Search Results (154)

Ultrasonic phased arrays have shown promise in generating virtual texture haptics through haptics feedback points. However, factors such as skin vibration speed, amplitude variations, acoustic interference, and energy loss can influence textural haptics. In this study, using Spatiotemporal Modulation (STM), virtual textures are produced through movement of the focal point. The acoustic field of the ultrasonic phased array as well as the stress and strain experienced by the skin during texture perception are simulated by numerical analysis. At the same time, psychophysical experiments are conducted by volunteers to evaluate these textures. The experimental results indicate that as the focal rotation frequency increases, regions closer to the center experience more significant shear wave effects, resulting in longer shear wave propagation, reduced tangential stress amplitude, and a larger affected area. Moreover, as the frequency of the shear wave interference shifts, it results in increasingly complex textural representations. Full article

Surface finishing processes are required to produce the final shape of components made of the silicon-infiltrated silicon carbide composite Cesic^® from ECM (Engineered Ceramic Materials GmbH, 85452 Moosinning, Germany). Electrical discharge machining (EDM) is still the most effective method for manufacturing pockets and mounts in 3D-shaped ceramic satellite components for space applications. NC-grinding is not used, because it results in high grinding loads and rapid tool wear when applied to Cesic^®. In contrast to planar machining, tool wear during NC-grinding with small tools is particularly critical, as it alters the tool geometry and consequently causes deviations in the workpiece geometry. Ultrasonic-assisted grinding offers a promising alternative to overcome the low material removal rates and long processing times associated with EDM while simultaneously enhancing tool life, thus enabling more economical and reliable production. In this experimental study, both conventional grinding (CG) and ultrasonic-assisted grinding (UAG) processes are compared and used to machine Cesic^®. In order to verify the effect of the ultrasonic vibration, analyses of amplitude and frequency are performed. During machining experiments, the grinding loads are measured. The influence of different machining conditions on surface quality is evaluated concerning the roughness of the machined specimens. Compared to CG, UAG shows lower tool wear, owing to the self-cleaning effects caused by the ultrasonic oscillation of the tool. Consequently, the stability of the NC-grinding process is significantly improved. Full article

Conventional characterization of ultrasonic testing (UT) transducers primarily focuses on determining centre frequency and usable bandwidth. However, the relative amplitude distribution across different frequency components—particularly in low-frequency transducers used for civil engineering applications—remains largely overlooked. This paper introduces a comprehensive methodology to assess the influence of transducer coupling and specimen geometry on ultrasonic pulse velocity signals. The novel approach combines high-frequency laser Doppler vibrometry, real-time photoelastic imaging, and computer simulations using commercial semi-analytical wave-propagation software. The methodology is applied to the characterization of a 250 kHz UT transducer, with particular emphasis on how coupling with a solid test medium alters its frequency response. A glass specimen with an acoustic impedance comparable to that of concrete is used to simulate practical testing conditions. Vibration patterns recorded at the distal end of the specimen are analysed through computer simulations and validated experimentally using a novel photoelastic system capable of capturing wave–specimen interactions at ultrasonic frequencies in real time. The findings offer valuable insights into frequency-dependent signal behaviour and transducer–medium interactions, providing practical guidance for the design and optimization of UT inspections in concrete and other highly attenuative materials commonly encountered in civil engineering. Full article

Ultrasonic welding is an efficient and precise joining technology widely applied in aerospace, electronics, and medical industries. To overcome the limitations of conventional oscillators in high-frequency applications, this study proposes an innovative cylindrical oscillator design incorporating a 3.71 mm acoustic matching layer, operating at 1.76 MHz based on acoustic propagation theory. Through finite element analysis, a miniaturized oscillator with dimensions of 28 mm in diameter and 18 mm in height was developed, achieving optimized dynamic performance. Experimental validation via laser Doppler vibrometry confirmed a working surface amplitude exceeding 50 nm, while vibrations on non-functional walls were suppressed below 5 nm, with less than 5% deviation from simulation results. Prototype welding tests identified optimal process parameters—85 N welding pressure, 4 s welding time, and 3 s holding time—resulting in PVC joint tensile strengths exceeding 45 N. This work provides both an optimized hardware design and validated process guidelines, advancing the application of high-frequency micro-ultrasonic welding in precision, space-constrained environments. Full article

