This paper presents an analytical method for calculating the radial force and predicting the acoustic noise in switched reluctance machines (SRMs). The main source of acoustic noise in an SRM is the radial magnetic force inducing resonant vibration with circumferential mode shapes of the stator. An analytical relationship between radial force and radial vibration is determined, which can be used to predict the noise power level at the frequency of operation. The vibration and sound are functions of machine dimensions, material properties, and rotational speed. The knowledge of the circumferential mode shapes of vibration, the natural mode frequencies of the stator, and the frequency spectrum of the radial magnetic force can be effectively utilized to design SRMs with minimal noise through geometrical design variations. The effect of the number of stator and rotor poles on acoustic noise can also be analyzed with the model presented in this paper. Magnetodynamic simulation by finite-element analysis software has also been carried out to verify the calculation of radial force using the proposed analytical model.

Radial force calculation and acoustic noise prediction in switched reluctance machines

An energy method for free vibration analysis of stiffened circular cylindrical shells

A new frequency formula for closed circular cylindrical shells for a large variety of boundary conditions

A semi-analytical approach eccentrically stiffened functionally graded circular cylindrical shells surrounded by an elastic medium subjected to external pressure is presented The elastic medium is assumed as two-parameter elastic foundation model proposed by Pasternak. Based on the classical thin shell theory with the geometrical nonlinearity in von Karman–Donnell sense, the smeared stiffeners technique and Galerkin method, this paper deals the nonlinear dynamic problem. The approximate three-term solution of deflection shape is chosen and the frequency–amplitude relation of nonlinear vibration is obtained in explicit form. The nonlinear dynamic responses are analyzed by using fourth order Runge–Kutta method and the nonlinear dynamic buckling behavior of stiffened functionally graded shells is investigated according to Budiansky–Roth criterion. Results are given to evaluate effects of stiffener, elastic foundation and input factors on the frequency–amplitude curves, natural frequencies, nonlinear responses and nonlinear dynamic buckling loads of functionally graded cylindrical shells.

Nonlinear dynamic analysis of eccentrically stiffened functionally graded circular cylindrical thin shells under external pressure and surrounded by an elastic medium

Free vibration of a thin cylindrical shell with discrete axial stiffeners

Vibration tests and analysis of thin cylindrical shells with and without longitudinal stiffeners

https://ntrs.nasa.gov/api/citations/19680024266/downloads/19680024266.pdf

J. L. Sewall

Papers

An experimental and analytical vibration study of thin cylindrical shells with and without longitudinal stiffeners