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Acoustic steady-state excitation spatial spectroscopy (ASSESS) is a full-field, ultrasonic non-destructive evaluation (NDE) technique used to locate and characterize defects in plate-like structures. ASSESS generates a steady-state, single-tone ultrasonic excitation in a structure and a scanning laser Doppler Vibrometer (LDV) measures the resulting full-field surface velocity response. Traditional processing techniques for ASSESS data rely on wavenumber domain analysis. This paper presents the alternative use of a convolutional neural network (CNN), trained using simulated ASSESS data, to predict the local plate thickness at every pixel in the wavefield measurement directly. The defect detection accuracy of CNN-based thickness predictions are shown to improve for defects of greater size, and for defects with higher thickness reductions. The CNN demonstrates the ability to predict thickness accurately in regions where Lamb wave dispersion relations are complex or unknown, such as near the boundaries of a test specimen, so long as the CNN is trained on data that accounts for these regions. The CNN also shows generalizability to ASSESS experimental data, despite an entirely simulated training dataset., (Copyright © 2021. Published by Elsevier B.V.)

As we all know, development and utilization of clean energy is the only way for society to achieve its sustainable development. Although natural gas hydrates is a new type of clean energy, uncontrollable hydrate dissociation and accompanying methane leakage in drilling operation threaten drilling safety, as well as marine environment. However, the dissociation range of natural gas hydrates around wellbore cannot be reasonably determined in previous investigations, which may lead to the inaccurate estimation of borehole collapse and methane leakage. Then, the marine environment will be greatly damaged or affected. The purpose of the present work is to experimentally explore the dissociation characteristics of gas hydrates around wellbore in drilling operation and analyze the influence law and mechanism of various factors (such as hydrate saturation) on hydrate dissociation. It is expected to provide reference for exploring effective engineering measures to avoid the uncontrolled hydrate dissociation, borehole collapse and accompanying methane leakage. The experimental results demonstrate that acoustic velocity of hydrate-bearing sediment can be accurately expressed as quadratic polynomial of hydrate saturation, which is the theoretical basis for determination of hydrate saturation in subsequent experiments. Owing to the fact that hydrate dissociation is an endothermic reaction, hydrate dissociation gradually slows down in experiment. Throughout the experiment, the maximum dissociation rate at the beginning of the experiment is 8.69 times that at the end of the experiment. In addition, sensitivity analysis found that the increase in the stabilizer concentration in drilling fluid can inhibit hydrate dissociation more effectively than the increase in the hydrate saturation. Hydrate dissociation was completely inhibited when the concentration of soybean lecithin exceeds 0.60wt%, but hydrate dissociation definitely occurs in the near-wellbore region no matter what hydrate saturation is. In this way, based on the requirements of drilling safety and/or environment protection, hydrate dissociation and accompanying methane leakage can be controlled by designing and adjusting the stabilizer concentration in drilling fluid., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The purpose of this work was to develop a multichannel ultrasonic measurement method for monitoring a spatially non-uniform blood clotting process. This novel method is based on simultaneous multi-channel measurements of ultrasound propagation velocities in different horizontal cross-sections of clotting blood. The most common method used for determining blood-clotting time is the capillary tube method. For this purpose ultrasonic methods based on measurements of the velocities of ultrasound waves in clotting blood are also used. Measurement results essentially depend on the propagation path of the ultrasonic wave in a blood sample. The ultrasound velocity changes as fresh blood transforms into clot plus serum. The objective of this work was to develop a measurement method that allows one to measure ultrasound velocity and its evolution in time and space in an evolving clot while avoiding the influence of serum. To achieve this objective, a novel method has been proposed that is based on ultrasound propagation velocity measurements in different horizontal cross-sections of clotting blood using a pulse-echo mode. Such a technique enables researchers to monitor the clotting process and a clot's spatial structure, which are different in different layers due to the influence of gravity. The four-channel measurement chamber utilizing this method has been designed and manufactured. For the generation and reception of ultrasonic waves of high frequency, wide band (3-20MHz at -6dB) ultrasonic transducers were developed. To verify that the multi-channel measurement system was operational, a special procedure based on monitoring of a polymerisation process in the acrylamide solution was proposed. Performance of the developed method was investigated by measuring clotting blood (sample volumes of less than 0.6ml) at the frequency of 12MHz. The results revealed that a clot structure indeed varies within a blood sample due to the influence of gravity; clotting times are different in different horizontal layers of the clot and range from 9 to 15min, defined by the standard capillary method. Clotting times are determined precisely from abrupt increases in ultrasound velocity. Uncertainty of the ultrasound velocity measurements was less than ±0.05m/s. The experiments were performed at 36.90±0.01°C. The proposed method may be exploited for monitoring polymerisation reactions in the chemistry field, as well., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The use of reinforced concrete is foundational to modern infrastructure. Acknowledging this, it is imperative that health monitoring techniques be in place to study corrosion within these structures. By using a non-destructive method for detecting the early formation of cracks within reinforced concrete, the method presented in this paper seeks to improve upon traditional techniques of monitoring corrosion, within reinforced concrete structures. In this paper, the authors present a method to evaluate the physical characteristics of reinforced concrete subject to corrosion using a poro-elastic acoustic model inversion technique applied to a set of ultrasonic measurements, which constitutes a novel approach to the problem of observing the impact of corroding rebars and resulting concrete damage. A non-contact ultrasonic transducer is operated at a carrier frequency of 500 [kHz], with a layer of saltwater separating the sensor from the concrete surface. Following this non-contact measurement collection of the surface and rebar echo responses, a poro-elastic model is used to model the sound propagation, through an adapted version of the Biot-Stoll model. At first, a set of default parameters, obtained from the physical characteristics of the reinforced concrete, are used to match experimental and simulated acoustic signature of the sample. Performing statistical averaging along the corroding rebar within three samples over a period of nearly nine months, a small but monotonous increase in the distance between the concrete surface and the top of the rebar, indicating gradual corrosion of the rebar. Next, a non-linear optimization algorithm is used to optimize the match between measured and simulated echoes. Through the implementation of this model parameter optimization, the root mean square error between measured and simulated responses was reduced by 63.7% for the full signal, and 62.6% for the rebar echo. [ABSTRACT FROM AUTHOR]

Aero-engines and rocket engines regularly experience unstable combustion phenomena. In order to reveal the complex mechanism, it is necessary to measure the jet gas–liquid interface disturbances. However, most techniques require optical access and the measurement fails when the optical access is limited. Ultrasonic method can be considered as an alternative under this condition. The present work proposes an acoustic approach for measuring the jet gas–liquid interface based on ultrasonic scattering. A thorough investigation of the scattered acoustic field by the jet is conducted by experimental methods. The high-speed imaging technology is used to verify the ultrasonic measurement results. The direct measurement results demonstrate a relationship between the perturbation of the jet gas–liquid interface and that of ultrasonic scattered acoustic pressure in certain measuring direction. The scattered acoustic field is analyzed theoretically and practically by using customized metal scatters of certain size. Based on these findings, a database is created to enable the ultrasonic measurements to be calibrated. The corrected result shows that the correlation of ultrasonic measurements and results from cameras has been greatly improved, and the maximum relative error of the ultrasonic measurements is 30.9%, the average relative measurement error is 2.1%. It is proved that the method of determining the gas–liquid interface of jet by ultrasonic scattering wave is feasible. The method may also be used for the measurement of the overall jet fluctuations and breakup. [ABSTRACT FROM AUTHOR]

