An ultrasound method for characterization of viscoelastic properties in frequency domain at small deformations

Background The ultrasound technique, usually based on the transmission mode, is capable of providing the viscoelastic properties of polymers. Further techniques involving pulse-echo methods were also described in literature, but they still exhibit inaccuracies in the evaluation of the acoustic properties. Objective The manuscript focuses on an innovative approach for the characterization of the viscoelastic behavior of polymers employing the ultrasound methodology. The proposed procedure is based on the pulse-echo method in order to overcome possible inaccuracies in acoustic properties evaluation and in issues related to transmitter mode applications. Methods Starting from the pulse-echo method adopted for the acquisition, a novel formulation for data processing has been developed and described, allowing to determine the wave attenuation coefficient, in comparison to the commonly employed procedures involving ultrasound in polymers characterization, based on transmitter mode inspections. To carry out the study, a specifically designed ultrasound bench has been set up and three different polymers have been tested in the temperature range of interest. Results According to the proposed methodology, the loss factor towards the temperature is determined starting from the data acquired considering the identified attenuation coefficient and the measured sound velocities. The trustworthiness of the novel procedure has been proved comparing the obtained viscoelastic loss factor quantities to the reference master curves obtained by the standard Dynamic Mechanical Analysis characterizations carried out on the same polymer specimens. Conclusions A novel methodology involving ultrasound technology aiming to evaluate the viscoelasticity of the polymers using non-destructive approach has been developed. The results obtained are agreement with the standard viscoelastic master curves determined through the DMA.

Implementation of Ultrasonic Ranger Finder

In this paper, the operation style of “measuring distance” is taken as the research content of this implementation. The expected goal is to use the characteristics of the double reflection type used in the transceiver circuit to perform the function of measuring distance. Finally, the operating principle of the adopted electric circuits and the performance of the proposed device are validated by experimental results. It reveals that the operations of the proposed device coincide with the requirements. Keywords: Ultrasound, Pulse echo method, Single frequency ranging, Verification.

APPLICATION OF ACOUSTIC PULSE ECHO-METHOD FOR THE INVESTIGATION OF DYNAMIC AND STRUCTURAL DYSLOCATION CHARACTERISTICS OF CRYSTALS

The multifunctional pulse equipment allowіng to use the method of amplitude-independent internal friction in the frequency range 7.5 to 232.5 MHz is described. Equipment gjves the possibility to investigate the peculiarities of the process of phonon-dislocation interaction in crystals, to carry out thermoactivation analysis of the process of dislocation of the dislocations about the stoppers under the action of temperature and elastic loading, to study processes of dislocation and mechanical relaxation in loaded samples in the quasi-elastic and plastic strain range.

Эскпериментальное исследование дифракции упругих волн на модели трещины

Small opening notches are used to simulate cracks in butt welds. The study of the influence of the notch edges orientation on their detectability when using pulse-echo and diffraction methods of ultrasonic testing. It is shown that the processes occurring during the elastic waves scattering on cracks must be modeled by a three-dimensional problem. However, theoretical analytical and numerical studies in this area most often concern two-dimensional problems of elastic waves diffraction, when the target studied edge is located on the acoustic axis of the ultrasound transmitter and / or receiver and is oriented perpendicular to the incident beam. The article presents experimental results illustrating the influence of the target point (edge) orientation in three-dimensional problems on the received signals both when using diffraction schemes of the TOFD type, and in the classical ultrasonic testing by the pulse-echo method according to the "tandem" scheme and with the turn of the transducers according to the "duet ".

Research of the echo-impulse method of control of drilled pieces (non-destructive control)

The results of field and computational experimental studies of the pulse echo method are presented. Typical reflectograms of bored piles are presented. The factors that complicate the interpretation of control data are noted. An analysis of the formation of the fronts of an acoustic pulse during its shock excitation is presented. Estimates of the influence of reinforcement on the estimates of the propagation velocity of an acoustic pulse are given.