Amplitude Of Ultrasonic Waves Research Articles

The degradation of landfill leachate in the presence of different catalysts by sonolytic and sonocatalytic processes

ABSTRACTIn the study, the degradation of landfill leachate by single ultrasound (sonolytic) and sonolytic combined with Fe2+ and TiO2 catalysts was carried out in laboratory conditions. The effect of pH and ultrasonic wave amplitude was also investigated in terms of color removal, total organic carbon (TOC) and chemical oxygen demand (COD) from leachate by the sonolytic degradation process. In this process, the color removal efficiency was recorded as 81.81% at 620 nm, pH = 2.0 and 70% wave amplitude. The sonocatalytic degradation of landfill leachate accompanied by different catalysts was studied by using the 70% wave amplitude at pH = 2.0 and room temperature for 20 min. The sonocatalytic degradation of leachate by using Fe2+ and TiO2 was found to be significantly higher than sonolytic degradation (p < 0.05). As the Fe2+ concentration increased from 1.0 to 3.0 mg/L, the COD and color removal of leachate significantly decreased (p < 0.05) from 50 to 35.7% and from 95.5 to 90.9%, respectively. The experimental data obtained from sonocatalytic degradation was analyzed using the Behnajady–Modirshahla–Ghanbery (BMG) kinetic models and found to be compatible. The results showed that the combination of catalyst and sonolysis was a highly effective way to remove color, COD and TOC from landfill leachate.

Evolution of spall-damage in iron caused by repeated plate impacts: Ultrasonic evaluation

This paper focuses on the developed of spall-damage that occurs in pure iron as a result of repeated impact. The employed low-frequency scanning acoustic microscopy (LF-SAM) observations combined with the measurements of ultrasonic wave velocity, attenuation, backscattering intensity and amplitude spectrum of the reflected wave, enabled us to provide a nondestructive evaluation. The spall-damage distribution was analyzed in the C-scan images, and we found the spall-damage increase with impact stress when the latter exceeds the characteristic spall-threshold stress. Moreover, we recorded the decreased sound velocity, amplitude ratio, and the increase of backscattering intensity, significant attenuation (the high frequency component of the reflected wave) for enhanced impact stress. It was also demonstrated that the tiny cracks generated in iron develop significantly during subsequent impacts either with lower or higher impact stress. Since the presented results concern for the first time the multiple-impact experiments, we contend that the applied ultrasonic investigations constitute the effective method of nondestructive spall-damage evaluation.

Acoustic Emission and Echo Signal Compensation Techniques Applied to an Ultrasonic Logging-While-Drilling Caliper.

A logging-while-drilling (LWD) caliper is a tool used for the real-time measurement of a borehole diameter in oil drilling engineering. This study introduces the mechanical structure and working principle of a new LWD caliper based on ultrasonic distance measurement (UDM). The detection range is a major performance index of a UDM system. This index is determined by the blind zone length and remote reflecting interface detection capability of the system. To reduce the blind zone length and detect near the reflecting interface, a full bridge acoustic emission technique based on bootstrap gate driver (BGD) and metal-oxide-semiconductor field effect transistor (MOSFET) is designed by analyzing the working principle and impedance characteristics of a given piezoelectric transducer. To detect the remote reflecting interface and reduce the dynamic range of the received echo signals, the relationships between the echo amplitude and propagation distance of ultrasonic waves are determined. A signal compensation technique based on time-varying amplification theory, which can automatically change the gain according to the echo arrival time is designed. Lastly, the aforementioned techniques and corresponding circuits are experimentally verified. Results show that the blind zone length in the UDM system of the LWD caliper is significantly reduced and the capability to detect the remote reflecting interface is considerably improved.

Optimization of low frequency sound absorption by cell size control and multiscale poroacoustics modeling

Sound absorption of a polyurethane (PU) foam was predicted for various geometries to fabricate the optimum microstructure of a sound absorbing foam. Multiscale numerical analysis for sound absorption was carried out by solving flow problems in representative unit cell (RUC) and the pressure acoustics equation using Johnson-Champoux-Allard (JCA) model. From the numerical analysis, theoretical optimum cell diameter for low frequency sound absorption was evaluated in the vicinity of 400μm under the condition of 2cm-80K (thickness of 2cm and density of 80kg/m3) foam. An ultrasonic foaming method was employed to modulate microcellular structure of PU foam. Mechanical activation was only employed to manipulate the internal structure of PU foam without any other treatment. A mean cell diameter of PU foam was gradually decreased with increase in the amplitude of ultrasonic waves. It was empirically found that the reduction of mean cell diameter induced by the ultrasonic wave enhances acoustic damping efficiency in low frequency ranges. Moreover, further analyses were performed with several acoustic evaluation factors; root mean square (RMS) values, noise reduction coefficients (NRC), and 1/3 octave band spectrograms.

