Description: Mathematical models for measuring the attenuation coefficient and ultrasonic propagation velocity (US) in ultrasonic fibers and films moving relative to the transducer are described, and the uncertainties of the results of their measurements are estimated. The principles of operation and the design of ultrasonic transducers developed by the authors, which allow, with sufficient reliability, accuracy and reliability, the excitation and reception of ultrasound during their movement relative to the transducers are considered. The main disadvantages of existing ultrasonic transducers are shown, in particular, the excitation of a noise signal in a receiving transducer, the level of which is several times higher than the level of the useful signal. The immersion ultrasonic transducers for excitation and reception of elastic vibrations in moving materials, developed by the authors in three versions, are described: a) with a constant angle of input (reception) of ultrasonic probing signals into a controlled object; b) with adjustable angle at normal (not high) temperatures; c) with adjustable angle at high temperatures. Adjustable angle transducers (options “b” and “c”) are noted to be more efficient than converters where the angle remains unchanged (option “a”), and therefore in an acoustic installation for continuous monitoring of moving fibers and films in a nonequilibrium state, we used precisely these converters. They allow you to concentrate ultrasonic vibrations on the surface or inside the object under test, both as a point (for filaments and fibers) and as a transverse line (for films). In order to efficiently transmit ultrasound from the focusing piezoelectric element through the layer of immersion liquid to the controlled material, the body is proposed to be made of a material with acoustic impedance close to the acoustic impedance of the controlled material. In order to be able to control the acoustic characteristics of moving materials at high temperatures (from 20 °C to 200 °C), the piezoelectric element is protected by a special thermo-insulating casing and “jacket” of the cooling immersion liquid. Using the described measurement technique and the proposed setup, the acoustic characteristics (propagation speed and attenuation coefficient of ultrasound) of a polycaproamide fiber in a non-equilibrium state were determined, and their uncertainties were estimated.
Keywords: model, acoustics, ultrasound, pulsed, oriented polymer, nonequilibrium state, error, uncertainty
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