ON THE INFLUENCE OF THE SIZE OF FLAKE GRAPHITE INCLUSIONS AND ITS VOLUME CONTENT ON THE ACOUSTIC PARAMETERS OF CAST IRON AND THE CHARACTERISTICS OF ULTRASONIC LONGITUDINAL WAVE SIGNALS

Abstract

Algorithms have been presented for calculating the velocity (in the approximation of a fine-layered model) and the attenuation coefficient of a longitudinal ultrasonic wave in cast iron, depending on the average size of graphite elements and its volume content, the calculation results for which are qualitatively confirmed experimentally. The calculation was performed using a fine-layered model of the structure, the graphite inclusions were described in the form of plane-parallel layers placed in an isotropic elastic medium (metal base). Computer simulation of acoustic paths for a mediumcast iron with flake graphite for standard direct converters is carried out in order to study the influence of such a medium on the characteristics of transmitted and received signals during ultrasonic testing. In the course of the research, a previously developed model was used to calculate the attenuation coefficient of longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions. Computer simulation of the acoustic characteristics of the signals of a direct linear probe with a phased array in cast iron with flake graphite was carried out, during which the shape of the acoustic pulses of the longitudinal wave was calculated, depending on the distance traveled by the wave and the value of the attenuation coefficient for various models of cast iron. The main modeled characteristics of the transducer include the directivity characteristic and the change in the signal amplitude along the acoustic axis. It is shown that for cast iron with flake graphite, there are cases when the directivity of the probe with a phased array transmitted into the cast iron is practically absent.