SIMULATION OF CRACK EFFECT ON SPECTRUM OF NATURAL OSCILLATIONS DURING MONITORING OF STRENGTH OF LARGE STRUCTURES

Abstract

This document contains monitoring results of structural strength of bearing beams of two large structures. To conduct the monitoring, beam natural oscillations were excited and their spectrum changes in case of possible defects were analysed. Simulators in the form of small-size plates pressed to the beams were used as possible defects (cracks). The specific feature of such a simulation is that the plate, pressed to the beam in an antinodal point of some mode of natural oscillations and damping it, also damps it in all the other antinodal points. The oscillations were excited and received by special transducers with mechanical filters at their inputs. This enables significant reduction of the spectrum of natural oscillations, reducing it to two or several dominant modes. It is shown that during the flaw detection with such a reduced spectrum, two processes take place – damping of natural oscillations and energy redistribution between their modes, which should be taken into account during the monitoring in automated mode.