Vibration Localization of Rotationally Periodic Structures

Abstract

Structures with uniform periodic spacing and repeated geometry are found in complex engineering systems. Examples include turbine blades, ship hull, aircraft fuselage and oil pipelines with periodic supports. The vibration characteristics of these periodic structures are highly sensitive to its mass distribution, stiffness distribution and geometrical properties. Parametric uncertainties in structures which arise out of material defects, structural damage or variations in material properties can break the symmetry of periodic structures. These uncertainties can drastically change and localize the vibration modes. Identification of severe mode localization in the design process can help prevent failure due to high cycle fatigue in periodic structures such as turbine blades. A 2-DOF system is used to demonstrate the effect of parametric uncertainties on eigenvalue veering and mode localization phenomenon. The Finite Element Method (FEM) was developed to study the free vibrations of two linearly un-damped systems, namely, two cantilever beams coupled system and an idealized turbine blade. The effect of parametric uncertainties on eigenvalue veering and mode localization is demonstrated and a novel numerical method using the Modal Assurance Criterion (MAC) to quantify mode localization in complex systems is proposed.

Effects of Crack on Vibration Characteristics of Mistuned Rotated Blades

“…Next, some related researches considered mistuning of blades and used mistuned model to study vibration behaviors of rotated blades. Chandrashaker and Adhikari [13] proposed the Modal Assurance Criterion Localization Factor which may help designers to easily obtain crucial information, such as the degree of localization for all the vibration modes in the system. Wang et al [14] analyzed resonance characteristics of blisk under random mistuning.…”