Longitudinal Acoustic Waves Research Articles

Features of amplitude frequency characteristics of ABS plastic 3D printed metamaterial sample

In this study, we investigated the acoustical properties of custom-designed phononic crystal-like acoustic metamaterials 3D printed from ABS plastic. The elastic properties of these metamaterials were studied experimentally and numerically. The metamaterial consisted of a set of plane parallel lattices the number of which could vary in different samples. Each lattice in the sample consisted of 16 parallel square rods. The amplitude-frequency characteristics (AFC) of the fabricated metamaterial sample were measured in the frequency range (35-100) kHz using longitudinal acoustic waves both in air and water. The propagation velocities of longitudinal and shear acoustic waves of ABS plastic itself were measured prior to the experiment. The band gaps (stop bands) were detected and investigated while measuring AFC of the metamaterials. We have found that the increase in the number of lattice layers in the sample led to the band gap acoustic wave attenuation coefficient increase along with the band gap narrowing, while the central frequency of the band gap remained the same. The numerical simulation of the sample frequency response was carried out in COMSOL. The results of experimental studies and numerical simulations were in satisfactory agreement. We have also investigated the ultrasound scattering diffraction pattern of the sample. The obtained results can be used in solid-state physics and material science, to create materials with controlled frequency-dependent acoustic properties.

Акустические и акустооптические свойства стекол Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- и Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- в случае дифракции на продольных и сдвиговых акустических волнах

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 µm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz.

Using Broadband Acoustic Spectroscopy with a Laser Source of Ultrasound to Study the Frequency Dependences of the Phase Velocity of Longitudinal Acoustic Waves in Porous Carbon Fiber Reinforced Plastic Composites

Using Broadband Acoustic Spectroscopy with a Laser Source of Ultrasound to Study the Frequency Dependences of the Phase Velocity of Longitudinal Acoustic Waves in Porous Carbon Fiber Reinforced Plastic Composites

Применение широкополосной лазерно-ультразвуковой спектроскопии для неразрушающего контроля пористости углепластиков с различным объемным содержанием углеродного волокна

In this work, to obtain the frequency dependences of the phase velocity of longitudinal acoustic waves in composite materials, we use the method of broadband laser-ultrasonic spectroscopy, based on laser thermo-optical excitation of broadband acoustic pulses. Unidirectional carbon fiber reinforced plasticsampes with different volume contents of the matrix and fiber were taken as objects of study.For the studied samples, the frequency dependences of the phase velocity were obtained in the spectral range of 0.8 – 10 MHz, and the existence of the phase velocity dispersion in this range was shown. The phase velocity dispersion of longitudinal acoustic waves in the sample was calculated using the phase spectra of the probe ultrasonic pulse and the pulse transmitted through the sample under study. It is also shown that the relative dispersion of the phase velocity characterizes the porosity of the sample, and the higher the porosity, the greater the relative dispersion. Empirical relations obtained for the relationship between porosity and relative dispersion can be used for the operational non-destructive assessment of the porosity of composites. The results obtained can be useful both for quality control of the materials obtained with the aim of modernizing manufacturing technologies and for predicting the behavior of structures and parts of this material under external loads.

Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta Co-Doped w-AlN.

Enhancement of piezoelectricity in w-AlN is desired for many devices including resonators for next-generation wireless communication systems, sensors, and vibrational energy harvesters. Based on density functional theory, we show that Li and X (X = V, Nb, and Ta) co-doping in 1Li:1X ratio transforms brittle w-AlN crystal to ductile, along with broadening the compositional freedom for significantly enhanced piezoelectric response, promising them to be good alternatives to expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization (e.g., about 1 C/m2 for Li0.125X0.125Al0.75N) with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. An increase in piezoelectric stress constant (e33) with a decrease in elastic constant (C33) results in an enhancement of piezoelectric strain constant (d33), which is desired for improving the performance of bulk acoustic wave (BAW) resonators for high-frequency radio frequency (RF) signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K332), transverse piezoelectric strain constant (d31), and figure of merit (FOM) for power generation. However, the enhancement in K332 is not as pronounced as that in d33 because co-doping increases dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable to that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5-7 km/s) despite the fact that the acoustic wave velocities, important parameters for designing resonators or sensors, decrease with co-doping or Sc concentration.

