Ultrasonic Technique Research Articles

Assessing cylinder damage using bounded ultrasonic beam scattering methodology

This paper proposes an effective ultrasonic detection methodology for assessing the damage state of cylindrical structures. The methodology depends on the interaction between a bounded ultrasonic beam and the cylinder. First, the theoretical derivation of the scattered sound field generated by a bounded ultrasonic beam incident obliquely onto a cylinder is presented. Next, by means of FE simulations and experimental verification, we demonstrate that when the bounded ultrasonic beam emitted by the transmitter is obliquely incident upon the cylinder at either the first or second critical angles, as defined within this study, the early initiation of damage results in a significant increase in the received sound pressure amplitude detected by the receiver positioned symmetrically relative to the transmitter. Specifically, the simulation results indicate that a mere 5 % decrease in the elastic modulus of the cylinder correlates with a staggering 447.88 % surge in the received sound pressure amplitude at the first critical angle. Experimental evidence also demonstrates that for varying states of impact-induced damage of the cylinder, the received sound pressure amplitude detected by the symmetric receiver exhibits highly sensitive characteristics when a bounded ultrasonic beam is incident at the first critical angle onto the cylinder. This approach represents a significant advancement over traditional ultrasonic detection techniques, combining the reliability and stability of linear ultrasonic methods with the sensitivity for early damage assessment provided by nonlinear ultrasonic techniques. The proposed assessment method holds great promise in providing fresh insights for inspecting cylindrical structures in practical applications.

Effect of Al‐Incorporation on the Sound Velocities of Superhydrous Phase B at High Pressure and High Temperature

AbstractSound velocities and densities of Al‐bearing superhydrous phase B (Al‐bearing SuB) were investigated up to 24 GPa and 1300 K by synchrotron X‐rays combined with ultrasonic interferometry techniques in a multi‐anvil apparatus. We found that Al + H incorporation decreases the adiabatic bulk modulus and shear modulus of SuB. Our results however suggest that this effect is less important than that of temperature. The presence of hydrous pyrolite with ∼10 wt.% Al‐bearing SuB in cold subducting slabs could explain up to ∼2% high velocity anomalies at the bottom of the mantle transition zone (500–660 km) while it turns into ∼7.7% low velocity anomalies below 660 km. Al‐bearing SuB is reportedly stable at mantle temperatures, where it could account for ∼12.2% low velocity anomalies beneath subduction zones in the uppermost lower mantle.

A novel objective evaluation method, shear wave elastography, in the treatment of atrophic vaginitis by nonablative intravaginal Er:YAG laser, a randomized-sham controlled pilot study.

The aim of the study was to investigate the effectiveness of intravaginal Er:YAG laser for treating atrophic vaginitis in postmenopausal women utilizing shear wave elastography. In this prospective randomized sham-controlled double-blind pilot study, 20 participants were included (laser group [n = 12] / sham-control group [n = 8]). A nonablative (Smooth mode) Er:YAG laser with a wavelength of 2,940 nm was used. Objective evaluation of laser treatment efficacy was conducted using a special ultrasonic technique: shear wave elastography. Ultrasonic velocity measurements were taken from the anterior and posterior vaginal walls. Mean elasticity (E mean ) was expressed in kilopascals (kPa). Additional outcome parameters were vaginal pH, Vaginal Health Index (VHI), Female Sexual Function Index (FSFI), and visual analog scale (VAS) scores for dyspareunia. Baseline clinical characteristics, vaginal pH, VHI, VAS and FSFI scores, and E mean values were comparable between the laser and sham-control groups. Statistically significant differences were observed in the final E mean values of the anterior vaginal wall (13.1 ± 6.3 vs 20.0 ± 3.3 kPA, P = 0.01) and posterior vaginal wall (12.7 ± 10.3 vs 19.4 ± 6.9 kPA, P = 0.04) between the laser and sham-control group. Despite comparable baseline E mean values, significant differences in vaginal wall stiffness posttreatment indicated a notable increase in tissue elasticity following laser treatment. Statistically significant differences were also observed in final vaginal pH values, VHI, VAS scores, and FSFI score improvement in favor of laser treatment. Shear wave elastography may be considered as a reliable and objective technique for evaluating the efficacy of Er:YAG laser treatment in women with atrophic vaginitis. However, additional studies with larger sample sizes are necessary to establish conclusive evidence.