Thermosonication as an Upcoming Technology in the Dairy Industry: An Overview

Ultrasound waves are longitudinal sound waves of frequency of 20 kHz or more. As low amplitude ultrasonic waves do not significantly modify the material under examination, they can be used to analyse the material. However, high amplitude ultrasonic waves can be used to process food as they have the capacity to alter the food material by cavitation. The use of ultrasound by itself may not be effective in destroying all the microbes in food. Hence, it can be coupled with pressure or heat or both to get the desired results. Thermosonication involves the simultaneous use of low frequency ultrasound waves (20 kHz) along with heat; and the both together have some synergistic effect. When heat and ultrasound is used together, the process temperature is considerably reduced compared to the conventional heating process, making it a green and economical technology as less energy is consumed; this in turn makes it a cost-efficient process. If thermosonication is seen to bring about the desired effects in milk, then it can be used as a commercial method to treat and homogenize milk in the future.

Application of Ultrasound to Pharmaceutical Industry : An Overview

The term “ultrasound” means vibrations similar to sound waves with a frequency higher than 20 kHz. US waves, apart from sharing the usual properties of sound, they also show some new properties owing to high energies. This makes ultrasonic waves to find use in engineering, material science and medicine. The ability to tune the frequency and amplitude of ultrasonic waves makes this technology attractive in pharmaceutical field also. Ultrasound is a promising technology with wide applications in pharmacy such as in controlling particle size, controlled crystallization, production of nano materials, enhancing the solubility of poorly soluble drug candidates. Furthermore, ultrasound can be used in effluent treatment, separation and concentration of particulate sub-populations based on dimensions and physical properties. US technology is also found useful in processing and formulating delicate biomolecules, such as proteins and nucleic acids because it ensures structural integrity of the molecules.

Microstructural and ultrasonic characterization of 2101 lean duplex stainless steel welded joint

In this paper, welded joint of a 2101 lean duplex stainless steel (DSS) was studied using ultrasonic attenuation measurements. Two plates were welded using gas metal arc welding (GMAW) process. Attenuation measurements were performed by the immersion ultrasonic pulse-echo technique using a high precision x, y, z scanner in order to generate c-scan images of the welded sample. Experimental measurements show that the longitudinal ultrasonic wave amplitude is significantly affected by the recrystallization of the microstructure caused by multi-pass welding.An increase in the attenuation coefficient of the ultrasonic wave was measured and related to coarser ferrite grains with bigger mean free ferrite distance while recrystallized zones with finer grains of intergranular austenite produce a substantial reduction in the attenuation coefficient. Similarly, it was found from Vickers microhardness maps, that finer microstructure show higher microhardness values while coarser grains present the lower values. The experimental evidence indicates that attenuation measurements can be used as nondestructive evaluation method to assess the microstructure of this type of welds.

Using response surface methodology to optimize ultrasound-assisted oxidative desulfurization

Latest strict environmental regulations have restricted the sulfur content of diesel fuels; therefore, deep desulfurization of fuels is required. Ultrasound-assisted oxidative desulfurization (UAOD) is an alternative for conventional desulfurization methods which can remove sulfur compounds from fuels under mild process conditions. In this study, UAOD of gasoil using tungstophosphoric acid catalyst and tetraoctylammonium bromide as a phase transfer agent in the presence of hydrogen peroxide as an oxidant was optimized. The optimal design of experiments was generated based on central composite face-centered design of Response surface methodology (RSM) to study effects of four process variables such as oxidant volume, mass of catalyst, mass of phase transfer agent and the ultrasonic wave amplitude on the sulfur conversion of gasoil. In addition, a predictive model of sulfur conversion was obtained based on RSM. The optimal values of process variables were evaluated to be 21.96 mL of oxidant, 1 gr of catalyst and 0.1 gr of phase transfer agent to achieve the maximum sulfur conversion of 95.92%.

