Excitation Of Ultrasonic Waves Research Articles

Longitudinal Wave Defect Detection Technology Based on Ablation Mechanism

For laser ultrasound in the thermoelastic mechanism, excitation of ultrasonic body wave signal is weak, it is not easy to realize the detection of deep defects inside the workpiece. While the ablation mechanism produces a high and practical ultrasonic signal-to-noise ratio, this paper is based on the generation mechanism of laser ablation excitation of ultrasonic waves, the establishment of laser ultrasound in the ablation mechanism in the aluminum plate excitation and propagation of ultrasonic numerical model, through the solution, obtained the ultrasonic acoustic field map, discussed the ablation mechanism of the laser ultrasonic body wave acoustic field directionality. Additionally, the preliminary verification of the validity of the model is presented. Then, in order to explore the application potential of high signal-to-noise ratio longitudinal waves in defect detection, defects of different depths are preset in the model for simulation calculations, and waveform and acoustic field analyses are performed on the simulation results to study the ultrasonic propagation paths inside the member and the interaction with the defects, and the transverse position and depth of the internal defects are judged by using B-scan imaging. Finally, experimental validation is carried out. The experimental results are highly consistent with the simulation model, and the defect experiments can qualitatively determine the location of internal defects and verify the practicality and accuracy of the model.

Determination of plastic deformation with variable ultrasonic excitation positions

For highly stressed mechanical components, information regarding the beginning of plastic deformation is of enormous importance. Therefore, nondestructive testing and structural health monitoring techniques are essential to examine said components and to make statements concerning the mechanical integrity. In this work, dislocation theory was extended and combined with ultrasonic wave excitation to obtain dislocations in isotropic materials. In the analytical derivation, the ultrasonic longitudinal waves were sent in different propagation directions relative to the uniaxial tensile load. The derived nonlinearity coefficients enabled the investigation as a function of these angles. The evaluated coefficient behaviour allows for statements about the position of the ultrasonic excitation relative to the tensile load to be made. Furthermore, a signature could be derived from which the degree of plasticity can be determined if a reference measurement is available. The newly derived coefficients and their behaviour make it possible to efficiently detect the beginning of plastic deformation and to predict the position of the applied load vector.

Ice-enhanced thermoelastic excitation of ultrasonic waves

The thermal expansion occurring when a laser beam is incident on the surface of a solid can be used to excite ultrasonic waves in the solid medium, without causing damage to the material. The resulting wavefield is characterized by a dominant shear wave and a weak compressional wave. This Letter demonstrates the possibility of generating a dominant compressional wavefield by coating the surface with a layer of clear ice. This is achieved by exploiting a minimum in the attenuation spectrum of light in ice, which occurs at around 500 nm and renders the coating transparent to green laser radiation. Ice coatings could, therefore, provide a path for the development of more sensitive laser-based nondestructive testing methods that have traditionally been affected by the poor excitability of compressional waves, especially along the direction orthogonal to the surface.

Particle propulsion from attached acoustic cavitation bubble under strong ultrasonic wave excitation

Particle propulsion by an attached acoustic cavitation bubble under strong ultrasonic wave excitation occupies the core of many applications, including ultrasonic cleaning, ultrasonography, targeted therapy, and microbubble motors. However, the driving capacity and mode of bubbles in the field of ultrasonics are far from being well understood, which severely limits its applicability in a variety of fields. In this study, a fluid–structure interaction model based on the boundary integral method is proposed to simulate complex interactions between a suspended spherical particle and an attached cavitation bubble. A one-to-one comparison between the numerical results and experimental data demonstrates the distinct advantage of our model over conventional approaches. Thereafter, we systematically investigate the dependence of bubble–particle interactions on the governing parameters, including the amplitude and phase of the ultrasonic wave, particle density, and particle-to-bubble size ratio. We also document different types of bubble dynamic behaviors under various governing parameters. Finally, we obtain scaling laws for the maximum displacement of the particle with respect to the governing parameters.

