Ultrasonic Beam Research Articles

Longitudinal MR imaging after unilateral MR-guided focused ultrasound thalamotomy: clinical and radiological correlation.

Magnetic-resonance-guided focused ultrasound (MRgFUS) thalamotomy uses multiple converging high-energy ultrasonic beams to produce thermal lesions in the thalamus. Early postoperative MR imaging demonstrates the location and extent of the lesion, but there is no consensus on the utility or frequency of postoperative imaging. We aimed to evaluate the evolution of MRgFUS lesions and describe the incidence, predictors, and clinical effects of lesion persistence in a large patient cohort. A total of 215 unilateral MRgFUS thalamotomy procedures for essential tremor (ET) by a single surgeon were retrospectively analyzed. All patients had MR imaging 1 day postoperatively; 106 had imaging at 3 months and 32 had imaging at 1 year. Thin cut (2 mm) axial and coronal T2-weighted MRIs at these timepoints were analyzed visually on a binary scale for lesion presence and when visible, lesion volumes were measured. SWI and DWI sequences were also analyzed when available. Clinical outcomes including tremor scores and side effects were recorded at these same time points. We analyzed if patient characteristics (age, skull density ratio), preoperative tremor score, and sonication parameters influenced lesion evolution and if imaging characteristics correlated with clinical outcomes. Visible lesions were present in all patients 1 day post- MRgFUS and measured 307.4 ± 128.7 mm3. At 3 months, residual lesions (excluding patients where lesions were not visible) were 83.6% smaller and detectable in only 54.7% of patients (n = 58). At 1 year, residual lesions were detected in 50.0% of patients (n = 16) and were 90.7% smaller than 24 h and 46.5% smaller than 3 months. Lesions were more frequently visible on SWI (100%, n = 17), DWI (n = 38, 97.4%) and ADC (n = 36, 92.3%). At 3 months, fewer treatment sonications, higher maximum power, and greater distance between individual sonications led to larger lesion volumes. Volume at 24 h did not predict if a lesion was visible later. Lesion visibility at 3 months predicted sensory side effects but was not correlated with tremor outcomes. Overall, lesions are visible on T2-weighted MRI in about half of patients at both 3 months and 1 year post-MRgFUS thalamotomy. Certain sonication parameters significantly predicted persistent volume, but residual lesions did not correlate with tremor outcomes.

Weld map tomography for determining local grain orientations from ultrasound

The complex structure of inhomogeneous welds poses a long-standing challenge in ultrasonic non-destructive testing. Elongated grains with spatially varying dominant orientations can distort and split the ultrasonic beam, hindering inspection data interpretation. One way to tackle this problem is to include material information in imaging and signal analysis; however, such information is often only gathered using destructive methods. This paper reports the development of a physics-based weld inversion strategy determining grain orientations using a ray tomography principle. The considered approach does not rely on a macroscopic weld description but may incorporate it to facilitate inversion. Hence, it is more general than other available approaches. The methodology is demonstrated in both numerical and experimental examples. The experimental work focuses on mock-up samples from the nuclear industry and a sample manufactured during this research. The ‘ground truth’ for the latter comes from an EBSD evaluation—the most accurate (yet destructive) examination technique available. Across the considered specimens, our methodology yielded orientation maps with average errors well below 20 ∘ , leading to time-of-flight errors below 0.05 μ s . Applying the result from inversion to ultrasonic imaging offered between 5 and 14 dB signal-to-noise ratio improvement for defect signatures.

