Ultrasonic Beam Research Articles

Enhancing Time-of-Flight Diffraction (TOFD) Inspection through an Innovative Curved-Sole Probe Design

Time-of-Flight Diffraction (TOFD) is a method of ultrasonic testing (UT) that is widely established as a non-destructive technique (NDT) mainly used for the inspection of welds. In contrast to other established UT techniques, TOFD is capable of identifying discontinuities regardless of their orientation. This paper proposes a redesign of the typical TOFD transducers, featuring an innovative curved sole aimed at enhancing their defect detection capabilities. This design is particularly beneficial for thick-walled samples, as it allows for deeper inspections without compromising the resolution near the surface area. During this research, an evaluation consisting in simulations of the ultrasonic beam distribution and experimental tests on a component with artificially manufactured defects at varying depths has been performed to validate the new design. The results demonstrate a 30 to 50% higher beam distribution area as well as an improvement in the signal-to-noise ratio (SNR) resulting in a 24% enhancement in the capability of defect detection compared to the traditional approach.

Impact of treatment trajectory on the thermal ablation rate and biological tissue volumetric lesion during irradiation by shock-wave focusing ultrasonic beam

Thermal ablation rates and the shapes of volumetric biological tissue lesion are compared in a numerical experiment, in which biological tissue is exposed to pulsed periodic shock-wave high intensity focused ultrasound. The comparison is performed across three different irradiation sequences of discrete foci placed uniformly within the target area.

Acoustically controlled bubble nucleation

Fundamental studies of single bubble heat transfer are crucial to improve our understanding of boiling phenomena and develop modeling and simulation tools for the design and optimization of boiling systems. However, conducting these kinds of experiments over a wide range of conditions is challenging and may involve expensive and complicated experimental techniques (e.g., lasers) to isolate and control bubble nucleation. In this work, we introduce a new technique to control nucleation with an ultrasonic beam. A low-cost and widely available piezoelectric disc driven at megahertz frequencies directed at a heated surface can increase the time-averaged pressure and suppress evaporation until the moment the transducer is turned off, allowing us to control the incipience of boiling to within 150 µs. We demonstrate this technique by measuring the physical and thermal footprint of natural and acoustically controlled bubbles with high-resolution infrared thermometry and phase detection diagnostics. We were able to raise the bubble nucleation temperature by over 30 K compared to a reference case with no acoustic control, which significantly changes bubble growth rate, microlayer formation and evaporation and departure diameter. We highlight the potential of this new low-cost and easy-to-use technique in a variety of different boiling heat transfer studies.

Assessment of Weld Microstructure Through Sound Velocity Measurements for Power Plant Applications

This research study employed an immersion-based micro-resolution ultrasonic velocity measurement technique (MUVT) to evaluate Grade 91 (9Cr-1Mo-V) steel welds. This process utilized a 20 MHz focused ultrasonic beam with a spot size of 250 µm, a 6 µm laser vibrometer spot size for detection, and an automated 3-axis raster scanner to accurately collect ultrasonic velocity data from two Grade 91 steel welds fabricated using cold metal transfer (CMT) and flux-cored arc welding (FCAW) processes. By analyzing the MUVT data, the Poisson’s ratio (υ) and modulus of elasticity (E), which are important mechanical properties for weldments, were calculated. The correlation between mechanical properties and ultrasonic velocity was examined. The results indicated that longitudinal ultrasonic velocity could effectively identify base metal, heat-affected zone (HAZ), and weld metal areas, showing a strong correlation with hardness. In particular, the distinctive V-shaped dip in velocity and hardness data across the HAZ areas of both samples highlighted changes in the microstructure of creep strength–enhanced ferritic steel welds. Importantly, the immersion-based MUVT demonstrated high accuracy in small sections of the weld, surpassing the conventional contact ultrasonic testing method in spatial resolution detection.

Analysis of the Suitability of Ultrasonic Testing for Verification of Nonuniform Welded Joints of Austenitic-Ferritic Sheets.

