An Analytical Method for Calculating the Natural Frequencies of a Motor Considering Orthotropic Material Parameters

In this paper, a novel analytical method is proposed for calculating the natural frequencies of a motor to reduce the large natural frequency calculation errors produced by common isotropic analytical models. First, a theoretical model of the equivalent cylindrical shell is established with five orthotropic material parameters by considering the simple-support boundary condition, the effect of the axial length, and the orthotropic characteristics of the motor. Then, the density of the equivalent cylindrical shell is obtained, and the composite material theory is employed to estimate the equivalent orthotropic material parameters. Finally, we find that the natural frequencies and the modal shapes obtained by the proposed analytical model are in good agreement with those of the experimental results, verifying the accuracy of the proposed model.