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20 pages, 4765 KB  
Article
Ultrasonic EDM for External Cylindrical Surface Machining with Graphite Electrodes: Horn Design and Hybrid NSGA-II–AHP Optimization of MRR and Ra
by Van-Thanh Dinh, Thu-Quy Le, Duc-Binh Vu, Ngoc-Pi Vu and Tat-Loi Mai
Machines 2025, 13(8), 675; https://doi.org/10.3390/machines13080675 - 1 Aug 2025
Viewed by 558
Abstract
This study presents the first investigation into the application of ultrasonic vibration-assisted electrical discharge machining (UV-EDM) using graphite electrodes for external cylindrical surface machining—an essential surface in the production of tablet punches and sheet metal-forming dies. A custom ultrasonic horn was designed and [...] Read more.
This study presents the first investigation into the application of ultrasonic vibration-assisted electrical discharge machining (UV-EDM) using graphite electrodes for external cylindrical surface machining—an essential surface in the production of tablet punches and sheet metal-forming dies. A custom ultrasonic horn was designed and fabricated using 90CrSi material to operate effectively at a resonant frequency of 20 kHz, ensuring stable vibration transmission throughout the machining process. A Box–Behnken experimental design was employed to explore the effects of five process parameters—vibration amplitude (A), pulse-on time (Ton), pulse-off time (Toff), discharge current (Ip), and servo voltage (SV)—on two key performance indicators: material removal rate (MRR) and surface roughness (Ra). The optimization process was conducted in two stages: single-objective analysis to maximize MRR while ensuring Ra < 4 µm, followed by a hybrid multi-objective approach combining NSGA-II and the Analytic Hierarchy Process (AHP). The optimal solution achieved a high MRR of 9.28 g/h while maintaining Ra below the critical surface finish threshold, thus meeting the practical requirements for punch surface quality. The findings confirm the effectiveness of the proposed horn design and hybrid optimization strategy, offering a new direction for enhancing productivity and surface integrity in cylindrical EDM applications using graphite electrodes. Full article
(This article belongs to the Section Advanced Manufacturing)
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22 pages, 2499 KB  
Article
Low-Power Vibrothermography for Detecting Barely Visible Impact Damage in CFRP Laminates: A Comparative Imaging Study
by Zulham Hidayat, Muhammet Ebubekir Torbali, Nicolas P. Avdelidis and Henrique Fernandes
Appl. Sci. 2025, 15(15), 8514; https://doi.org/10.3390/app15158514 - 31 Jul 2025
Cited by 1 | Viewed by 403
Abstract
This study explores the application of low-power vibrothermography (LVT) for detecting barely visible impact damage (BVID) in carbon fibre-reinforced polymer (CFRP) laminates. Composite specimens with varying impact energies (2.5–20 J) were excited using a single piezoelectric transducer with a nominal centre frequency of [...] Read more.
This study explores the application of low-power vibrothermography (LVT) for detecting barely visible impact damage (BVID) in carbon fibre-reinforced polymer (CFRP) laminates. Composite specimens with varying impact energies (2.5–20 J) were excited using a single piezoelectric transducer with a nominal centre frequency of 28 kHz, operated at a fixed excitation frequency of 28 kHz. Thermal data were captured using an infrared camera. To enhance defect visibility and suppress background noise, the raw thermal sequences were processed using principal component analysis (PCA) and robust principal component analysis (RPCA). In LVT, RPCA and PCA provided comparable signal-to-noise ratios (SNR), with no consistent advantage for either method across all cases. In contrast, for pulsed thermography (PT) data, RPCA consistently resulted in higher SNR values, except for one sample. The LVT results were further validated by comparison with PT and phased array ultrasonic testing (PAUT) data to confirm the location and shape of detected damage. These findings demonstrate that LVT, when combined with PCA or RPCA, offers a reliable method for identifying BVID and can support safer, more efficient structural health monitoring of composite materials. Full article
(This article belongs to the Special Issue Application of Acoustics as a Structural Health Monitoring Technology)
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19 pages, 4782 KB  
Article
PD Detection and Analysis Triggered by Metal Protrusion in GIS Through Various Methods
by Weifeng Xin, Wei Song, Manling Dong, Xiaochuan Huang, Xiaoshi Kou, Zhenyu Zhan, Xinyue Shi and Xutao Han
Appl. Sci. 2025, 15(14), 8113; https://doi.org/10.3390/app15148113 - 21 Jul 2025
Viewed by 457
Abstract
Defects in GIS can be effectively detected by detecting the partial discharge (PD). The common methods of detecting partial discharge are pulse current, ultrasonic and UHF (ultra-high frequency). However, the results of different methods may be different due to the different physical quantities [...] Read more.