Reference installation for measuring acoustic parameters of solids

The issues of providing working standards of the 1st category of metrological organizations of the country with regard to modern needs in the field of ultrasonic measurements in solids are considered. There is presented a modernized reference installation designed for precision measurements of propagation velocities of longitudinal and shear ultrasonic waves and damping coefficient of longitudinal ultrasonic waves in solids. Measurements of acoustic parameters of solid media are made by pulse-echo and resonance methods using contactless broadband capacitive methods of excitation and registration of ultrasonic waves. This installation is used as working standard of the 1st category in accordance with the state verification schedule for measuring instruments of the propagation velocities and damping coefficient of ultrasonic waves in solids. The technical means included in the installation (mechanical and electronic parts) have been improved, analog measuring means have been replaced with digital ones, methods for measuring acoustic parameters of solids based on the use of digital measuring means have been developed and the thickness range of installed ultrasonic measures has been expanded. The composition and main components of the reference installation, the used measurement methods and the principles of operation of the installation in various operating modes are described. The technical and metrological characteristics of the installation are given. Sources of measurement error (uncertainty) were analyzed. The field of application of the results is high-precision measurements of the acoustic characteristics of solid media, metrological ensuring of ultrasonic non-destructive testing and diagnostics.

Underwater Self‐Powered All‐Optical Wireless Ultrasonic Sensing, Positioning and Communication with Ultrafast Response Time and Ultrahigh Sensitivity

AbstractThe utilization of ultrasonic waves in the ocean has become an attractive topic for its applications in underwater sensor networks via a variety of research methods, such as sensing, positioning, and communication. However, it is still challenging to develop a cost‐effective, stable, fast, and accurate wireless underwater ultrasonic device with self‐power‐ability in various circumstances. Herein, a novel underwater self‐powered all‐optical wireless ultrasonic sensor (SAWS) based on triboelectrification‐induced electroluminescence (TIEL) has been proposed, in which efficient and stable TIEL can be generated under the excitation of ultrasonic waves. The SAWS has been demonstrated to accurately determine the location of the ultrasonic source with an error of less than 4.6%, and as a promising candidate for real‐time optical signal communication with an ultrafast response time of below 50 ms and an ultrahigh signal‐to‐noise ratio (SNR) of 26.02 dB. To date, the paradigm‐shift strategy for underwater ultrasonic sensing has been developed for the first time to be fully self‐powered without any wire connections. The SAWS proposed here paves a new path to the realization of a self‐powered underwater all‐optical wireless sensing system that can be effectively applied in underwater environmental monitoring, underwater robots, ocean sensor networks, etc.

Development and experimental testing of the technique of ultrasonic control of brazed joints of heat exchangers

High reliability requirements are imposed on the quality of the soldered joints. Typical defects in the soldered joints of heat exchangers are non-soldered. The minimum size of the non-penetration area that must be detected is about 1 square millimeter. The existing assessment of the quality of soldering is reduced to destructive tests. These tests include hydraulic and pneumatic tests. There are control technologies that use non-destructive methods. For example, the applicability of the ultrasonic echo method based on thermo-optical (laser) excitation of ultrasonic waves has been proven. However, continuous inspection of the liquid-propellant engine chamber using the traditional echo method is not rational, since the inspection speed is limited by the size of detected defects (1 square millimeter) and amounts to a few millimeters per minute. In order to increase the scanning speed without losing the ability to reliably detect defects such as “non-soldered”, it is proposed to use phased array antennas (PA) as a means of implementing the ultrasonic echo method. The paper considers the issues related to the interpretation of the information obtained when scanning the soldered joint, as well as issues related to modeling the acoustic field in the model of the soldered joint of the heat exchanger.

Impulsively-Laser Excitation and Propagation of Ultrasonic Waves through Nanomagnetic Fluid

Magnetic fluids belong to the class of nanomaterials with a high gain of light absorption, aggregative and sedimentation stability as well as controllability by external fields, which is of interest to use in the field of optoacoustics. The purpose of the work was to experimentally study the effect of the optoacoustic transformation in a magnetic fluid, depending on the concentration of magnetic colloidal particles, boundary conditions, intensity of the laser as well as to identify the possibilities of using the magnetic fluid as an element of the optoacoustic transformation in a number of applications.A brief analysis of the optoacoustic transformation mechanism in a magnetic fluid was carried out and a technique and an installation that implements the shadow measurement variant developed. A Lotis type laser was used as a source of ultrasonic pulse-laser excitation in magnetic fluids. A quartz and air were used as a material transmitting the energy of laser radiation in a magnetic fluid. Receiving of ultrasound signals was made by a piezoelectric probe at a working frequency of 5 MHz. In the measurement process, the concentration of the dispersed phase in tmagnetic fluid was varied from zero to 8 % and the energy in the impulse – from zero to 10 mJ.For the first time, it was established that: a) an amplitude of the function of the optoacoustic transformation in a magnetic fluid, depending on the concentration of the dispersed phase, has a maximum determined by the fluid physical properties and boundary conditions; b) for all samples within the measurement error, a quasilinear dependence of the specified amplitude of energy in the laser pulse in the range of 0–8 MJ has been established.A number ways of the optoacoustic effects in magnetic fluids to use in ultrasonic testing, measuring the intensity of the laser radiation had been suggested.

