Natural damped vibrations of anisotropic composite box beams. 2. Numerical experiment

Abstract

The results of numerical studies of the influence of reinforcing fibers orientation’s on values of natural frequencies and coefficients of mechanical losses associated vibrations unsupported symmetric and asymmetric box-shaped beams are discussed. The calculations were performed under the assumption of frequency the independence of the real parts of the complex moduli and coefficients of mechanical losses. The vibration modes identified by the form surfaces of the respective native forms. The boundaries of areas of mutual transformation of the interacting modes of vibrations were determined by joint analysis of dependencies and associated partial frequencies, and coefficients of mechanical losses from the orientation angle of reinforcing fibers. It is found that the vibrations of symmetrical box-shaped beam having two primary interactions: bending-torsion and longitudinal shear, combined into a single longitudinal-bending-torsion-shear interaction secondary interaction arising from the transverse shear deformations. For vibrations of asymmetric box-shaped beam arise longitudinal-torsional and flexuralflexural (in two mutually orthogonal planes) interaction. It is shown that in some cases the change of orientation angle of reinforcing fibers is accompanied by mutual the transformation of coupled mode oscillations. If the differential equation of natural vibrations contain derivatives of odd order eigenfunctions in the spatial variable (symmetric beam, flexural-flexural interaction in asymmetric beam), then changes in the orientation angle of reinforcing fibers leads to a mutual transformation of coupled vibration modes. If the equations contain only derivatives of even order (longitudinal-torsional interaction in asymmetric beam), the mutual transformation of the coupled vibration modes does not occur. Refs 4. Figs 7.