Study on vibration of cylindrical shells of variable stiffness

Аuthors

Girin A. M.^*, Povoljaev S. T.^*

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: k906@mai.ru

Abstract

Purpose
A set of shell structures are used in modern motor power plants of aircraft. These shells are often axisymmetric and have variable physical, mechanical (e.g. bending stiffness and tension-compression one), and geometrical (e.g., thickness and diameter) properties and often include some elements of fragile materials (such as ceramics, glass, tungsten etc.). The effect of high frequency vibration loads must be considered at the stage of the preliminary design of the mentioned shell structures.
Design / Methodology / Approach
The proposed method is based on the solution of the boundary integral equations and allows the quick and accurate determination of the resonance conditions. This method gives the working capacity boundaries of real complex shell structures on the basis of the vibration resistance criteria, or to change the properties of designed structures to ensure their working capacity in the given operating frequencies range. An experimental plant is designed to confirm the theoretical results and can be used for the vibration tests of full-scale objects as well as their models. A method of analysis of the free oscillations of cylindrical shells with variable properties, for instance, material density, elasticity modulus, and the wall thickness, is developed on the basis of the integral equations of the moment shell theory.
The hypotheses of the absence of the tension in the circumferential direction and of the shear in the shell midsurface, as well as the Kirchhoff-Love hypothesis have also been used. Findings The eigenfrequencies for the cylindrical shells with variable thickness along the generatrix are computed. An experimental plant permitting the automatic determination of the resonance frequencies, as well as circumferential and longitudinal oscillation modes is constructed. The theoretical values of the eigenfrequencies are in the good agreement with the experimental ones.
Originality / Value
The details and units of the power plants of modern aircrafts are subjected to the intense high-frequency vibration loads, so the information about the behavior of structural elements is very important at the preliminary design stage. The proposed method allows one to determine the optimum properties of shell structures and avoid any resonance modes in the real operation conditions. The designed experimental plant can be used to test the full-scale parts and structural elements of aircrafts under dynamic loads.

Keywords:

cylindrical shell, cylindrical shell, elastic properties, integral equations

References

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