Quantitative Measurement and Evaluation of High-Resolution Ultrasonic Sound Fields using a Novel Automated Ultrasonic Immersion Scanner

Ultrasonic probes are an integral part of the automated ultrasonic non-destructive inspection machines to detect and size the defects in a wide range of materials in production lines. A complete quantitative assessment of the performance characteristics of an application-specific ultrasonic probe is needed to be evaluated on the basis of the European Standard DIN EN ISO 22232-2. This requirement not only improves the quality assurance of the manufactured probes but also provides the useful technical data to the end-user to optimize the ultrasonic testing on-site. In addition, the evaluation of probe characteristics should be carried periodically throughout their service life. The main aim of this work is to develop and validate a novel ultrasonic immersion scanner for the quantitative measurement and evaluation of ultrasonic sound beam characteristics of an application-specific UT Probe. A novel ultrasonic immersion scanner integrated with high-precision motion control unit (Hexapod) with six axes is developed to measure the full ultrasonic probe characteristics, which include the squint angle measurement in three different planes (XY, XZ, and YZ), RF-signal and its frequency spectrum at watersteel interface and sound beam parameters including the angle of beam divergence in different directions. The automated scanning, data acquisition, evaluation, visualization and test report generation are performed based on DIN EN ISO 22232-2. The measured sound beam characteristics of both focused and non-focused applicationspecific ultrasonic probes with center frequencies ranging from 0.2 - 15 MHz using the pulse-echo technique on a 3 mm half-ball steel reflector are presented. The quantitative analysis of the measured sound field parameters and the acceptance criteria in accordance with DIN EN ISO 22232-2 are discussed. By using the newly developed automated immersion scanner, we achieved a few micrometer (~15 µm) spatial resolution in the measured sound field patterns and a good angular resolution (~0.05°) in the squint angle measurement of a wide range of UT probes.

Comparison of grain structure models for wave propagation analysis in centrifugally cast stainless steel

Centrifugally cast stainless steel (CASS) is widely used in primary coolant piping of pressurized water reactor plants because of its high corrosion resistance and high strength. An in-service inspection based on ultrasonic testing (UT) has to be conducted for weld joints of primary coolant piping on the basis of JSME Rules on Fitness-forService for Nuclear Power Plants. However, it is difficult to detect and size flaws in CASS components with high accuracy because of the following reasons: Ultrasonic waves are scattered and attenuated due to coarse grains, and anisotropic and heterogeneous properties in CASS lead to ultrasonic beam skewing. Numerical simulations are useful and reasonable ways for better understanding the ultrasonic wave propagation behavior in CASS. To effectively achieve this, the simulation model should include a three-dimensional (3D) grain structure. In this study, we modeled three kinds of the solidification grain structures of centrifugally CASS. One is obtained by using a cellular automaton method, another consists of many hexagonal columns with the same dimensions, and the other is transversely isotropic material. Then these structures were fed into an explicit finite element model for simulating wave propagation and the simulated results were compared with those measured by a laser Doppler vibrometer. Through the comparison, we investigated the applicability of these three kinds of solidification grain structure models to simulation for wave propagation.

Comparative study of advanced image reconstruction algorithms for complex arbitrary components

Accurate ultrasonic imaging and inspection of specimens with non-planar complex surfaces are often challenging from both transducer coupling and imaging perspectives. Several inspection strategies have been developed to inspect such complex interfaced components such as flat arrays with flexible wedges or water-filled chambers with a flexible membrane. In these methods, firstly surface profiles are estimated and then Fermat’s principle or other algorithms are applied to calculate delay laws. The main drawback of these methods is the longer computation time and therefore real time inspection is limited, also a coupling problem due to the complex geometries. Alternative approaches have been developed to compute the ultrasonic beam paths such as the Fast-Marching Method (FMM), Dijkstra’s algorithms, numerical analysis, bisection and root-finding algorithms for the inspection of complex surface components. These algorithms can be applied in two and three-dimensional domains resulting in high computation time. This work presents an experimental comparison of an iterative beamforming method for arbitrary shaped surface profile imaging against both Full Matrix Capture-Total Focusing Method (FMC-TFM) and CIVA simulation on an aluminium calibration block with Side drilled holes (SDHs) at various depths in the range of 15-80 mm. The performance of the iterative beamforming method is evaluated in terms of sensitivity, Signal to Noise Ratio (SNR) and Array Performance Indicators (API). The method provides a 2 dB improved SNR when compared to FMC-TFM.