The purpose of the presented research was to determine the suitability of using ultrasonic testing (UT) to inspect heterogeneous, from a material point of view, welded joints on the example of the joints of a ferritic steel element with elements made of an austenitic steel. The echo technique with transverse (SEK) and longitudinal wave heads (SEL) addressed this issue. Due to the widespread use of 13CrMo4-5 and X2CrNiMo17-12-2 steel grades in the energy industry, they were selected as the test materials for the study. The objects of the presented research were welded joint specimens with thicknesses of 8, 12, and 16 mm and dimensions of 300 × 300 mm, made using the 135 metal active gas (MAG) process with the use of the Lincoln 309LSi wire-a ferritic-austenitic filler material. The stages of the research task were (1) making distance-amplitude curve (DAC) patterns from the test materials; (2) preparation of specimens of welded joints with artificial discontinuities in the form of through-holes; (3) performing UT tests on welded joints with artificial discontinuities using heads with 60° and 70° angles for the transverse wave and angle heads for longitudinal waves with similar beam insertion angles; (4) selection, by radiographic testing (RT), of welded joint specimens with natural discontinuities in the form of a lack of sidewall fusion; (5) performing UT tests on welded joints with natural discontinuities, using heads as welded joints with artificial discontinuities. It was found that (1) the highest sensitivity of discontinuity detection was obtained by performing tests on the ferritic steel side, which is due to the lower attenuation of the ultrasonic wave propagating in ferritic steel compared to austenitic steel; (2) the best detection of discontinuities could be obtained using a longitudinal ultrasonic wave; (3) there is a relationship between the thickness of the welded elements, the angle of the ultrasonic beam introduction, and the effectiveness of discontinuity detection.

A methodology for evaluating damage in thin-walled cylindrical shells using bounded ultrasonic beam scattering

This paper introduces an ultrasonic detection methodology specifically designed to assess damage in thin-walled cylindrical shells, which crucially relies on the interaction between a bounded ultrasonic beam and a thin-walled cylindrical shell immersed in fluid, considering both water-filled and air-filled cavities. Initially, we derive the scattered sound field expression for a bounded ultrasonic beam obliquely striking the shell. Subsequently, through finite element simulations and experimental verification, we observe that when the incident bounded beam is emitted at the critical angles defined in this study, early damage significantly enhances the received sound pressure amplitude detected by a symmetrically positioned receiver. Notably, a mere 5 % decrease in the shell's elastic modulus leads to a notable 233.69 % increase in the area under the amplitude-frequency curve of the received sound pressure for water-filled cavities and a remarkable 642.85 % surge in area for air-filled cavities. Experimental data further validates the sensitivity of this method towards varying corrosion damage states. This approach combines the reliability of linear ultrasonic methods with the enhanced sensitivity of nonlinear ultrasonic techniques, offering a significant advancement over traditional ultrasonic detection methods for inspecting cylindrical shells. The proposed assessment method holds immense potential in providing novel insights for inspecting cylindrical shells in practical applications.

Mitigating RGB-D camera errors for robust ultrasonic inspections using a force-torque sensor

ABSTRACT Robot-based phased array ultrasonic testing is widely used for precise defect detection, particularly in complex geometries and various materials. Compact robots with miniature arms can inspect constrained areas, but payload limitations restrict sensor choice. RGB-D cameras, due to their small size and light weight, capture RGB colour and depth data, creating colourised 3D point clouds for scene representation. These point clouds help estimate surface normals to align the ultrasound transducer on complex surfaces. However, sole reliance on RGB-D cameras can lead to inaccuracies, affecting ultrasonic beam direction and test results. This paper investigates the impact of transducer pose and RGB-D camera limitations on ultrasonic inspections and proposes a novel method using force-torque sensors to mitigate errors from inaccurately estimated normals from the camera. The force-torque sensor, integrated into the robot end effector, provides tactile feedback to the controller, enabling joint angle adjustments to correct errors in the estimated normal. Experimental results show the successful application of ultrasound transducers using this method, even with significant misalignment. Adjustments took approximately 4 seconds to correct deviations from 12.55°, with an additional 4 seconds to ensure the probe was parallel to the surface, enhancing ultrasonic inspection accuracy in complex, constrained environments.

Nonlinear sound-sheet microscopy: imaging opaque organs at the capillary and cellular scale.

Light-sheet fluorescence microscopy has revolutionized biology by visualizing dynamic cellular processes in three dimensions. However, light scattering in thick tissue and photobleaching of fluorescent reporters limit this method to studying thin or translucent specimens. Here we show that non-diffractive ultrasonic beams used in conjunction with a cross-amplitude modulation sequence and nonlinear acoustic reporters enable fast and volumetric imaging of targeted biological functions. We report volumetric imaging of tumor gene expression at the cm 3 scale using genetically encoded gas vesicles, and localization microscopy of currently uncharted cerebral capillary networks using intravascular microbubble contrast agents. Nonlinear sound-sheet microscopy provides a ∼64x acceleration in imaging speed, ∼35x increase in imaged volume and ∼4x increase in classical imaging resolution compared to the state-of-the-art in biomolecular ultrasound.