Gas leaks can cause disasters at process sites, including fires and explosions, and thus, effective gas-leak detection systems are required. This study investigated the limitations of conventional detectors and introduced an innovative ultrasonic sensor-based approach for continuous monitoring. A new configuration for a stationary remote ultrasonic gas-leak monitoring system is proposed. The selected material was 1-Butene. The detection probability was assessed through a simulation based on a gas-leak scenario, detailing the selection criteria for leak sites and simulation conditions. Computational fluid-dynamics (CFD) simulations were used to evaluate the detection capability of the existing system, whereas Monte Carlo simulations were used to compare it with the proposed ultrasonic system. The CFD simulation was performed by setting the lower detection limit of the concentration-measurement-type gas detector to 600 ppm, and the leak-detection time was approximately 8.895 s. A Monte Carlo simulation accounting for wind direction showed that the existing system's average detection probability was 3.41%. By integrating the existing and new systems, the detection probability increased by 96.58% and 3.92% compared with that using only the concentration-measurement and ultrasonic measurement methods, respectively. These rates provide valuable insights for future applications in oil refining and petrochemical industries. [ABSTRACT FROM AUTHOR]

An ultrasonic interferometer with variable separation between the transducer and reflector is widely used for the measurement of ultrasonic propagation velocity in liquids. The inherent limitation of such an interferometer is due to the mechanical movement of its reflector for ultrasonic wavelength measurement in a liquid medium. It is observed that the ultrasonic velocity measurement precision is adversely affected at higher frequencies compared to lower ones. For instance, in our experimentation, a standard deviation of ±21.5 m/s (±1.43%) was obtained for velocity measurement at 1.84 MHz with the consideration of two consecutive maxima, which increases drastically to ±76.8 m/s (±5.12%) at 9.4 MHz. These measurements can significantly be improved by considering many maxima and averaging for wavelength estimation. However, it still requires design attention and improvement, particularly for higher frequencies. In this article, a sweep-frequency based ultrasonic interferometer design with a fixed separation for liquid characterization is proposed and described. This technique overcomes the limitations of mechanical movement systems and also provides a better and uniform precision for lower as well as higher frequencies. The functionality of the developed sweep frequency method was tested in water, carbon tetrachloride, ethylene glycol, and glycerol, which shows good agreement with literature values. The velocity measurement in double distilled water by the developed technique at 1 Hz sweep resolution has shown an improved standard deviation of ±0.74 m/s (±0.05%) at 9.4 MHz. [ABSTRACT FROM AUTHOR]

A series of triaxial creep tests were carried out on red sandstone under the conditions of high temperature, high pore pressure, and high confining pressure, and the creep mechanism was analyzed in terms of the velocity and energy variations in the ultrasonic waves emitted during the creep test. Changes in porosity and pore distribution in the samples were investigated by nuclear magnetic resonance (NMR) for different creep stages, and the evolution of the internal microstructure of the samples was examined. The experimental results showed that shear microcracks were mainly initiated during the primary creep stage, these microcracks coalescing to form macroshear cracks in the accelerated creep stage. In addition, the changes in porosity exponentially increased with increased deviatoric stress, with small pores developing into medium pores, while the number of large pores was basically stable. [ABSTRACT FROM AUTHOR]

In this paper, ultrasonic P-wave is used to ascertain the mean grain diameter of heterogeneous D'Euville limestone. A previous model of P-wave is used to yield phase velocity (Vp) and the quality factor due to viscous squirt (Qps) in the ultrasonic band, for the limestone saturated with water. As the limestone has grain diameter (d) ranging from 400 to 1000 μm, we set the mean d to be 800, 600 and 400 μm in turn. Vp is fitted precisely as possible between the model and ultrasonic measurement. The emission frequency was 500 kHz. With the mean d of 800 μm, the model yields Qps agreeing with the measurement not very accurately and the average frequency (between emission and receiving) is inverted as 251 kHz (which is too low). With the mean d of 600 μm, the model yields Qps agreeing with the measurement surprisingly well and the average frequency is inverted as 355 kHz (which is very reasonable). With the mean d of 400 μm, neither Vp nor Qps fits well between the model and measurement and the average frequency is inverted as 631 kHz (which is unreasonable). It is concluded that the mean d of D'Euville limestone is 600 μm. Highlights: Phase velocity and the quality factor of ultrasonic P-wave in water-saturated D'Euville limestone are accurately simulated The mean grain diameter of heterogeneous D'Euville limestone is 600 μm Phase velocity and the quality factor of the limestone are featured with novel spikes in the frequency domain [ABSTRACT FROM AUTHOR]

In ultrasonic testing, the amplitude of echoes is determined by the sound pressure along the acoustic axis. When the workpiece has a local curved surface, the ultrasonic field redistribution has a close relationship with the curvature of the incident local region, which raises questions of testing validity and accuracy. In order to develop the curvature adaptation window for a given test condition, the influence of local curved interface on the ultrasonic transmission and reflection field is analyzed quantitatively in this paper. Based on the multi-Gaussian beam model, the distribution of transmitted and reflected sound pressure in the local curved region is calculated by using matrix transformation technique. Furthermore, the relationship between interface curvature and sound pressure along the acoustic axis is obtained. To validate the accuracy of proposed calculation model, developed relationship has been compared against a finite element method computed using COMSOL Multiphysics. It is indicated that the proposed calculation model is more efficient and the regular changes of sound pressure are basically consistent with that of finite element method. [ABSTRACT FROM AUTHOR]

The detection of ductile damage by image-based methods is time-consuming and typically probes only small areas. It is therefore of great interest for various cold forming processes, such as sheet-bulk metal forming, to develop new methods that can be used during the forming process and that enable an efficient detection of ductile damage. In the present study, ductile damage in DC04 was examined using ultrasonic testing. First, different grain sizes were set by heat treatment. Subsequently, the sheet metal was formed by cold rolling. A clear correlation between the average void diameter and the measured ultrasonic velocity could be shown. The ultrasonic velocity showed a clear decrease when the average void size increased because of the increasing forming degree. The ultrasonic measurements were finally employed to calculate a damage parameter D to determine the amount of ductile damage in the microstructure for different grain sizes after cold rolling. [ABSTRACT FROM AUTHOR]