Amplitude and phase measurements of continuous diffuse fields for structural health monitoring of concrete structures

Measuring amplitude and phase of continuous ultrasonic waves with a lock-in amplifier is shown to give similarly sensitive indicators of concrete damage as pulsed coda wave analysis, but maintains its sensitivity at considerably much lower signal levels. Continuous and pulsed measurements were performed on a concrete slab subjected to cyclically increased damage level. In the unloaded phase each measurement type was performed at varying transmit signal levels. The result indicates the possibility of using a larger distance between transducers in high frequency health monitoring systems of concrete structures, where attenuation of propagating waves is strong.

Diffraction of Light by Finite Amplitude Ultrasonic Waves

In the late 1950s the Ultrasonic Group at Michigan State University introduced light di raction to study distortion of ultrasonic waves in liquids under the direction of Prof. Egon Hiedemann. In this paper some results of these studies will be presented with detailed description of the author's measurements of B/A. The rate at which the harmonics are developed (the wave distortion is an indication of the harmonics present) during the propagation of the initially sinusoidal ultrasonic wave depends on the nonlinearity of the medium. The light which is di racted by the distorted wave results in asymmetric pattern contrary to the Raman Nath theoretical prediction. From the light intensity measurements due to the generated second harmonics ltered out by a metal plate the nonlinearity parameter B/A was determined. Developments in studying nite amplitude standing ultrasonic waves in a liquid lled cavity will be also discussed. Using light di raction measurements it was observed that above a threshold amplitude, fractional harmonics of the driver transducer are also generated in addition to the generated harmonics. It was recently observed that above a second threshold value of the driver amplitude the system undergoes chaotic behavior. Further increase of the driver amplitude returns the system from chaos to stable oscillation.

Recent Advances in the Development and Application of Power Plate Transducers in Dense Gas Extraction and Aerosol Agglomeration Processes

Power ultrasound (PU) is an emerging, innovative, energy saving and environmental friendly technology that is generating a great interest in sectors such as food and pharmaceutical industries, green chemistry, environmental pollution, and other processes, where sustainable and energy efficient methods are required to improve and/or produce specific effects. Two typical effects of PU are the enhancement of mass transfer in gases and liquids, and the induction of particle agglomeration in aerosols. These effects are activated by a variety of mechanisms associated to the nonlinear propagation of high amplitude ultrasonic waves such as diffusion, agitation, entrainment, turbulence, etc. During the last years a great effort has been jointly made by the Spanish National Research Council (CSIC) and the company Pusonics towards introducing novel processes into the market based on airborne ultrasonic plate transducers. This technology was specifically developed for the treatment of gas and multiphasic media characterized by low specific acoustic impedance and high acoustic absorption. Different strategies have been developed to mitigate the effects of the nonlinear dynamic behavior of such ultrasonic piezoelectric transducers in order to enhance and stabilize their response at operational power conditions. This work deals with the latter advances in the mitigation of nonlinear problems found in power transducers; besides it describes two applications assisted by ultrasound developed at semi-industrial and laboratory scales and consisting in extraction via dense gases and particle agglomeration. Dense Gas Extraction (DGE) assisted by PU is a new process with a potential to enhance the extraction kinetics with supercritical CO2. Acoustic agglomeration of fine aerosol particles has a great potential for the treatment of air pollution problems generated by particulate materials. Experimental and numerical results in both processes will be shown and discussed.

Use of acoustoelastography to evaluate tendon healing after surgical repair of an Achilles mechanism laceration and rehabilitation with a custom tarsal orthotic splint in a dog

Achilles mechanism laceration in dogs is commonly treated by suture repair and temporary tarsal immobilisation. Acoustoelastography is an ultrasound technique that can relate changes in ultrasonic wave amplitude to a...

