Pub Date : 2026-01-16DOI: 10.1016/j.ultras.2026.107964
Ali Rezaei , David Fernández Rivas , Guillaume Lajoinie , Michel Versluis
Microbubble contrast agents are well-known in the biomedical field for their ability to enhance the contrast in ultrasound imaging and to facilitate targeted drug delivery within the body. Upon injection into the vasculature, these bubbles are strongly influenced by the viscoelastic properties of surrounding soft tissues. Here, we simulate the scattered pressure from a single phospholipid-coated microbubble placed in a uniform viscoelastic medium. We use a modified Rayleigh–Plesset equation that incorporates the viscoelastic response of the phospholipid shell and a Kelvin–Voigt model to represent tissue viscoelasticity. Our simulations aim to investigate the relationship between the viscoelasticity of the medium and that of the bubble shell, and its influence on bubble dynamics as a function of driving pressure, bubble radius, and medium elastic modulus. Results show that the frequency of maximum scatter response increases with the elastic modulus of the medium. While the radial excursion of a radius bubble can decrease by as much as 45% in a medium with an elastic modulus of 200 kPa as compared to that in water, the scattered pressure can increase by 50%. In contrast, the change in harmonic scattering is negligible: simulations predict a increase of only 5% for a bubble when increasing the medium elasticity from 0 to 200 kPa at a driving pressure of 120 kPa. Furthermore, subharmonics generated by driving the bubble at its resonance frequency (TR) are comparable to the subharmonics generated at twice the resonance frequency at lower driving pressures. For elevated pressures the TR/T2R subharmonic ratio increases with increasing elastic modulus. This is in sharp contrast with the resonance behavior of a microbubble in water. These results bear consequences for strategies that exploit the fundamental, harmonic, and subharmonic response of microbubble contrast agents.
{"title":"Modeling nonlinear scattering of phospholipid-coated microbubbles in elastic media","authors":"Ali Rezaei , David Fernández Rivas , Guillaume Lajoinie , Michel Versluis","doi":"10.1016/j.ultras.2026.107964","DOIUrl":"10.1016/j.ultras.2026.107964","url":null,"abstract":"<div><div>Microbubble contrast agents are well-known in the biomedical field for their ability to enhance the contrast in ultrasound imaging and to facilitate targeted drug delivery within the body. Upon injection into the vasculature, these bubbles are strongly influenced by the viscoelastic properties of surrounding soft tissues. Here, we simulate the scattered pressure from a single phospholipid-coated microbubble placed in a uniform viscoelastic medium. We use a modified Rayleigh–Plesset equation that incorporates the viscoelastic response of the phospholipid shell and a Kelvin–Voigt model to represent tissue viscoelasticity. Our simulations aim to investigate the relationship between the viscoelasticity of the medium and that of the bubble shell, and its influence on bubble dynamics as a function of driving pressure, bubble radius, and medium elastic modulus. Results show that the frequency of maximum scatter response increases with the elastic modulus of the medium. While the radial excursion of a <span><math><mrow><mn>2</mn><mo>.</mo><mn>0</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> radius bubble can decrease by as much as 45% in a medium with an elastic modulus of 200 kPa as compared to that in water, the scattered pressure can increase by 50%. In contrast, the change in harmonic scattering is negligible: simulations predict a increase of only 5% for a <span><math><mrow><mn>2</mn><mo>.</mo><mn>0</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> bubble when increasing the medium elasticity from 0 to 200 kPa at a driving pressure of 120 kPa. Furthermore, subharmonics generated by driving the bubble at its resonance frequency (TR) are comparable to the subharmonics generated at twice the resonance frequency at lower driving pressures. For elevated pressures the TR/T2R subharmonic ratio increases with increasing elastic modulus. This is in sharp contrast with the resonance behavior of a microbubble in water. These results bear consequences for strategies that exploit the fundamental, harmonic, and subharmonic response of microbubble contrast agents.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"162 ","pages":"Article 107964"},"PeriodicalIF":4.1,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146012492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 10.1016/j.ultras.2026.107961
Chuanming Jia, Hongjie Zhang, Xinyue Gao, Yi Zhang
This study presents a novel mode-selectable piezoelectric ultrasonic transducer (PUT) with a traditional sandwich structure, developed through systematic integration of modular design, electro-mechanical equivalent four-terminal network method, modal optimization techniques, and vibration conversion principles. To evaluate the performance of the proposed PUT, a prototype was fabricated and underwent a series of comprehensive excitation tests. Experimental results indicate that the PUT exhibits two fundamental mechanical resonance modes: a lower-frequency mode characterized by longitudinal-bending (L-B) coupled vibration, and a higher-frequency mode corresponding to pure longitudinal (L) vibration. The proposed transducer enables flexible and seamless switching among the L mode, L-B coupled mode, and a hybrid mode that incorporates both fundamental vibrations, while maintaining excellent energy conversion stability and efficiency during prolonged operation. By adjusting the voltage amplitudes of different frequency components in a dual-frequency composite excitation signal, the vibration at the transducer’s working end can be switched among rectilinear, elliptical, and parallelogram-like trajectories. This enables direct control over the ultrasonic energy action zone. The unique combination of mode-selectable and trajectory-control capabilities gives the proposed transducer significant potential for ultrasonic-assisted precision manufacturing applications.
