INVESTIGATION OF THE EFFECT OF ATTENUATION OF ELASTIC LONGITUDINAL WAVES IN CAST IRON WITH FLAKE GRAPHITE ON THE CHARACTERISTICS OF SIGNALS DURING ULTRASONIC TESTING

Abstract

The model of estimation of damping coefficient of elastic longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions, considering the deviation of the modulus of bulk elasticity of the phases of cast iron (metal base and graphite) from the mean value, is developed according to the theory of Mason. At the same time, the characteristics of cast iron used for calculations include the value of the longitudinal wave velocity, the mass content of graphite inclusions and their average size. In the process of studying the effect of attenuation of elastic longitudinal waves in cast iron with flake graphite on the characteristics of signals with narrow, medium width and wide spectra, a difference in the nature of the spectra changes due to frequency-dependent attenuation depending on the nominal pulse frequencies, cast iron models and the distance traveled by the ultrasonic wave is established. It is shown that the shorter the pulse, the greater the shift of the spectrum maximum in the frequency range less than the nominal. The effect of attenuation of longitudinal waves in cast iron with flake graphite on the impulse directivity characteristic of the round piezoplate depending on the cast iron model and pulse spatial length is established. The expansion of pulse directivity characteristics with increasing of the distance traveled by the wave in cast iron is shown, the greater the wider the pulse spectrum.