Defects in GIS can be effectively detected by detecting the partial discharge (PD). The common methods of detecting partial discharge are pulse current, ultrasonic and UHF (ultra-high frequency). However, the results of different methods may be different due to the different physical quantities detected. It is important to research the differences between the PD detection methods for the PD detection and analysis. In this study, we designed metal protrusion defects in GIS, including protrusion on the conductor and enclosure. Then, we detected the PD of defects using pulse current, UHF and ultrasonic methods at the same time. The PRPD patterns, maximum discharge amplitude of different defects and PD inception voltage (PDIV) detected by the three methods were analyzed. The PRPD patterns and discharge amplitude of the different methods were very similar to each other, but the PDIVs were different. It can be concluded that the process from the PD inception to breakdown can be divided into four sections based on the PRPD and the maximum discharge amplitude. The similarity between the three methods is because their signals are all related to the pulse current during the PD process, and differences in their PDIVs are caused by the differences in sensitivity. The sensitivity of the pulse current is the lowest among the three methods due to its poor anti-jamming capability. The sensitivity of UHF is higher, and that of ultrasonic is the highest. Full article
(This article belongs to the Special Issue Advances in Monitoring and Fault Diagnosis for Power Equipment)
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17 pages, 3228 KB  
Article
Research on the Laser Ablation Threshold of the Graphene/Aluminum Foil Interface Surface
by Ying Xu, Yi Lv, Dongcheng Zhou, Yixin Chen and Boyong Su
Coatings 2025, 15(7), 853; https://doi.org/10.3390/coatings15070853 - 20 Jul 2025
Cited by 1 | Viewed by 633
Abstract
The aim was to investigate the impact of laser parameters on the surface morphology of ablated graphene and elucidate the interaction mechanism between carbon materials and femtosecond lasers. A pulsed laser with a wavelength of 1030 nm is employed to infer the ablation [...] Read more.
The aim was to investigate the impact of laser parameters on the surface morphology of ablated graphene and elucidate the interaction mechanism between carbon materials and femtosecond lasers. A pulsed laser with a wavelength of 1030 nm is employed to infer the ablation threshold of the surface and interface of graphene coatings formed through ultrasonic spraying. The ablation threshold of the coating–substrate interface is verified by numerical simulation. Incorporating the data of groove width and depth obtained from a three-dimensional profilometer and finite element simulation, an in-depth analysis of the threshold conditions of laser ablation in coating materials is accomplished. The results indicate that when the femtosecond laser frequency is 10 kHz, the pulse width is 290 fs, and the energy density reaches 0.057 J/cm2, the graphene material can be effectively removed. When the energy density is elevated to 2.167 J/cm2, a complete ablation of a graphite coating with a thickness of 1.5 μm can be achieved. The findings of this study validate the evolution law and linear relationship of ablation crater morphology, offering new references for microstructure design and the selection of controllable laser processing parameters. Full article
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23 pages, 6645 KB  
Article
Encapsulation Process and Dynamic Characterization of SiC Half-Bridge Power Module: Electro-Thermal Co-Design and Experimental Validation
by Kaida Cai, Jing Xiao, Xingwei Su, Qiuhui Tang and Huayuan Deng
Micromachines 2025, 16(7), 824; https://doi.org/10.3390/mi16070824 - 19 Jul 2025
Viewed by 2720
Abstract
Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. [...] Read more.
Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. This approach integrates in-depth electro-thermal simulation (LTspice XVII/COMSOL Multiphysics 6.3) with micro/nano-packaging processes (sintering/bonding). Firstly, a multifunctional double-pulse test board was designed for the dynamic characterization of SiC devices. LTspice simulations revealed the switching characteristics under an 800 V operating condition. Subsequently, a thermal simulation model was constructed in COMSOL to quantify the module junction temperature gradient (25 °C → 80 °C). Key process parameters affecting reliability were then quantified, including conductive adhesive sintering (S820-F680, 39.3 W/m·K), high-temperature baking at 175 °C, and aluminum wire bonding (15 mil wire diameter and 500 mW ultrasonic power/500 g bonding force). Finally, a double-pulse dynamic test platform was established to capture switching transient characteristics. Experimental results demonstrated the following: (1) The packaged module successfully passed the 800 V high-voltage validation. Measured drain current (4.62 A) exhibited an error of <0.65% compared to the simulated value (4.65 A). (2) The simulated junction temperature (80 °C) was significantly below the safety threshold (175 °C). (3) Microscopic examination using a Leica IVesta 3 microscope (55× magnification) confirmed the absence of voids at the sintering and bonding interfaces. (4) Frequency-dependent dynamic characterization revealed a 6 nH parasitic inductance via Ansys Q3D 2025 R1 simulation, with experimental validation at 8.3 nH through double-pulse testing. Thermal evaluations up to 200 kHz indicated 109 °C peak temperature (below 175 °C datasheet limit) and low switching losses. This work provides a critical process benchmark for the micro/nano-manufacturing of high-density SiC modules. Full article
(This article belongs to the Special Issue Recent Advances in Micro/Nanofabrication, 2nd Edition)
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13 pages, 7320 KB  
Article
Determination of Main Bearing Dynamic Clearance in a Shield Tunneling Machine Through a Broadband PMUT Array with a Decreased Blind Area and High Accuracy
by Guoxi Luo, Haoyu Zhang, Delai Liu, Wenyan Li, Min Li, Zhikang Li, Lin Sun, Ping Yang, Ryutaro Maeda and Libo Zhao
Sensors 2025, 25(13), 4182; https://doi.org/10.3390/s25134182 - 4 Jul 2025
Cited by 1 | Viewed by 479
Abstract
Traditional PMUT ultrasonic ranging systems usually possess a large measurement blind area under the integrated transmit–receive mode, dramatically limiting its distance measurement in confined spaces, such as when determining the clearance of large bearing components. Here, a broadband PMUT rangefinder was designed by [...] Read more.
Traditional PMUT ultrasonic ranging systems usually possess a large measurement blind area under the integrated transmit–receive mode, dramatically limiting its distance measurement in confined spaces, such as when determining the clearance of large bearing components. Here, a broadband PMUT rangefinder was designed by integrating six types of different cells with adjacent resonant frequencies into an array. Through overlapping and coupling of the bandwidths from the different cells, the proposed PMUTs showed a wide –6 dB fractional bandwidth of 108% in silicon oil. Due to the broadening of bandwidth, the device could obtain the maximum steady state with less excitation (5 cycles versus 14 cycles) and reduce its residual ring-down (ca. 6 μs versus 15 μs) compared with the traditional PMUT array with the same cells, resulting in a small blind area. The pulse–echo ranging experiments demonstrated that the blind area was effectively reduced to 4.4 mm in air or 12.8 mm in silicon oil, and the error was controlled within ±0.3 mm for distance measurements up to 250 mm. In addition, a specific ultrasound signal processing circuit with functions of transmitting, receiving, and processing ultrasonic waves was developed. Combining the processing circuit and PMUT device, the system was applied to determine the axial clearance of the main bearing in a tunneling machine. This work develops broadband PMUTs with a small blind area and high resolution for distance measurement in narrow and confined spaces, opening up a new path for ultrasonic ranging technology. Full article
(This article belongs to the Section Industrial Sensors)
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11 pages, 1586 KB  
Article
Quantification of Sensitization in Aluminum–Magnesium Alloys Through Frequency-Dependent Ultrasonic Attenuation
by Songwei Wang and Haiying Huang
Sensors 2025, 25(13), 3983; https://doi.org/10.3390/s25133983 - 26 Jun 2025
Viewed by 441
Abstract
Aluminum–Magnesium (Al–Mg) alloys undergo sensitization, i.e., the precipitations of β-phase (Al2Mg3) at the grain boundaries, when exposed to elevated temperature. This microstructural change increases the susceptibility of Al–Mg alloys to intergranular corrosion, exfoliation, and stress corrosion cracking. This study [...] Read more.