Phased Array Ultrasonic Testing on Thick Glass Fiber Reinforced Thermoplastic Composite Pipe Implementing the Classical Time-Corrected Gain Method

Thermoplastic composite pipe is gaining popularity in the oil and gas and renewable energy industries as an alternative to traditional metal pipe mainly due to its capability of being spooled onto a reel and exceptional corrosion resistance properties. Despite its corrosion-proof nature, this material remains susceptible to various defects, such as delamination, fiber breakage, matrix degradation and deformation. This study employed the phased array ultrasonic testing technique with the implementation of the classical time-corrected gain method to compensate for the significant spatial signal attenuation beyond the first interface layer in the thick multi-layered thermoplastic composite pipe. Initially, the ultrasonic signals from the interface layers and back wall were detected with good signal-to-noise ratios. Subsequently, flat-bottom holes of varying depths, simulating one-sided delamination, were bored and the proposed method effectively identified ultrasonic signals from these holes, clearly distinguishing them from the background noise and interface layer signals. Finally, a defect deliberately fabricated within the composite laminate layers during the pipe manufacturing process was successfully identified. Subsequently, this fabricated defect was visualized in a three-dimensional representation using the X-ray computed tomography for a qualitative and quantitative comparison with the proposed ultrasonic method, showing a high level of agreement.

Synergistic effects of Li-based ferrite and graphene oxide in microwave absorption applications

The successful fabrication of composites consisting of ferrites with a composition of Li0.4Mg0.25Zn0.25Fe2.2O4 and Graphene oxide was carried out using the ultra-sonication technique. The current study examined the impact of graphene oxide in spinel ferrite employing X-ray diffraction, dielectric, and magnetic susceptibility studies. The X-ray diffraction investigation confirmed the spinel phase formation in ferrite and graphene oxide synthesis. The measured range for the size of crystallites was found to be between 48.43 and 30.07 nm. The DC resistivity of cubic ferrite at room temperature was determined to be 1.715 ×1010 ohm-cm by a two-probe approach. Furthermore, it was observed that the resistivity fell significantly as the content of graphene oxide increased. The dielectric constant exhibited behavior consistency with the Maxwell-Wagner phenomenon of interfacial polarization. The rise in graphene oxide content in ferrite results in high AC conductivity of composites due to the relatively large value of conductivity of graphene oxide and the improved charge hopping mechanism. The magnetic susceptibility of all the samples demonstrated a progressive decline as the temperature increased, which can be attributed to the disruption of spin alignment at the Curie temperature. The observed Curie temperature of all samples was 413–473 K. Integrating spinel ferrite with Graphene oxide has significantly improved the magneto-electrical characteristics, indicating potential applications in supercapacitors, high-frequency electromagnetic devices, and microwave absorption.

Automatic image alignment and stitching for ultrasound-based robotic inspection of complex geometry components

Robotic inspection of complex geometry components using immersion ultrasonic techniques is relevant for many ultrasonic Non-Destructive Testing (NDT) applications in different industries. To image large component, ultrasonic probe is manipulated around the component immersed in water using a robotic guided system to create a tiled image of the entire component. Due to the mechanical vibrations of the high-speed robotic arm, the probe position coordinates provided by the robotic system are not precise enough to ensure an accurate reconstruction (stitching) of a composite image from all individual images. In this work, we propose a stitching method specifically designed to create a single 2D image of the surface of an inspected component from a stack of Total Focusing Method (TFM) images. This stitching method uses Iterative Closest Point (ICP) registration to estimate a 2D rigid transformation between two consecutive 2D images, by maximizing the overlap between the surface geometries extracted from each image. The capabilities of this imaging technique are illustrated by various simulated and experimental results carried out in a water tank. Significant improvements in surface image quality, leading to accurate surface reconstruction, are shown for vertical vibrations with displacements of more than two operating wavelengths and for rotational vibrations with deviation angles of less than 1°. The results also show that the resolving power of the ICP algorithm decreases for strong rotational vibrations.