THE USE OF PHASED ARRAYS AND THE DIFFRACTION-TIME METHOD FOR QUALITY CONTROL OF ANTICORROSIVE SURFACING INSIDE CYLINDRICAL HOLES (CHANNELS) WITH DIAMETERS FROM 42 TO 440 MM IN FORGINGS

Ultrasonic Testing (UT) of anticorrosive surfacing for the quality of fusion with the base metal and the presence of subsurface cracks is mandatory for use in nuclear, petrochemical and other industries. However, the control of subsurface cracks in holes with a diameter of 42 mm or more is not provided for in the regulatory documentation. The experience of using the UT of anticorrosive surfacing inside cylindrical holes with a diameter from 42 to 440 mm in the forgings of valve blocks of underwater gas production systems is presented below. At the same time, phased arrays were used to control the quality of fusion of anticorrosive surfacing with the base metal, and the diffraction-time method (TOFD) of control by specially developed non-standard asymmetrical ultrasonic beams sensors was used to control the subsurface cracks.

Feasibility Study for a High-Frequency Flexible Ultrasonic Cuff for High-Precision Vagus Nerve Ultrasound Neuromodulation.

In the emerging research field of bioelectronic medicine, it has been indicated that neuromodulation of the vagus nerve (VN) has the potential to treat various conditions such as epilepsy, depression, and autoimmune diseases. In order to reduce side effects, as well as to increase the effectiveness of the delivered therapy, sub-fascicle stimulation specificity is required. In the electrical domain, increasing spatial selectivity can only be achieved using invasive and potentially damaging approaches like compressive forces or nerve penetration. To avoid these invasive methods while obtaining a high spatial selectivity, a 2-mm diameter extraneural cuff-shaped proof-of-concept design with integrated lead zirconate titanate (PZT) based ultrasound (US) transducers is proposed in this article. For the development of the proposed concept, wafer-level microfabrication techniques are employed. Moreover, acoustic measurements are performed on the device, in order to characterize the ultrasonic beam profiles of the integrated PZT-based US transducers. A focal spot size of around [Formula: see text] is measured for the proposed cuff. Moreover, the curvature of the device leads to constructive interference of the US waves originating from multiple PZT-based US transducers, which in turn leads to an increase of 45% in focal pressure compared to the focal pressure of a single PZT-based US transducer. Integrating PZT-based US transducers in an extraneural cuff-shaped design has the potential to achieve high-precision US neuromodulation of the VN without requiring intraneural implantation.

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.

Ultrasonic wave propagation analyses in centrifugally cast stainless steel using solidification grain structure models

Several components of nuclear power plants are made from cast austenitic stainless steel (CASS) because of its high corrosion resistance and strength. CASS that is centrifugally fabricated in a rotating mold is used in primary coolant piping. In-service inspection based on ultrasonic testing (UT) has to be conducted for primary coolant piping in accordance with fitness-for-service codes. However, a high-accuracy evaluation of flaws in CASS components through UT is difficult because the ultrasonic waves are scattered and attenuated by the coarse grains, and the ultrasonic beam is distorted by the anisotropy resulting from the grain orientations. Some works have attempted to improve UT capability for CASS components. For more improvement, it is essential to understand how ultrasonic waves propagate in the solidification structure of CASS. Numerical simulations are a useful and reasonable way for this purpose. The simulation model should account for a three-dimensional grain structure. In this study, we prepared three different models of solidification structures for centrifugally CASS, and we fed these structures into an explicit finite element model to simulate the propagation of ultrasonic waves. Afterward, we compared the simulated wave propagations with those measured by a laser Doppler vibrometer to determine an appropriate model that showed good agreement between the simulated and experimental results.