Ultrasonic sectorial inspection in the presence of temperature gradients

Ultrasonic nondestructive testing is a precise tool for equipment inspections. Among the usual methods, sectorial scanning stands out within contact-based techniques, as it provides broad angular sweeps without the need to physically steer the transducer, and the configuration of the beams hinges on the geometry of the tested objects. However, in high-temperature scenarios (e.g., oil treatment vessels), thermal gradients along the propagation path result in inaccurate sizing of discontinuities, given that the presence of such gradients is responsible for variations in the velocities and distortions of the ultrasonic beams. This paper proposes a method to compensate for these distortions during the sectorial inspection. Optimal linear approximation parameters are determined offline from a controlled Full Matrix Capture (FMC) test, in which the setup consists of a phased array transducer, a high-temperature resistant wedge and an aluminium test block with flaws at known positions. The positions of the flaws are measured on the Total Focusing Method (TFM) reconstructions, and the parametric velocity models for specific instants of heating time are estimated through the minimization of a cost function. Then, focal laws are calculated from the parameters using the ray tracing technique and stored in a text file to be interpreted by the instruments as a native focal law. An online test is proposed for validating the method at the controlled temperature of 70oC. The results show that the positions of the flaws, and the distance between them in the S-scan image, present improved accuracy (with errors reduced by approximately 64%) when the proposed correction is applied.

The Residual Stress Control of Thin-walled Sleeve Parts with Weak Rigidity

Photoelectric products in the military industry tend to be lightweight in design, requiring the part to be lightweight and have high specific strength. As one of the structural parts of photoelectric products, the thin-walled sleeve part has the peculiarity of lightweight and thin wall thickness. Nevertheless, the residual stress during machining processing poses an adverse effect on the accuracy of the parts. In this paper, the influence of residual stress on the accuracy of the parts during the processing was studied. Before fine machining, the residual stress was reduced by artificial aging techniques and ultrasonic beam control methods. Finally, the effect of the two stress relief methods was evaluated according to the qualified rate of the processing accuracy of the parts. The research results show that the axial residual stress of the part is larger than the circumferential residual stress. Both artificial aging techniques and ultrasonic beam control can eliminate residual stress, and the ultrasonic beam control method is more targeted and uniform.

Research on Photoacoustic Synthetic Aperture Focusing Technology Imaging Method of Internal Defects in Cylindrical Components.

Cylindrical components are parts with curved surfaces, and their high-precision defect testing is of great significance to industrial production. This paper proposes a noncontact internal defect imaging method for cylindrical components, and an automatic photoacoustic testing platform is built. A synthetic aperture focusing technology in the polar coordinate system based on laser ultrasonic (LU-pSAFT) is established, and the relationship between the imaging quality and position of discrete points is analyzed. In order to verify the validity of this method, small holes of Φ0.5 mm in the aluminum alloy rod are tested. During the imaging process, since a variety of waveforms can be excited by the pulsed laser synchronously, the masked longitudinal waves reflected by small holes need to be filtered and windowed to achieve high-quality imaging. In addition, the influence of ultrasonic beam angle and signal array spacing on imaging quality is analyzed. The results show that the method can accurately present the outline of the small hole, the circumferential resolution of the small hole is less than 1° and the dimensional accuracy and position error are less than 0.1 mm.

Analytical Model of Three-Dimensional Ultrasonic Beam Interaction with an Immersed Plate

This paper proposes an analytical model to describe the interaction of a bounded ultrasonic beam with an immersed plate. This model, based on the Gaussian beams decomposition, takes into account multiple reflections into the plate. It allows predicting three-dimensional spatial distributions of both transmitted and reflected fields. Thereby, it makes it easy to calculate the average pressure over the receiver’s area taking into account diffraction losses. So the acoustical parameters of the plate can be determined more accurately. A Green’s function for the interaction of an ultrasonic beam with the plate is derived. The obtained results are compared to those given by the angular spectrum approach. A good agreement is seen showing the validity of the proposed model.