The ultrasonic testing method is a prospective technique adopted for measuring the axial force acting on a bolt; the method is a nondestructive testing method employed for structural health monitoring. In ultrasonic testing, the ultrasonic time of flight (ToF) is obtained, and the axial force is computed using the mathematical relationship between the ultrasonic ToF and the axial force acting on the bolt. Therefore, it is essential to accurately compute the axial force from the ToF. However, existing theoretical equations do not reflect actual scenarios that bolt/nut assemblies may encounter under varying mechanical and thermal conditions. Therefore, the practical application of this method in engineering practices is limited. Establishing a mathematical relationship by considering mechanical and thermal deformation could serve as a fundamental solution for providing more accurate axial force measurement results in ultrasonic testing. In this study, we proposed calibration equations that could be applied to various types of bolts, which are primarily used in mechanical components. The calibration coefficients obtained from the experiments were substituted into the theoretical equations to improve the estimation accuracy of the ultrasonic ToF. Additionally, we compared the experimental results acquired using various types of bolts: M8, M10, M12, and M14, with the results obtained from the theoretical equations using the calibration coefficients. It was verified that it could make the axial force measurement of the bolt accurate as a calibration of the change of the ToF by the bolt deformation from the mechanically stressed region and the thermal conditions with 8.8% error. We expect that the theoretically and experimentally verified calibration equations can improve the reliability and robustness of mechanical components. [ABSTRACT FROM AUTHOR]

An ultrasonic wave mode-based method for density measurement in highly foamed batters was developed. Therefore, a non-contact ultrasonic sensor system was designed to generate signals for batch-wise processes. An ultrasonic sensor, containing a piezoelectric ceramic at the fundamental longitudinal frequency of 2 MHz, was used to take impedance measurements in pulse-echo mode. The ultrasonic signals were processed and analysed wave-mode wise, using a feature-driven approach. The measurements were carried out for different mixing times within a container, with the attached ultrasonic sensor. Within the biscuit batter, the change to the ultrasonic signals caused by density changes during the batter-mixing process was monitored (R2 = 0.96). The density range detected by the sensor ranges between 500 g/L and 1000 g/L. The ultrasonic sensor system developed also shows a reasonable level of accuracy for the measurements of biscuit batter variations (R2 > 0.94). The main benefit of this novel technique, which comprises multiple wave modes for signal features and combines these features with the relevant process parameters, leads to a more robust system as regards to multiple interference factors. [ABSTRACT FROM AUTHOR]

Permanently installed ultrasonic sensors have found increasing applications in the field of structural health monitoring (SHM), in particular with respect to thickness measurement and corrosion monitoring. As ultrasonic velocity is temperature dependent, the state and temperature distribution of a component contribute to much of the measurement uncertainties of an ultrasonic SHM system. On the other hand, the temperature dependency of ultrasonic velocity has also led to various temperature sensing methods for measuring temperature distributions within solid materials. While conventional ultrasound-based techniques can measure either a component's thickness at a given temperature, or the internal temperature distributions at a given component thickness, measurement fluctuations and drifts can occur if both variables are set to change simultaneously. In this study, we propose a dual-wave approach to overcome the limitations of the existing methods. 'Co-located' shear and longitudinal pulse-echo measurements are used to simultaneously track the thickness change and through-thickness temperature variation of a steel plate in complex environmental conditions. Results of the verification experiments showed that, in the given conditions, the proposed dual-wave correction method could reduce thickness measurement uncertainties by approximately a factor of 5 and eliminate 90% of the drift in temperature predictions. [ABSTRACT FROM AUTHOR]

Aim: To investigate the potential value of ultrasonography in evaluating the pathophysiology of obstructive sleep apnoea-hypopnoea syndrome (OSAHS) by assessing the correlation of critical ultrasonic anatomical characteristics of the oropharynx with the severity of OSAHS.Materials and Methods: One hundred and seventy-one patients with suspected OSAHS underwent oropharyngeal sonographic examination and overnight polysomnography. Ultrasonic measurement was compared with the apnoea-hypopnoea index (AHI) and other parameters. An ordinal logistic regression model was used to identify potential ultrasonic anatomical markers for OSAHS.Results: The AHI was significantly correlated with lingual height (r=0.40, p<0.01), maximal width of the tongue (r=0.35, p<0.01), and distance from the symphysis of the mandible to the hyoid bone (M-HB) (r=0.24, p<0.01). A positive relationship between Friedman tongue position (FTP) grades and lingual height (r=0.24, p<0.01), between FTP grades and maximal width of the tongue (r=0.23, p<0.01), and between FTP grades and width of tongue base (TB; r=0.17, p<0.05) was found. Multivariate models adjusted for sex, age, and body mass index (BMI) revealed that lingual height (95% confidence interval [CI]: 1.04-1.24; p=0.004) is independently associated with a higher risk for the severity of OSAHS.Conclusions: Ultrasonography may be a potential imaging method for providing additional useful information about the correlation between ultrasound findings and the severity of OSAHS. Lingual height could be considered an ultrasonic anatomical marker for determining the severity of OSAHS patients independent of age, sex, and BMI. [ABSTRACT FROM AUTHOR]

Objectives: Stroke patients with high intracranial pressure (ICP) may have poor prognosis. Non-invasive ultrasonic optic nerve sheath diameter (ONSD) could evaluate increased ICP. To investigate whether ONSD is valuable for prognosis of patients with acute ischemic stroke (AIS). Methods: AIS receiving intensive care were recruited with the Glasgow Coma Scale (GCS) score. Patients in group A underwent ultrasonic ONSD to assess ICP voluntarily, whereas group B without ONSD. Patients were followed up at discharge and once a week for 3 months with Glasgow Outcome Scale (GOS) score (four to five scores indicated good prognosis and one to three scores indicated poor prognosis). Results: Forty-nine patients were included. GCS scores did not differ significantly between groups A (26 patients) and B (8 ± 3 vs. 7 ± 3, p < 0.05). In group A, ONSD was 5.01 ± 0.48 mm, which correlated with GCS score (p < 0.05). At discharge, the GOS score was higher in group A than in group B (3.35 ± 1.35 vs. 2.57 ± 1.121, p = 0.034). The proportion of patients with a good prognosis was higher in group A than in group B (46.2% vs. 13.0%, p = 0.006). At discharge and after 3 months of follow-up, ONSD at admission was correlated with the GOS score in group A (r = -0.648 [p < 0.05] and -0.731 [p < 0.05], respectively). After 3 months of follow-up, the GOS score was higher in group A than group B (3.00 ± 1.673 vs. 2.04 ± 1.430, p < 0.05). The proportion of patients with a good prognosis was higher in group A than in group B (46.2% vs. 21.2%, p = 0.039). The Kaplan-Meier curve showed a higher rate of good prognosis in group A than in group B. ONSD (p < 0.05) was an independent predictor of poor prognosis.Conclusion: Non-invasive ultrasonic ONSD could be useful in improving the prognosis of patients with AIS receiving intensive care. [ABSTRACT FROM AUTHOR]