Joining of Various Kinds of Metal Plates Using Ultrasonic Vibrations

Joining of dissimilar metal plates by using ultrasonic vibrations was investigated. Plastic flow appeared when joining two aluminium plates by applying a zero amplitude ultrasonic wave (stress amplitude is at a maximum). Over time, the plastic flow became larger and resulted in a stirring phenomenon of the materials. By utilizing this stirring phenomenon, an aluminium plate was joined to a steel plate. The resultant plate was analysed with cross tension test and cross section observation. These results revealed the relation between ultrasonic conditions and cross tensile load. When joining an aluminum plate to various kinds of metal plate, the cross tensile load of the joint reached a maximum value of 200N. The cross tension tests reveal that the fracture of the materials resulted in plug failure mode. Therefore, the achieved maximum cross tensile strength is determined by the tensile strength of the aluminum plate. The strength of the bonding was stronger than the tensile strength of the aluminum plate. These results led us to the conclusion that joining of dissimilar metal plates has been attained using ultrasonic vibrations.

Inactivation of Listeria monocytogenes and Escherichia coli by Ultrasonic Waves Under Pressure at Nonlethal (Manosonication) and Lethal Temperatures (Manothermosonication) in Acidic Fruit Juices

The inactivation of Listeria monocytogenes and Escherichia coli suspended in apple and orange juices by ultrasound under pressure at nonlethal (manosonication, MS) and lethal temperatures (manothermosonication, MTS) was evaluated. Significant differences were found in the MS resistance (35 °C, 110 μm, 200 kPa) of three strains of L. monocytogenes and three of E. coli in pH 3.5 buffer, L. monocytogenes STCC 5672 and E. coli O157:H7 being the most resistant strains. Regarding the interspecific differences, L. monocytogenes showed higher MS resistance than E. coli. Although the pH and treatment medium composition did not significantly change the bacterial MS resistance, the effectiveness of ultrasound increased by both raising the amplitude of ultrasonic waves and the pressure. The energy transmitted to the fruit juices by ultrasonic waves at different combinations of amplitudes (46.5, 90, 110, and 130.5 μm) and pressures (0, 100, and 200 kPa) was also studied, obtaining an exponential relationship between the D MS values and power input: an increase of 116 W increased the inactivation rate approximately 10-fold in both juices. The MS resistance of both species decreased when heat was applied jointly with ultrasound (MTS), which was more effective in inactivating L. monocytogenes and E. coli than the sum of MS and heat acting simultaneously but independently. Therefore, MTS showed a synergistic lethal effect in acidic juices, whose magnitude was dependent on the treatment conditions.

Effects of ultrasonic vibration on the micro-molding processing of polylactide

A new ultrasonic micro-molding system was used to process polylactide (PLA) and fabricate reduced dimension specimens. Plasticization and molding of PLA were achieved by applying ultrasonic waves after feeding the polymer into a plasticizing chamber. Chemical and physical characteristics of processed PLA varied depending on the processing window (i.e. changes in ultrasonic wave amplitude between 14.2 and 48.1μm and molding pressure between 0.5 in 6bars). In terms of chemical effects, the application of ultrasound can lead to lower molecular weights (e.g. decreases of more than 45% in the weight average molecular weight), revealing partial degradation of the material. Also, the processed materials exhibited slightly higher thermal degradability than pure PLA because ultrasonic vibrations break molecular linkages and worsen the polymer structure. Finally, the processing conditions for the preparation of PLA specimens could be optimized without causing degradation and preserving structural characteristics and mechanical properties. Specifically, the use of an amplitude of 48.1μm and a pressure of 3bars gave samples with the same molecular weight as the raw material (i.e. 117,500g/mol as opposed to 117,300g/mol for Mw).

Enhanced biodesulfurization of bunker oil by ultrasound pre-treatment with native microbial seeds

This work investigated the effect of ultrasound on the biodesulfurization of bunker oil by the native microbial cells in oil/water biphasic system. The operational parameters for the desulfurization procedure such as ultrasonic irradiation time, ultrasonic wave amplitude, biocatalyst initial concentration and ratio of oil phases to aqueous phases were studied. An obviously positive effect was observed after introduction of ultrasound into the BDS system. The sulfur content of bunker oil did not decrease in absence of ultrasound pre-treatment. After ultrasonic pre-treatment, about 10–20% of sulfur was removed for the samples without any additive and was dependent on ultrasonic irradiation time, ultrasonic wave amplitude, biocatalyst initial concentration and ratio of oil phases to aqueous phases. During the desulfurization, even though an easily available carbon source, glycerol, was supplied, some low molecular weight hydrocarbons can be consumed by cells as carbon source, resulting in a loss in the fuel value or energy loss.

