Vibration characteristics of multi-span elastically supported fuel rods based on an improved Fourier series method

The research has developed a vibration analysis method that reasonably characterizes the dynamic properties of fuel rods, by equivalencing the grid constraints to compression-tension springs and torsional springs, and establishing a multi-span elastically supported fuel rod mechanical model based on Euler-Bernoulli beam theory.

The model incorporates auxiliary terms to ameliorate boundary discontinuities and demonstrates superior computational accuracy. The study analyzed the influence of positioning grid constraints on the vibration characteristics of fuel rods: the equivalent stiffness of the compression-tension springs after grid equivalencing plays a dominant role in the overall variation pattern of the fuel rod's natural vibration frequencies; the impact of torsional springs on the vibration characteristics of fuel rods is contingent upon the values of the compression-tension spring stiffness, and when the compression-tension spring stiffness is low, the influence of torsional spring stiffness is not significant.