Aluminum–Magnesium (Al–Mg) alloys undergo sensitization, i.e., the precipitations of β-phase (Al2Mg3) at the grain boundaries, when exposed to elevated temperature. This microstructural change increases the susceptibility of Al–Mg alloys to intergranular corrosion, exfoliation, and stress corrosion cracking. This study introduces a time-frequency analysis (TFA) technique to determine the frequency-dependent ultrasonic attenuation parameter and correlate the frequency-attenuation slope to the Degree of Sensitization (DoS) developed in heat-treated Al–Mg alloy samples. Broadband pitch-catch signal was generated using a laser ultrasonic testing (LUT) system, from which the narrowband pitch-catch signal at different frequencies can be digitally generated. The attenuation parameters of sensitized Al–Mg samples were determined from these narrowband pitch-catch signals using the primary pulse-first echo (PP-FE) method. By identifying the frequency range within which the attenuation parameter is linearly proportional to the frequency, the slopes of the frequency-attenuation relationship were determined and correlated with the DoS values of the sample plates. The experimental results validate that the frequency-attenuation slope has a higher sensitivity and lower scattering as compared to other conventional ultrasonic attenuation measurement techniques. Full article
(This article belongs to the Special Issue Feature Papers in Optical Sensors 2025)
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20 pages, 9176 KB  
Article
Research on Drive and Detection Technology of CMUT Multi-Array Transducers Based on MEMS Technology
by Chenyuan Li, Jiagen Chen, Chengwei Liu, Yao Xie, Yangyang Cui, Shiwang Zhang, Zhikang Li, Libo Zhao, Guoxing Chen, Shaochong Wei, Yu Gao and Linxi Dong
Micromachines 2025, 16(6), 604; https://doi.org/10.3390/mi16060604 - 22 May 2025
Viewed by 2641
Abstract
This paper presents an ultrasonic driving and detection system based on a CMUT array using MEMS technology. Among them, the core component CMUT array is composed of 8 × 8 CMUT array elements, and each CMUT array element contains 6 × 6 CMUT [...] Read more.
This paper presents an ultrasonic driving and detection system based on a CMUT array using MEMS technology. Among them, the core component CMUT array is composed of 8 × 8 CMUT array elements, and each CMUT array element contains 6 × 6 CMUT units. The collapse voltage of a single CMUT unit obtained through finite element analysis is 95.91 V, and the resonant frequency is 3.16 MHz. The driving section achieves 64-channel synchronous driving, with key parameters including an adjustable excitation signal frequency ranging from 10 kHz to 5.71 MHz, a delay precision of up to 1 ns, and an excitation duration of eight pulse cycles. For the echo reception, a two-stage amplification circuit for high-frequency weak echoes with 32 channels was designed, achieving a gain of 113.72 dB and −3 dB bandwidth of 3.89 MHz. Simultaneously, a 32-channel analog-to-digital conversion based on a self-calibration algorithm was implemented, with a sampling rate of 50 Mbps and a data width of 10 bits. Finally, the experimental results confirm the successful implementation of the driving system’s designed functions, yielding a center frequency of 1.4995 MHz and a relative bandwidth of 127.9%@−6 dB for the CMUT operating in silicone oil. This paper successfully conducted the transmit–receive integrated experiment of the CMUT and applied Butterworth filtering to the echo data, resulting in high-quality ultrasonic echo signals that validate the applicability of the designed CMUT-based system for ultrasonic imaging. Full article
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20 pages, 9417 KB  
Article
The Effect of Ultrasonic Probes on the Ability to Inspect Adhesive Joints
by Jakub Kowalczyk
Materials 2025, 18(9), 1946; https://doi.org/10.3390/ma18091946 - 24 Apr 2025
Viewed by 546
Abstract
Ultrasonic tests are widely used, both in laboratory and industrial settings, to assess the quality of joints, mainly welded joints. Studies are being carried out on the possibility of ultrasonic evaluation of adhesive joints. This study was conducted using signal analysis in the [...] Read more.
