics of Integrally Bladed Disk

This paper presents a numerical investigation of the modal characteristics of an integrally bladed disk known as blisk, in both tuned and mistuned conditions. The tuned blisk is modelled by a sector of the structure and using the cyclic symmetry option in ANSYS. Then the length of each blade is changed randomly and applied to the blisk structure to generate mistuned blisk. The entire model is used to obtain the frequencies and mode shapes of the mistuned blisk. Also, the mode shapes and natural frequencies of a single cantilever blade are studied and compared with the blisk. The scattering of the first bending frequency of blades has been extracted in tuned and mistuned conditions and the frequency mistuning pattern was obtained. The results show that small geometrical deviations of blades can lead to the emergence of new phenomena in the mode shapes and differences in natural frequencies of mistuned blisk which increases the possibility of initiation and propagation of cracks and blade tip fractures due to high cycle fatigue.

Keywords:

mistuning blisk , mode shape , natural frequency , finite element analysis.