Ultrasonic flowmeters play an important role in industrial production, aerospace and other fields. In this paper, a high-precision ultrasonic flowmeter based on the cross-correlation method is designed, and the commercial finite element software COMSOL Multiphysics 5.6 is used to simulate the propagation process of ultrasonic waves during flow measurement, and the implementation process of the cross-correlation algorithm is simulated by Python language. The flowmeter adopts the cross-correlation algorithm to improve the measurement accuracy of ultrasonic time of flight and adopts the method of combining FPGA and an embedded microprocessor to improve operation efficiency. In order to verify the performance of the flowmeter, we tested the flowmeter on the National Institute of Metrology and the self-built test platform, using the still water dragging method, the dynamic volume method and the field comparison method, respectively. The results show that the flowmeter has the ability to test the flow under the condition of high flow velocity (26 m/s) and a pipe diameter in the range of DN6~DN1600, that the absolute value of the relative indication error does not exceed 0.815% and that the repeatability does not exceed 0.150%. The designed ultrasonic flowmeter has high measurement accuracy, good repeatability, strong stability and a wide application range. [ABSTRACT FROM AUTHOR]

This work proposes the slope of the phase spectrum as a signal processing parameter for the ultrasonic monitoring of the water content of water-in-crude oil emulsions. Experimental measurements, with water volume fractions from 0 to 0.48 and test temperatures of 20 °C, 25 °C, and 30 °C, were carried out using ultrasonic measurement devices operating in transmission–reception and backscattering modes. The results show the phase slope depends on the water volume fraction and, to a lesser extent, on the size of the emulsion droplets, leading to a stable behavior over time. Conversely, the behavior of the phase slope as a function of the volume fraction is monotonic with low dispersion. Fitting a power function to the experimental data provides calibration curves that can be used to determine the water content with percentage relative error up to 70% for a water volume fraction of 0.06, but less than 10% for water volume fractions greater than 0.06. Furthermore, the methodology works over a wide range of volume fractions. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) are seeing increasing adoption to automated remote and in situ inspection of industrial assets, removing the need for hazardous manned access. Aerial manipulator architectures supporting pose-decoupled exertion of force and torque would further enable UAV deployment of contact-based transducers for sub-surface structural health assessment. Herein, for the first time, we introduce an over-actuated multirotor deploying a dry-coupled ultrasonic wheel probe as a novel means of wall thickness mapping. Using bi-axial tilting propellers in a unique tricopter layout, this system performs direct thrust vectoring for efficient omnidirectional flight and application of interaction forces. In laboratory testing, we demonstrate stable and repeatable probe deployment in a variety of representative asset inspection operations. We obtain a mean absolute error (MAE) in measured thickness of under 0.10 mm when measuring an aluminum sample with varying wall thickness. This is maintained over repeated exit and reentry of surface contact and when the sample is mounted vertically or on the underside of a 45° overhang. Furthermore, when rolling the probe dynamically across the sample surface in an area scanning modality, an MAE in wall thickness below 0.28 mm is recorded. Multi-modal operational confidence bounds of the system are thereby quantitatively defined. Note to Practitioners—Motivation for this article stems from the desire to enhance the speed and level of insight into structural health currently offered through remote aerial inspection processes. We approach this by integration of a thrust vectoring multirotor platform with a dry-coupling wheel probe for aerial ultrasonic thickness measurement. This system reliably presses the probe into the target surface and obtains point measurements across various surface orientations without a stabilizing frame. This broadens applicability and permits novel inspections where couplant gel would otherwise contaminate the surface and require manual cleaning. We profile thickness along a scanned linear section, a mode suited to corrosion mapping of large surface areas such as petrochemical storage tanks, pipework, or similar assets. We also make detailed consideration toward measurement accuracy, repeatability, and localization, an aspect commonly overlooked in literature. Future work to characterize variable friction effects currently limiting rolling scan speed and measurement coverage density may be beneficial. Quantitative study of the effectiveness of dry-couplant in the presence of any uncommon surface contaminants specific to a desired use-case is also advised. [ABSTRACT FROM AUTHOR]

Numerous studies have performed in vitro ultrasonic measurements of cancellous bone in water to develop techniques for ultrasonic bone assessment. Because cancellous bone is a highly porous medium, ultrasonic reflections at the water-bone interface may be frequency dependent. The goal of this study was to investigate the effect of porosity on the frequency dependence of the reflected power. Ultrasonic measurements were performed in a water tank at room temperature on 15 specimens of cancellous bone prepared from the proximal end of 9 human femurs using single element, broadband transducers with center frequencies of 3.5, 5, 7.5, and 10 MHz. Power spectra of pulses reflected from the water-specimen interface were corrected for the frequency response of the measurement system to obtain the reflected power in decibels RdB(f). To suppress random phase cancellation effects, RdB(f) was averaged over multiple sites on multiple specimens. A frequency dependence of RdB(f) was observed in the 2.6–10 MHz range. The frequency dependence was moderate, with a maximum change of less than 6 dB over the entire frequency range. RdB(f) was greatest for low porosity specimens. The frequency averaged intensity reflection coefficient ranged from 7.4 × 10−4 to 7.8 × 10−3 for high and low porosity specimen groups, respectively. [ABSTRACT FROM AUTHOR]

Objectives: Ultrasound technology is currently used in many areas, such as imaging, analysis, and process monitoring. The noninvasive implementation, nondestructive effect on the material to be applied, and low cost of the needed components give an advantage to the ultrasonic systems when compared to other methods for analysis and process monitoring studies. However, the current ultrasonic analysis setups used in the studies require additional devices such as a signal generator and oscilloscope. These devices used in the setup increase the cost, size, usage difficulty of the system and, most importantly, decrease the portability and stability. In order to prevent these disadvantages, an ultrasonic system that can work in real‐time and its software are developed to be used in analysis and process monitoring without any additional devices. Methods: This system was designed by using a microcontroller. The developed system is portable, has a small size, and a Bluetooth Low Energy connection. It has a battery for using standalone. Results: Therefore, it can be easily used in different small and closed measurement environments such as incubators and controlled remotely. In addition, a mixture was analyzed with both the designed system and a commercial module. When the results are compared, two systems are found highly correlated r2=1. Conclusion: In this study, an embedded ultrasonic measurement system and its software are developed to be used in analysis studies, density measurements, and real‐time process monitoring as a stand‐alone device. [ABSTRACT FROM AUTHOR]

Picosecond ultrasonics is a powerful tool for nanoscale metrology, giving access to dimensions and mechanical, thermal, and optical properties of nanomaterials. By monitoring the temporal evolution of the interaction of light with coherent acoustic phonons, also known as Brillouin oscillations, phonon lifetime and optical absorption can be measured. However, the extraction of these quantities can be inaccurate due to the common assumption of the infinite coherence length of probe pulses. Here, we demonstrate the effect of probe pulse duration on picosecond ultrasonic measurements numerically and experimentally. We establish a model that shows how the probe coherence length affects the measured signal loss and how we can overcome this limitation and measure an upper limit of the acoustic attenuation factor. The model is verified experimentally on a GaAs bulk substrate by varying the probe pulse duration, showing a strong effect for sub-100 fs pulses. Finally, we applied to CH3NH3PbBr3, where we reveal a high acoustic attenuation factor, which is in line with recent claims of strong anharmonicity in halide perovskites. [ABSTRACT FROM AUTHOR]

