Effects Of Acoustic Vibration Research Articles

FEATURES OF FORMING THE VT1-0+AMG5 JOINT DURING EXPLOSION WELDING WITH THE INFLUENCE OF ACOUSTIC VIBRATIONS

The work is devoted to the study of the influence of the introduction of acoustic vibrations during explosion welding of the VT1-0 + AMg5 pair. A comparative study of joints obtained by the conventional method of explosion welding and explosion welding with the effect of acoustic vibrations in various welding modes has been carried out. The results of the study of the microstructure and mechanical properties allow us to speak about the positive effect of the introduction of acoustic vibrations during welding VT1-0 + AMg5, which consists in expanding the weldability area and reducing the volume of the melted metal in the joint zone. It is also shown in the work that the nature of surface preparation before welding can have a significant effect on the strength of the joint.

Effect of Acoustic Vibrations on a Liquid-Phase Reaction with Kinetic Instability upon the Association of Reagents

Effect of Acoustic Vibrations on a Liquid-Phase Reaction with Kinetic Instability upon the Association of Reagents

Acoustic vibration effects in classical nucleation theory

Acoustic vibration is often used to improve the yield of crystals and nanoparticles growing from solutions and melts. As there is still a debate on how acoustic vibration actually works, we have examined the possibility that acoustic pressure can affect the rate of nucleation. Our method is based on an expansion of the free energy of the nucleus in powers of the acoustic pressure. With the assumption that the period of the sound wave is short as compared to the time scale for nucleation, we replace the powers of the acoustic pressure by their time averages, retaining the average of the square of the acoustic pressure as the leading term. By assuming a nucleus having spherical shape, we use the Young-Laplace equation to relate the pressure inside the nucleus to the ambient pressure. Without making further approximations not already standard in classical nucleation theory, we find that the proximate effect of acoustic pressure is to reduce both the size of the critical nucleus as well as the work required to form it from monomers. As the work serves as the activation energy, the ultimate effect of acoustic pressure is to increase the rate of nucleation. If we assume that the atomic structure of the nucleus is the same as that of an ordinary solid, however, we find the compressibility is too small for acoustic vibration effects to be noticeable. If on the other hand, we assume that the structure is similar to that of a loosely bound colloidal particle, then the effects of acoustic vibration become potentially observable.

The effects of acoustic vibration on fibroblast cell migration

Cells are known to interact and respond to external mechanical cues and recent work has shown that application of mechanical stimulation, delivered via acoustic vibration, can be used to control complex cell behaviours. Fibroblast cells are known to respond to physical cues generated in the extracellular matrix and it is thought that such cues are important regulators of the wound healing process. Many conditions are associated with poor wound healing, so there is need for treatments/interventions, which can help accelerate the wound healing process. The primary aim of this research was to investigate the effects of mechanical stimulation upon the migratory and morphological properties of two different fibroblast cells namely; human lung fibroblast cells (LL24) and subcutaneous areolar/adipose mouse fibroblast cells (L929). Using a speaker-based system, the effects of mechanical stimulation (0–1600Hz for 5min) on the mean cell migration distance (μm) and actin organisation was investigated. The results show that 100Hz acoustic vibration enhanced cell migration for both cell lines whereas acoustic vibration above 100Hz was found to decrease cell migration in a frequency dependent manner. Mechanical stimulation was also found to promote changes to the morphology of both cell lines, particularly the formation of lamellipodia and filopodia. Overall lamellipodia was the most prominent actin structure displayed by the lung cell (LL24), whereas filopodia was the most prominent actin feature displayed by the fibroblast derived from subcutaneous areolar/adipose tissue. Mechanical stimulation at all the frequencies used here was found not to affect cell viability. These results suggest that low-frequency acoustic vibration may be used as a tool to manipulate the mechanosensitivity of cells to promote cell migration.

Effect of cavitation on high-temperature silicate melts

The effect of acoustic vibrations in the cavitation regime on high-temperature high-viscosity slag melt is evaluated experimentally. It is determined that ultrasonic treatment greatly increases the crystallization power of melt; this could be due to depolymerization of the silicon-oxygen framework of silicate melt and the creation of an extended interface between the gaseous and liquid phases in the melt. It is shown that acoustic treatment promotes dispersion of a refractory solid phase in the melt.