{"title":"Design and performance of a novel mode-selectable piezoelectric ultrasonic transducer with controllable output trajectory","authors":"Chuanming Jia, Hongjie Zhang, Xinyue Gao, Yi Zhang","doi":"10.1016/j.ultras.2026.107961","DOIUrl":"10.1016/j.ultras.2026.107961","url":null,"abstract":"<div><div>This study presents a novel mode-selectable piezoelectric ultrasonic transducer (PUT) with a traditional sandwich structure, developed through systematic integration of modular design, electro-mechanical equivalent four-terminal network method, modal optimization techniques, and vibration conversion principles. To evaluate the performance of the proposed PUT, a prototype was fabricated and underwent a series of comprehensive excitation tests. Experimental results indicate that the PUT exhibits two fundamental mechanical resonance modes: a lower-frequency mode characterized by longitudinal-bending (L-B) coupled vibration, and a higher-frequency mode corresponding to pure longitudinal (L) vibration. The proposed transducer enables flexible and seamless switching among the L mode, L-B coupled mode, and a hybrid mode that incorporates both fundamental vibrations, while maintaining excellent energy conversion stability and efficiency during prolonged operation. By adjusting the voltage amplitudes of different frequency components in a dual-frequency composite excitation signal, the vibration at the transducer’s working end can be switched among rectilinear, elliptical, and parallelogram-like trajectories. This enables direct control over the ultrasonic energy action zone. The unique combination of mode-selectable and trajectory-control capabilities gives the proposed transducer significant potential for ultrasonic-assisted precision manufacturing applications.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"162 ","pages":"Article 107961"},"PeriodicalIF":4.1,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146024102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-06DOI: 10.1016/j.ultras.2025.107947
Trésor Kanyiki
This article presents an experimental study of the effects of temperature variations on ultrasonic waves and proposes a methodology to improve the robustness of damage-detection indicators under such environmental conditions. The investigation is based on laboratory tests carried out in air on specimens instrumented with embedded piezoelectric sensors and subjected to controlled thermal cycles. As a first step, the well-known time-stretching technique is applied to correct propagation delays induced by thermal expansion and the temperature dependence of wave speed. Interestingly, while this method remains effective for moderate excursions, its performance degrades at higher temperatures due to strong waveform distortion. Under such conditions, classical indicators relative velocity variation and correlation coefficient-lose reliability.
To overcome this limitation, we evaluate three processing chains that combine time-stretching with (i) an autoassociative neural network (autoencoder), (ii) principal component analysis (PCA), and (iii) a support vector machine (SVM). The first two approaches extract features that are more resilient to thermal effects and provide better stability when temperature fluctuates. In addition, the squared Euclidean distance between the input and its reconstruction is used as a damage indicator, while extreme value statistics (EVS) are employed to define adaptive alarm thresholds; among the candidate tail models, the Fréchet distribution proves particularly suitable for representing the extremes of the indicator. By contrast, in our protocol, the SVM approach does not yield a significant gain.
Overall, the results show that coupling time-stretching with dimensionality reduction (linear or nonlinear) and EVS-based thresholding markedly improves monitoring reliability, distinguishing healthy from damaged states with an acceptable false-alarm rate under variable environmental conditions.