Ultrasonic tests are widely used, both in laboratory and industrial settings, to assess the quality of joints, mainly welded joints. Studies are being carried out on the possibility of ultrasonic evaluation of adhesive joints. This study was conducted using signal analysis in the time and frequency domains. The ultrasonic probes used in the tests were selected on the basis of the properties of the test elements. For example, when testing welded joints, ultrasonic probes with a water delay line bounded by a thin diaphragm were used. Since adhesives have different acoustic properties, it is necessary to evaluate the capabilities of different ultrasonic probes to test adhesive joints. Tests were conducted for two different adhesives (cyanoacrylate and structural) and eight ultrasonic probes with a frequency range of 1.660 to 13.70 MHz. In the literature, no studies have analyzed the use of ultrasonic probes at such different frequencies. Frequency has the greatest effect on the attenuation of ultrasonic waves and the ultrasonic wavelength, and it was noted that the adhesive could cause a 25 percent change in the maximum frequency of the ultrasonic pulse. It was also found that it is necessary to make reference samples before ultrasonic testing of adhesive joints, since specific frequencies can produce erroneous signals for the selected adhesives. Full article
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15 pages, 28548 KB  
Article
Non-Contact Laser Ultrasound Detection of Internal Gas Defects in Lithium-Ion Batteries
by Dongxia Tang, Chenguang Xu, Guidong Xu, Sen Cui and Sai Zhang
Sensors 2025, 25(7), 2033; https://doi.org/10.3390/s25072033 - 25 Mar 2025
Cited by 1 | Viewed by 1511
Abstract
Non-contact laser ultrasonic detection technology provides an innovative solution for evaluating the internal conditions of lithium-ion batteries (LIBs), offering significant advantages in gas defect assessment and structural defect identification. This study proposes a method for evaluating internal gas defects in LIBs based on [...] Read more.
Non-contact laser ultrasonic detection technology provides an innovative solution for evaluating the internal conditions of lithium-ion batteries (LIBs), offering significant advantages in gas defect assessment and structural defect identification. This study proposes a method for evaluating internal gas defects in LIBs based on a non-contact laser ultrasonic system. The system uses a pulsed laser to generate ultrasonic waves, with a full-optical probe receiving the signals, enabling high-resolution imaging of the internal features of the battery. The study analyzes key ultrasonic characteristics under different laser parameters (energy, pulse width, and focal length) and their correlation with defective regions. Through both time-domain and frequency-domain analysis of the ultrasonic features, the results demonstrate that the signal amplitude attenuation characteristics of ultrasound in media with acoustic impedance mismatches can be used for precise detection and quantitative characterization of gas defect regions within the battery. This non-contact technology offers a promising method for real-time, non-destructive monitoring of the internal condition of lithium-ion batteries, significantly enhancing battery safety and reliability. Full article
(This article belongs to the Topic Advances in Non-Destructive Testing Methods, 3rd Edition)
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12 pages, 3121 KB  
Article
Analysis and Tracking of Intra-Needle Ultrasound Pleural Signals for Improved Anesthetic Procedures in the Thoracic Region
by Fu-Wei Su, Chia-Wei Yang, Ching-Fang Yang, Yi-En Tsai, Wei-Nung Teng and Huihua Kenny Chiang
Biosensors 2025, 15(4), 201; https://doi.org/10.3390/bios15040201 - 21 Mar 2025
Viewed by 679
Abstract
Background: Ultrasonography is commonly employed during thoracic regional anesthesia; however, its accuracy can be affected by factors such as obesity and poor penetration through the rib window. Needle-sized ultrasound transducers, known as intra-needle ultrasound (INUS) transducers, have been developed to detect the pleura [...] Read more.