Enhancement of signal amplitude of surface wave EMATs based on 3-D simulation analysis and orthogonal test method

The amplitude of an ultrasonic signal generated by electromagnetic acoustic transducers (EMATs) is typically low when compared to those generated by contacting transducers, which restricts the application of EMATs in the fields of nondestructive testing and nondestructive evaluation. The transmission process of a surface wave EMAT is studied, based on a previously established 3-D model, with the aim of enhancing the amplitude of ultrasonic waves generated by the EMAT. The effect of changing various EMAT parameters on the surface wave is investigated, by utilizing the orthogonal test method. Results indicate that after optimization, the signal amplitude of the EMAT has increased by 25.2%.

Evolution of ultrasonic velocity and dynamic elastic moduli with shear strain in granular layers

Ultrasonic wave transmission has been used to investigate processes that influence frictional strength, strain localization, fabric development, porosity evolution, and friction constitutive properties in granular materials under a wide range of conditions. We present results from a novel technique using ultrasonic wave propagation to observe the evolution of elastic properties during shear in laboratory experiments conducted at stresses applicable to tectonic faults in Earth’s crust. Elastic properties were measured continuously during loading, compaction, and subsequent shear using piezoelectric transducers fixed within shear forcing blocks in the double-direct-shear configuration. We report high-fidelity measurements of elastic wave properties for normal stresses up to 20 MPa and shear strains up to 500 % in layers of granular quartz, smectite clay, and a quartz-clay mixture. Layers were 0.1–1 cm thick and had nominal contact area of \(5 \mathrm{cm} \!\times \! 5 \mathrm{cm}\). We investigate relationships among frictional strength, granular layer thickness, and ultrasonic wave velocity and amplitude as a function of shear strain and normal stress. For layers of granular quartz, P-wave velocity and amplitude decrease by 20–70 % after a shear strain of 0.5. We find that P-wave velocity increases upon application of shear load for layers of pure clay and for the quartz-clay mixture. The P-wave amplitude of pure clay and quart-clay mixtures first decreases by \(\sim \)50 and 30 %, respectively, and then increases with additional shear strain. Changes in P-wave speed and wave amplitude result from changes in grain contact stiffness, crack density and disruption of granular force chains. Our data indicate that sample dilation and shear localization influence acoustic velocity and amplitude during granular shear.

Chaos and beyond in a water filled ultrasonic resonance system

Finite amplitude ultrasonic wave resonances in a one dimensional liquid-filled cavity are reported. The resonances are observed to include not only the expected harmonic and subharmonic signals but chaotic signals as well. The nonlinear features of this system were recently investigated and are the focus of this presentation. An ultrasonic interferometer having optical precision was constructed. The transducers having the frequency range 1-10 MHz, driven by a high power amplifier. Both an optical diffraction system and a receiving transducer were used to assess the generated resonance response in the cavity. Five regions of excitation are identified: 1. Linear region: at low intensity of the ultrasonic wave the diffraction pattern of a light beam is symmetric. 2. Nonlinear region: with increased sound amplitude the diffraction pattern becomes asymmetrical. 3. Subharmonic region: further increase of the amplitude above a threshold value leads to the generation of subharmonics. 4. Chaos: increasing the drive amplitude to a second threshold level the diffraction pattern is smeared out indicating a time-chaotic region. 5. Beyond chaos: further increase of the amplitude results again a stable diffraction pattern. A first-principle-based explanation is presented. This work is supported by the Aircraft Aging Program, at NASA Langley Research Center.

Ultrasound-assisted oxidative desulfurization of bunker-C oil using tert-butyl hydroperoxide

This work investigated the ultrasonic assisted oxidative desulfurization of bunker-C oil with TBHP/MoO3 system. The operational parameters for the desulfurization procedure such as ultrasonic irradiation time, ultrasonic wave amplitude, catalyst initial concentration and oxidation agent initial concentration were studied. The experimental results show that the present oxidation system was very efficient for the desulfurization of bunker-C oil and ∼35% sulfur was removed which was dependent on operational parameters. The application of ultrasonic irradiation allowed sulfur removal in a shorter time. The stronger the solvent polarity is, the higher the sulfur removal rate, but the recovery rate of oil is lower. The sulfur compounds in bunker-C oil reacted with TBHP to produce corresponding sulfoxide, and further oxidation produced the corresponding sulfone.