{"title":"Development of an automatic damage detection methodology using ultrasonic piezoelectric sensors under varying temperature conditions","authors":"Trésor Kanyiki","doi":"10.1016/j.ultras.2025.107947","DOIUrl":"10.1016/j.ultras.2025.107947","url":null,"abstract":"<div><div>This article presents an experimental study of the effects of temperature variations on ultrasonic waves and proposes a methodology to improve the robustness of damage-detection indicators under such environmental conditions. The investigation is based on laboratory tests carried out in air on specimens instrumented with embedded piezoelectric sensors and subjected to controlled thermal cycles. As a first step, the well-known time-stretching technique is applied to correct propagation delays induced by thermal expansion and the temperature dependence of wave speed. Interestingly, while this method remains effective for moderate excursions, its performance degrades at higher temperatures due to strong waveform distortion. Under such conditions, classical indicators relative velocity variation and correlation coefficient-lose reliability.</div><div>To overcome this limitation, we evaluate three processing chains that combine time-stretching with (i) an autoassociative neural network (autoencoder), (ii) principal component analysis (PCA), and (iii) a support vector machine (SVM). The first two approaches extract features that are more resilient to thermal effects and provide better stability when temperature fluctuates. In addition, the squared Euclidean distance between the input and its reconstruction is used as a damage indicator, while extreme value statistics (EVS) are employed to define adaptive alarm thresholds; among the candidate tail models, the Fréchet distribution proves particularly suitable for representing the extremes of the indicator. By contrast, in our protocol, the SVM approach does not yield a significant gain.</div><div>Overall, the results show that coupling time-stretching with dimensionality reduction (linear or nonlinear) and EVS-based thresholding markedly improves monitoring reliability, distinguishing healthy from damaged states with an acceptable false-alarm rate under variable environmental conditions.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107947"},"PeriodicalIF":4.1,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145939875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-06DOI: 10.1016/j.ultras.2026.107953
Meng Qinghang , Gu Bin , Yuan Weifeng , Deng Mingxi , Ding Xiangyan , Hu Ning , Wang Jishuo
The nonlinear ultrasonic technique is an effective method for characterizing early-stage damage, such as initial corrosion, plastic deformation, and creep. However, the nonlinear response signal induced by micro-damage is typically one or two orders of magnitude weaker than the fundamental wave. This low signal-to-noise ratio is one of the main factors limiting the broader application of nonlinear ultrasonic technology. To address this issue, this study systematically investigates the quasi-static component pulse (QSCP) generated during the propagation of the longitudinal critically refracted (LCR) wave. The feasibility of assessing early corrosion damage in 7075 aluminum alloy was evaluated using the QSCP, a signal feature resulting from the interaction between corrosion-induced microcrack and LCR wave. Both numerical simulation and experimental results demonstrate a positive correlation between the QSCP-based acoustic nonlinearity parameter (ANP) and the extent of corrosion-induced microcrack, which is attributed to the increase in microcrack. Simulation results show that the ANP increases monotonically with the number of microcrack. This trend is experimentally validated, with the ANP showing a significant increase of approximately 54.8% by the fourth stage of corrosion compared to the baseline. These findings confirm the effectiveness and feasibility of the QSCP-based ANP method for detecting early-stage corrosion damage, offering a promising nondestructive approach with high sensitivity for assessing incipient corrosion in critical metallic structures.