Nyomásfüggő akusztikus sebesség adatok globális inverziója új kőzetfizikai modell alapján

A cikkben a korábban már publikált egyszeres exponenciális kőzetfizikai modell továbbfejlesztését, az új többszörös exponenciális kőzetfizikai modellt mutatjuk be, amely leírja az akusztikus longitudinális hullámsebesség nyomásfüggését. Mivel a kőzetben a nyomás fokozásával egyidejűleg több relaxációs folyamat (pl. mikrorepedések vagy, pórustérfogat záródása, vagy szemcsehatárokon történő súrlódás, stb.) is okozhatja a terjedési sebesség növekedését, a modell egyszerre több mechanizmust képes kezelni. A korábban alkalmazott linerizált inverziós eljárás a lokális minimumban elakadhat, ezért az abszolút minimumot adó globális optimalizálás módszerét alkalmaztuk a laboratóriumban mért longitudinális sebesség-nyomás adatok feldolgozása során. A kifejlesztett modellegyenletet Simulated Annealing algoritmusban válaszegyenletként alkalmazva a modell kőzetfizikai paramétereit meg lehetett határozni. Az inverziós eredmények igazolták, hogy az új modellel és algoritmussal számított adatok pontosabban illeszkednek a kőzetmintán mért adatokhoz.

Ultrafast strain engineering and coherent structural dynamics from resonantly driven optical phonons in LaAlO3

Strain engineering has been extended recently to the picosecond timescales, driving ultrafast metal–insulator phase transitions and the propagation of ultrasonic demagnetization fronts. However, the nonlinear lattice dynamics underpinning interfacial optoelectronic phase switching have not yet been addressed. Here we perform time-resolved all-optical pump-probe experiments to study ultrafast lattice dynamics initiated by impulsive light excitation tuned in resonance with a polar lattice vibration in LaAlO3 single crystals, one of the most widely utilized substrates for oxide electronics. We show that ionic Raman scattering drives coherent rotations of the oxygen octahedra around a high-symmetry crystal axis. By means of DFT calculations we identify the underlying nonlinear phonon–phonon coupling channel. Resonant lattice excitation is also shown to generate longitudinal and transverse acoustic wave packets, enabled by anisotropic optically induced strain. Importantly, shear strain wave packets are found to be generated with high efficiency at the phonon resonance, opening exciting perspectives for ultrafast material control.

Laser Optoacoustic Method for Quantitative Estimation of Porosity in Cast Dispersion-Strengthened Metal-Matrix Composite Materials

A laser optoacoustic method for quantitative assessment of the volumetric porosity of cast dispersion-strengthened metal-matrix composite materials has been proposed and experimentally implemented. The method is based on a statistical analysis of the distribution of amplitudes of backscattered broadband pulses of longitudinal acoustic waves in the tested materials. Laser excitation and piezoelectric recording of ultrasound is implemented with one-way access to the test object using a special laser-ultrasonic transducer. Silumin-based composites reinforced with silicon carbide microparticles in various volume concentrations (0.033–0.135) and composites obtained by reaction injection moulding based on aluminum reinforced with intermetallic $${\text{A}}{{{\text{l}}}_{3}}{\text{Ti}}$$ (volume concentration 0.04–0.115) have been studied. For both types of composites, the distribution of amplitudes of backscattered ultrasonic signals is approximated by a Gaussian distribution function applicable for a large number of statistically independent quantities. The empirically obtained dependence of the half-width of this distribution on the volumetric porosity of composites of two different types is approximated by the same linear function regardless of the manufacturing technology, as well as of the type, size, and concentration of strengthening particles.

High-Pressure Elasticity of Baltic Amber Studied by Brillouin Spectroscopy

The high-pressure elasticity of Baltic amber was investigated up to ∼12 GPa for the first time by using Brillouin spectroscopy. Two scattering geometries were adopted to derive the pressure dependence of the mode frequency of longitudinal acoustic waves, the longitudinal sound velocity, the refractive index and the density. These properties showed rapid changes at low pressures below ∼4 GPa while their changes were more sluggish at higher pressures. This crossover behavior was attributed to the collapse of free volume, which seems to be a rather common behavior of many amorphous materials. Since Baltic amber is a unique glass produced by vitrification under extremely long time, the first investigation of high-pressure elasticity reported in this study may be a good starting point for further in-depth research in this super-aged glassy system.

Effect of the Hydrocarbon Chain Disorder in Phosphatidylcholine Bilayers on Gigahertz Sound Velocity.

