Frequency analysis of the longitudinal and transverse vibrations of lattice cylindrical shell with openings

For over thirty years composite lattice cylindrical shells with high specific strength and stiffness are used in rocket and space technology. Lately composite lattice cylindrical shells are widely used as casings of spacecrafts. Lattice shell is the supporting structure to which devices and spacecraft mechanisms are attached. One edge of this shell is attached to the launch vehicle through the adapter. Today lattice cylindrical shells which used as casings of spacecrafts do not have cutouts and holes in their structure. This fact is significantly complicates the installation of equipment, docking of connector cables and pipes located inside the lattice cylinder.Obviously, the presence of openings in the shell facilitates the installation of equipment,but at the same time affects the stiffness characteristics of shell. This article describes an algorithm for creating a finite-element model of lattice cylindrical shell with openings made by composite material. The problem of determining the first frequency of the longitudinal and transverse vibrations for shell, one end of which is rigidly fixed and on the other end is attached an absolutely hard disk, is solved. It is analyzed the influence of the hole size and stiffness of bordering rib on the magnitude of the first frequency. Values of the first frequency of the longitudinal and transverse vibrations for lattice shell with openings of different sizes are shown.Graphs of the first frequency of the longitudinal and transverse vibrations depending on the width of the bordering rib are presented. The value of the first frequency of the longitudinal or transverse vibrations of shell is a characteristic of rigidity of the structure.Therefore, modal analysis results allow us to draw some conclusions about the impact of openings on the stiffness parameters of the lattice shell.Obviously, the openings decrease the first frequency of the longitudinal and transverse vibrations of shell. Bordering rib improves the rigidity of shell with openings.With increasing the width of the rib there is an increase the respective first frequency oscillations.Influence of the width of bordering rib the more noticeable than the larger size has an opening in the lattice structure.The obtained results can be used in designing of power constructions in spacecrafts.