Project-based learning (PBL) provides an effective practical application to the learners. Further, PBL develops problem-solving, critical thinking, etc., in the learner. This paper describes a type of project offered to the students at the collegiate level to enhance the students' ability to work in a team, manage a project, and present their results. These projects use acoustic waves in the ultrasound frequency range that can be used as a powerful nondestructive tool for the characterization of the materials. In situ measurement of the ultrasonic longitudinal velocity and evaluation of the elastic constants carried out on the materials in solid pellet form over a wide range of temperatures at a fundamental frequency of 5 MHz enables the study of various phase transitions, such as metal to insulator, ferromagnetic to paramagnetic, and even structural phase transitions that occur in the materials. Here, the investigation is elaborated on using ultrasonic waves on some materials in pellet form and the results obtained are presented. [ABSTRACT FROM AUTHOR]

This paper reports the degradation behaviour of Super304H during the creep process. The failure mechanism of this Super304H is the typical intergranular damage, the creep voids and micro-crack are mainly concentrated on the GBs and triple point GBs. Meanwhile, there is a lot of precipitates inside void chain, those particles are the M23C6 phase, which indicate that the coarsening and growth of M23C6 phase are detrimental to the microstructural property of Super304H. Besides, the GND density of Super304H increased remarkably at the creep acceleration period, and the dislocation structure also changed from the pattern of straight-line to the zigzag. In addition, the nonlinear ultrasonic measurement results showed that there is a general upward trend of nonlinear parameter β' of Super304H during creep. The increase of the nonlinearity effect in Super304H could be due to several factors such as the precipitates precipitation, dislocation density/structure change, and the microdefects formation. [ABSTRACT FROM AUTHOR]

In this study, we performed customized ultrasonic measurements of the stone block foundation of the Sungnyemun Gate, which is representative of the stone architectural heritage in the Republic of Korea. Furthermore, the weathering evaluation standards, which are extensively used in stone heritage, were improved considering the type of rock and its provenance site. In particular, the absolute weathering grade used the ultrasonic velocity (P-wave) of a universal hard rock, whereas the relative weathering grade used the differences between the ultrasonic velocities of the materials in the stone block foundation of the Sungnyemun Gate (weathered stone) and the fresh rocks in the provenance. Among these, the absolute weathering grade was observed to be constant regardless of the type of rock; however, the relative weathering grade varied depending on the type dof rock. Because the average ultrasonic velocity of the original blocks of the stone block foundation of the Sungnyemun Gate was 2665 m/s, it was estimated that their ultrasonic velocity reduced by approximately 2.1 m/s per year as compared to that observed in case of fresh rocks (average 3932 m/s) in the provenance site. Furthermore, the weathering evaluation exhibited that there were approximately two stages of difference between the original blocks and the new blocks. As compared to the relative weathering grade, the absolute weathering grade was observed to underestimate the overall ultrasonic velocity of the stone block foundation of the Sungnyemun Gate. This study presents a customized method for performing ultrasonic measurements and for evaluating weathering. It is assumed that the results of this study will be extensively used in diagnosing and monitoring the stone architectural heritage. [ABSTRACT FROM AUTHOR]

Ultrasonic backscatter techniques may offer a useful approach for detecting changes in bone caused by osteoporosis. The goal of this study was to investigate how bone mineral density (BMD) and the microstructure of human cancellous bone affect three ultrasonic backscatter parameters that have been identified as potentially useful for ultrasonic bone assessment purposes: the apparent integrated backscatter (AIB), the frequency slope of apparent backscatter (FSAB), and the frequency intercept of apparent backscatter (FIAB). Ultrasonic measurements were performed with a 3.5-MHz broadband transducer on 54 specimens of human cancellous bone prepared from the proximal femur. Microstructural parameters and BMD were measured using X-ray microcomputed tomography (micro-CT). Relationships between AIB, FSAB, FIAB, and the micro-CT parameters were investigated using univariate and multivariate statistical analysis techniques. Moderate-to-strong univariate correlations were observed between the backscatter parameters and microstructure and BMD in many cases. The partial correlation analysis indicated that the backscatter parameters are dependent on microstructure independently of BMD in some cases. Multiple stepwise linear regression analysis used to generate multivariate models found that microstructure was a significant predictor of the backscatter parameters in most cases. [ABSTRACT FROM AUTHOR]

It is well known that nonlinear ultrasound is sensitive to some microstructural characteristics in material. This paper investigates the dependence of the nonlinear ultrasonic characteristic on Al-Cu precipitation in heat-treated 2219-T6 aluminum alloy specimens. The specimens were heat-treated at a constant temperature 155XC for different exposure times up to 1800 min. The nonlinearity parameter and the changes of precipitates phase were measured for each of the artificially aged specimens. The experimental results show fluctuations in the fractional change in nonlinear parameter (Δβ/β0) and the changes of precipitated phase over the aging time, but with an interesting correlation between the fractional change in nonlinear parameter (Δβ/β0) and the change of precipitate phase over the aging time. Through the experimental data results, the fractional change in nonlinear parameter (Δβ/β0) and the change of precipitate phase over the aging time were fitted curve. Microstructural observations confirmed that those fluctuations are due to the formation and evolution of precipitates that occur in a unique precipitation sequence in this alloy. These results suggest that the nonlinear ultrasonic measurement can be useful for monitoring second phase precipitation in the 2219-T6 aluminum alloy. [ABSTRACT FROM AUTHOR]

The aim of this study is to assign the provenance of Roman marble statues and assess their condition in order to use this information as a guideline for their future conservation treatments. Several analytical methods were applied to investigate the provenance of the statues including petrography, X-ray diffraction, and mass spectrometry. The deterioration level of the statues was assessed by non-destructive ultrasonic velocity measurements. The provenance investigation showed that four statues were most probably made of the dolomitic marble quarried from Thasos Island, Greece and one statue was made of the Proconnesus marble quarried from Marmara Island, Turkey. The condition assessment study revealed that the statutes are still in a good condition, although they exhibit weathering in the form of increasing porosity. Consequently, suitable conservation measures and recommendations for preserving the marble statues and preventing future damage were proposed. In general, the ultrasonic technique proved to be effective for assessing marble condition and identifying and prioritizing required conservation work in a fast, reliable, and non-destructive way. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel method for real-time detection of NaCl concentration based on ultrasonic impedance method. Specifically, our method is based on the fact that different concentration of NaCl leads to differences in acoustic characteristics of ultrasonic waves. We conducted an experimental study on the relationship between the concentration and the amplitude of ultrasonic echo. Our evaluations show that our approach can push the linear fitting degree ${r}^{{2}}$ to 0.9967. Then we used the BP neural network to classify and identify the collected sample data and achieved 100% classification accuracy. We also established a concentration–amplitude prediction model based on the BP neural network, and the result shows that the error between the predicted value and the ground truth is less than 8.36%. This method realizes non-contact measurement and can be applied to real-time monitoring of NaCl concentration in large, closed containers. [ABSTRACT FROM AUTHOR]

