METHOD FOR DETERMINING NATURAL FREQUENCIES AND VIBRATION MODES OF FREE STRUCTURE FROM TEST RESULTS OF THIS DESIGN WITH SUPERIMPOSED LINKS

摘要

FIELD: physics.;SUBSTANCE: invention relates to classical experimental modal analysis of structures. When implementing the method, a design dynamic model of the free structure is constructed, which is corrected based on the results of ground modal tests. For the period of testing, the research object is fixed with a special system of elastic hanging, the characteristics of which are introduced into the design model by imposing external links. Tests are used to isolate natural tone of the structure in a given frequency range by phase resonance. Frequency of phase resonances are used to determine natural frequencies of tone oscillations, which are used for direct correction of stiffness and/or mass matrices of the design model. Then design model is released from external links: fixed model is "installed" on movable platform, which has inertial characteristics of initial free structure. System of equations of motion of the fixed model is supplemented with equations of motion of the platform. Obtained equations do not violate the symmetry of stiffness and mass matrices. Frequencies and forms of natural oscillations of the released model are close to corresponding frequencies and forms of free model.;EFFECT: technical result consists in excluding the effect of rigidity of the elastic hanging system on the error of determining natural frequencies and vibration modes of the free structure based on the results of ground modal tests.;1 cl, 1 dwg