{"title":"Evaluation of early-stage corrosion damage using quasi-static component pulse generated by longitudinal critically refracted (LCR) wave","authors":"Meng Qinghang , Gu Bin , Yuan Weifeng , Deng Mingxi , Ding Xiangyan , Hu Ning , Wang Jishuo","doi":"10.1016/j.ultras.2026.107953","DOIUrl":"10.1016/j.ultras.2026.107953","url":null,"abstract":"<div><div>The nonlinear ultrasonic technique is an effective method for characterizing early-stage damage, such as initial corrosion, plastic deformation, and creep. However, the nonlinear response signal induced by micro-damage is typically one or two orders of magnitude weaker than the fundamental wave. This low signal-to-noise ratio is one of the main factors limiting the broader application of nonlinear ultrasonic technology. To address this issue, this study systematically investigates the quasi-static component pulse (QSCP) generated during the propagation of the longitudinal critically refracted (LCR) wave. The feasibility of assessing early corrosion damage in 7075 aluminum alloy was evaluated using the QSCP, a signal feature resulting from the interaction between corrosion-induced microcrack and LCR wave. Both numerical simulation and experimental results demonstrate a positive correlation between the QSCP-based acoustic nonlinearity parameter (ANP) and the extent of corrosion-induced microcrack, which is attributed to the increase in microcrack. Simulation results show that the ANP increases monotonically with the number of microcrack. This trend is experimentally validated, with the ANP showing a significant increase of approximately 54.8% by the fourth stage of corrosion compared to the baseline. These findings confirm the effectiveness and feasibility of the QSCP-based ANP method for detecting early-stage corrosion damage, offering a promising nondestructive approach with high sensitivity for assessing incipient corrosion in critical metallic structures.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"162 ","pages":"Article 107953"},"PeriodicalIF":4.1,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145941409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-06DOI: 10.1016/j.ultras.2026.107954
Alberto Almuna-Morales , Danilo Aballay , Pierre Gélat , Reza Haqshenas , Elwin van ’t Wout
Transcranial ultrasound therapy uses focused acoustic energy to induce therapeutic bioeffects in the brain. Ultrasound must be transmitted through the skull, which is highly attenuating and heterogeneous, causing beam distortion, reducing focal pressure, and shifting the target location. Computational models are frequently used to predict beam aberration, assess cranial heating, and correct the phase of ultrasound transducers. These models often rely on computed tomography (CT) images to build patient-specific geometries and estimate skull acoustic properties. However, the coarse voxel resolution of CT limits accuracy for differential equation solvers at ultrasound frequencies. This paper presents an efficient numerical method based on volume-surface integral equations to model full-wave acoustic propagation through heterogeneous skull bone. We show that our approach effectively simulates transcranial ultrasound, even when using the original CT voxels as the computational mesh, where the 0.5 mm voxel length is relatively coarse compared to the shortest wavelength of 3 mm. The method is validated against a high-resolution boundary element model using an averaged skull representation. Simulations using a CT-based skull model and a bowl transducer reveal significant beam distortion of 7.8 mm attributed to the skull’s heterogeneous acoustical properties.
{"title":"Full-wave modeling of transcranial ultrasound using volume-surface integral equations and CT-derived heterogeneous skull data","authors":"Alberto Almuna-Morales , Danilo Aballay , Pierre Gélat , Reza Haqshenas , Elwin van ’t Wout","doi":"10.1016/j.ultras.2026.107954","DOIUrl":"10.1016/j.ultras.2026.107954","url":null,"abstract":"<div><div>Transcranial ultrasound therapy uses focused acoustic energy to induce therapeutic bioeffects in the brain. Ultrasound must be transmitted through the skull, which is highly attenuating and heterogeneous, causing beam distortion, reducing focal pressure, and shifting the target location. Computational models are frequently used to predict beam aberration, assess cranial heating, and correct the phase of ultrasound transducers. These models often rely on computed tomography (CT) images to build patient-specific geometries and estimate skull acoustic properties. However, the coarse voxel resolution of CT limits accuracy for differential equation solvers at ultrasound frequencies. This paper presents an efficient numerical method based on volume-surface integral equations to model full-wave acoustic propagation through heterogeneous skull bone. We show that our approach effectively simulates transcranial ultrasound, even when using the original CT voxels as the computational mesh, where the 0.5 mm voxel length is relatively coarse compared to the shortest wavelength of 3 mm. The method is validated against a high-resolution boundary element model using an averaged skull representation. Simulations using a CT-based skull model and a bowl transducer reveal significant beam distortion of 7.8 mm attributed to the skull’s heterogeneous acoustical properties.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107954"},"PeriodicalIF":4.1,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145935264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.ultras.2026.107952
Liu Yang , Peipei Liu , Kiyoon Yi , Tam Van Huynh , Hanbi Byun , Jeaseung Kim , Hyunsung Hwang , Hoon Sohn
Accurate and efficient non-destructive evaluation (NDE) techniques are essential for ensuring the structural integrity of metallic components, where surface defects, as one of the most common types, can severely compromise fatigue life and mechanical performance. Laser ultrasonics provides a non-contact and high-fidelity approach for inspecting metallic components through wavefield-based analysis. However, reconstructing complete ultrasonic fields and identifying defects from limited measurements remain challenging problems. This study proposes a defect-parameterized physics-informed neural network (DP-PINN) for the forward and inverse modeling of laser ultrasonic wavefield, with the objective of characterizing sub-millimeter surface defects in metallic components. The proposed framework embeds defect-related parameters into the governing elastodynamic equations to reconstruct the full wavefield and estimate the wave velocity field, thereby revealing defect characteristics including location and size. To comprehensively assess the method’s performance, four different defect cases are simulated, incorporating different defect characteristics. Furthermore, six practical scenarios are analyzed based on different levels of prior knowledge about material properties and data sparsity. Results demonstrate that defect characterization and full wavefield reconstruction can be achieved with limited measurement data of 0.42 MB. The proposed method maintains consistent detectability across varying defect cases and yields a mean Intersection over Union () of 0.387, indicating quantitative accuracy.