Nowadays, measuring residual stress in welded parts is of great importance in the industry. Based on the measured residual stress and the operational conditions of the part, a suitable factor of safety is defined for the design. Destructive methods have most often been used to determine residual stresses. Given limitations such as high cost, non-destructive testing (NDT) methods have replaced destructive methods in recent years. The ultrasonic method has attracted much attention in recent years for determining residual stress. In addition to its simplicity, low cost, and the need for only a few pieces of equipment, this method has additional advantages such as the ability to measure residual stress at various depths. In this paper, the feasibility of the ultrasonic method in measuring residual stress in the fusion welding of two aluminum sheets was studied and compared with the simulation result. The longitudinal residual stress was measured using the ultrasonic method via 1, 2, 4, and 5 MHz transducers at a depth near the surface. An ultrasonic wedge based on Snell's equation was built to create the LCR wave and transmit it into the part. Next, the results obtained from the ultrasonic measurement were compared with those obtained through the numerical simulation in Abaqus software. Overall, it was found that the ultrasonic simulation method could predict with high accuracy the residual stress at various depths of the part. Furthermore, the results demonstrated that the accuracy of this method declined with an increase in the ultrasonic frequency. [ABSTRACT FROM AUTHOR]

Hydrogen has a wide range of energy applications, but hydrogen energy systems can suffer from high-concentration leaks that pose security risks, therefore making the measurement of high-concentration hydrogen very important. Traditional ultrasonic gas-detection methods are based mainly on ultrasonic time-of-flight measurements and can be divided into threshold-detection and phase-difference techniques. Threshold detection suffers from low resolution and a complex structure in gas detection, while the phase-difference technique has high resolution and a simple structure but can only measure the time of flight within one period of the ultrasonic signal. In this study, a dual-frequency phase-difference technique is proposed that solves the problem of multi-period phase detection with the phase-difference technique and can be used to detect high-concentration hydrogen. Simulation analysis and an experiment show that the proposed technique can measure the multi-period phase difference accurately. The maximum hydrogen concentration can reach 50% with an uncertainty of less than 5%, which meets commercial requirements. [ABSTRACT FROM AUTHOR]

This study aims to investigate the feasibility of quantitative ultrasonic backscatter in evaluating human cortical and trabecular bone densities in vivo based on a head-down-tilt bed rest study, with 36 participants tested through 90 d of bed rest and 180 d of recovery. Backscatter measurements were performed using an ultrasonic backscatter bone diagnostic instrument. Backscatter parameters were calculated with a dynamic signal-of-interest method, which was proposed to ensure the same ultrasonic interrogated volume in cortical and trabecular bones. The backscatter parameters exhibited significant correlations with site-matched bone densities provided by high-resolution peripheral quantitative computed tomography (0.33 < |R| < 0.72, p < 0.05). Some bone densities and backscatter parameters exhibited significant changes after the 90-d bed rest. The proposed method can be used to characterize bone densities, and the portable ultrasonic backscatter bone diagnostic device might be used to non-invasively reveal mean bone loss (across a group of people) after long-term bed rest and microgravity conditions of spaceflight missions. [ABSTRACT FROM AUTHOR]

In this article, we present a Doppler-effect-compensated ranging system that can be applied to subcentimeter-precision ultrasonic distance measurement for moving targets using a direct sequence spread spectrum (DSSS). First, the theory of the Doppler compensation technique is explained, and then, the evaluation results obtained using maximum-length-sequence coded ultrasonic signals are discussed. In this study, we employ a 128-b DSSS code with three wavelengths per bit. The experimental results demonstrate that the proposed system can measure a target accelerating at 9.8 m/s2 with a speed of up to 2 m/s in the range of 0.1–1.6 m, with a standard deviation of less than 5 mm. We also confirmed by simulation that the system can track a target accelerating at 30 m/s2 with a speed of up to 5.5 m/s in the range of 4–6 m. [ABSTRACT FROM AUTHOR]

• To extract multiple PD signals and estimate DOA from signals collected by acoustic sensor array accurately, the mnc-FastICA method with KPCA psedudo-whitening tackles the complex received data. • Azimuth and pitch angles can be derived from the separated matrix of KPCA-mnc-FastICA. • The angle error correction matrix is designed to compensate for the sensor's phase inaccuracy. • The DOA estimation perfromances of the scheme is compared with empirical methods such as MUSIC, CAPON and mnc-FastICA, in terms of accuracy, robustness against array error. Empirical studies into partial discharge (PD) localization face the difficulty of signal contamination from external noise and interference. To extract relevant information from PD signals collected by acoustic sensor array, Kernel Principal Component Analysis (KPCA) pseudo-whitening with modified noncircular Fast Independent Component Analysis (mnc-FastICA) were used. By this approach, separated matrix and observed signals can be achieved. The reconstructed array manifold matrix created from the separated matrix generated by KPCA-mnc-FastICA may be used in the Direction of Arrival (DOA) estimation approach. An angle error correction matrix is designed to compensate for the sensor's phase inaccuracy. The simulation results show that angle identification accuracy is outstanding, with mistakes limited to a small margin of 2°. Furthermore, the results of trials show that this technique can efficiently isolate individual target signals even when they are polluted with significant noise and interference. The average errors in azimuth and pitch angle are less than 2° and 1.1°, respectively. These data support the effectiveness of the approach for effectively separating signals and estimating DOA of numerous signal sources. [ABSTRACT FROM AUTHOR]

This paper presents a low-power hardware architecture that facilitates the simultaneous transmission and reception of ultrasonic signals when using coded excitations for ultrasonic measurements. With this architecture, long pseudo-periodic coded excitations, which have previously been unsuitable for pulse-echo measurements, can be used to produce high Signal-to-Noise Ratio (SNR) results without an increase in signal dead-zone and without introducing filter artefacts within a set measurement window. We show that a low-power system (± 2 V peak excitation amplitude without receiver amplification) utilising such coded excitations can achieve the same level of performance as a conventional high-power system (− 200 V peak excitation amplitude with 15 dB receiver amplification) by producing 45 dB SNR measurements whilst maintaining a high Pulse Repetition Frequency (PRF) of ≥ 0.5 kHz. The use of pseudo-periodic sequences to produce quasi-orthogonal sequence families is then demonstrated to allow an arbitrary number of acquisition channels to be used simultaneously with complete crosstalk removal within a set measurement window. Therefore, the work presented here can open the door for the development of simplified low-power multi-channel acquisition systems without sacrificing system performance. [ABSTRACT FROM AUTHOR]

The assimilation of simulated and measured data is essential for advancing technology in NDE 4.0. In this study, a particle filter (PF) was applied to identify the geometry of flaws for ultrasonic nondestructive testing. A PF based on a probabilistic approach that allows errors in measurement and simulation models may be of great assistance for the data assimilation. In the PF, state variables are expressed by random data samples called particles, together with their associated weights. The PF estimates the probabilistic density function of the state variables by merging simulation data with measured data. Data types must be physically identical in the simulation and measurement to enhance the accuracy and to accelerate the convergence speed in the PF. Here, the scattering component, which is specific information related to the flaw geometry, was used for the likelihood evaluation in the PF. The simulation, which needed many particles, was conducted using the elastodynamic finite integration technique accelerated by parallel computing with graphics processing units. The proposed PF approach was demonstrated in ultrasonic measurement, and the geometries of artificial flaws in aluminum specimens were identified using only one pulse-echo signal at a single transducer. [ABSTRACT FROM AUTHOR]

