Vibration characteristics of a twisted square rod comparing with that of an equivalent simple beam model

It is general practice to use a simple beam model in the analysis of the vibration characteristics of a slender rod for the simplicity and easiness to get the results. Besides the circular cross-section, fuel rods may have twisted square cross section in order to enhance the mechanical and thermo-hydraulic performance. In this case the modeling for the analysis of the vibration takes much efforts to simulate it properly. Instead of the more complex solid modeling, a simple beam model can be used if the simulation is properly done. In this study, the validity of the use of a simple beam model for the twisted square rod are discussed and the results of the two calculations are evaluated. The results show that the simple equivalent beam model also can be applied for this type of the rod on the vibration analysis and the effect of the twisted form on the rigidity of the rod is negligibly small