Background: Ultrasonography is commonly employed during thoracic regional anesthesia; however, its accuracy can be affected by factors such as obesity and poor penetration through the rib window. Needle-sized ultrasound transducers, known as intra-needle ultrasound (INUS) transducers, have been developed to detect the pleura and fascia using a one-dimensional radio frequency mode ultrasound signal. In this study, we aimed to use time-frequency analysis to characterize the pleural signal and develop an automated tool to identify the pleura during medical procedures. Methods: We developed an INUS system and investigated the pleural signal it measured by establishing a phantom study, and an in vivo animal study. Signals from the pleura, endothoracic fascia, and intercostal muscles were analyzed. Additionally, we conducted time- and frequency-domain analyses of the pleural and alveolar signals. Results: We identified the unique characteristics of the pleura, including a flickering phenomenon, speckle-like patterns, and highly variable multi-band spectra in the ultrasound signal during the breathing cycle. These characteristics are likely due to the multiple reflections from the sliding visceral pleura and alveoli. This automated identification of the pleura can enhance the safety for thoracic regional anesthesia, particularly in difficult cases. Conclusions: The unique flickering pleural signal based on INUS can be processed by time-frequency domain analysis and further tracked by an auto-identification algorithm. This technique has potential applications in thoracic regional anesthesia and other interventions. However, further studies are required to validate this hypothesis. Key Points Summary: Question: How can the ultrasound pleural signal be distinguished from other tissues during breathing? Findings: The frequency domain analysis of the pleural ultrasound signal showed fast variant and multi-band characteristics. We suggest this is due to ultrasound distortion caused by the interface of multiple moving alveoli. The multiple ultrasonic reflections from the sliding pleura and alveoli returned in variable and multi-banded frequency. Meaning: The distinguished pleural signal can be used for the auto-identification of the pleura for further clinical respiration monitoring and safety during regional anesthesia. Glossary of Terms: intra-needle ultrasound (INUS); radio frequency (RF); short-time Fourier transform (STFT); intercostal nerve block (ICNB); paravertebral block (PVB); pulse repetition frequency (PRF). Full article
(This article belongs to the Special Issue Biosensors for Monitoring and Diagnostics)
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12 pages, 6050 KB  
Article
Nondestructive Monitoring of Textile-Reinforced Cementitious Composites Subjected to Freeze–Thaw Cycles
by Nicolas Ospitia, Ali Pourkazemi, Eleni Tsangouri, Thaer Tayeh, Johan H. Stiens and Dimitrios G. Aggelis
Materials 2024, 17(24), 6232; https://doi.org/10.3390/ma17246232 - 20 Dec 2024
Cited by 1 | Viewed by 1003
Abstract
Cementitious materials are susceptible to damage not only from mechanical loading, but also from environmental (physical, chemical, and biological) factors. For Textile-Reinforced Cementitious (TRC) composites, durability poses a significant challenge, and a reliable method to assess long-term performance is still lacking. Among various [...] Read more.
Cementitious materials are susceptible to damage not only from mechanical loading, but also from environmental (physical, chemical, and biological) factors. For Textile-Reinforced Cementitious (TRC) composites, durability poses a significant challenge, and a reliable method to assess long-term performance is still lacking. Among various durability attacks, freeze–thaw can induce internal cracking within the cementitious matrix, and weaken the textile–matrix bond. Such cracks result from hydraulic, osmotic, and crystallization pressure arising from the thermal cycles, leading to a reduction in the stiffness in the TRC composites. Early detection of freeze–thaw deterioration can significantly reduce the cost of repair, which is only possible through periodic, full-field monitoring of the composite. Full-field monitoring provides a comprehensive view of the damage distribution, offering valuable insights into the causes and progression of damage. The crack location, size, and pattern give more information than that offered by single-point measurement. While visual inspections are commonly employed for crack assessment, they are often time-consuming. Technological advances now enable crack pattern classification based on high-quality surface images; however, these methods only provide information limited to the surface. Elastic wave-based non-destructive testing (NDT) methods are highly sensitive to the material’s mechanical properties, and therefore are widely used for damage monitoring. On the other hand, electromagnetic wave-based NDTs offer the advantage of fast, non-contact measurements. Micro- and millimeter wave frequencies offer a balance of high resolution and wave penetration, although they have not yet been sufficiently explored for detecting damage in cementitious composites. In this study, TRC specimens were subjected to up to 150 freeze–thaw cycles and monitored using a combination of active elastic and electromagnetic wave-based NDT mapping methods. For this purpose, transmission measurements were conducted at multiple points, with ultrasonic pulse velocity (UPV) employed as a benchmark and, for the first time, millimeter wave (MMW) spectrometry applied. This multi-modal mapping approach enabled the tracking of damage progression, and the identification of degraded zones. Full article
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18 pages, 3844 KB  
Article
Experimental Study of Mechanical Wave Propagation in Solidifying Cement-Based Composites
by Luboš Jakubka, Libor Topolář, Anna Nekorancová, Richard Dvořák, Kristýna Hrabová, Felix Černý, Szymon Skibicki and Luboš Pazdera
Materials 2024, 17(23), 5971; https://doi.org/10.3390/ma17235971 - 6 Dec 2024
Viewed by 1602
Abstract
In this paper, a new measurement procedure is presented as an experimental study. In this experimental study, a measurement system using the pass-through pulsed ultrasonic method was used. The pilot application of the measurement setup was to monitor mechanical wave changes during the [...] Read more.