In this paper, an active single‐object localization system with U‐shaped ultrasonic module array is presented. The proposed algorithm in this system has two stages. The first stage is time‐of‐flight (TOF) estimation of reflected ultrasonic signals. We analyze several distortion cases of reflection signals and provide solutions to improve the performance of TOF estimation. The second stage is TOF‐based object localization. A good localization algorithm can suppress the problems caused by inaccurate TOF estimation and improve the accuracy of target positioning. We propose two object‐localization algorithms to estimate the object location. One is the unconstrained least‐squares method, and the other is the constrained weighted least‐squares method based on the eigenvalues‐analyzing technique. The simulation results suggest that the performance of the proposed constrained weighted method is better than that of the unconstrained method. In addition, the median smoother and the outlier exclusion scheme are implemented in the overall system to make the object location estimation more stable. The performance of the proposed system is confirmed by the experiment results, which show that the single‐object localization has a considerable degree of accuracy and stability. [ABSTRACT FROM AUTHOR]

Transducers for ultrasonic sensing and measurement are often operated with a short burst signal, for example a few cycles at a specific excitation voltage and frequency on the generating transducer. The vibration response of a narrowband transducer in detection is usually dominated by resonant ringing, severely affecting its ability to detect two or more signals arriving at the receiver at similar times. Prior researchers have focused on strategies to damp the ringing of a transducer in transmission, to create a temporally short output pressure wave. However, if the receiving transducer is narrowband, the incident pressure waves can create significant ringing of this receiving transducer, irrespective of how temporally short the incident pressure waves are on the receiving transducer. This can reduce the accuracy of common measurement processes, as signals are temporally long and multiple wave arrivals can be difficult to distinguish from each other. In this research, a method of damping transducers in reception is demonstrated using a flexural ultrasonic transducer (FUT). This narrowband transducer can operate effectively as a transmitter or receiver of ultrasound, and due to its use in automotive applications, is the most common ultrasonic transducer in existence. An existing mathematical analog for the transducers is used to guide the design of an engineered pressure wave to actively damp the receiving FUT. Experimental measurements on transducers show that ultrasonic receiver resonant ringing can be reduced by 80%, without significantly compromising sensitivity and only by using a suitable driving voltage waveform on the generating transducer. [ABSTRACT FROM AUTHOR]

Ultrasonic computerized tomography is a promising technique for damage detection by enabling ultrasonic waves via multiple measurement paths leading to accurate localization of structural damage. Unlike traditional ultrasonic computerized tomography that requires numerous measurements and costly computation, a compressive sampling advancing both the measuring phase and the imaging phase is proposed in this study to achieve accurate identification with no low-speed traditional ultrasonic computerized tomography technique measurements or costly computation in real-world applications. The proposed rapid ultrasonic computerized tomography approach advances both the measuring phase and the imaging phase. In the measuring phase, far few ultrasonic measurement paths are randomly selected to capture the characteristics of the ultrasonic waves carrying the underlying damaged information. And in the imaging phase, ℓ 1-norm minimization optimization algorithm is used to reconstruct the internal damage, rendering the sparest solution related to the physical damages. The functionality of the proposed approach is validated by both numerical simulation and experimental testing. The results indicate that the improved ultrasonic computerized tomography technique in compressive sampling framework has a great potential for rapid damage detection, which is a game-changing technique for accurate and cost-efficient damage detection in real-world applications. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the ability of a pencil-type transducer connected to a pulser-receiver to measure remaining dentin thickness (RDT). Methods: A total of 24 freshly extracted bovine incisors were used to prepare dentin disks with certain thicknesses (0.5,1.0,1.5 and 2.0 mm). The thicknesses of the specimens were measured with an ultrasonic technique using a pencil-type transducer, and the data obtained were compared with the direct measurement obtained using a micrometer. The Bland-Altman comparison method and paired t-test were performed at a 0.05 significance level. Results: The agreement between different measurement methods was analyzed to evaluate the intermethodology variation. The Bland-Altman comparison method revealed a mean di Kerence of 0.0098 * 0.724 mm between the ultrasonic technique and the direct measurement. with the 95% Bland-Altman limits of agreement ranging from 0.1322 to 0.1517 mm. [ABSTRACT FROM AUTHOR]

Lithium-Ion batteries are used in ever more demanding applications regarding operating range and safety requirements. This work presents a series of high-temperature abuse experiments on a nickel-manganese-cobalt oxide (NMC)/graphite lithium-ion battery cell, using advanced in-operando measurement techniques like fast impedance spectroscopy and ultrasonic waves, as well as strain-gauges. the presented results show, that by using these methods degradation effects at elevated temperature can be observed in real-time. These methods have the potential to be integrated into a battery management system in the future. Therefore they make it possible to achieve higher battery safety even under the most demanding operating conditions. [ABSTRACT FROM AUTHOR]

Understanding the behaviour of engine and gear oils, especially the viscosity, under temperature and shear is important to improve machine operation. A novel viscometer using ultrasound is presented and used under a range of temperatures. A single cross-temperature (between 20 ° C and 60 ° C) ultrasonic calibration is shown to be sufficient. Next, the ultrasonic viscometer is compared to a conventional viscosity measurement technique for Newtonian and non-Newtonian lubricants. Newtonian viscosity standard fluids and shear-thinning engine oils are studied. Both viscosity measurement techniques match for Newtonian fluids but ultrasonic measurements are consistently lower for shear-thinning fluids. It suggests that the ultrasonic viscometer is similar to a high-shear viscometer with a shear rate of about 1 0 6 s − 1 . [ABSTRACT FROM AUTHOR]

In bulk solid handling, measuring the fill volume of vessels with powders is complex due to the uneven material surface. This research presents a method using an array of narrow-beam ultrasonic range finders in a powder discharge vessel. The vessel's cross-sectional area was divided into equal sub-sections, each measured by a range finder. The total fill volume was calculated by summing up the volumes of these sections. This system allows quick volume estimates at around 0.9 Hz under various flow states. In static conditions, tests on flat, concave, and convex powder surfaces showed a volume discrepancy of <5% of vessel capacity. For a vessel discharging polyethylene pellets, the estimated fill volume was under 0.6% uncertainty (confidence interval: 0.95). The findings underscore the utility of ultrasonic range finders for accurate volume determination in powder discharge vessels. [Display omitted] • Ultrasonic rangefinders can measure fill volume for discharging material in real time. • Ultrasonic range finders can measure material flow rate during discharge. • Real-time fill volume error is <5% of vessel capacity. • Ultrasonic rangefinder placement affects depth measurement accuracy. • Vessel wall imperfections affect measurement precision. [ABSTRACT FROM AUTHOR]

