THE RESULTS OF EXPERIMENTAL STUDIES OF THE PROCESS OF REDISTRIBUTION OF SELF-OSCILLATION ENERGY UNDER THE INFLUENCE OF ATTENUATES

Abstract

Below given are the results of experimental studies of the process of damping of self-oscillation of the beam which is a long plate with rectangular cross-section. The studies were aimed at demonstration of the process (accompanying the damping) of energy redistribution between the modes and harmonics of self-oscillations under the conditions when this energy is essentially bounded. The artificial damper was used which was a small-size slightly pressed plate. The same local damping effect is created by cracks in the parts when there are oscillations, plastic deformation at the apex of crack. Specially developed transducers operating in split mode as part of multifunction acoustic impedance fault detector were used as measuring equipment. The receiver-transducer was attached at the end of the beam, the generator-transducer was attached at the centre of the beam so as to induce oscillation train consisting of five dominant flexural modes of self-oscillations of the beam. Limitation of energy inducing self-oscillations was determined by the rigidity of spring-plates of generator-transducer. The rigidity of the plates was chosen so as oscillation energy was sufficient only for extraction of the given train amplitudes as being dominant, whereas the rest modes of self-oscillations were either not induced at all or were induced with small amplitude. It is demonstrated that redistribution process, when inducing energy is limited, is highly sensitive to attenuants, which allows to use it as a crack indicator during integral nondestructive testing of parts and entire assemblies. For this reason it is concluded that the process of energy redistribution between different harmonics and modes of self-oscillations under the influence of damping factors is advanced for computer-aided nondestructive testing.