The Effect of Dynamic Beam Deflection and Focus Shift on the Acoustic Field Distribution Inside the Ultrasonic Ring Array

This paper presents the results of acoustic field distribution simulations for the 1024-element ultrasonic ring array intended for the diagnosis of female breast tissue with the use of ultrasound tomography. For the purpose of analysing data, all acoustic fields created by each elementary transducer were combined. The natural position of the focus inside the ultrasonic ring array was changed by altering activation time of individual transducers in sectors consisting of 32, 64, and 128 ultrasonic transducers. Manipulating the position of the focus inside the array will allow to concentrate the ultrasonic beam in a chosen location in the interior space of the ring array. The goal of this research is to receive the best possible quality of images of cross-sections of the female breast. The study also analysed the influence of the acoustic field distribution on the inclination of the beam. The results will enable to choose an optimal focus and an optimal number of activated transducers.

Supporting Imaging of Austenitic Welds with Finite Element Welding Simulation—Which Parameters Matter?

The basic principle of ultrasound is to relate the time of flight of a received echo to the location of a reflector, assuming a known and constant velocity of sound. This assumption breaks down in austenitic welds, in which a microstructure with large oriented austenitic grains induces local velocity differences resulting in deviations of the ultrasonic beam. The inspection problem is further complicated by scattering at grain boundaries, which introduces structural noise and attenuation. Embedding material information into imaging algorithms usually improves image quality and aids interpretation. Imaging algorithms can take the weld structure into account if it is known. The usual way to obtain such information is by metallurgical analysis of slices of a representative mock-up fabricated using the same materials and welding procedures as in the actual component. A non-destructive alternative to predict the weld structure is based on the record of the welding procedure, using either phenomenological models or the finite element method. The latter requires detailed modelling of the welding process to capture the weld pool and the microstructure formation. Several parameters are at play, and uncertainties intrinsically affect the process owing to the limited information available. This paper reports a case study aiming to determine the most critical parameters and levels of complexity of the weld formation models from the perspective of ultrasonic imaging. By combining state-of-the-art welding simulation with time-domain finite element prediction of ultrasound in complex welds, we assess the impact of the modelling choices on the offset and spatial spreading of defect signatures. The novelty of this work is in linking welding simulation with ultrasonic imaging and quantifying the effect of the common assumptions in solidification modelling from the non-destructive examination perspective. Both aspects have not been explored in the literature to date since solidification modelling has not been used to support ultrasonic inspection extensively. The results suggest that capturing electrode tilt, welding power, and weld path correctly is less significant. Bead shape was identified as having the greatest influence on delay laws used to compute ultrasonic images. Most importantly, we show that neglecting mechanical deformation in FE, allowing for simpler thermal simulation supplemented with a phenomenological grain growth loop, does not reduce the quality of the images considerably. Our results offer a pragmatic balance between the complexity of the model and the quality of ultrasonic images and suggest a perspective on how weld formation modelling may serve inspections and guide pragmatic implementation.

New submodels describing attenuation of the ultrasonic beams in 3-d cubic nonlinear medium in the absence of dissipation