Suspensions of multilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and hydrated and dehydrated aligned multilamellar samples of DMPC were studied by Brillouin spectroscopy in the temperature range from 90 to 333 K. The sound velocity of the longitudinal acoustic wave was evaluated from the Brillouin spectra. It was found that phase transition, hydration state, and planar or vesicular form of bilayers affect the gigahertz sound velocity. Usually, the temperature dependence of the sound velocity is weak in solid substances. Amazingly, the sound velocity of hydrated DMPC samples showed significant temperature-induced changes of up to 1.8 times, even within the solid-like gel phase. We explained this effect by temperature-induced excitations of the disordered conformational states of the hydrocarbon chains as well as anharmonic effects. In addition, the relevance of the gigahertz sound velocity to the description of subterahertz Raman features was demonstrated.

Theoretical and Experimental Study of the Effects of Impact Drilling Parameters on the Properties of Surrounding Rock Damage

Using a self-designed hydraulic impact drilling test-bed and rock core drill, six groups of cylindrical granite specimens (93 mm dia. × 200 mm) containing central axial holes formed either by impact or nonimpact drilling methods were tested in uniaxial compression to failure on an Instron 1346 universal testing machine to investigate their mechanics and damage properties. The longitudinal acoustic wave velocities were measured before testing. The rock specimens were grouped according to the method of drilling the central hole (impact load exerted by different impact power and different frequencies for an approximately identical impact power, or nonimpact drilling). In this study, a statistical constitutive damage model based on Weibull distribution was used to calculate the degree of rock damage after drilling center holes. The experimental curves were measured to analyze the damage evolution process and the radius of rock damage. These indicate that rock damage increased with the increase of impact power and decreased with increasing impact frequency at constant impact power. This was also verified by the measured longitudinal wave velocity in all rock specimens. These results have significance for guiding the design of composite rock drilling tools that are dedicated to improving rock-breaking efficiency.

Experimental determination of full matrices of the piezo-optic and elasto-optic coefficients for Pb5Ge3O11 crystals.

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals, Pb5Ge3O11, using Dixon-Cohen and interferometric methods. Two different types of samples are studied, single- and multi-domain. We show that the correct data for the Pb5Ge3O11 crystals can be obtained only with single-domain samples, since the domain structure induces a number of features that make the final results unreliable. We demonstrate that the acousto-optic figures of merit reach high-enough values at the isotropic acousto-optic interactions with longitudinal acoustic waves propagating along the principal x and z axes (63×10-15 and 37×10-15s3/kg), respectively. At the same time, the efficiency of the acousto-optic interactions with transverse acoustic waves is low. The same is true concerning anisotropic acousto-optic diffraction, since the appropriate elasto-optic coefficients are small enough.

Application of Laser-Ultrasonic Technique of Acoustic Impedance Measurement with Signals Detection by Backward-Mode Scheme for Porosity Content Evaluation in CFRP Laminates

The aim of this work is the development and experimental implementation of the laser-ultrasonic method for CFRPs porosity assessment with one-side access to an investigated object. The scheme with the laser thermooptical generation and backward-mode piezoelectric detection of longitudinal acoustic waves is used. The proposed method is based on the measurement of the acoustic impedance of a composite specimen by using the value of the integral of the ultrasonic pulse reflected from an immersion layer-specimen interface. The existence of the relationship between the porosity content, ultrasound velocity, and material’s density allows one to assess the porosity of CFRPs by the measured acoustic impedance. The proposed method does not require plane parallelism of the input and output surfaces of the studied objects, as well as measuring the thickness of the object. This allows studying CFRP structures with complex shapes. This method may be of use for various types of composite materials, regardless of acoustical waves propagating features related to a periodical material’s structure. CFRP specimens with three reinforcement schemes and different average volume porosity contents were investigated. It is shown that the local porosity distribution in the studied CFRPs is nonuniform along the fiber stacking plane. The porosity content obtained by the laser-ultrasonic method was checked using the X-ray computer tomography. The porosity values, averaged from the laser-ultrasonic measurement results, coincide with the X-ray tomography data within the error limits. The method can be useful for quality control of obtained composite structures with the aim of modernization of technology processes and selecting optimal production conditions and also for the detection of changes in composite structures during their operation or during fatigue testing processes.

