Characteristics Of Acoustic Waves Research Articles

Evaluation of fatigue damage of structural steel based on attenuation of laser-induced surface acoustic wave

ABSTRACT In this paper, the fatigue damage degree of low-alloy structural steel is evaluated by using the attenuation characteristics of laser-induced surface acoustic wave (SAW) during propagation. Taking the typical structural steel material Q345 as an example, a cracks model of fatigue damage is established, and the finite element method is used to solve the model. The results showed that the attenuation coefficient of SAW can reflect the depth and density of fatigue cracks. The surface measurement experiments of specimens with stress cycles of 0, 50000, 100000, 150000, and 200,000 showed that with the increase of stress cycles, the attenuation coefficient of SAW increases as a whole, indicating that it is feasible to evaluate the fatigue damage degree based on the attenuation of SAW. A method of applying tensile stress to the material to improve the sensitivity of fatigue damage evaluation is proposed. The tensile stress is used to offset the horizontal amplitude of the SAW, keeping the fatigue cracks in an open state and increasing the attenuation coefficient of SAW. The attenuation coefficient measurement experiment shows that this method is feasible.

The acoustic Galton board

Phononic crystals are a class of materials with periodic structures that influence the propagation characteristics of acoustic waves through periodically arranged structural units. Here, we have developed the acoustic Galton board (AGB), a groundbreaking apparatus that serves as a cost-effective and user-friendly tool for demonstrating phononic crystal properties such as band gaps, Bragg scattering, and local resonance. The device comprises an elastic wave signal generator, an enhanced Galton board featuring a sophisticated pillar-nail array, and a signal receiver. The experimental results we have obtained demonstrate the significant impact of the AGB on elastic wave dispersion, effectively creating bandgaps that impede wave transmission within specific frequency ranges while allowing unhindered propagation in others. Furthermore, the AGB can simulate phononic crystals using both the Bragg scattering mechanism, achieved through the design of periodic rigid pillar-nail arrays, and the locally resonant mechanism, facilitated by the design of pillar-nail arrays with composite material structures. Additionally, the AGB can extend its applications to serve as a simulation tool for elastic metamaterials.

Ultrasensitive liquid sensor based on an embedded microchannel bulk acoustic wave resonator

The high-frequency and high-quality factor characteristics of bulk acoustic wave (BAW) resonators have significantly advanced their application in sensing technologies. In this work, a fluidic sensor based on a BAW resonator structure is fabricated and investigated. Embedded microchannels are formed beneath the active area of the BAW device without the need for external processes. As liquid flows through the microchannel, pressure is exerted on the upper wall (piezoelectric film) of the microchannel, which causes a shift in the resonant frequency. Using density functional theory, we revealed the intrinsic mechanism by which piezoelectric film deformation influences BAW resonator performance. Theoretically, the upwardly convex piezoelectric film caused by liquid flow can increase the resonant frequency. The experimental results obtained with ethanol solutions of different concentrations reveal that the sensor, which operates at a high resonant frequency of 2.225 GHz, achieves a remarkable sensitivity of 5.1 MHz/% (221 ppm/%), with an ultrahigh linearity of 0.995. This study reveals the intrinsic mechanism of liquid sensing based on BAW resonators, highlights the potential of AlN/Al0.8Sc0.2N composite film BAW resonators in liquid sensing applications and offers insights for future research and development in this field.