Finite series approach for the calculation of beam shape coefficients in ultrasonic and other acoustic scattering

Partial wave expansions with spherical wave functions are usually employed to describe complex velocity potentials or pressure fields in ultrasonic and acoustic scattering by spherical particles. The expansion coefficients – known as the beam shape coefficients (BSCs) – can be calculated using different approaches which have been largely unexplored in the acoustical literature. Here, we formally present the Finite Series method for the evaluation of BSCs of ultrasonic and acoustic arbitrary-shaped beams. Such a series, which relies on Neumann expansion theorem, is an alternative to quadratures whenever analytical solutions cannot be obtained from direct integration over polar and azimuthal spherical angles. As examples of application, we consider the calculation of BSCs of Bessel, Laguerre–Gauss and Gaussian beams under on-axis configuration, including a discussion on a modified version of the finite series method recently presented in the context of optical fields.

Deep margin assessment by intraoperative ultrasound in tongue cancer- dust trial

Introduction: Oral cancer ranks sixth among all cancers globally and India has the most significant number of cases, one-third of the total burden of oral cancer cases globally. The aim of the study was to conduct deep margin assessment using intraoperative ultrasound in superficial oral tongue carcinomas, ensuring adequate surgical resection for early-stage oral tongue cancer minimizing loco regional recurrence risks. Methodology: This is a prospective observational study involving 91 diagnosed tongue malignancies. The study included biopsy verified tongue cancer. During the surgical procedure and effect of general anaesthesia the tongue lesions of the patient were evaluated with intraoral sonography. An intraoral transducer probe characterized by an 8 to 10 MHz ultrasonic beam Siemens Acuson NX3 was used to assess the deep margin, tumor thickness, margins, and other findings like lingual nodes are noted. Results: A total of 91 patients that underwent resection using intraoperative USG were included in the study. The majority of the patients were in the age group 41 - 60 years. As carcinoma tongue is more common in males our study has a sex distribution of 63 male and 28 females. The mean deep margin assessed by USG - is 0.901cm and the mean deep margin assessed by the frozen section is 0.762 cm. The mean deep margin assessed by final histology is 0.748 cm. Conclusion: USG guided resection of early tongue cancers is a technique that is able to increase the frequency of free margins and decrease the close margin and positive margin frequency when compared to conventional treatment. USG being noninvasive is a very fast method in comparison to the frozen section and seems to be a promising technique. Larger studies are needed with control groups to possibly confirm a statistically significant difference in adequate deep resection margin and improvement in DSS and quality of life in future. Keywords: deep margin; tongue; carcinoma

Investigation of HIFU beam propagation through acoustic holograms in water

We investigated variations in the HIFU beam of a clinical system as it traverses acoustic holograms—small artificial objects of different types—within a tank that was filled in with the degassed deionized water. The pressure distribution within the HIFU beam was assessed in multiple planes perpendicular to the beam axis. The ultrasound transducer with the focal length of 14 cm inside the Sonalleve table top (Profound Medical, Mississauga, ON, Canada) generated the focusing ultrasonic beam, which propagated through the water. Each hologram was positioned 3 cm below the focal plane, with precise adjustments of positions and angles for each measurement. Pressure measurements were conducted using the needle hydrophone HNA-0400 (ONDA Corp, Sunnyvale, CA, USA) mounted on a 3D positioning system. The motors of the positioning system were controlled, and pressure values were recorded using a GUI generated in LabVIEW. The displacement step created by the motors on each axis was 0.01 mm. The properties of the holograms were reconstructed, considering the experimental data obtained. Our findings demonstrated that the shape, size, elasticity, and placement of each acoustic hologram significantly influenced the observed field pattern. This work was supported by the German Federal Ministry of Education and Research (“MR-HIFU-Pancreas”, FKZ:13GW0364D).

Ultrasonic braided ring beams generated by phase modulation metasurfaces

Coaxial coupling between two quasi-perfect ultrasonic vortices (QPUVs) with distinct ring radii and topological charges (TCs) has been suggested and implemented to create ultrasonic braided ring beams (UBRBs). It is possible to switch between a double-ring pattern, a braided ring pattern, and a petal-like pattern in the linked ultrasonic field distribution by varying the coupling strength of two QPUVs. We focus on the braided ring pattern and investigate the influence of TCs on the acoustic intensity and phase distributions. It is found that the UBRB contains multiple individual phase singularities, and the number of singularities is determined by the TCs of the two QPUVs. Furthermore, a phase modulation metasurface (PMM) composed of photosensitive resin cubes is well designed to produce the UBRB in water. The effectiveness of the single-layer PMM in producing the UBRB is confirmed by both simulations and experimental results. The proposed UBRBs based on metasurfaces could potentially have uses in multi-particle manipulation and acoustic communication.

