FINITE ELEMENT MODEL OF A BUNDLE ASSEMBLY CONSISTED OF 25 SLENDER RODS SUPPORTED BY SPRING SYSTEM

摘要

A free vibration analysis is performed by ABAQUS computer code for the bundlernassembly consisted of 25 rods and 5 guide structures. The rods of 2.2 m tall andrn9.5 mm diameter are diametrically arranged in the same pitch. Since one to fourrnrods among the 25 rods is(are) welded to five guide structures for constructing thernrod bundle, they are called structure rod. Rests of the rods within the rod bundlernare supported by four springs attached on the guide structure at five pointsrnlongitudinally. It is resulted that lower 6 modes are associated with the purernbundle vibration modes, what is called beam modes, and the fundamental modernamong them is calculated at 2.07 Hz for one structural rod while at 4.92 Hz forrnfour structural rods. A few modes which appeared just after the pure bundlernvibration modes are believed to be the modes coupled with the single rodrnvibration mode. The fundamental mode of the rod is calculated at 26.63 Hz torn26.64 Hz no matter how many the structural rods are. Not only the naturalrnfrequencies but also the mode shapes are the same as the ones obtained from thernsingle rod analysis.