Nonlinear Ion Acoustic Waves in Multicomponent Plasmas with Nonthermal Electrons-positron and Bipolar Ions

Abstract This paper studied the propagating characteristics of (2+1) dimensional nonlinear ion acoustic waves in a multicomponent plasma with nonthermal electrons, positrons and bipolar ions. The dispersion relations are initially explored by using the small amplitude wave's dispersion relation. Then, the Sagdeev potential method is employed to study large amplitude ion acoustic waves. The analysis involves examining the system's phase diagram, Sagdeev potential function, and solitary wave solutions through numerical solution of an analytical process in order to investigate the propagation properties of nonlinear ion acoustic waves under various parameters. It is found that the propagation of nonlinear ion acoustic waves is subject to the influence of various physical parameters, including the ratio of number densities between the unperturbed positrons, electrons to positive ions, nonthermal parameters, the masses ratio of positive ions to negative ions, and the charge numbers ratio of negative ions to positive ions, the ratio of the electrons’ temperature to positrons’ temperature. In addition, the multicomponent plasma system has a compressive solitary waves with amplitude greater than zero or a rarefactive solitary waves with amplitude less than zero, in the meantime, compressive and rarefactive ion acoustic wave characteristics depend on the charge numbers ratio of negative ions to positive ions.

Acoustics of wet porous media with evaporation/condensation

This paper investigates acoustic wave propagation in wet rigid-frame porous media accounting for evaporation and condensation. At equilibrium, the solid walls are covered by a thin water film, and water vapor in the air is at its temperature-dependent saturation pressure. Small acoustic perturbations cause water to vaporize or condense, which together with the reversibility of the phase change, lead to a linear problem where the usual local poro-acoustics physics is enriched with the (i) Clapeyron relation linking liquid-wall temperature, vapor pressure, and latent heat of vaporization, (ii) latent heat transfer in the solid frame, (iii) diffusion equation for water vapor in air, and (iv) water vapor's equation of state. The equilibrium temperature highly influences the vapor concentration and the physical parameters of saturated moist air. Using the two-scale asymptotic homogenization method, it is shown that the dynamic permeability is determined similarly to classical porous media, while the effective compressibility is modified by evaporation/condensation and the equilibrium temperature. This modification is influenced by vapor mass and heat flows associated with phase changes through a local fully coupled heat transfer and water vapor diffusion problem, with specific boundary conditions at the gas–water interface. The analysis identifies dimensionless parameters and characteristic frequencies defining the upscaled model's features. Depending on equilibrium temperature, the theory qualitatively and quantitatively determines the characteristics of acoustic waves propagating through the media. The results are illustrated and discussed with analytically developed models.

Response Patterns of Acoustic Wave Characteristics to Reservoir Petrophysical Parameters in Different Bedding Directions: A Case Study of Low- and Middle-Rank Coals in Xinjiang, China.

The physical properties of coal reservoirs, important parameters for evaluating the production potential of coalbed methane (CBM) resources, can be assessed nondestructively and in real-time using acoustic wave technology. In this study, we collected 48 low- and middle-rank coal samples oriented in different bedding directions from seven typical coal mines, encompassing the Zhunan, Tuha, and Kuqa-Bay coalfields in Xinjiang, China. We clarified the characteristics of the physical parameters (apparent density, fracture, porosity, and permeability) and acoustic wave of coal variations through acoustic wave, porosity, and permeability experiments, revealing the response law of acoustic wave characteristics to the physical parameters of coal. The results indicated that the acoustic wave velocity and dynamic elastic modulus (E d) of coal samples oriented in the perpendicular bedding direction are larger than those oriented in the parallel bedding direction; however, the dynamic Poisson's ratio (μd) of coal samples oriented in different bedding directions does not significantly differ. The existence of fractures significantly reduces the acoustic wave velocity and E d of the coal. The greater the apparent density of coal, the tighter its structure, resulting in a faster acoustic wave velocity. The larger the porosity of coal, the greater its internal voids, leading to a more pronounced attenuation of acoustic energy and a slower acoustic wave velocity. The more developed and interconnected the bedding fractures of coal bodies oriented in the parallel bedding direction, the higher their permeability, resulting in a smaller decrease in acoustic wave velocity. Conversely, the more developed the bedding fractures of coal bodies oriented in the perpendicular bedding direction, the more pronounced their attenuation of acoustic wave velocity. Finally, the regression equations for E d with the square of P-wave velocity (V P 2) and μd with the square ratio of V P to S-wave velocity (V P 2/V S 2) were established for coal. The study findings can help evaluate and predict the reservoir quality of coal seams, assess CBM, and improve the safety and efficiency of its extraction.