{"title":"Defect-parameterized physics-informed neural network for forward and inverse modeling of laser ultrasonic wavefield","authors":"Liu Yang , Peipei Liu , Kiyoon Yi , Tam Van Huynh , Hanbi Byun , Jeaseung Kim , Hyunsung Hwang , Hoon Sohn","doi":"10.1016/j.ultras.2026.107952","DOIUrl":"10.1016/j.ultras.2026.107952","url":null,"abstract":"<div><div>Accurate and efficient non-destructive evaluation (NDE) techniques are essential for ensuring the structural integrity of metallic components, where surface defects, as one of the most common types, can severely compromise fatigue life and mechanical performance. Laser ultrasonics provides a non-contact and high-fidelity approach for inspecting metallic components through wavefield-based analysis. However, reconstructing complete ultrasonic fields and identifying defects from limited measurements remain challenging problems. This study proposes a defect-parameterized physics-informed neural network (DP-PINN) for the forward and inverse modeling of laser ultrasonic wavefield, with the objective of characterizing sub-millimeter surface defects in metallic components. The proposed framework embeds defect-related parameters into the governing elastodynamic equations to reconstruct the full wavefield and estimate the wave velocity field, thereby revealing defect characteristics including location and size. To comprehensively assess the method’s performance, four different defect cases are simulated, incorporating different defect characteristics. Furthermore, six practical scenarios are analyzed based on different levels of prior knowledge about material properties and data sparsity. Results demonstrate that defect characterization and full wavefield reconstruction can be achieved with limited measurement data of 0.42 MB. The proposed method maintains consistent detectability across varying defect cases and yields a mean Intersection over Union (<span><math><mrow><mi>I</mi><mi>o</mi><mi>U</mi></mrow></math></span>) of 0.387, indicating quantitative accuracy.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107952"},"PeriodicalIF":4.1,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145918512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.ultras.2026.107949
Zhengshi Lu , Zhichao Cai , Riteng Sun , Jianfen Wang , Wenhua Hu , Jing Rao
Oblique-incidence EMAT inspection can cover large areas and reduce blind zones, but traditional shear-vertical EMATs (TSV-EMATs) suffer from low conversion efficiency, weak directivity and severe modal interference. This work proposes an Optimized Shear-Vertical EMAT (OSV-EMAT) that uses a permanent-magnet array and a tailored FPC meander-line coil to reshape the magnetic field and enhance SV-wave excitation, purity and steering. A physics-guided semi-analytical model is built to map design parameters to SV-wave displacement and, together with a Kriging surrogate and an off-the-shelf swarm optimiser, performs multi-parameter optimisation without extensive transient finite-element simulations, achieving a 51× speed-up while retaining the optimal geometry. For imaging, a multi-mode variable-frequency synthetic aperture focusing technique (VF-SAFT) scheme steers the SV beam by frequency modulation, avoiding mechanical repositioning, and is combined with a lightweight GRDB-based fusion network to mitigate blind zones from direct and secondary modes. Experiments on a semi-circular aluminium plate show that the OSV-EMAT yields stronger, purer and more directional SV echoes than a TSV-EMAT and attains defect localisation errors below 1.52%, demonstrating an efficient solution for EMAT-based defect imaging.
