ВИЗНАЧЕННЯ ДИНАМІЧНИХ МОДУЛІВ ПРУЖНОСТІ ПОЛІМЕРНИХ АУКСЕТИКІВ ЗА ДОПОМОГОЮ ІМПУЛЬСНИХ ІМЕРСІЙНИХ ВИМІРЮВАНЬ ШВИДКОСТЕЙ ПОШИРЕННЯ УЛЬТРАЗВУКОВИХ ХВИЛЬ

Abstract

The method of measuring the propagation velocities of longitudinal and transverse ultrasonic waves and their absorption coefficients using the impulsive immersion method is presented. Determination of ultrasonic wave propagation velocities is based on the comparison of the results of direct measurements of the propagation time of the probe pulse through immersion fluid in the absence of a sample and in the presence of a sample between the emitter and the signal receiver. When measuring the velocity of a longitudinal wave, the sample with strictly parallel surfaces is placed perpendicular to the direction of propagation of the wave in immersion liquids. The measurement of the velocity of the transverse ultrasound wave is based on the fact that when a longitudinal wave falls at a certain angle at the fluid separation line - the solid in the latter case generally propagates two waves: longitudinal and transverse. The method of rotating plate allows to determine the critical angle at which the longitudinal wave is transformed into the surface, and only the transverse wave propagates in the sample. According to the experimental values of the velocities of propagation of longitudinal and transverse ultrasonic waves, the Poisson's ratio of a number of metalfilled polymer auxetics with a polyurethane matrix was calculated. Determination of absorption coefficients of longitudinal and transverse ultrasonic waves as they pass through samples of the studied materials. Calculations of real and imaginary parts of complex dynamic modulus of elasticity: Young's modulus, shear modulus, bulk deformation modulus and mechanical loss tangent for longitudinal, transverse and bulk deformations. The obtained results indicate the possibility of using the impulsive immersion method in measuring the velocity of propagation of ultrasonic waves to determine the Poisson's ratio and the dynamic modulus of elasticity of polymer auxetics.