Painlevé integrability and multiple soliton solutions for the extensions of the (modified) Korteweg-de Vries-type equations with second-order time-derivative

This work introduces two (3+1)-dimensional expansions of the Korteweg–de Vries (KdV) and modified KdV (mKdV) equations. These extensions incorporate a second-order time-derivative term, similar to the Boussinesq equation. The Painlevé test is utilized to verify the integrability of each extended model. The bilinear form is employed to investigate the existence of multiple-soliton (MS) solutions for each system under consideration. Furthermore, we provide solutions in the form of lumps for the extended KdV equation. The multidimensional KdV-type equations surpass the standard KdV equation. However, they offer enhanced accuracy by representing a broader spectrum of nonlinear phenomena in plasma physics, fluid mechanics, tsunami phenomena, and other science disciplines. Furthermore, the aforementioned equations can be employed to analyze the characteristics of various acoustic waves (AW) in different plasma models, such as their amplitude, width, frequency, and dispersion, as well as the phase shifts after collisions.

Leak detection and localization of fluid-filled pipeline using accelerometer pairs and mode separation method

Acoustic methods are commonly used to detect and locate leaks in pipelines, but they often overlook important multimodal characteristics of acoustic waves, limiting their applicability. Based on propagation theories regarding F(1,1) mode signal extraction, a new and easy-to-use method for leak detection and localization in pressurized pipelines is proposed. The F(1,1) mode signals are obtained using accelerometer pairs and mode separation method, which are then used to train detection models and to estimate the time difference of arrival (TDOA) for leak localization. Mode separation empowers the data-driven models with physically meaningful samples, aiming to broaden their applicability. The mode consistency between TDOA and velocity is achieved to ensure accurate leak localization. Experiments in buried water-filled ductile iron pipe (experiment A) and in fuel-filled iron pipe (experiment B) are conducted and the longest test distance reaches 72 m. The results validate that the employment of mode separation notably improves current leak detection and localization methods which primarily rely on original signals. The recognition rates rise about 3 %∼11 %, and the false alarm rates reduce about 1 %∼2 %, even when confronted with pipe junction interferences. Also, the leak localization errors are overall lower, with absolute errors below 2 m and relative errors less than 5 % of the test segment length for most cases.

Analyzing surface acoustic wave characteristics through first-principles computational methods

Surface acoustic wave (SAW) characteristics were analyzed through first-principles calculations utilizing density functional theory. This study computed and compared the elastic constants, piezoelectric constants, dielectric constants, and densities of LiTaO3 and LiNbO3, which are standard materials for SAW filters, against empirical values. The velocities of SAWs and the electromechanical coupling coefficients for both Rayleigh and leaky waves were also determined, demonstrating the method’s sufficient precision for assessing SAW attributes. In addition, this approach was extended to the nitride perovskite LaWN3, evaluating its SAW characteristics. LaWN3 is projected to exhibit an electromechanical coupling coefficient comparable to that of LiTaO3 and LiNbO3, indicating its potential as a novel material for SAW filter applications.

Calibrating ultrasonic sensor measurements of crop canopy heights: a case study of maize and wheat.