Defect detection on the curved surface of a wind turbine blade using piezoelectric flexible line sensors

Blades play a critical role in the wind turbine system. Therefore, their structural health monitoring is very important. Blades are damaged by sudden changes in wind load, cracks due to collision of foreign objects, and disasters, such as lightning strikes, hail, and typhoons. Moreover, blades are expensive to maintain. Defects or damages to wind turbine blades reduce the life span and power generation efficiency of the wind turbine and increase safety risks and maintenance costs. Therefore, it is very important to detect blade damage to prevent problems in the wind turbine. Ultrasonic inspection is suitable for blades made of composite materials. Piezoelectric ceramic, which is a typical piezoelectric element, has relatively high sensitivity compared to other sensors. However, it suffers from brittle fractures and thus difficult to apply to curved structures. To overcome the limitations of piezoelectric ceramics, a piezoelectric flexible line sensor that can be applied to curved surfaces was manufactured using the dice-and-fill method for a [Pb(Li0.25Nb0.75)]0.06 [Pb(Mg0.33Nb0.67)]0.06 [Pb(Zr0.50Ti0.50)]0.88O3 with 0.7 wt% MnO2 (PZTNMML) ceramic disc. Instead of a typical ultrasonic inspection method with limited surface contact, a laser capable of producing ultrasonic excitation of ultrasonic waves over a large area from a long distance was used. The possibility of detecting a defect on the wind turbine blade using a piezoelectric flexible line sensor and laser ultrasound was confirmed in this study.

A New Laser Ultrasonic Inspection Method for the Detection of Multiple Delamination Defects.

Delamination is one of the most common types of defects for carbon fiber reinforced plastic (CFRP) composites. The application of laser techniques to detect delamination faces difficulties with ultrasonic wave excitation because of its low thermal conductivity. Much of the research that can be found in the literature has only focused on the detection of a single delamination. In this study, aluminum foil was pasted onto the surface of the composite so that it was vulnerable to ablation and could acquire a usable signal. Using a fully noncontact system with laser excitation at a fixed point and a scanning laser sensor, the effects of different aluminum foil sizes and shapes on the wavefield were studied for the composites; we decided to use a rectangle with 3 mm length and 5 mm width for laser excitation experiments. Wavefield characteristics of the composite plates were analyzed with single- and multi-layered Teflon inserts. Taking the time window for standard ultrasonic testing as a reference, the algorithms for localized wave energy with appropriate time windows are presented for the detection of single and multiple defects. The appropriate time window is meaningful for identifying each delamination defect. The algorithm performs well in delamination detection of the composites with one or multiple Teflon inserts.

Analysis and Validation of Ultrasonic Probes in Liquid Level Monitoring Systems.

Selecting and designing the optimum ultrasonic probe is vital for ultrasonic measurements and experiments. The amplitude of the emitted ultrasonic wave excitation signal as well as the diameter and the natural frequency of the probe seriously affect the validity of the probe results. In this paper, we analyze the significance of the key parameters of the ultrasonic probe theoretically. Further, an external fixed-point liquid level monitoring system was assembled according to the principle of ultrasonic reflection and transmission. On this experimental platform, we study the key parameters of the ultrasonic probe that affect the system evaluation through a simulation and experiment, and select the optimal sensor parameters for this experiment. The evaluations show that under the experimental conditions where the tested container is made of aluminum alloy and its wall thickness is 3 mm, the best results are obtained when the diameter of the ultrasonic sensor is 15 mm, the amplitude of the emitted excitation signal is ±15 V, and the frequency is 1 MHz. The results’ average deviation is less than ±0.22 V. The evaluations are consistent with the simulation results. This research can effectively monitor the liquid in the closed, ultra-thin-walled container, and can realize non-contact measurement. It provides an effective basis for the parameters selection and design of the ultrasonic probe in the ultrasonic-based experiments and tests.