In Vivo Polymer Mechanochemistry with Polynucleotides.

Polymer mechanochemistry utilizes mechanical force to activate latent functionalities in macromolecules and widely relies on ultrasonication techniques. Fundamental constraints of frequency and power intensity have prohibited the application of the polymer mechanochemistry principles in a biomedical context up to now, although medical ultrasound is a clinically established modality. Here, a universal polynucleotide framework is presented that allows the binding and release of therapeutic oligonucleotides, both DNA- and RNA-based, as cargo by biocompatible medical imaging ultrasound. It is shown that the high molar mass, colloidal assembly, and a distinct mechanochemical mechanism enable the force-induced release of cargo and subsequent activation of biological function in vitro and in vivo. Thereby, this work introduces a platform for the exploration of biological questions and therapeutics development steered by mechanical force.

Altering the physical properties of NiO thin films grown through the ultrasonic spray pyrolysis method by incorporating impurity lead dopants

The technology of p-type transparent semiconductors is utilized in various fields, and enhancing their performance holds industrial significance. Thus, improving the versatility and efficiency of the p-type transparent conducting oxides (TCO) has become critical for the semiconductor industries and technologies. To be used as hole carrier layes in optoelectronic devices, this study aimed to modify the physical features of nickel oxide (NiO) through a doping approach which may broaden and strengthen the usage of NiO. A cost-effective ultrasonic pyrolysis spray technique was employed for pure and lead (Pb) doped nickel oxide thin film production. The influence of the lead concentration on optical, structural, and morphological traits of the NiO nanostructures was examined via various analyses, including energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), Photoluminescence, UV–visible spectroscopy, X-Ray Diffraction, and Raman spectroscopy, were utilized to investigate the optical and structural characteristics of these films. In correlation, the X-Ray Diffraction results indicated that the Pb doping induced strain and altered lattice parameters of the grown nanostructures while the cubic phase of NiO maintained. The crystallite size of NiO samples ranged from 31.49 nm to 18.75 nm based on Pb doping concentration which was notably influenced by species and doping content. The UV–vis measurements demonstrated that optical parameters, such as optical band gap, were sensitive to Pb doping ratios. The Raman spectrum analysis confirmed the successful incorporation of Pb ions into NiO. Additionally, the intensity of the PL spectra decreased with increasing Pb content, offering potential applications as window layers in solar cells, smart windows, and other optoelectronic devices.

Sideband Peak Count – a new nonlinear ultrasonic technique for monitoring damage progression in engineering materials

Linear ultrasonic (LU) techniques used by majority of the researchers working in material damage monitoring, are reliable for detecting relatively large defects. If the defect dimensions are in the range of the ultrasonic wavelength or larger, then those defects can be detected by analyzing the scattered ultrasonic fields. Material damage affects LU parameters such as ultrasonic wave speed and attenuation and their changes are detectable for relatively large defects. However, for small defects (when defect dimensions are significantly smaller than the wavelength of the propagating signal) the changes in the LU parameters are too small to detect or measure reliably. For detecting small defects engineers often use high frequency ultrasonic signals to make the defect dimensions greater than the wavelength. However, high frequency signals attenuate quickly and therefore, only very small regions near the ultrasonic probe can be inspected in this manner. Inspecting large structures by high frequency ultrasonic signals requires moving the probe mechanically from one point to the next and therefore, can be very time consuming. Nonlinear ultrasonic (NLU) technique on the other hand does not need to satisfy this restricting condition that the wavelength of the signal must be smaller than the defect size. NLU works well when the signal wavelength is much larger than the defect size. Therefore, relatively low frequency signals that can propagate a long distance and monitor a large area of a structure can be used for NLU measurements. Different NLU techniques can be used for detection and monitoring of small damages in a specimen. A relatively new NLU technique called the Sideband Peak Count-Index or SPC-I technique has been developed by the author and his collaborators. SPC-I technique for monitoring different types of materials – composites, metals, concrete, and other cement-based materials has been found to be effective. Along with those success stories of SPC-I the effect of topography and the advantage of topological sensing is also discussed in this presentation.