Canopy height serves as an important dynamic indicator of crop growth in the decision-making process of field management. Compared with other commonly used canopy height measurement techniques, ultrasonic sensors are inexpensive and can be exposed in fields for long periods of time to obtain easy-to-process data. However, the acoustic wave characteristics and crop canopy structure affect the measurement accuracy. To improve the ultrasonic sensor measurement accuracy, a four-year (2018-2021) field experiment was conducted on maize and wheat, and a measurement platform was developed. A series of single-factor experiments were conducted to investigate the significant factors affecting measurements, including the observation angle (0-60°), observation height (0.5-2.5 m), observation period (8:00-18:00), platform moving speed with respect to the crop (0-2.0 m min-1), planting density (0.2-1 time of standard planting density), and growth stage (maize from three-leaf to harvest period and wheat from regreening to maturity period). The results indicated that both the observation angle and planting density significantly affected the results of ultrasonic measurements (p-value< 0.05), whereas the effects of other factors on measurement accuracy were negligible (p-value > 0.05). Moreover, a double-input factor calibration model was constructed to assess canopy height under different years by utilizing the normalized difference vegetation index and ultrasonic measurements. The model was developed by employing the least-squares method, and ultrasonic measurement accuracy was significantly improved when integrating the measured value of canopy heights and the normalized difference vegetation index (NDVI). The maize measurement accuracy had a root mean squared error (RMSE) ranging from 81.4 mm to 93.6 mm, while the wheat measurement accuracy had an RMSE from 37.1 mm to 47.2 mm. The research results effectively combine stable and low-cost commercial sensors with ground-based agricultural machinery platforms, enabling efficient and non-destructive acquisition of crop height information.

Temperature Characteristics of Rayleigh Wave and Leaky Surface Acoustic Wave Propagating in Langasite and its Application in Temperature Sensor

Temperature Characteristics of Rayleigh Wave and Leaky Surface Acoustic Wave Propagating in Langasite and its Application in Temperature Sensor

Earthquake source impacts on the generation and propagation of seismic infrasound to the upper atmosphere

SUMMARY Earthquakes with moment magnitude (Mw) ranging from 6.5 to 7.0 have been observed to generate sufficiently strong acoustic waves (AWs) in the upper atmosphere. These AWs are detectable in Global Navigation Satellite System satellite signals-based total electron content (TEC) observations in the ionosphere at altitudes ∼250–300 km. However, the specific earthquake source parameters that influence the detectability and characteristics of AWs are not comprehensively understood. Here, we extend our approach of coupled earthquake-atmosphere dynamics modelling by combing dynamic rupture and seismic wave propagation simulations with 2-D and 3-D atmospheric numerical models, to investigate how the characteristics of earthquakes impact the generation and propagation of AWs. We developed a set of idealized dynamic rupture models varying faulting types and fault sizes, hypocentral depths and stress drops. We focus on earthquakes of Mw 6.0–6.5, which are considered the smallest detectable with TEC, and find that the resulting AWs undergo non-linear evolution and form acoustic shock N waves reaching thermosphere at ∼90–140 km. The results reveal that the magnitude of the earthquakes is not the sole or primary factor determining the amplitudes of AWs in the upper atmosphere. Instead, various earthquake source characteristics, including the direction of rupture propagation, the polarity of seismic wave imprints on the surface, earthquake mechanism, stress drop and radiated energy, significantly influence the amplitudes and periods of AWs. The simulation results are also compared with observed TEC fluctuations from AWs generated by the 2023 Mw 6.2 Suzu (Japan) earthquake, finding preliminary agreement in terms of model-predicted signal periods and amplitudes. Understanding these nuanced relationships between earthquake source parameters and AW characteristics is essential for refining our ability to detect and interpret AW signals in the ionosphere.

Numerical study of the pulsatile flow and aeroacoustics of straight and curved pipes

From an engineering point of view pulsatile pipe flows, which include the hydrodynamic and acoustic fluctuations, can cause many problems such as vibration, noise and structural fatigue etc. Knowledge of the characteristics of hydrodynamic fluctuations (pseudo sound) and acoustic waves inside pipes particularly those with bends make is crucial to pipeline vibration and noise reduction. Numerical simulation of the pulsatile pipe flows shows challenges especially in curved pipes with different flow modes compounded, and predicting the acoustic fluctuations is even tougher. In this work, the unsteady flows of a straight and curved pipe with a 90° elbow induced by a pulsatile pressure inlet were calculated by Detached Eddy Simulations (DES). The pipe acoustic fields are solved through an acoustic perturbation equation, which takes the time derivative of hydrodynamic pressure as the aeroacoustic source. The characteristics of the flow and sound fields are discussed detailly, and special attention is paid to the influence of the 90° elbow on the curved pipe flow. The results show that the amplitude of hydrodynamic pressure fluctuations decrease almost linearly along the straight pipe, and the 90° elbow has obvious local influence on the flow pressure and velocity especially in the downstream side. The acoustic field is of 1-D standing wave pattern because of the fundamental pulsation frequency lower than the pipe cutoff frequency, and the 90° elbow has only negligible effect on the acoustic field in the flow frequency range.