For a three-dimensional generalized model of nonlinear hydroacoustics by Khokhlov–Zabolotskaya–Kuznetsov in a cubic nonlinear medium in the absence of dissipation, we studied the attenuation of ultrasonic beams after the formation of shock fronts. Earlier, in the work of one of the authors for this model, submodels were obtained and studied, described by non-stationary solutions, invariant with respect to some three-dimensional subgroups of the main ten-parameter group of the differential equation that defines this model. In our paper we obtained and studied four non-stationary submodels of this model that are invariant with respect to four-parameter subgroups of the main group of this differential equation. These submodels are new submodels and have not been previously noted in the literature. They are given by invariant solutions of rank 1. Among these 4 submodels, 2 submodels describe axisymmetric ultrasonic beams, the remaining 2 describe one-dimensional ultrasonic beams. The search for invariant solutions that define these 4 submodels is reduced to solving of nonlinear integral equations, the implicit solutions of which are obtained in the form of nonlinear algebraic equations containing transcendental functions. These submodels are used to study the propagation of ultrasonic beams, for which either the acoustic pressure and its rate of change or the acoustic pressure and its gradient are given at the initial time at a fixed point. Conditions are obtained that ensure the existence and uniqueness of solutions to boundary value problems describing these processes. This makes it possible to correctly carry out numerical calculations in the study of these processes. As a result of the numerical solution of these boundary value problems for some values of the parameters characterizing these processes, pressure distribution graphs were obtained. In all cases, ultrasonic beams are weaken monotonically with time and completely fade away in a finite time. At each point, the time of complete attenuation of ultrasonic beams is found.The obtained and studied new submodels are another step towards the creation of a database of physically significant submodels of the three-dimensional generalized model of nonlinear hydroacoustics by Khokhlov–Zabolotskaya–Kuznetsov in a cubic nonlinear medium in the absence of dissipation, which describes the attenuation of ultrasonic beams after the formation of shock fronts.

Evaluation of material damage using non-specular reflection of a bounded ultrasonic beam at a liquid-solid interface

This paper proposes an effective method for evaluating the level of material damage using the non-specular reflection of a bounded ultrasonic beam at a liquid-solid interface. Non-specular reflection occurs when a bounded ultrasonic beam is obliquely incident from a liquid onto a solid surface. This paper formally formulates the acoustic field of the non-specular reflection of a bounded ultrasonic beam and analyzes the influences of some factors such as the incident angle and the level of material damage (characterized by a decrease in Young's modulus) on the non-specular reflection field. To characterize the effect of the non-specular reflection of a bounded ultrasonic beam, this paper defines a specific parameter called the specular reflection coefficient (SRC) of a bounded ultrasonic beam. A finite-element (FE) model is established to quantitatively observe the response of the defined SRC to the incident angle and the level of material damage. The FE simulations are conducted for the bounded ultrasonic beam obliquely incident at longitudinal, transverse, and Rayleigh critical angles, respectively. The simulations demonstrate that the change rate of SRC at the Rayleigh critical angle exhibits a monotonically sensitive response to the level of material damage, providing an effective means for accurately evaluating it. To validate this method, we conducted an experiment with oblique incidence testing of the bounded ultrasonic beam at the Rayleigh critical angle of the water-aluminum interface. The experimental results are consistent with the FE simulations, and show that the change rate of SRC at the Rayleigh critical angle has a monotonous and sensitive response to the level of material damage. The consistency of theoretical predictions, FE simulations, and experimental results confirms the feasibility of using the non-specular reflection of a bounded ultrasonic beam incident at the Rayleigh critical angle as an effective method for evaluating the level of material damage.

A Correction Method for the Measurement of Frequency-Dependent Attenuation Coefficient With Curved Surface Specimens Using Normal Contact Transducer