Optimization of Flavonoid Extraction from Abelmoschus manihot Flowers Using Ultrasonic Techniques: Predictive Modeling through Response Surface Methodology and Deep Neural Network and Biological Activity Assessment.

Understanding the optimal extraction methods for flavonoids from Abelmoschus manihot flowers (AMF) is crucial for unlocking their potential benefits. This study aimed to optimize the efficiency of flavonoid extraction from AMF. After comparing extraction methods, the ultrasonic cell crusher demonstrated superior performance over conventional techniques. Four key factors-solid-to-liquid ratio (1:10 to 1:50 g·mL-1), ethanol concentration (55% to 95%), ultrasonic time (10 to 50 min), and ultrasonic power (5% to 25% of 900 W)-were investigated and normalized using the entropy weight method. This led to a comprehensive evaluation (CE). Optimization of extraction conditions for the ultrasonic cell crusher was achieved through response surface methodology and a deep neural network model, resulting in optimal parameters: ethanol volume fraction of 66%, solid-to-liquid ratio of 1:21 g/mL, extraction efficiency of 9%, and extraction duration of 35 min, yielding a CE value of 23.14 (RSD < 1%). Additionally, the inhibitory effects of the optimized extracts against Streptococcus mutans (S. mutans) were assessed. The results revealed that AMF extract (AMFE) exhibits inhibitory effects on S. mutans, with concomitant inhibition of sucrase and lactate dehydrogenase (LDH). The MIC of AMFE against planktonic S. mutans is 3 mg/mL, with an MBC of 6 mg/mL. Within the concentration range of 1/8 MIC to 2 MIC of AMFE, the activities of sucrase and LDH decreased by 318.934 U/mg prot and 61.844 U/mg prot, respectively. The antioxidant activity of AMFE was assessed using the potassium ferricyanide reduction and phosphomolybdenum methods. Additionally, the effect of AMFE on DPPH, ABTS, and ·OH free radical scavenging abilities was determined. The concentrations at which AMFE exhibited over 90% scavenging rate for ABTS and DPPH free radicals were found to be 0.125 mg/mL and 2 mg/mL, respectively.

Laser generated Ultrasound System (LUS) and its application for the Non-Destructive Testing of metallic components

One of the investigation areas regarding the Ultrasonic Non-Destructive Test (UT-NDT) is the development of non-contact technologies like Air-Coupled UT, EMAT or UT generated by Laser. These technologies show several interesting advantages like no couplant needed or their application to the inspection of components with complex geometries and extreme surface conditions (temperature, roughness, radiation…). In the Laser Ultrasonics Techniques (LUS), ultrasound is generated by a pulsed laser that produces a thermal expansion of the surface where it impacts and generates vibrations at ultrasonic frequencies. These vibrations can travel through the inside of the material and its surface; and they are reflected, refracted or diffracted in the defects or discontinuities of the material. The disturbances generated by the interaction of the vibration with the defects are detected in another point of the material using a secondary detection system. Tecnatom is working with LUS technology since 2010, acquiring, installing and optimizing a laboratory system for its implementation in the inspection of metallic materials (aluminum, carbon steel and stainless steel). During this time, several works have been carried out to determine the scope of the technology as: initial study for the characterization of the waves generated by the laser; studies in test blocks without discontinuities to determine the experimental conditions in which ultrasonic disturbances are generated in thermo-elastic and ablative regime; simulations and microstructural studies of the pieces to determine both the structural state and the residual stresses caused by the incidence of the laser; inspection of blocks with artificial reflectors, both superficial and embedded, and set-up techniques to increase the amplitude of the detected signal; optimization of the detection system through the combination of technologies and identification of safety criteria, use and improvement of the system for validation use in industrial environments. In this work, Tecnatom presents the main conclusions of the development carried out to determine the capacities and limitations of the techniques based on Laser Ultrasonics for its application in Non-Destructive Testing for the inspection of metallic components.