Characteristics of Nonlinear Dust Acoustic Waves (DAWs) Propagating in an Inhomogeneous Collisionless Magnetized Dusty Plasma

Characteristics of Nonlinear Dust Acoustic Waves (DAWs) Propagating in an Inhomogeneous Collisionless Magnetized Dusty Plasma

Propagation Characteristics of Acoustic Emission Waves in Three Different Asphalt Pavement Materials

Propagation Characteristics of Acoustic Emission Waves in Three Different Asphalt Pavement Materials

Propagation characteristics of nonlinear dust acoustic solitary waves in complex plasma with nonthermal electrons and trapped ions

The propagation characteristics of nonlinear dust acoustic solitary waves in a complex plasma system with nonthermal electrons and trapped ions are investigate in this work. The nonlinear dispersion relation of dust acoustic waves is obtained by using the linear method, and the two-dimensional autonomous system governing the motion of nonlinear dust acoustic waves is derived by using the Sagdeev potential method. At the same time, the specific expression of the Sagdeev potential function is obtained based on the Sagdeev potential equation. The numerical simulations are used to analyze the phase portraits of the two-dimensional autonomous system, revealing the linear periodic wave orbits, nonlinear periodic wave orbits, and homoclinic orbits co-existing in the complex dusty plasma system with nonthermal electrons and trapped ions. Furthermore, from the variations of the Sagdeev potential function with different system parameters it follows that only the compressive solitary waves exist in this complex plasma system. The significant influences of various system parameters on the amplitude, width, and waveform of the nonlinear dust acoustic solitary wave in the complex plasma system are discussed in detail. The results demonstrate that the Mach number, the nonthermal electrons and trapped ions, undisturbed dust particle number density, temperature, and charge have important effects on the propagating characteristics of the nonlinear dust acoustic solitary waves in a complex plasma with nonthermal electrons and trapped ions.

Surface acoustic wave digital microfluidics with surface wettability gradient.

This paper reports a digital microfluidic technology that combines surface wettability gradient and surface acoustic waves. The technology enables selection of the driven object, facilitating reactions among multiple droplets and improving the precision of droplet control. Octagonal patterns with a wetting gradient and orthogonally distributed interdigital transducers were created on the surface of a LiNbO3 wafer by photolithography. Leveraging the propagation characteristics of surface acoustic waves on different wetting models, the latter serve as a switch for microfluidic motion, successfully achieving selection of the driven object and demonstrating sequential reactions among multiple droplets. Also, under the excitation of standing surface acoustic waves, droplets on the wetting gradient surface move slightly in the direction of wetting gradient descent, significantly enhancing the positional accuracy of the droplets to the micrometer level. With the advantages of surface acoustic wave digital microfluidics, this technology addresses the challenges of multi-droplet digital manipulation and improved droplet positional accuracy.