The ultrasonic pulse-echo technique has been widely employed for the measurement of the frequency-dependent attenuation coefficient in polycrystalline metals. However, the nonuniform thickness of the coupling layer between the transducer piston and the curved surface is inevitable for curved specimens, resulting in a significant overestimation. In addition, the curved surface also affects the diffraction loss caused by the divergence and convergence of ultrasonic beams during the propagation path. In this study, a correction method is proposed for the experimental calculation of the frequency-dependent attenuation with the curved surface components using a contact transducer. First, with the analysis of the nonuniform coupling layer created by the curved surface and transducer piston, the integral over the effective cross-sectional area is introduced to determine the reflection coefficient. Second, an equivalent rectangular transducer sound field model is proposed to calculate the diffraction loss for different curvatures and propagation distances based on the multi-Gaussian beam (MGB) theory. Then, a correction model is established to compensate for the deviation caused by the curved surfaces. To verify the feasibility of the proposed method, two cylindrical bars and five blanks with different curvatures were designed. The experimental results show that the proposed correction method can effectively eliminate the deviation caused by the curved surface and improve the stability of measurement. With the correction, the variation of the attenuation spectrum for the curved specimens is reduced by approximately 5%. This facilitates researchers to better develop and use frequency-dependent attenuation coefficients of materials for further applications.

Coupling effect of ultrasonic vibration and beam oscillation on FQZ soften inhibition of laser welded Al-Mg alloy joints

A novel ultrasonic vibration assisted laser beam oscillation welding (UV-LBOW) method was developed and applied on the butt-welding of Al-Mg alloy sheets. Due to the synergistic enhancement of the molten pool flow by ultrasound vibration and laser beam oscillation, the microstructure morphology of fusion zone (FZ) was comprised of equiaxed grains. Additionly, a uniform element distribution was generated from the boundary to the center of the FZ. An enhanced tensile strength of 347 MPa and a fraction elongation of 19.0 % were obtained due to the grain refinement and solid solution strengthening effects.

Design of additive manufactured reference block with disk reflectors for sensitivity calibration of ultrasonic angle beam probes

Design of additive manufactured reference block with disk reflectors for sensitivity calibration of ultrasonic angle beam probes

History effects in the creep of a disordered brittle material

We study the creep behavior of a disordered brittle material (concrete) under successive loading steps, using acoustic emission and ultrasonic sensing to track internal damage. The primary creep rate is observed to follow a (Omori-type) power-law decay in the strain rate, the number of acoustic emission events, as well as the amplitudes of the ultrasonic beams, supporting a brittle-creep mechanism. The distribution of acoustic emission event energies is observed to have a scale-free power-law distribution instead of a truncated one expected for a system approaching a critical point at failure. The main outcome is, however, the discovery of unexpected history effects that make the material less prone to creep when it has been previously deformed and damaged under primary creep. With the help of a progressive damage model implementing thermal activation, we interpret this as an aging-under-stress phenomenon: During an initial creep step at relatively low applied stress, the easy-to-damage sites are exhausted first, depleting the excitation spectrum at low stress gap values. Consequently on reloading, although previously damaged, the primary creep restarts but the material creeps (and damages) less than it would under the same stress but without precreeping. Besides shedding a new light on the fundamental physics of creep of disordered brittle materials, this has important practical consequences in the interpretation of some experimental procedures, such as stress-stepping experiments.

Multiple ultrasounds assisted phase separation and monotectic solidification of liquid ternary Al81.5Cu14.7Bi3.8 immiscible alloy

Multiple power ultrasounds were employed to investigate the phase transition process of ternary Al81.5Cu14.7Bi3.8 immiscible alloy by various exerting modes. As the ultrasonic sources increased, the liquid phase separation pattern transformed from (Bi)-rich layered macrosegregation into the uniform distribution of secondary (Bi) droplets. Meanwhile, the primary (Al) phase evolved from coarse dendrites into plenty of small spherical grains and also tended to be uniformly dispersed. The subsequently formed ternary (Al) + (Al2Cu) + (Bi) monotectic structure, featured by the alternative (Al) and (Al2Cu) lamellar structure with fine (Bi) grains distributed, was coarsened first and then refined. Numerical simulations showed that the transient cavitation and the acoustic streaming strength were significantly enhanced by increasing ultrasonic beams, with the fourfold ultrasounds producing the most prominent effects on the phase separation process. The intensive and enlarged cavitation areas greatly accelerated the nucleation of both the secondary liquid phase and primary solid phase, which refined the growing (Bi) droplets and (Al) dendrites. The strength and morphology of acoustic streaming were the key factors in offsetting Stokes motion and carrying the growing grains to various regions, resulting in a uniform microstructure. Furthermore, increasing ultrasonic sources improved the friction and wear properties of the solidified alloy, which indicated that the Al81.5Cu14.7Bi3.8 immiscible alloy may become an excellent wear-resistant material owing to the uniform monotectic structure fabricated by the fourfold ultrasounds.