{"title":"Full-region internal imaging of metals using multi-mode VF-SAFT and surrogate model-assisted optimization of EMAT","authors":"Zhengshi Lu , Zhichao Cai , Riteng Sun , Jianfen Wang , Wenhua Hu , Jing Rao","doi":"10.1016/j.ultras.2026.107949","DOIUrl":"10.1016/j.ultras.2026.107949","url":null,"abstract":"<div><div>Oblique-incidence EMAT inspection can cover large areas and reduce blind zones, but traditional shear-vertical EMATs (TSV-EMATs) suffer from low conversion efficiency, weak directivity and severe modal interference. This work proposes an Optimized Shear-Vertical EMAT (OSV-EMAT) that uses a permanent-magnet array and a tailored FPC meander-line coil to reshape the magnetic field and enhance SV-wave excitation, purity and steering. A physics-guided semi-analytical model is built to map design parameters to SV-wave displacement and, together with a Kriging surrogate and an off-the-shelf swarm optimiser, performs multi-parameter optimisation without extensive transient finite-element simulations, achieving a 51× speed-up while retaining the optimal geometry. For imaging, a multi-mode variable-frequency synthetic aperture focusing technique (VF-SAFT) scheme steers the SV beam by frequency modulation, avoiding mechanical repositioning, and is combined with a lightweight GRDB-based fusion network to mitigate blind zones from direct and secondary modes. Experiments on a semi-circular aluminium plate show that the OSV-EMAT yields stronger, purer and more directional SV echoes than a TSV-EMAT and attains defect localisation errors below 1.52%, demonstrating an efficient solution for EMAT-based defect imaging.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107949"},"PeriodicalIF":4.1,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145912982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.ultras.2026.107950
Wu Wenjun, Wu Wentao, Wang Li, Su Yonghang, Zhang Ben
Small-bore tubes, which typically serve as critical industrial components, are challenging to inspect due to their inaccessibility and small dimensions. This paper investigates inspections of small-bore tubes with bends using the flexural guided-wave mode F(1,1). A magnetostrictive patch transducer for F(1,1) excitation is proposed, sharing the same architecture as conventional T(0,1) transducers but driven by opposite alternating currents. To address the challenge arising from the significant curvature of small-bore tubes when exciting pure F(1,1) modes, magnetic field simulations were performed to optimize the transducer’s magnetic field uniformity and directivity. The wave motion of F(1,1) is thoroughly studied. It is found that the F(1,1) mode has two focusing regions separated by 90 degrees in circumstance, one for the circumferential vibration focus and the other for the radial vibration focus. Then, the scattering of the F(1,1) mode with varying circumferential or radial focusing positions as it propagates through the bend is numerically analyzed. It is found that when the F(1,1) mode’s circumferential displacement focus aligns with the outward bend, it converts to the T(0,1) mode with each passage through the bend, with no L(0,1) mode generated, and the wave energy at the outward bend is enhanced. When the F(1,1) mode’s radial displacement focus aligns with the outward bend, it converts to the L(0,1) mode with no T(0,1) mode observed, and the wave energy is further focused at the inward bend. When the F(1,1) mode’s circumferential displacement focus is located 45° from the outward bend, both the T(0,1) and L(0,1) modes are scattered. Experiments were conducted to validate the F(1,1) excitation and the numerical simulation results for F(1,1) bend scattering. Furthermore, F(1,1)-based inspections of bent tubes were conducted to experimentally assess the bend scattering behavior and defect detectability. The weak reflections of the F(1,1) mode from the bend itself do not mask flaw signals, thereby enabling the effective detection of crack-like defects with a 6% cross-sectional area loss. The F(1,1) mode with its circumferential displacement focus aligned with the outward bend is more sensitive to flaws located at the outward bend, whereas the F(1,1) mode with its radial displacement focus aligned with the outward bend is more sensitive to flaws located at the inward bend, in good agreement with the simulation results.
