Random vibrations of bladed-disk assembly under cyclostationary excitation

TR Number



Journal Title

Journal ISSN

Volume Title


Virginia Tech


Random vibration of a bladed-disk assembly is studied. A stochastic model for the excitation is developed. A unique feature of this model is the statistical periodicity of the blade forces called cyclostationary. A random process is called wide sense eyeclostationary and its statistics are periodic in time. Factors like the turbulent nature of the flow around the blades, the variability in their geometry, and their nonuniform deterioration contribute to the uncertainty in the excitation. In periodic structures, like the bladed-disk assembly, small variation in the blade excitation may lead to high variability in the response.

The model developed includes both random and deterministic excitation. A comparison of the responses due to the random and the deterministic part shows the significance of taking into account the variability in the blade forces.

Therefore the assumption that the blade forces are all equal, used by all methods for vibration analysis of bladed disk assemblies, may lead to erroneous estimates of their response, reliability and expected life.

It is shown that the response is a cyclostationary process. Therefore the cyclostationary property is preserved from the input to the output. Furthermore the frequency of the second moment of the response is equal to two times the frequency of the excitation.