Extraction of Flaw Signals from the Mixed 1-D Signals by Denoising Autoencoder

Ultrasonic testing (UT) is one of the most popular non-destructive evaluation (NDE) techniques used in many industries to evaluate structural integrity. The commonly used NDE techniques are basic inspection techniques, such as visual testing (VT), penetration testing (PT), and magnetic testing (MT), and advanced inspection techniques, such as UT, radiography testing (RT), eddy current testing (ECT), and phased array ultrasonic testing (PAUT). Among the numerous advanced techniques, ultrasonic testing (UT) is usually used for the inspection of welds in various industries. However, the application of UT still has some shortcomings to overcome. One major shortcoming that reduces the precision of UT is the extra signals from the geometrical interface of a specimen. UT uses the reflection indications of the ultrasonic beam. However, the reflection signals from the welding interface and geometry along with the target flaw signal produce mixed signals. The inspectors use a 1-D reflection outcome called the ultrasonic A-scan to evaluate the welding integrity. The mixed ultrasonic A-scan signals are often very difficult to analyze because inspectors must distinguish the target flaw signal of welding from the mixed ultrasonic A-scan signal, which includes the flaw indication as well as the background signal. Therefore, a method to distinguish between the flaw signal and the background signal must be developed for the efficiency of UT. Autoencoder is an artificial neural network that is made for feature extraction from the input. Denoising autoencoder (DAE) is one of the derivative models of the autoencoder which adds or eliminates random noise signals to extract the prominent features. DAE is already widely used in the denoising of images and sound data. The characteristics of DAE are used in this research to distinguish the ultrasonic flaw signal from the mixed ultrasonic A-scan signal. For the training, 2463 mixed A-scan signals were obtained from 45 different standard blocks in which 5 different types of flaws were embedded. For testing, we used 1000 mixed A-scan signals. The performance of the network was evaluated using a point-by-point comparison method. The autoencoder was trained to denoise the background signal from the mixed ultrasonic A-scan, and the target flaw signal was extracted from the original A-scan signal.

Research on ultrasonic process fusing tomography for numerical and laboratory imaging in liquid-background two-phase flow

Real-time ultrasonic process tomography (UPT) could be suitable for the conditions including various sizes and locations as well as amount of the interesting targets and different pipelines. However, the difficulty in determining flow-pattern segmentation in the back-projection for both transmission mode and reflection mode was not overcome for real-time imaging. This work focused on an ultrasonic process fusing tomography (UPFT) for implementing both reflection-mode and transmission-mode tomography draw support from an 8-channel scanning technique. The behavior of fan-shaped ultrasonic beam propagation and the characteristics of acoustic field in two phases had been studied, by which the tomographic size resolution about UPFT had been analyzed numerically. The resultant impact on reconstructed image quality due to the operation conditions was discussed in detail. Transmitted waves were adopted as a base of imaging, and reflected waves were integrated as supplementary information to execute threshold optimization. To carry out a validation, a digital 8-channel prototype of UPFT was developed for the laboratory investigation of stratified flow with continuous injection of water. It was found that such ultrasonic tomography yielded significant improvements in reconstruction, compared to single-mode imaging merely using transmitted or reflected waves. At the same time, quantitative results showed that the proposed method facilitated automatic and reasonable flow-pattern identification, and the developed system represented a fast data acquisition and processing as well as strong noise resistance capability.