Improved Formulae for Low-Frequency Ultrasonic Attenuation in Metals

A range of ultrasonic techniques associated with the nondestructive evaluation of metals involves the propagation of low-frequency elastic waves. Metals that are isotropic and homogeneous in the macroscopic length scale contain elastic heterogeneities, such as grain boundaries within the microstructures. Ultrasonic waves propagating through such microstructures get scattered from the grain boundaries. As a result, the propagating ultrasound attenuates. The mass density and the elastic anisotropy in each constituent grain govern the degree of heterogeneity in the polycrystalline aggregates. Existing elastodynamic models consider first-order scattering effects from grain boundaries. This paper presents the improved attenuation formulae, for the first time, by including the next order of grain scattering effects. Results from investigating 759 polycrystals reveal a positive correlation between the effects of higher-order scattering from grain boundaries and the degree of heterogeneity. Thus, higher-order grain scattering effects are now known. These results motivate further investigation into higher frequencies and strongly scattering alloys in the future.

Facile fabrication of SnO2/MnTe nanocomposite as an efficient electrocatalyst for OER in basic media

There is a strong demand for developing an extremely effective and robust electrocatalyst to facilitate oxygen evolution reaction in water electrolysis applications. Herein, we successfully produced SnO2/MnTe using an efficient ultrasonication technique that is cost-effective and readily accessible along with improved catalytic behavior. The physical properties of fabricated catalysts are examined to analyze textural, structural and morphological characteristics. The SnO2/MnTe nanocomposite exhibited the low overpotential (181 mV) at 10 mA cm−2 and smaller Tafel slope of 33 mV dec−1 in alkaline (1.0 M KOH) medium. Moreover, the material also showed prolonged and excellent stability over 50 h following 5000 stability cycles. Electrochemical impedance spectroscopy studies demonstrated that charge transfer kinetics at the catalyst-electrolyte interface could be achievable, with lower Rct values (0.8Ω) directing it to increase electrochemical behavior. The acquired outcomes obtained from electrochemical activity demonstrate the potential of SnO2/MnTe as a highly promising electrocatalyst for future electrochemical energy generation.

Three-dimensional Cobalt-MOF/ CNF microstructured assembly as a bifunctional electrocatalyst for effective overall water-splitting in alkaline media

The electrocatalyst Co-MOF/CNF microstructure exhibits excellent stability and charge transfer efficiency synthesized via ultrasonication technique. The composite has a lower Rct value of 2 Ω. The larger Cdl value of Co-MOF/CNF (12.3 mF/dec) is responsible for the high catalytic activity for both HER and OER reactions. The composite has strong catalytic activity in HER and OER, with low overpotentials of 193 mV and 250 mV at 10 mA/cm2. Furthermore, excellent water electrolyzer activity was achieved by Co-MOF/CNF||Co-MOF/CNF with a cell voltage of 1.49 V at 10 mA/cm2 and is stable over 24 h, proving the long-term efficacy in sustainable energy systems.

Effects of Access Cavity Design and Placement Techniques on Mineral Trioxide Aggregate Obturation Quality in Simulated Immature Teeth: A Micro-Computed Tomography Study.

