Papers by Keyword: Acoustic Wave

Abstract: The paper assesses the possibility of using the reverberation phenomenon to control the imperfections and the stress-strain state of solid dielectric materials by the method of mechanoelectrical transformations. The main advantage of reverberation is the repeated intersections of the excitation zones of inhomogeneities by acoustic waves, that is displayed in response parameters. The reverberation makes it possible to accumulate distortions of wave fronts. A comparative analysis of the responses from the sample under condition of uniaxial compression under different loads was performed. Differential analysis for the deterministic time component of the response in the interval (0–0.3) ms, and a statistical analysis of the differences for the pseudo-random component in the interval (0.8–1.8) ms were performed. For the statistical analysis, the distribution of the pulse flow is selected. The response was calculated according to the mathematical model under the conditions of a change in the speed of sound, which simulates a change in the sample inhomogeneity under load. The calculation showed a qualitative similarity with changes in responses in a real experiment. According to the obtained results, it was concluded that it is possible to use the deterministic and pseudo-random components of the responses in the reverberation condition to control the change in defectiveness and the degree of heterogeneity under the action of the mechanical load on the sample.

Abstract: During the processing of tubing premium threaded made up, the degree of the thread sealing surface intactness will directly affect the sealing performance of the string. Nevertheless, there are some difficulties to detect the damage of the engaged sealing surface effectively. In the present study the sealing surface damage was judged by the sealing surface contact stress’s relative changes according to the acoustic elasticity theory,. At the same time, the wear defects generated at the tubing sealing surface, during the tubing made up, contrasted with the wear and unworn surface roughness of coupling ultrasonic detected about the sealing surface. The results showed that with the acoustic amplitude evaluated the sealing contact stress was susceptible to the influence of surface roughness of coupling. But the reflection wave with the center frequency on the sealing surface characterization of the contact stress could avoid this problem effectively.

Abstract: The applicability of the method mechanoelectrical transformations (MET) to determine the depth of the macrodefects location in the sample on parameters of the electromagnetic response is evaluated. As the response parameter it was used the phase characteristic of the signal analytical representation.On the one-dimensional mathematical model it was shown the possibility to detect phase response changes when reflected from defect acoustic wave is mixed with the signal spurious component generated by a distributed MET sources. Experimental verification of mathematical model on a sample of concrete was conducted. It has been shown that the sensitivity of the method MET to evaluation of the macrodefect locate depth depends on the wavelength of the excitation pulse and the area of the macrodefect border closest to the emitter-receiver system.

Abstract: One of the topical material science problems today is the problem of analyzing the evolution of the mechanical properties of metallic materials, predicting their behavior under thermomechanical influences. To solve this problem, it is suggested to use methods of acoustomicrouscopy flaw detection or AMD-methods [1]. They make it possible to obtain, with the aid of acoustic waves (AB), images of the structure at various depths from the surface of the object. This does not require any additional surface treatment, including chemical etching. The advantages of analyzing the evolution of the mechanical properties of alloys using AMD methods are related to the fact that acoustic waves and their characteristics are sensitive both to the parameters of the structural elements and to their changes associated with external influences.

Abstract: Oilwell cementing is part of completing a well prior to production. As a casing is installed after a section of the well is drilled, cement is pumped downhole. Reservoir fluid such as oil which may encroach into the wellbore due to naturally fractured or unconsolidated formation would mix with the cement pumped downhole. Recent studies have shown that the presence of oil affect cement quality to an extent where the cement compressive strength is greatly reduced. Early detection of possible oil contamination into cement may prevent well integrity problem. With intense application of acoustic principle into wellbore, however, not many references available to detect the presence of oil in cement system using this principle. This study investigates whether acoustic waves can detect oil in cement. Class G cement is mixed with both water and brine where crude oil is then added to the mixture. The resulting slurry were cured using High Pressure High Temperature (HPHT) curing chamber at 120°C and 4,000 psi for 24 hours and is then cored into 1-inch cylinder. SonicViewer-SX is used to propagate acoustic waves through the core sample where the transit time is recorded and analyzed. It is found that oil can be detected in cement using acoustic waves since oil-filled samples have slower P-waves and S-waves velocities than cement-filled samples. The case is also proven when water is replaced by brine as the mixing fluid which oil-filled samples have lower P-waves and S-waves velocities to that of cement-filled samples.

Abstract: This paper presents an acousto-optics analysis on free space optical signals modulated by two distinguishable non-resonant acoustic waves. The acoustic waves were directed at two different directions and locations along a laser beam and created non-interference modulated optical signals. The photonics microphone deploys low-powered eye-safe continuous-wave 633-nm laser; high-speed photodiode and a series of Fourier lenses. Two transducers generating 20 Hz to 20 kHz acoustic waves were directed across the laser beam. The receiving modulated signal was filtered and amplified electronically by two sets of passive bandpass filter separated by a transimpedance amplifier and connected to a computer for analysis. The signal was further digitally filtered and amplified to enhance the signal-to-noise ratio via MATLAB software. These signals were analyzed in time and frequency domains using Fast Fourier Transform (FFT) and Spectrogram. It was found that the recorded signals demonstrated higher signal intensities for lower acoustic frequencies with digital signal-to-noise ratio (SNR) ranging from 10.77 to 71.92 for frequency of 1 kHz to 20 kHz and 20 Hz to 1 kHz respectively. The frequencies of both transducers were simultaneously swept through from 20 Hz and 20 kHz respectively. These scanning frequencies approached one another and crossover with no resonant frequency was observed. This illustrates that it is able to detect multiple acoustic signals for any given frequencies along the laser beam and found its applications in stealth sound detection and long range sound sensor. Though low-powered 1-mW laser was used, a relatively high signal-to-noise ratio with clear-recorded playback was achieved.

Abstract: The paper presents numerical solution of the problem of acoustic waves attenuation in metal barriers. We investigated separately the plates from steel, lead or copper as metal barriers. The acoustic wave attenuation was compared after passing the barrier, depending on the quantity of plates of the particular barrier and the distance between them.

Abstract: In this paper, we investigate an acoustic remote control technology through the annulus channel in an oil-well. To establish a reliable communication, we first evaluated the acoustic charateristic of the aunnulus channel through field experiments. Then, a remote control system was implemented with a ground equipment serving as an acoustic source, and an underground equipment used as a receiver. A demonstrative experiment, in which we succeded in remoting an intelligent valve over 1257 m, has been presented to verify the proposed technology.

Abstract: Using the elementary theory of the acousto-optic nonlinear interaction,an empirical formula is developed for the diffracted light in terms of the acoustic power. Using this formula, closed-form expression, in terms of the modified Bessel functions, are obtained for the diffracted-light components resulting from interaction with a multisinusoidal acoustic wave.

Abstract: An acoustic wave propagation simulating method based on semi-symplectic theory is developed. The acoustic wave equations with n degree of freedom in space domain of Lagrange System which are obtained in FEM are converted to equations with 2n degree of freedom in Hamiltonian System with the Legendre’s Transformation. These equations are then integrated with the Precision Integration algorithm in time domain. The algorithm is employed to simulate the acoustical wave propagation in two dimensional medium. We demonstrate the remarkable stability of the presented algorithm by comparison of the results of the FEM and that of the Semi-Sympectic Theory under different time steps. The results presented in this paper show that the proposed algorithm is effective, accurate, and not sensitive to time step.