{"title":"Flexural-guided-wave mode F(1,1) based inspections for small-bore tubes with bends","authors":"Wu Wenjun, Wu Wentao, Wang Li, Su Yonghang, Zhang Ben","doi":"10.1016/j.ultras.2026.107950","DOIUrl":"10.1016/j.ultras.2026.107950","url":null,"abstract":"<div><div>Small-bore tubes, which typically serve as critical industrial components, are challenging to inspect due to their inaccessibility and small dimensions. This paper investigates inspections of small-bore tubes with bends using the flexural guided-wave mode F(1,1). A magnetostrictive patch transducer for F(1,1) excitation is proposed, sharing the same architecture as conventional T(0,1) transducers but driven by opposite alternating currents. To address the challenge arising from the significant curvature of small-bore tubes when exciting pure F(1,1) modes, magnetic field simulations were performed to optimize the transducer’s magnetic field uniformity and directivity. The wave motion of F(1,1) is thoroughly studied. It is found that the F(1,1) mode has two focusing regions separated by 90 degrees in circumstance, one for the circumferential vibration focus and the other for the radial vibration focus. Then, the scattering of the F(1,1) mode with varying circumferential or radial focusing positions as it propagates through the bend is numerically analyzed. It is found that when the F(1,1) mode’s circumferential displacement focus aligns with the outward bend, it converts to the T(0,1) mode with each passage through the bend, with no L(0,1) mode generated, and the wave energy at the outward bend is enhanced. When the F(1,1) mode’s radial displacement focus aligns with the outward bend, it converts to the L(0,1) mode with no T(0,1) mode observed, and the wave energy is further focused at the inward bend. When the F(1,1) mode’s circumferential displacement focus is located 45° from the outward bend, both the T(0,1) and L(0,1) modes are scattered. Experiments were conducted to validate the F(1,1) excitation and the numerical simulation results for F(1,1) bend scattering. Furthermore, F(1,1)-based inspections of bent tubes were conducted to experimentally assess the bend scattering behavior and defect detectability. The weak reflections of the F(1,1) mode from the bend itself do not mask flaw signals, thereby enabling the effective detection of crack-like defects with a 6% cross-sectional area loss. The F(1,1) mode with its circumferential displacement focus aligned with the outward bend is more sensitive to flaws located at the outward bend, whereas the F(1,1) mode with its radial displacement focus aligned with the outward bend is more sensitive to flaws located at the inward bend, in good agreement with the simulation results.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107950"},"PeriodicalIF":4.1,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145939876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.ultras.2026.107951
Yiwei Liu , Meng Wang , Tribikram Kundu , Shili Chen , Jian Li , Zhoumo Zeng , Yang Liu
Ultrasonic guided waves are widely used for structural health monitoring, while traditional stress detection methods based on weak nonlinear elasticity theory suffer from limited sensitivity. This study presents a numerical investigation using the highly sensitive Sideband Peak Count-index (SPC-I) technique for improved stress assessment in plates. A finite element (FE) model is developed to analyze the transient evolution of higher-order harmonics under various uniaxial stress states. This study explores the influence of both stress magnitude and its orientation relative to the wave propagation direction, establishing a quantitative link to the acoustic nonlinear parameter, . The results demonstrate that SPC-I is a robust indicator, sensitive not only to the stress magnitude but also to its orientation. Notably, the proposed method significantly enhances measurement sensitivity. Experimental validation confirms that SPC-I values exhibit a pronounced change with stress variations, representing a marked improvement over conventional ultrasonic techniques. The findings establish a theoretical framework for ultrasonic stress detection and provide essential technical guidance for structural health monitoring (SHM) applications.