Background and Objectives: In teeth with open apices, performing single session apexification is a challenging treatment due to the difficulty in handling mineral trioxide aggregate (MTA). Minimally invasive approaches in dentistry have also influenced the cavity designs in endodontics. Until now, different techniques have not been investigated in addition to manual condensation during the process of placing MTA in traditional (TradACs) or conservative (ConsACs) endodontic access cavities. The aim of this in vitro study was to compare and evaluate the obturation quality of MTA apical plugs placed with different techniques in TradACs or ConsACs. Materials and Methods: Sixty upper central teeth were divided into two main groups based on cavity design, and then each main group was further divided into three subgroups according to MTA placement techniques (n = 10): TradAC-manual, TradAC-manual + indirect ultrasonic activation, TradAC-manual + XP-endo Shaper (XPS), ConsAC-manual, ConsAC-manual + indirect ultrasonic activation, and ConsAC-manual + XPS. Subsequently, the porosity percentages in the MTA apical plug were analyzed using micro-computed tomography. The statistical analysis was performed using the Kruskal-Wallis H test and Mann-Whitney U test. Statistical significance was set at p < 0.05. Results: There were differences in volume of porosity percentages (%) according to cavity designs and MTA application techniques (p < 0.05). Except for the XPS group, more porosity was observed in ConsACs compared to TradACs. In TradACs, the significantly lowest open and total porosity was observed in the manual, ultrasonic, and XPS techniques, respectively. In ConsACs, the significantly lowest porosity was observed in the manual, XPS, and ultrasonic techniques, respectively (p < 0.05). Conclusions: In MTA obturation, cavity designs and application techniques had an impact on the MTA porosity. Creating an apical plug in ConsACs may result in more porosity compared to TradACs, especially when manual or indirect ultrasonic activation is preferred. Opting for the manual technique alone may be considered sufficient for controlling porosity for both TradACs and ConsACs.

Influence of ultrasonic excitation on the melt pool and microstructure characteristics of Ti-6Al-4V at powder bed fusion additive manufacturing solidification velocities

Cavitation and acoustic streaming created by in situ high-intensity ultrasound have been exploited for microstructural refinement during directed energy deposition (DED) additive manufacturing (AM) of alloy Ti‐6Al‐4V. Whether the same ultrasound-driven mechanisms are applicable to powder bed fusion (PBF) of Ti‐6Al‐4V remains uncertain. The primary factors that control the microstructure during deposition processing are the solidification velocity and temperature gradient, which are orders of magnitude higher for PBF than DED processes. This work examines the role of high-intensity ultrasound on the melt pool and resulting microstructure of Ti‐6Al‐4V under PBF solidification conditions. The effect of the laser scanning velocity and ultrasonic excitation on the melt pool and grain structure characteristics is interrogated through controlled line scans and area scans without powder. Temperature field simulations are used to estimate the solidification velocities and temperature gradients and to compare the processing conditions with previously characterized columnar-to-equiaxed transition diagrams. The acoustic pressures during processing are estimated using a coupled field acoustic-elastic finite element simulation and used in a Keller-Miksis model to assess the likelihood of cavitation vs. cavity size. The microstructure of the samples with or without ultrasonic excitation was characterized, allowing the equivalent grain diameters and aspect ratios to be compared. All samples, including those exposed to scanning velocities where cavitation did not occur, showed a reduction in grain aspect ratio when subjected to ultrasonic excitation, but the effect on equivalent grain diameter was inconclusive. A key finding is that the primary effects of ultrasonic excitation may be attributed to acoustic streaming, rather than cavitation, during PBF processing. Further development of the ultrasonic excitation technique explored may permit tailoring of the microstructure and texture characteristics in bulk AM parts.

Efficacy of Lasers in Debonding Ceramic Brackets: Exploring the Rationale and Methods.

The development ofceramic brackets in orthodonticsthree decades agoemerged as a response to the increasingpatientdemand for less visible orthodontic appliances.While these brackets provide superior aesthetics, they are characterized by lower fracture toughness and higher bond strength in contrast to metal brackets. These properties present challenges during the debonding step, including the risk of enamel micro-fractures and cracks. Historically, various strategies have been developed to address challenges associated with debonding, reduce patient discomfort, and ensurethat the bondfailure site is confined to the bracket-adhesive interface. This included the use of specially designed debonding pliers, electrothermal debonding, ultrasonic technique, and chemical agents. Recently, there has been a shift towards utilizing different types of laser irradiation for this purpose. The burgeoning strategy, however, requires diligent scientific scrutiny to establish a standardized protocol with particular laser parameters and ultimately achieve the goal of enhancing the patient experience by reducing discomfort. This article offers a narrative review of laser-aided debonding of ceramic brackets, aimed at comparing different laser types, presenting their benefits and downsides, validating the efficiency of each method, and summarizing the published literature on this subject.It also provides insights for orthodontists on reducing patient discomfort that usually accompanies debonding ceramic brackets by delving into the science behindthe use oflasersfor this purpose.