Cu–graphite composites are widely used in pantograph sliders and crane brushes. Conventional sintering protocols, however, mandate processing temperatures above 860 °C with prolonged holding periods, which inevitably introduce defects within copper matrices. Drawing inspiration from ultrasonic machining, this study presents an innovative ultrasonic-assisted hot-press sintering (UAHP) technique. Using this novel method, Cu–graphite composites with graphite contents ranging from 0 to 30 vol.% were fabricated at a reduced temperature of 700 °C and a short holding time of 10 min, achieving a ca. 160 °C reduction in densification temperature. Aside from the high densification efficiency, enhanced mechanical properties were also obtained for UAHP-sintered Cu–graphite composites. The Cu–15 vol.% graphite composite exhibited a yield strength of 232 MPa, showing only a 7.2% decrease compared to pure Cu. The friction coefficient decreased with increasing graphite content, reaching a plateau value of 0.140 at 15 vol.% graphite, representing a 77.16% reduction compared to pure Cu. The wear rate initially decreased but gradually increased with the increase in graphite content. The superior tribological performance is attributed to the insitu-formed graphite lubricating film, while the primary wear mechanisms are deemed to be oxidative and abrasive wear. The ultrasonic vibration provides additional sintering driving force and enhances elemental diffusion, establishing UAHP as an innovative technical route for fabricating composites with an optimized microstructure and superior comprehensive properties. Full article

Piezoelectric catalytic technology has attracted much attention in the field of dye wastewater treatment, in which inorganic piezoelectric materials have been widely studied. Its core mechanism involves utilizing the piezoelectric effect to generate positive and negative charges, which react with oxygen ions and hydroxyl radicals, respectively, to generate reactive oxygen species to degrade organic pollutants. Currently, while organic piezoelectric catalysts theoretically offer significant advantages such as low cost and high processability, there has been a notable lack of research in this area, which presents an innovative opportunity for the exploration of new organic piezoelectric catalytic materials. In this study, new research using natural nanocellulose (FC) suspension as an efficient organic piezoelectric catalyst is reported for the first time. The experimental results showed that the catalyst exhibited excellent degradation performance for Rhodamine B (RhB), Acid Orange 7 (AO7), and Methyl Orange (MO) under ultrasonic vibration (40 kHz, 200 W): the degradation rates reached 95.4%, 72.4%, and 31.2%, respectively, for 150 min, and the corresponding first-order reaction kinetic constants were 0.0205, 0.00858, and 0.00249 min⁻¹, respectively. It is noteworthy that the RhB solution can achieve the optimal degradation efficiency without adjustment under neutral initial pH conditions, which significantly enhances the practical application feasibility. The experimental results showed that the catalyst, with a measurable piezoelectric coefficient (d33 = 4.4 pm/V), exhibited excellent degradation performance for Rhodamine B (RhB), Acid Orange 7 (AO7), and Methyl Orange (MO) under ultrasonic vibration (40 kHz, 200 W). This organic piezoelectric catalyst, based on renewable biomass, innovatively converts mechanical vibration energy in the environment into the power to degrade pollutants. It not only expands the application boundaries of organic piezoelectric materials but also provides a new solution for sustainable water treatment technology, demonstrating extremely promising application prospects in the field of green and environmentally friendly water treatment. Full article