Laser ultrasonic monitoring of reversible/irreversible modification of a real crack under photothermal loading

We study the responses of laser-generated acoustic waves to localized reversible/irreversible modifications of microscopic asperities on crack surfaces during crack closure, which is an essential process in nonlinear photoacoustic/photothermal crack detection techniques. Our laser ultrasonics technique involves optical measurement of the transmission and mode conversion of the laser-generated surface acoustic waves caused by the crack. Reversible/irreversible modifications of asperities can be achieved via non-contact photothermal loading of the crack. Three photothermal loading cycles were realized in individual succession and were monitored using the laser ultrasonics technique at various experimental locations along the crack. In our experiments, each photothermal loading cycle includes multiple successive subcycles, in which the material is first heated and then cooled to its equilibrium temperature, thereby initiating local closing, followed by opening of the crack. Each subcycle is monitored twice using the laser ultrasonics technique, once each at the end of heating and cooling. Furthermore, each successive subcycle is accomplished at a higher power of heating laser than that of the previous subcycle. Significant differences in the peak-to-peak amplitude of the surface skimming longitudinal acoustic wave, which is excited by mode conversion of the Rayleigh wave by the crack, are revealed during the first cycle of photothermal loading. These differences clearly indicate a partial irreversibility of the mechanical processes occurring in the crack surfaces during subcycles of the first cycle. In a larger temporal scale, irreversible modification of crack surfaces is observed from the significant difference between the experimental results of the first photothermal loading cycle and the subsequent two cycles, whereas a reversible response of the crack surface to thermoelastic loading is observed from the similarity of the measurements accumulated during the two subsequent cycles.

A NEW ACOUSTIC-WAVE ANALYSIS METHOD OF STRUCTURAL-MECHANICAL POLYMERBETON ROADS PARAMETERS

The longitudinal and transverse reflection waves problem from the boundary of the liquid and the homogeneous elastic medium ¬ roads polymer concrete pavement is considered - taking into account that the longitudinal acoustic wave is excited in the liquid. Since the energy distribution between incident, reflected, transformed and excited waves is determined by the structural and mechanical parameters of the media (density, velocities of longitudinal and transverse waves) according to the Poisson's ratio, to model such an elastic medium as pavement, used material belonging to heterogeneous and structural materials class under the general name "auxetics", having a negative Poisson's ratio. As a result of researches amplitudes of reflected and transformed acoustic waves potentials in the elastic auxetic medium and amplitudes excitation of an acoustic wave in the liquid covering a polymer-concrete covering of the road were defined potentials It was proved that the reflection, transformation and excitation coefficients when the longitudinal and transverse waves fall on the boundary between the auxetic medium and the liquid nature depends on the Poisson's ratio and the acoustic contact media stiffness The conditions of critical angles depending on physical parameters of these environments occurrence are substantiated.The results obtained in this work can be further used to improve and refine engineering methods for calculating the parameters of diagnostic equipment used to determine the thermoelastic state of pavement, both at the stage of design and construction of such devices and in their actual operation.

Self-Similar Acoustic Waves in the Media with a Power-Law Hysteresis Nonlinearity

We present the results of the studies of propagation of longitudinal acoustic waves in the media with a power-law hysteresis nonlinearity. Exact analytical solutions for the self-similar periodic waves propagating in such media without changing their forms are given. The spectral characteristics of these waves are studied.

Acoustic Characterization of Polydimethylsiloxane for Microscale Acoustofluidics

Polydimethylsiloxane (PDMS) is widely used in acoustofluidic devices among other lab-on-a-chip systems, but a systematic study of its acoustic parameters is lacking, making it difficult to study the acoustic-PDMS interactions accurately during device designs and evaluations. Here the phase velocities and attenuation coefficients of longitudinal and shear acoustic waves propagating in Sylgard 184 samples are measured throughout the frequency band from 3.0 to 7.0 MHz. Five sample groups are prepared, corresponding to different base-agent mixing ratios $\ensuremath{\sigma}$ and curing temperatures $T$, $\left(\ensuremath{\sigma},\phantom{\rule{0.2em}{0ex}}T\right)=(10:1,\phantom{\rule{0.2em}{0ex}}85{\phantom{\rule{0.1em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C})$, (7:1, 85 ${}^{\ensuremath{\circ}}\mathrm{C}$), (5:1, 85 ${}^{\ensuremath{\circ}}\mathrm{C}$), (10:1, 65 ${}^{\ensuremath{\circ}}\mathrm{C}$), and (10:1, 100 ${}^{\ensuremath{\circ}}\mathrm{C}$). The shear wave measurements involved examining the change of the reflection coefficient at a solid surface caused by the attachment of the samples. For longitudinal waves, the parameters are obtained by analyzing their round-trip transmissions inside double-layered solid-PDMS structures. Apart from these, the influence of sample aging on the concerned parameters are also examined. With the measured results, the parameters lead to fitted functions based on the Kramers-Kronig principle, which should benefit users working outside the studied frequency range. Finally, the two independent parameters in the elastic matrix of PDMS are provided.