Improved laser-ultrasonic excitation for imaging of seismic physical modeling

In this study, a laser ultrasonic technology (LUT) was employed for seismic physical model (SPM) imaging. To promote an efficient light-to-ultrasonic-wave conversion, a functionalised Au film was used as a medium because of its stronger photoacoustic (PA) effect. Numerical analysis and experiments were performed to characterise the entire SPM imaging process, including the generation of PA signals, transmission of PA inside the SPM, and collection of echo data for the reconstruction of SPM images using the time-of-flight algorithm. The results show that the Au film coating on the SPM produces a strong PA effect, which significantly improves the imaging depth and resolution of the SPM based on the strong high-frequency ultrasonic wave excitation. The proposed method opens new avenues for SPM imaging using optical technology.

An electromagnetic acoustic transducer with electromagnetic pulse restraining

Electromagnetic acoustic transducers (EMATs) are widely used in non-destructive testing (NDT). However, when ultrasonic waves are excited, the transmitting coil generates a strong alternating magnetic field, resulting in the generation of an electromagnetic pulse. To address this problem, an EMAT with electromagnetic pulse restraining is presented in this paper. First, the cause of the electromagnetic pulse is investigated. Second, the conditions for restraining the electromagnetic pulse using the new transmitting coil are analysed. Finally, the design method for the new transmitting coil is provided through evaluation of the magnetic field model of the new transmitting coil. The experimental results demonstrate that the new transmitting coil has a significant effect on the excitation of ultrasonic waves in the tested material and the restraining of electromagnetic pulses. Therefore, the method proposed in this study can self-compensate for the strong alternating magnetic field generated by the transmitting coil, reduce the interference of the electromagnetic pulse with the ultrasonic wave and improve the signal-to-noise ratio (SNR) of EMATs.

Optimizing the driving trajectories for guided ultrasonic wave excitation using iterative learning control

In this work, iterative learning control (ILC) is used to generate precise, guided ultrasonic wave pulses for nondestructive testing (NDT) purposes. The premise of ILC is that the performance of a system, which is repetitively executing the same task, can be improved by learning from previous attempts. In order to develop a systematic approach for the ILC design, an H∞-synthesis method is employed. To this end, an experimental modal analysis is conducted for commonly used guided ultrasound transducers, and a low-order model is fitted to the resulting data near the transducer’s peak frequency. Based on this model, appropriate L- and Q-filters are synthesized and the ILC is trained to generate the desired wave packet in simulation. The simulation results indicate convergence of the proposed ILC algorithm to the optimal driving trajectory. By employing this trajectory in laboratory experiments, it is shown that ringing effects, i.e. distortions of the induced wave packets, are significantly reduced. The ILC is also trained in the experiment, and robustness and convergence are discussed. Lastly, to demonstrate the impact of such an improvement to the induced guided ultrasonic waveform, NDT experiments in the form of edge and delamination detection are performed. It is shown that a significant improvement in reliability can be achieved using the proposed approach. For the MSSP Special Issue in Honor of Professor Lothar Gaul.

Laser Wavelengths Suitable for Generating Ultrasonic Waves in Resin-Coated Carbon Fiber Composites

Abstract For the non-destructive inspection of carbon fiber-reinforced plastic (CFRP), lasers can be used to generate ultrasonic waves. It is important to optimize the wavelength of the laser to ensure the intense excitation of a usable propagating mode. Real CFRP components used in the construction of airplanes and automobiles are often coated with several types of resin to protect against weathering. These resin layers change the excitation of the ultrasonic waves. Thus, the optimum laser wavelength may be changed by the coating resin. In this paper, we investigated the excitation of ultrasonic waves in a resin-coated CFRP plate using different laser wavelengths. We conducted experiments to convert the laser wavelength using periodically poled LiNbO3 (PPLN) devices. By injecting mid-infrared laser to a coated sample, we observed excited ultrasonic waves using a laser Doppler vibrometer. We found that transparent resins significantly increase the amplitude of the first-arriving longitudinal wave. Furthermore, when the laser was strongly absorbed in the surface layer, the excitation of longitudinal waves was suppressed. These results were clarified by a one-dimensional model of the thermal generation of ultrasonic waves. We concluded that a laser passing through a resin layer is a viable candidate for the effective inspection of coated CFRP by laser ultrasonic waves.