Monitoring damage growth and topographical changes in plate structures using sideband peak count-index and topological acoustic sensing techniques

Some topographies in plate structures can hide cracks and make it difficult to monitor damage growth. This is because topographical features convert homogeneous structures to heterogeneous one and complicate the wave propagation through such structures. At certain points destructive interference between incident, reflected and transmitted elastic waves can make those points insensitive to the damage growth when adopting acoustics based structural health monitoring (SHM) techniques. A newly developed nonlinear ultrasonic (NLU) technique called sideband peak count – index (or SPC-I) has shown its effectiveness and superiority compared to other techniques for nondestructive testing (NDT) and SHM applications and is adopted in this work for monitoring damage growth in plate structures with topographical features. The performance of SPC-I technique in heterogeneous specimens having different topographies is investigated using nonlocal peridynamics based peri-ultrasound modeling. Three types of topographies – “X” topography, “Y” topography and “XY” topography are investigated. It is observed that “X” and “XY” topographies can help to hide the crack growth, thus making cracks undetectable when the SPC-I based monitoring technique is adopted. In addition to the SPC-I technique, we also investigate the effectiveness of an emerging sensing technique based on topological acoustic sensing. This method monitors the changes in the geometric phase; a measure of the changes in the acoustic wave’s spatial behavior. The computed results show that changes in the geometric phase can be exploited to monitor the damage growth in plate structures for all three topographies considered here. The significant changes in geometric phase can be related to the crack growth even when these cracks remain hidden for some topographies during the SPC-I based single point inspection. Sensitivities of both the SPC-I and the topological acoustic sensing techniques are also investigated for sensing the topographical changes in the plate structures.

High-pressure elasticity of novel (VNbTaTi)C high-entropy carbides

Acoustic velocities and elasticity of high P-T synthesized new (VNbTaTi)C high-entropy carbides (HECs) are reported at high pressure using large volume press (LVP)-based ultrasonic interferometry technique. Using the finite-strain equation approach, the bulk modulus and shear rigidity, and their pressure dependences, are derived from the current experimental data, yielding B0 = 261.6(2) GPa, G0 = 191.4(3) GPa, ∂B/∂P = 4.34(18), and ∂G/∂P = 1.83(6). Interestingly, the (VNbTaTi)C HECs is more incompressible than the superhard γ-B (∼213.9 GPa), and almost as incompressible as superhard PcBN (∼254 GPa). Meanwhile, its shear rigidity (∼191.4 GPa) is comparable to the superhard B6O-B4C composite (G = 202 GPa), and as stiff as the (TiZrNbTa)C (193 ∼ 195 GPa) HECs. More strikingly, the fracture toughness is enhanced up to ∼4.6(3) MPa·m1/2, and the Vickers hardness of (VNbTaTi)C HECs is ∼22.6(2) GPa, which are significantly stronger than other high-entropy carbides. These new findings and results may be very important for its applications in extreme environments.

Optimised design of aviation stainless steel sheet SH guided wave focusing PPM EMAT

ABSTRACT Electromagnetic Acoustic Transducer (EMAT) is an ultrasonic testing technique that generates sound in the part inspected instead of the transducer. Electromagnetic ultrasonic guided wave detection technology has problems such as low energy conversion efficiency and the great influence of environmental noise, resulting in low echo signal amplitude. When the two rows of permanent magnets are arranged non-parallel, the sound beam will be focused at the intersection point of the axes of the two rows of permanent magnets. This article uses this rule to optimise the design parameters of PPM EMAT. Distance amplitude curve (DAC) is a method of compensating. However, large-scale detection requires a flat DAC curve. In addition, the increase in the angle and length of the permanent magnets and the number of pairs of permanent magnets will improve the intensity of the defect wave indication intensity. However, the increase in the angle of the permanent magnets will increase the signal attenuation. After simulation and experiments, when the angle, length and number of permanent magnet pairs are 4°, 25 mm and 8 pairs, the corresponding EMAT has the optimal axis radiation sound field and a smoother DAC, which is more suitable for stainless steel sheets, long-distance rapid guided wave detection.