Analysis of longitudinal leaky surface acoustic waves on LiNbO3/amorphous layer/quartz structure

Recently, bonded structures comprising a quartz substrate and a LiNbO3 (LN) or LiTaO3 thin-plate have been attracting attention as a means of obtaining enhanced properties for surface acoustic wave (SAW) devices. It was reported that the bonding strength was extremely improved by utilizing an amorphous thin film as a middle layer. In this research, the propagation and resonance characteristics of longitudinal leaky SAWs on an amorphous layer inserted to the boundary between an X-cut 36°Y-propagating LN (X36°Y-LN) and X35°Y-quartz were investigated. For the metallized surface of an X36°Y-LN/Al2O3/X35°Y-quartz structure, an attenuation of 0.0001 dB /λ was obtained at an LT thin-plate thickness of 0.072λ (λ: wavelength), which was better than that of an X36°Y-LN/X35°Y-quartz structure. Utilizing a finite element method, we found that the admittance ratio and Q factor for the X36°Y-LN/Al2O3/X35°Y-quartz model were improved owing to the reduction of the leakage due to the shear-vertical particle displacement.

Experimental and Numerical Characterization of a Liquid Jet Injected into Air Crossflow with Acoustic Forcing

The current work presents a study on spray dynamics in aeronautical injectors. More particularly, the experimental characterization of a liquid jet in an oscillating gaseous cross flow (LJIOGCF) atomization is presented and compared to numerical simulations. The experimental setup consists of a water jet transversally injected into an oscillating subsonic air flow at ambient conditions. In a first step, a cross-comparison is performed in order to validate the numerical model and the tools used to quantitatively analyze the experimental data in the case of steady air flows. In a second step, the air flow is submitted to longitudinal acoustic waves using a pneumatic loudspeaker. A detailed database, representative of the actual dynamics of LJIOGCF configurations, is obtained using both experiments and numerical simulations. Visualizations with a back lighting approach are employed to characterize the liquid jet close to the injection location while phase doppler anemometry is used to determine the characteristics of the crossflow and the spray in terms of droplet size, velocity and concentration. Phase-averaging is performed to characterize the response of the liquid jet, the air velocity field and the spray oscillations during the excitation cycle. The numerical simulation relies on a multi-scale large eddy simulation approach. This method couples a multi-fluid solver for the liquid jet main body with a dispersed phase solver for the atomized spray. The acoustic perturbation is imposed as a fluctuating air inflow condition. The experimental results show that the acoustic forcing induces a flapping motion of the liquid jet. As a consequence, velocity and concentration waves travelling downstream the liquid jet appear. Coupling phenomena between the crossflow, the atomization of the liquid jet and the transport of droplets are observed, revealing different wave transport velocities. It further appears that spray dynamics are both driven by liquid column and crossflow oscillations. The numerical simulation is able to capture the global flapping dynamics of the liquid jet’s main body. More quantitative comparisons show a very good agreement between simulation and experiments regarding the jet trajectories over the entire excitation cycle. Numerical droplet average velocities are also in good agreement with experiments. Finally, the numerical simulation partly reproduces the coupling between acoustics and spray dynamics observed in the experiments.

Determinating the Volume Content of a Polymeric Matrix in CFRP Structures Using a Laser-Ultrasonic Method

An acoustic method for a quantitative assessment of the volume content of a polymeric matrix in CFRPs is proposed and realized experimentally. For this purpose, a laser-ultrasonic method based on the thermo-optical excitation of broadband pulses of longitudinal acoustic waves is used. A formula for calculating the volume content of the polymeric matrix in a CFRP from experimentally measured phase velocities of longitudinal acoustic waves in this material is proposed. Distributions of the volume content of the matrix in a control CFRP specimen and in a CFRP structure made under similar conditions are obtained. It is shown that the laser-ultrasonic method allows one to detect the areas with excess and deficient matrix content in CFRP specimens and areas of CFRP constructions and to quantitatively assess the spread of matrix content. The spread between the maximum and minimum matrix content observed depends on the shape of the investigated area of the structure. This method can be used for the quality control of composite structures before their exploitation.