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

From the point of view of the intelligent operation and maintenance of high-speed train tracks, this paper examines the research status of high-speed train rail damage detection technology in the field of high-speed train track operation and maintenance detection in recent years, summarizes the damage detection methods for high-speed trains, and compares and analyzes different detection technologies and application research results. The analysis results show that the detection methods for high-speed train rail damage mainly focus on the research and application of non-destructive testing technology and methods, as well as testing platform equipment. Detection platforms and equipment include a new type of vortex meter, integrated track recording vehicles, laser rangefinders, thermal sensors, laser vision systems, LiDAR, new ultrasonic detectors, rail detection vehicles, rail detection robots, laser on-board rail detection systems, track recorders, self-moving trolleys, etc. The main research and application methods include electromagnetic detection, optical detection, ultrasonic guided wave detection, acoustic emission detection, ray detection, vortex detection, and vibration detection. In recent years, the most widely studied and applied methods have been rail detection based on LiDAR detection, ultrasonic detection, eddy current detection, and optical detection. The most important optical detection method is machine vision detection. Ultrasonic detection can detect internal damage of the rail. LiDAR detection can detect dirt around the rail and the surface, but the cost of this kind of equipment is very high. And the application cost is also very high. In the future, for high-speed railway rail damage detection, the damage standards must be followed first. In terms of rail geometric parameters, the domestic standard (TB 10754-2018) requires a gauge deviation of ±1 mm, a track direction deviation of 0.3 mm/10 m, and a height deviation of 0.5 mm/10 m, and some indicators are stricter than European standard EN-13848. In terms of damage detection, domestic flaw detection vehicles have achieved millimeter-level accuracy in crack detection in rail heads, rail waists, and other parts, with a damage detection rate of over 85%. The accuracy of identifying track components by the drone detection system is 93.6%, and the identification rate of potential safety hazards is 81.8%. There is a certain gap with international standards, and standards such as EN 13848 have stricter requirements for testing cycles and data storage, especially in quantifying damage detection requirements, real-time damage data, and safety, which will be the key research and development contents and directions in the future. Full article

Over recent years, ultrasonic atomization, especially with regard to liquid metals, has become an object of increased interest, mainly from industry, for additive manufacturing, but also from investigators, for research purposes. A strong correlation between the average particle size, distribution of particle sizes, and other process parameters like frequency and vibration amplitude was noted based on the analysis of available theoretical studies, simulations and experiments. The influence of parameters of the atomized fluid-like viscosity and surface tension on process parameters was also mentioned. The objective of this study is further research on the feasibility of using ultrasonic atomization to examine the properties of liquids, especially metals in liquid state. It attempts to close a gap in existing knowledge in searching for a new, possibly simple and cost-effective method to study the properties of liquid metals and further clarify the relationship between ultrasonic atomization parameters (amplitude, frequency, characteristics of metal being spilled on a vibrating surface) and obtained atomization results meant by average particle size and atomization time. Using numerical modeling (finite element method and computational fluid dynamics) as a methodology, combined with tests of using ultrasonic atomization as an instrument to determine properties of liquid metals, was considered as an introduction to a series of experiments. These tests were followed by real experiments that are also presented. At the first stage, numerical modeling was applied to a case of a specific liquid being spilled over a vibrating surface of different angles of inclination and specified, constant frequency and amplitude. The results of the simulation are in line with the current state of knowledge about ultrasonic atomization. Moreover, they can provide some more information on scalability, thus easing the comparison of the results of other experiments presented in the available literature. As a result, the relationship between fluid properties and the average size of atomized particles was demonstrated independently of the surface inclination angle. In the same way, the dependence of successful atomization on a sufficiently thin layer of a liquid was demonstrated. Thirdly, a correlation between the aforementioned layer thickness and the value of vibration amplitude has also been shown. Taking all the above into consideration, ultrasonic atomization can also be considered a research method and can be applied to study the properties of liquid metals. Further research, simulations and experimentation will be conducted to verify, develop and describe this method in full. Full article

Introduction: Intradural extramedullary and intramedullary spinal tumors are rare, complex to treat, and require advanced surgical techniques. Ultrasonic aspirators, commonly used for tumor removal, can cause sensory and motor deficits, including loss of motor evoked potentials (MEPs). This study aims to evaluate the safety and efficacy of ultrasonic aspirators in intramedullary tumor surgery using a swine model, comparing different systems and techniques. Methods: Ten pigs underwent D1-D3 laminectomy and myelotomy, with adipose tissue simulating a tumor. The ultrasonic aspirators were tested under varying conditions (fragmentation power, suction, application time, and vibration mode). The primary endpoint is to evaluate the impact of the chosen variables on motor function damage. The secondary endpoints are histological evaluation of the type of damage caused by ultrasound aspirators and the effect of steroid drugs on MEPs’ impairment recovery. Results: Ultrasound aspirators can cause a significant MEP signal reduction when used in continuous mode, with fragmentation power >30 for more than 2 min (p < 0.001). Suction does not affect MEPs. When used in alternating/pulsatile mode, fragmentation power and application time do not affect MEPs. The two-way ANOVA analysis on the interaction between fragmentation power and application time in continuous mode did not demonstrate a significant interaction (p = 0.155). Time alone does not affect motor damage (p = 0.873). Betamethasone can restore MEPs’ signal after damage if administered immediately. Conclusions: Using ultrasonic aspirators in an animal model of intramedullary tumor surgery is safe. The main factor that resulted in the responsibility of motor function impairment is the fragmentation power. Full article