{"title":"Effective stress monitoring in structures using sideband peak count-index of nonlinear guided waves","authors":"Yiwei Liu , Meng Wang , Tribikram Kundu , Shili Chen , Jian Li , Zhoumo Zeng , Yang Liu","doi":"10.1016/j.ultras.2026.107951","DOIUrl":"10.1016/j.ultras.2026.107951","url":null,"abstract":"<div><div>Ultrasonic guided waves are widely used for structural health monitoring, while traditional stress detection methods based on weak nonlinear elasticity theory suffer from limited sensitivity. This study presents a numerical investigation using the highly sensitive Sideband Peak Count-index (SPC-I) technique for improved stress assessment in plates. A finite element (FE) model is developed to analyze the transient evolution of higher-order harmonics under various uniaxial stress states. This study explores the influence of both stress magnitude and its orientation relative to the wave propagation direction, establishing a quantitative link to the acoustic nonlinear parameter, <span><math><mi>β</mi></math></span>. The results demonstrate that SPC-I is a robust indicator, sensitive not only to the stress magnitude but also to its orientation. Notably, the proposed method significantly enhances measurement sensitivity. Experimental validation confirms that SPC-I values exhibit a pronounced change with stress variations, representing a marked improvement over conventional ultrasonic techniques. The findings establish a theoretical framework for ultrasonic stress detection and provide essential technical guidance for structural health monitoring (SHM) applications.</div></div>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"161 ","pages":"Article 107951"},"PeriodicalIF":4.1,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145918477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-08-09DOI: 10.1016/j.ultras.2025.107779
Francesco Simonetti
The transmission of compressional ultrasonic waves into a rigid and dense solid with a doubly-curved surface is impeded when the solid is placed in a liquid medium and its surface is irradiated with waves traveling through the liquid. Measurable power transmission is only possible when the incident ultrasonic beam is close to normal to the surface. This condition is difficult to realize when the waves are excited and detected by a linear array of transducers and limits the possibility of forming cross-sectional images of the solid from the array data. Here, it is shown that the interior of the solid can be imaged with enhanced fidelity if the water is frozen. The high speed of compressional waves in polycrystalline ice (approximately 4000 ms-1) along with its rigid behavior ensure that ultrasonic waves can be transmitted through the surface over a broad range of angles of incidence. However, due to the double curvature, the rays that form the ultrasonic beam can be deflected outside the array azimuthal plane after entering the solid. Therefore, the two-dimensional images obtained from the linear array data may not be consistent with the fully three-dimensional structure of the ray paths. The analysis of this phenomenon for the special case of solid spheres reveals that the image, to a good approximation, corresponds to a section of the sphere that is parallel to the azimuthal plane and at a standoff distance from it. The distance increases with the angle that the normal to the surface forms relative to the azimuthal plane while it decreases as the velocity contrast between ice and the material of the sphere decreases. While this property is not expected to hold for more complex surfaces, the ray-based framework used in this study is applicable to more general surface configurations and can be used to correlate the images to the structure of the solid. These findings are relevant to the inspection of metallic components with complex geometry which represents a long-standing challenge in the field of nondestructive testing.
{"title":"Ultrasonic imaging of spherical solids embedded in ice.","authors":"Francesco Simonetti","doi":"10.1016/j.ultras.2025.107779","DOIUrl":"10.1016/j.ultras.2025.107779","url":null,"abstract":"<p><p>The transmission of compressional ultrasonic waves into a rigid and dense solid with a doubly-curved surface is impeded when the solid is placed in a liquid medium and its surface is irradiated with waves traveling through the liquid. Measurable power transmission is only possible when the incident ultrasonic beam is close to normal to the surface. This condition is difficult to realize when the waves are excited and detected by a linear array of transducers and limits the possibility of forming cross-sectional images of the solid from the array data. Here, it is shown that the interior of the solid can be imaged with enhanced fidelity if the water is frozen. The high speed of compressional waves in polycrystalline ice (approximately 4000 ms<sup>-1</sup>) along with its rigid behavior ensure that ultrasonic waves can be transmitted through the surface over a broad range of angles of incidence. However, due to the double curvature, the rays that form the ultrasonic beam can be deflected outside the array azimuthal plane after entering the solid. Therefore, the two-dimensional images obtained from the linear array data may not be consistent with the fully three-dimensional structure of the ray paths. The analysis of this phenomenon for the special case of solid spheres reveals that the image, to a good approximation, corresponds to a section of the sphere that is parallel to the azimuthal plane and at a standoff distance from it. The distance increases with the angle that the normal to the surface forms relative to the azimuthal plane while it decreases as the velocity contrast between ice and the material of the sphere decreases. While this property is not expected to hold for more complex surfaces, the ray-based framework used in this study is applicable to more general surface configurations and can be used to correlate the images to the structure of the solid. These findings are relevant to the inspection of metallic components with complex geometry which represents a long-standing challenge in the field of nondestructive testing.</p>","PeriodicalId":23522,"journal":{"name":"Ultrasonics","volume":"157 ","pages":"107779"},"PeriodicalIF":4.1,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144822733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号