Manipulation of directional acoustic spin angular momentum density based on gradient-structured waveguides

In recent years, the discovery of the transverse spin of acoustic wave in a structural acoustic field and acoustic structural surface wave has expanded our knowledge of the basic characteristics of acoustic waves and opened up new avenues for their manipulation. On the structured surface, however, the distribution of acoustic surface waves often presents a uniform distribution, which restricts the local modification of acoustic spin angular momentum and particle manipulation capabilities. In this study, we develop some acoustic waveguides with gradients that are flat, up-convex, and down-concave in order to manipulate the lateral spin distributions of acoustic surface waves. We verify the direction-locking near-field acoustic spin-momentum, explore the pressure field distribution and the spin angular momentum density distribution of a spin acoustic source excited in each of the three gradient structures, and we also show how to manipulate the spin intensity distributions of acoustic surface waves in the gradient waveguides through theoretical analysis and numerical simulation. The numerical calculation results show that when the acoustic surface wave is excited by a clockwise rotating spin source and propagates along the left side of the waveguide, the spin angular momentum density is positive on the upper surface of the structured waveguide and negative on the lower surface. The spin angular momentum distribution and the direction of propagation of acoustic wave are entirely changed when the spin source is rotated counterclockwise. Specifically, an unequal distribution of acoustic spin angular momentum is produced by the upper convex-type waveguide and bottom concave-type waveguide when we convert the flat-type acoustic structure waveguide into a gradient-type waveguide. According to the computation results, the down-concave type waveguide exhibits a stronger density of acoustic spin angular momentum at the end and the acoustic surface waves gather at the end of the constructed waveguide. On the other hand, the waveguide collects acoustic waves close to the structure center when it is an up-convex structural waveguide. The findings can open up new avenues for manipulating particles using acoustic waves, by providing a means for controlling the acoustic spin angular momentum density and improving our understanding of symmetry in acoustic near-field physics.

Effect of trapping and reflection on dust acoustic solitary waves in nonthermal opposite polarity dust plasmas

The study of resonant wave-particle interactions (WPIs) is crucial in plasma systems where charged plasma particles interact via long-range electromagnetic waves. Our research focuses on exploring the impact of trapping and reflection, along with the superthermality of Kappa resonance electrons and ions, on the characteristics of dust acoustic waves (DAWs) in opposite polarity dust plasma (OPDP). Both linear and non-linear analyses were conducted. Two distinct types of dust acoustic modes, namely fast and slow, have been observed in the linear regime of two different instances of WPIs. Moving on to the non-linear regime, the Schamel KdV (SKdV) equation has been derived using the reductive perturbation technique. In both cases, a stationary solution in the form of a dust acoustic double-layer wave (DADLW) has been successfully obtained. Our findings are highly relevant to astrophysical plasma environments with non-thermal trapped and reflected particles.

On the characteristics of DA shock waves in a polarized electron-depleted plasma with a mixed nonextensive high energy-tail ion distribution

A first theoretical attempt is made to understand the characteristics of dust acoustic shock waves (DASWs) in a polarized electron-depleted plasma with a mixed nonextensive high energy–tail ion distribution and to examine the impact of the generalized nonthermal polarization force on DASWs in an electron-depleted dusty plasma. First, a short numerical investigation illustrating the behavior of the mixed nonextensive high energy–tail (or Cairns–Tsallis) ion distribution and the domain of validity of its two parameters (q and [Formula: see text]) is carried out. Next, the generalized nonthermal polarization acting on dust grain in electron-depleted dusty plasma is determined within the context of Tsallis’ statistical mechanics. The behavior of this generalized polarization force is significantly affected by the nonextensive character of the nonthermal ions. Specifically, we have shown that, for both space and experimental dusty plasmas, the magnitude of the polarization force (in the case where [Formula: see text]) decreases as the nonextensivity of the nonthermal ions becomes significant. As an application, we have analyzed the changes caused by the nonthermal nonextensive polarization force on the main characteristics of DASW (viz. phase velocity, polarity, amplitude, width, etc.). Numerical results showed that our plasma model supports rarefactive and compressive DASWs that are significantly affected by the effects of nonthermal ion nonextensivity and polarization force. In particular, we have shown that for large values of the nonthermal parameter [Formula: see text], the increase in q allows the transition from rarefactive to compressive DASW structures. The present theoretical investigation is helpful to fully understand electrostatic disturbances in space and experimental dusty plasmas.