This paper presents an intelligent navigation wearable device for visually impaired individuals. The system aims to improve their independent travel capabilities and reduce the negative emotional impacts associated with visible disability indicators in travel tools. It employs an RGB-D camera and an inertial measurement unit (IMU) sensor to facilitate real-time obstacle detection and recognition via advanced point cloud processing and YOLO-based target recognition techniques. An integrated intelligent interaction module identifies the core obstacle from the detected obstacles and translates this information into multidimensional auxiliary guidance. Users receive haptic feedback to navigate obstacles, indicating directional turns and distances, while auditory prompts convey the identity and distance of obstacles, enhancing spatial awareness. The intuitive vibrational guidance significantly enhances safety during obstacle avoidance, and the voice instructions promote a better understanding of the surrounding environment. The device adopts an arm-mounted design, departing from the traditional cane structure that reinforces disability labeling and social stigma. This lightweight mechanical design prioritizes user comfort and mobility, making it more user-friendly than traditional stick-type aids. Experimental results demonstrate that this system outperforms traditional white canes and ultrasonic devices in reducing collision rates, particularly for mid-air obstacles, thereby significantly improving safety in dynamic environments. Furthermore, the system’s ability to vocalize obstacle identities and distances in advance enhances spatial perception and interaction with the environment. By eliminating the cane structure, this innovative wearable design effectively minimizes social stigma, empowering visually impaired individuals to travel independently with increased confidence, ultimately contributing to an improved quality of life. Full article

A spin-coating technique was used to produce new thin films of fluoride-doped hydroxyapatite (HApF) and fluoride-doped hydroxyapatite in a dextran matrix (HApF-Dx) with the potential to be used as nanocoatings for various biomedical implants. The stability of the suspensions used in obtaining the thin films was confirmed by ultrasonic measurements with double-distilled water as a reference. The HApF and HApF-Dx thin films obtained by spin-coating showed diffraction patterns corresponding to hexagonal hydroxyapatite. The X-ray photoelectron spectroscopy studies confirmed the partial substitution of hydroxyl groups (-OH) by fluoride ions. The FTIR studies were conducted in order to highlight the presence of the functional group specific for the HAp in the samples and the influence of the dextran addition on the vibrational characteristics. The surface morphologies of the HApF and HApF-Dx thin films were explored using scanning electron microscopy (SEM), atomic force microscopy (AFM), and metallographic microscopy (MM). The surfaces of the HApF and HApF-Dx thin films were found to be smooth, homogenous, and nanostructured. The biocompatibility assays on HGF-1 cells confirmed that both coatings exhibited good cell viability for all the tested time intervals (24 and 48 h). The findings highlighted the potential of HApF and HApF-Dx coatings for biomedical applications. Additional information about the HGF-1 adherence and development on the surface of the HApF and HApF-Dx coatings was obtained using metallographic microscopy, scanning electron microscopy, and atomic force microscopy techniques. This research demonstrates that the spin-coating method can be successfully used to fabricate HApF and HApF-Dx nanocoatings for potential biomedical applications. Full article