Effects of acoustic vibration on nano and sub-micron powders fluidization

Fluidization of nano and sub-micron powders with and without acoustic vibration was investigated. The effects of sound pressure level and frequency were studied. Loudspeakers located under the distributor plate were used as the sound source to disintegrate larger agglomerates concentrated at the bottom of the bed. Nanoparticles showed fluid-like behavior similar to Geldart's A group and application of sound vibration improved their fluidization quality. Submicron particles were hard to fluidize and their fluidization quality was partially improved by sound excitation. Bed compaction, caused by rearranging of the agglomerates, was observed for submicron particles at low gas velocities while the bed was fixed. Nanoparticles did not experience any bed compaction. Sound vibration led to a decrease in minimum fluidization velocity and an increase in bed pressure drop and bed expansion for both types of particles. The fluidization quality of both particles increased at low frequencies, while the reverse was observed at higher frequencies. Fluidization of these particles was improved by increasing sound pressure level. There was a critical sound pressure level of 110 dB, below which the effect of sound vibration was insignificant. A novel technique was employed to find the apparent minimum fluidization velocity from pressure drop signals.

Acoustically driven micro-thermal-bubble dynamics in a microspace

In this paper, vapor-bubble dynamics confined in a microspace under the effect of an acoustic field, defined as acoustic-thermal-bubble dynamics, is investigated not only for theoretical understanding of this complex bubble dynamic phenomenon but also for development of new microfluidic devices. The micro thermal bubble is generated by a microheater which is fabricated by a standard MEMS (microelectromechanical system) technique and integrated into a transparent channel. Using a high-speed digital camera, the thermal-bubble dynamics is studied qualitatively under two different conditions: normal condition and acoustic condition. The fluid is stationary for the experiments and the effect of the flow rate is not determined in the current research. Through theoretical analysis, the whole complex bubble dynamic process under two conditions can be roughly divided into four steps: (1) bubble generation, (2) satellite bubble movement, (3) bubble evolution and (4) bubble shrinkage/removal. The effects of acoustic vibration on all these four steps are found to be distinctly different. The mechanisms behind these effects are examined by analyzing the high-speed visualization results of two-phase flow phenomena. The current experimental investigation has a number of potential applications in the development of novel microfluidic devices.

Hot topics in physical acoustics.

The field of physical acoustics touches a broad range of technical areas important to fundamental science and society. This “Hot Topics” presentation will reflect the breadth of this impact by discussing the following three topics: sound waves in the early cosmos, acoustics in slip-stick friction systems, and acoustic metamaterials. The early universe, composed of hot ionized matter, was able to support acoustic waves until the temperature cooled enough to allow the formation of neutral atoms. The imprint of these relic acoustic waves is still evident in the cosmic microwave background and yields new information about key cosmological constants and dark matter. Earthquakes are perhaps the most destructive of natural disasters, as was painfully demonstrated by recent events in China. Studies on the effects of acoustic vibrations in slip-stick friction systems have begun to shed light on triggering mechanisms for earthquakes and may lead to better early warning systems. Metamaterials are man-made materials in which precise geometric arrays of structures are engineered to produce coherent scattering effects on scales much larger than the structures themselves. These systems can exhibit such exotic properties as a negative index of refraction, band gaps, and a negative effective elastic modulus.

Discrete Fourier Transform Analysis of Chronoamperometric Currents Obtained Under Ultrasound

AbstractA discrete Fourier transform (DFT) technique was used to analyze chronoamperometric currents at a Pt microdisk electrode (Ø=15 μm) in an electrolyte containing [Fe(CN)6]3−/[Fe(CN)6]4− under ultrasound at a frequency of 26.3 kHz and the powers of 0–50 W. The currents were measured by a high‐speed data acquisition card. Considering the effects of acoustic vibrations and cavitations on the limiting currents, a microdisk electrode and a high frequency sampling (10 MHz) were used to collect the current signals to restrain the deviation of average from sampling period in other methods. The results show that the amplitudes at 0 Hz and 26.3 kHz are related to the decay of ultrasound at constant power output when the separation between sono‐horn and electrode increases, and also related to the reactant concentration at the same ultrasonic conditions. The frequency signals are always shown in frequency spectrum despite different ultrasonic conditions. The amplitudes reflect the intensity of ultrasound and the concentration of reactant in solution, so they can be called specific frequencies. This method can be used to analyze quantitatively the effects of ultrasound on electrochemical reaction, determine the reactant concentration and measure the distribution of ultrasonic intensity in a solution.

Effect of acoustic vibrations on a gas flame burning in a confined space

Effect of acoustic vibrations on a gas flame burning in a confined space

Effect of acoustic vibrations on the nonlinear properties of crystals

Effect of acoustic vibrations on the nonlinear properties of crystals