A localized approximation approach for the calculation of beam shape coefficients of acoustic and ultrasonic Bessel beams

The description of acoustical waves can be achieved using an expansion over basic functions with weighting coefficients which may be called beam shape coefficients (BSCs). There is a strong analogy between the scalar formalism of acoustical waves and the vectorial electromagnetic formalism, known as generalized Lorenz–Mie theory (GLMT), describing the interaction between a homogeneous sphere and an arbitrary illuminating beam. In particular, BSCs have been introduced as well in GLMT and the mathematical arsenal to evaluate them, developed since several decades, can be used mutatis mutandis to evaluate BSCs in acoustics. In particular, the present paper introduces a method named localized approximation to the evaluation of the acoustical BSCs, similar to the localized approximation used to evaluate electromagnetic BSCs, in the case of Bessel beams. Such a formalism akin to the electromagnetic GLMT may be viewed as an acoustical GLMT and should allow a renewal of the calculation of various properties of acoustical wave scattering, in particular to the design of acoustical tweezers similar to optical tweezers.

Utilizing non-specular reflection of bounded ultrasonic beams for assessing damage in solid plates

This paper investigates the potential of utilizing non-specular reflection of a bounded ultrasonic beam in a liquid-solid-liquid structure as a method for assessing damage in solid plates. The study focuses on understanding the acoustic field formulation resulting from this type of reflection, as well as examining the impact of incident angles and material damage (indicated by reduced Young's modulus) on the non-specular reflection field. To quantify the effects of non-specular reflections, the specular reflection coefficient (SRC) proposed by the authors is employed (Wang and Deng, 2023) [1]. A finite-element (FE) model is developed to analyze the SRC response concerning the incident angle and material damage. Through FE simulations involving obliquely incident bounded ultrasonic beams at different angles, the research reveals a significant, monotonically increasing sensitivity of the SRC change rate at the S0 critical angle to the level of material damage. This finding offers a precise approach for accurately evaluating material damage in plates. Experimental tests are conducted on a water-aluminum sheet-water structure, which validates the theoretical predictions and FE simulation results. The experimental results consistently demonstrate an increased change rate of the SRC at the S0 critical angle in response to the fatigue cycle, confirming the effectiveness of using non-specular reflection of a bounded ultrasonic beam at the S0 critical angle as a method for evaluating material damage in plates.

Continuously monitoring of muscle fatigue based on a wearable micromachined ultrasonic transducer probe

Ultrasound based methods can assess muscle fatigue by penetrating deep muscles and are not susceptible to electrical noise, but traditional ultrasound probes have bulky size that hinders integration and wearability, making them impractical to continuously monitor muscle status. This paper proposed a wearable probe based on piezoelectric micromachined ultrasonic transducers (PMUTs), where a polymer acoustic lens was incorporated to focus ultrasonic beam and enhance the emitted acoustic pressure (increased by >20%). The fatigue dynamics of upper arm muscles during sustained exertion was investigated by continuously monitoring thickness changes with the PMUTs-based probe, revealing a temporal pattern characterized by swift and subsequent gradual thickening. Several muscle fatigue metrics were derived by piecewise linear fitting, including the initial and secondary deformation rate and the transition time, offering insight into muscle status and fatigue resistance. Additionally, an outlier elimination method for thickness profiles was utilized, mitigating the influence of uncontrollable motion on findings. Leveraging PMUTs technology and acoustic lens integration, this proposed wearable approach holds promise for real-time assessment of muscle fatigue.

Precision Measurement of the Group Velocity of Ultrasound in Samples with Millimeter Thickness

A methodology is proposed for high-precision local measurement of the group velocity of longitudinal waves in solid samples with millimeter thickness. Achievement of the required accuracy involves laser thermo-optical excitation of submicrosecond ultrasonic video pulses and ultrawideband piezoelectric recording of acoustic signals reflected from the test sample. Plane-parallel samples made of duralumin, quartz, and steel with a thickness of 2–6 mm are studied. To achieve the required accuracy in measuring the group velocityof ultrasound, the signal shape is mathematically processed with compensation for diffraction of the ultrasonic beam as it propagates through the sample. The possibility of ensuring the uncertainty in measuring the group velocity of ultrasound in the 1–15 MHz frequency range at a level of 0.1% in samples with millimeterthickness is demonstrated.