In this paper, a new measurement procedure is presented as an experimental study. In this experimental study, a measurement system using the pass-through pulsed ultrasonic method was used. The pilot application of the measurement setup was to monitor mechanical wave changes during the solidification and hardening of fine-grained cement-based composites. The fine-grained composites had different water–cement ratios. The measured results show apparent differences in the recorded mechanical wave parameters. Significant differences were observed in the waveforms of the amplitude increase in the passing mechanical waves. At the same time, the frequency spectra of the five most dominant frequencies are presented, where the frequency lines are clear, indicating the quality of the hydration process. Based on the results, it can be concluded that the new method is usable for fine-grained cement-based materials but is not limited to that. The advantages of this method are its high variability and non-destructive character. The experimental study also outlines the possible future applications of the pulsed passage ultrasonic method. Full article
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14 pages, 5226 KB  
Article
Porous Metal Backing for High-Temperature Ultrasonic Transducers
by Guy Feuillard, Dang Chi Nguyen, Marc Lethiecq, Mathieu Jean and Frédéric Navacchia
Acoustics 2024, 6(4), 1074-1087; https://doi.org/10.3390/acoustics6040058 - 25 Nov 2024
Viewed by 1698
Abstract
Improving the performance of high-temperature ultrasonic transducers is a goal of major importance in many industrial applications. To this aim, we propose to use porous metals that support high temperatures as backings. Thus, the acoustic properties of stainless steel and porous stainless steel [...] Read more.
Improving the performance of high-temperature ultrasonic transducers is a goal of major importance in many industrial applications. To this aim, we propose to use porous metals that support high temperatures as backings. Thus, the acoustic properties of stainless steel and porous stainless steel with porosity of 25% and 35% are determined at ambient temperature and up to 400 °C. Over the temperature range, the longitudinal wave velocity variation is comprised between 5% and 6% in the porous metals. We find that temperature does not significantly affect the attenuation in the material. The pulse-echo response and frequency response of a LiNbO3-based transducer with a porous backing are simulated using a one dimensional electroacoustic model. These simulations, compared to those of a reference transducer, show that the axial resolution with such a design allows these transducers to be used for imaging and/or Non-Destructive Testing and evaluation at high temperature. Full article
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15 pages, 5501 KB  
Article
Recognition of Heat-Damaged Corn Seeds Based on Fusion of Laser Ultrasonic Signal and Infrared Image Features
by Tao Lu, Zihua Wang, Zhongyi Zhao and Zhike Zhao
Agronomy 2024, 14(11), 2567; https://doi.org/10.3390/agronomy14112567 - 1 Nov 2024
Cited by 1 | Viewed by 1095
Abstract
Corn is widely cultivated on a global scale. However, high temperatures during storage and transportation can lead to thermal damage to the kernels, negatively impacting their quality. Traditional methods for identifying heat-damaged grains primarily rely on manual inspection, which is characterized by low [...] Read more.
Corn is widely cultivated on a global scale. However, high temperatures during storage and transportation can lead to thermal damage to the kernels, negatively impacting their quality. Traditional methods for identifying heat-damaged grains primarily rely on manual inspection, which is characterized by low efficiency and accuracy. This study proposes a novel identification method that integrates laser ultrasonic signals with infrared image texture features. A pulsed laser stimulates the seeds to generate laser ultrasonic signals, while an infrared camera captures infrared images of the seeds. We extract time-domain, frequency-domain, and Hilbert-domain features from the laser ultrasonic signals, in addition to texture features from the infrared images. These features are combined using Canonical Correlation Analysis (CCA). Subsequently, the fused features are classified using a Backpropagation (BP) neural network, Support Vector Machine (SVM), and Particle Swarm Optimization–Support Vector Machine (PSO–SVM). The results indicate that the recognition rate achieved with the fused ‘signal-image’ features reaches 99.17%, providing a novel approach for detecting heat-damaged corn seeds. Full article
(This article belongs to the Section Precision and Digital Agriculture)
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