Nonlinear dynamics of a cavitation bubble pair near a rigid boundary in a standing ultrasonic wave field

The dynamics of a micrometer-sized bubble pair in water near a rigid boundary under standing ultrasonic wave excitation is investigated in this study. The viscous effect in the boundary layer at the air-water interface is considered following the viscous correction model. The evolution of the bubble surface at the collapsing stage of the bubble pair is presented for different parameter sets. The field pressure near the rigid boundary, which is induced by the oscillating bubble pair, and the high-speed water jet at the collapse stage, form the main focus of the analysis. This reveals that a horizontal configuration of the bubble pair retards the strength of the bubble jet towards the boundary, whilst a vertical configuration, especially with differently-sized bubbles, can enhance the bubble collapse. This study may help to understand the interaction of multiple bubbles in an acoustic field and its application to surface cleaning.

Non-contact characterization of debonding in lead-alloy steel bonding structure with laser ultrasound

This paper presents the non-contact characterization of debonding defects in lead-alloy steel bonding structure with ultrasonic waves generated and detected by lasers. Using the 3D finite element (FE) method, the thermoelastic excitation and propagation of ultrasonic waves are simulated. The effect of debonding defects on wave field distribution are clarified. Combining experiment method, the feature signal for characterizing the debonding defects are extracted, the appropriate wave frequency and probe position are obtained. The characterization of debonding defects in different sizes are analyzed, and the laser ultrasonic C-scan imaging of the specimen with simulated debonding defects is realized. The results prove that the noncontact characterization of debonding defects in lead-alloy steel bonding structure can be realized with laser ultrasound, and the circular debonding defects greater than 4 mm in diameter are characterized through C-scan method.

Dynamic behaviour of a two-microbubble system under ultrasonic wave excitation

Acoustic bubbles have wide and important applications in ultrasonic cleaning, sonochemistry and medical ultrasonics. A two-microbubble system (TMS) under ultrasonic wave excitation is explored in the present study, by using the boundary element method (BEM) based on the potential flow theory. A parametric study of the behaviour of a TMS has been carried out in terms of the amplitude and direction of ultrasound as well as the sizes and separation distance of the two bubbles. Three regimes of the dynamic behaviour of the TMS have been identified in terms of the pressure amplitude of the ultrasonic wave. When subject to a strong wave with the pressure amplitude of 1 atm or larger, the two microbubbles become non-spherical during the first cycle of oscillation, with two counter liquid jets formed. When subject to a weak wave with the pressure amplitude of less than 0.5 atm, two microbubbles may be attracted, repelled, or translate along the wave direction with periodic stable separation distance, depending on their size ratio. However, for the TMS under moderate waves, bubbles undergo both non-spherical oscillation and translation as well as liquid jet rebounding.

Simulation of guided-wave ultrasound propagation in composite laminates: Benchmark comparisons of numerical codes and experiment

Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools.

High efficient harvesting of underwater ultrasonic wave energy by triboelectric nanogenerator

Ultrasonic waves are existing in water and in our living environment, but harvesting the sonic wave energy especially in water is rather challenging, simply because of the high pressure generated by water. In this work, a triboelectric nanogenerator (TENG) has been designed using spherical pellets as the media for performing the contact-separation operation during ultrasonic wave excitation for energy harvesting. The fabricated TENG can attain an instantaneous output current from several milliamps to about one hundred milliamps and achieve an output power of 0.362W/cm2 at an ultrasonic wave frequency of 80kHz. The average power conversion efficiency of the TENG has reached 13.1%. The equivalent output galvanostatic current is 1.43mA, which is the highest value reported so far. The developed TENG pellets has been demonstrated to continuously power up to 12 lamps with 0.75 W each, and can continuously drive a temperature-humidity meter, an electronic watch, and directly drive a health monitor. This study presents the outstanding potential of TENG for underwater applications.