In the field of nondestructive evaluation (NDE) using ultrasonic guided waves, accurately assessing the aging failure of insulation coatings remains a challenging and prominent research topic. While the application of ultrasonic guided waves in material testing has been extensively explored in the existing literature, there is still a significant gap in quantitatively evaluating the aging failure of insulation coatings. This study innovatively proposes an NDE method for assessing insulation coating aging failure by integrating signal processing and machine learning technologies, thereby effectively addressing both theoretical and practical gaps in this domain. The proposed method not only enhances the accuracy of detecting insulation coating aging failure but also introduces new approaches to non-destructive testing technology in related fields. To achieve this, an accelerated aging experiment was conducted to construct a cable database encompassing various degrees of damage. The effects of aging time, temperature, mechanical stress, and preset defects on coating degradation were systematically investigated. Experimental results indicate that aging time exhibits a three-stage nonlinear evolution pattern, with 50 days marking the critical inflection point for damage accumulation. Temperature significantly influences coating damage, with 130 °C identified as the critical threshold for performance mutation. Aging at 160 °C for 100 days conforms to the time-temperature superposition principle. Additionally, mechanical stress concentration accelerates coating failure when the bending angle is ≥90°. Among preset defects, cut defects were most destructive, increasing crack density by 5.8 times compared to defect-free samples and reducing cable life to 40% of its original value. This study employs Hilbert–Huang Transform (HHT) for noise reduction in ultrasonic guided wave signals. Compared to Fast Fourier Transform (FFT), HHT demonstrates superior performance in feature extraction from ultrasonic guided wave signals. By combining HHT with machine learning techniques, we developed a hybrid prediction model—HHT-LightGBM-PSO-SVM. The model achieved prediction accuracies of 94.05% on the training set and 88.36% on the test set, significantly outperforming models constructed with unclassified data. The LightGBM classification model exhibited the highest classification accuracy and AUC value (0.94), highlighting its effectiveness in predicting coating aging damage. This research not only improves the accuracy of detecting insulation coating aging failure but also provides a novel technical means for aviation cable health monitoring. Furthermore, it offers theoretical support and practical references for nondestructive testing and life prediction of complex systems. Future studies will focus on optimizing model parameters, incorporating additional environmental factors such as humidity and vibration to enhance prediction accuracy, and exploring lightweight algorithms for real-time monitoring. Full article

Promoting alternative modes of transportation such as cycling represents a valuable strategy to minimize environmental impacts, as confirmed in the main targets set out by the European Commission. In this regard, in cities throughout the world, there has been a significant increase in the construction of bicycle paths in recent years, requiring effective maintenance strategies to preserve their service levels. The continuous monitoring of road networks is required to ensure the timely scheduling of optimal maintenance activities. This involves regular inspections of the road surface, but there are currently no automated systems for monitoring cycle paths. In this study, an integrated monitoring and assessment system for cycle paths was developed exploiting Raspberry Pi technologies. In more detail, a low-cost Inertial Measurement Unit (IMU), a Global Positioning System (GPS) module, a magnetic Hall Effect sensor, a camera module, and an ultrasonic distance sensor were connected to a Raspberry Pi 4 Model B. The novel system was mounted on a e-bike as a test vehicle to monitor the road conditions of various sections of cycle paths in Rome, characterized by different pavement types and decay levels as detected using the whole-body vibration $a_{wz}$ index (ISO 2631 standard). Repeated testing confirmed the system’s reliability by assigning the same vibration comfort class in 74% of the cases and an adjacent one in 26%, with an average difference of 0.25 m/s², underscoring its stability and reproducibility. Data post-processing was also focused on integrating user comfort perception with image data, and it revealed anomaly detections represented by numerical acceleration spikes. Additionally, data positioning was successfully implemented. Finally, $a_{wz}$ measurements with GPS coordinates and images were incorporated into a Geographic Information System (GIS) to develop a database that supports the efficient and comprehensive management of surface conditions. The proposed system can be considered as a valuable tool to assess the pavement conditions of cycle paths in order to implement preventive maintenance strategies within budget constraints. Full article

Ultrasonic vibration can effectively improve the efficiency of rock breaking. In the actual process of drilling and breaking rocks, rocks will be affected by symmetrical ground stress in the formation. Therefore, in this paper, symmetrical confining pressure is applied to four surfaces of rocks by self-developed experimental equipment to simulate the symmetrical ground stress of the formation, and 64 groups of mixed tests are carried out with confining pressure, static load and vibration time as variables. The damage degree is evaluated by comparing the compressive strength of rock before and after vibration. The experimental results show that ultrasonic vibration can reduce the compressive strength of rock, increase the static load and vibration time during vibration, and increase the damage degree of rock. When the symmetric confining pressure increases, the formation and expansion of rock cracks can be inhibited, and the damage effect of ultrasonic high-frequency vibration on rock can be reduced. At the same time, a theoretical model is established to explain these phenomena. Full article