Ensuring adequate tightening is imperative for securing bolted connections in steel structures. Moreover, bolted joints are affected by corrosion. This paper describes a method of non-destructively assessing the condition of bolted joints. An ultrasonic pulse transmission technique for inspection of bolted joints has been described. Steel plates have been bolted by applying different levels of torque. Transmission of ultrasonic pulse through the joint with varying tightening is studied. A set of plated joints have been subjected to tensile testing to characterise the joints. The other set of joints have been subjected to accelerated corrosion and the ultrasonic measurement has been conducted regularly. After the exposure period, the joints have been subjected to tensile tests to compare with the control specimens. It is observed that the ultrasonic pulse transmission can be correlated with the initial tightening of the bolt. The effect of corrosion was also discerned through ultrasonic measurement. It is observed that the tensile behaviour of the joints due to corrosion is affected significantly by the initial tightening. The proposed method can be applied for non-invasive inspection of fresh and corroded steel structures. • Extent of corrosion damage in the bolted joint depends on the bolt torque. • Ultrasonics based technique can be used monitor the condition of bolted joints. • Corrosion's effects on the load capacity of the joints depend on the bolt tightening [ABSTRACT FROM AUTHOR]

Highlights • The technique was tested with five substances covering a wide viscosity range. • Newtonian behavior was observed at ultrasonic frequencies for all liquids. • An unexpected oscillatory behavior in the viscosity was observed. • The alternative signal processing methodologies show improvement in accuracy. Abstract This work deals with two alternative methodologies for data post-processing resulting from the ultrasonic shear-wave reflectance method used for liquid viscosity measurement. In the shear-wave reflectance method, the measurement principle is the small transference of energy to the liquid when the wave strikes a solid–liquid interface, causing a detectable change in the reflection coefficient. A measurement cell that uses mode conversion for the generation of the shear waves was employed and samples of five different substances were tested, covering a viscosity range of three orders of magnitude. Ultrasonic results were compared to the values obtained by conventional viscometry. Despite the wide range of viscosity and the different nature of the liquids, Newtonian behavior was observed with all samples at the working frequencies. This can be concluded from the coincidence between the values obtained by ultrasound and by the rotational viscometer. However, the viscosity values show an oscillating behavior when calculated for different frequencies along the band of the transducer. This oscillating behavior induces big errors when the viscosity is calculated at a single frequency, forcing the development of alternative methodologies. Two methodologies that calculate the reflection coefficient in a frequency band instead of a single frequency were analyzed, showing more accuracy and precision. [ABSTRACT FROM AUTHOR]

• Measurements of the ultrasonic pulse velocity (UPV) in cement-stabilized soil were carried out. • Standard UPV device was equipped with an oscilloscope to extend its functionality. • Signal analysis revealed the phenomenon of masking key elements of the wave, which caused difficulties in UPV detection. • To improve the measurement accuracy, deep learning method was applied. • High quality pulse and soil–cement strength recognition results were obtained, improving the standard UPV device accuracy. Soil–cement materials are widely used in civil engineering. Previous studies described problems related to errors in ultrasonic measurements of the unconfined compressive strength (UCS) of low-strength soil–cements. In the presented experiments, a standard ultrasonic pulse velocity (UPV) measuring device was equipped with an oscilloscope to extend its functionality. An analysis of the ultrasound signal revealed the phenomenon of masking key elements of the longitudinal wave, which caused difficulties in the detection of noise and the correctness of measurements using classical detection methods (without prediction). The important goals of this study were to build an error removal method and UPV universal detection mechanism without human interference. To improve the measurement efficiency, a deep learning method was implemented. High-quality pulse and strength recognition results were obtained, improving the accuracy of the standard ultrasonic pulse measuring device. Based on the results, the multivariate correlations of UCS with the material UPV, maturation time and cement content are described. [ABSTRACT FROM AUTHOR]

• The typical damage types and their effects on composite materials are introduced. • Ultrasonic measurement methods for determining the parameters of composite materials are reviewed to enhance the damage detection accuracy. • This paper outlines the acoustic models, detection techniques, and imaging methods based on the ultrasonic bulk wave or guided wave detection technologies. • The damage diagnosis of composite materials, criteria for damage assessment, and analytical methods for predicting the remaining service life of damaged composite materials are reviewed in detail. Advanced composite materials are prone to various types of damage during - manufacturing and long-time service. Ultrasonic detection methods have been widely employed to detect damage because of their high accuracy and reliability. This study gives a comprehensive review of the ultrasonic detection methods for damage diagnosis and assessment of advanced composite materials. Firstly, the typical damage types and their effects on composite materials are introduced. Ultrasonic measurement methods for determining the parameters of composite materials are reviewed to enhance damage detection accuracy. In addition, acoustic models, detection techniques, and imaging methods based on ultrasonic bulk wave or guided wave detection technologies are discussed. Further, the damage diagnosis of composite materials, criteria for damage assessment, and analytical methods for predicting the remaining service life of damaged composite materials are reviewed in detail. Finally, insights into the application prospects of advanced composite materials, including the acoustic modeling of different composites, integration of multiple ultrasonic testing technologies, development of fast damage monitoring systems, establishment of damage diagnosis criteria, and lifespan prediction of damaged composites, are provided. [ABSTRACT FROM AUTHOR]

Abstract In this work, an improved acoustic model based on virtual material is proposed to provide an accurate measurement of interfacial contact stiffness using ultrasound. The rough interface is assumed to be a thin layer of virtual material to incorporate the effect of ultrasound attenuation at the interface. The derived acoustic model shows that the developed contact stiffness expression is a refinement of the general spring model by considering the interfacial property and is related to the material properties of the virtual material thin layer. The analytical solutions of the material parameters for the virtual material are further deduced based on the statistical micro-contact theory. It reveals that the surface roughness parameters of the contact interface and the material property of the contact body are other information required to improve the measurement accuracy of contact stiffness, in addition to the ultrasonic measurement parameters in the original spring model. The accuracy of the developed acoustic model for contact stiffness measurement is verified by comparison with the spring model and the statistical contact models. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nondestructive testing method for measuring the wave velocity in the thickness direction of anisotropic material plates was proposed. • The wave velocity in the thickness direction can be obtained by analyzing the images of the ultrasonic polar scan. • The thickness measurement accuracy of the anisotropic material samples has significantly improved. Ultrasonic polar scan (UPS) records the amplitude in transmission for a wide range of incidence angles, providing a UPS image with characteristic contours reflecting the acoustic parameters of the material. This study focused on a newly developed wave velocity measurement of the DD6 single-crystal material plate by analyzing the UPS image to realize the ultrasonic thickness measurement of the DD6 single-crystal material plate accordingly. Firstly, considering transducer contour size compensation, the UPS images are obtained by numerical simulation on the DD6 single-crystal material plates with different crystal orientations. Secondly, the fitting equations are obtained by analyzing the UPS images to calculate wave velocity in the thickness direction. Finally, a 5-joint UPS scanner is designed to validate the accuracy of wave velocity simulation results experimentally, and it indicates a good agreement with conventional ultrasonic velocity measurement. The measurement results demonstrated that the UPS method could evaluate the wave velocity in the through-thickness direction of the DD6 single-crystal material plate with high precision. [ABSTRACT FROM AUTHOR]