Search Results (238)

The lateral vibration of propulsion shafting is a critical factor affecting the acoustic stealth performance of underwater vehicles. As the main vibration isolation component in transmitting vibrational energy, the damping efficiency of the propulsion shafting support system (PSSS) holds particular significance. This study investigates the dynamic characteristics of the PSSS with the integral squeeze film damper (ISFD). A dynamic model of ISFD–PSSS is developed to systematically analyze the effects of shaft speed and external load on its dynamic behavior. Three test bearings (conventional, 1S, and 3S structure) are designed and manufactured to study the influence of damping structure layout scheme, damping fluid viscosity, unbalanced load, and shaft speed on the vibration reduction ability of ISFD–PSSS through axis orbit and vibration velocity. The results show that the damping effects of ISFD–PSSS are observed across all test conditions, presenting distinct nonlinear patterns. Suppression effectiveness is more pronounced in the vertical direction compared to the horizontal direction. The 3S structure bearing has better vibration reduction and structural stability than other schemes. The research results provide a reference for the vibration control method of rotating machinery. Full article

The subject of ship structural dynamics has faced new technological obstacles due to scientific and technological advancements, and one of the main concerns in related sectors is how to effectively reduce the vibration levels of different ships. This article focuses on the application scenarios of ship floating raft isolation systems, establishing a wave propagation model for acoustic black hole (ABH) structures based on the idea of the ABH effect. Then, a transfer matrix model for serially connected ABH structures is derived, which serves as a basis for subsequent structural designs. Second, the finite element method is used to study the energy distribution and vibration characteristics of a symmetrically distributed periodic non-uniform multi-level ABH structure. Meanwhile, it examines its bandgap distribution under a one-dimensional periodic arrangement and then investigates the vibration properties of non-uniform multi-level ABH thin-plate constructions with different periods from the perspective of engineering applications. Moreover, parameter optimization studies of non-uniform multi-level ABH structures with finite periods are carried out with an emphasis on engineering applications. The first step is to use the design space to determine the range of values for the parameters that need to be optimized. The hyper Latin cubic sampling method is then employed to select samples, and the EI criterion and PSO optimization algorithm are applied to add new samples to improve the Kriging surrogate model’s accuracy. When the optimal structural parameters have been determined, they are applied to the raft rib plate to verify the isolation effect of the non-uniform multi-level ABH structure by analyzing the vibration level difference at specific raft positions before and after embedding it. Full article

The presented article analyzes the impact of internal defects on the modal responses of polyamide parts subjected to bending. Samples with defects of various sizes (0, 3, 5, 7, and 10 mm) located at the neutral bending line were tested. Modal properties were measured via an acoustic and a vibration sensor, using impulse excitation and fast Fourier transform (FFT) analysis. Modal properties include peak frequency, damping and amplitude. Non-defective samples show lower peak frequency and stronger amplitude for both detectors. Moreover, defects larger than 3 mm have minimal impact on peak frequency. The vibration detector is more sensitive to delamination presented at 7 and 10 mm defects. In addition, elevated peak frequency at 3 mm is the result of local hardening at the defect edge. Moreover, a neutral line position reduces damping when the defect size approaches 5 mm. Conversely, acoustic detectors ignore delamination and reveal lower damping and amplitude at 7 and 10 mm defects. Furthermore, internal sound diffusion from 3 and 5 mm defects enhances air losses and damping. Acoustic detectors only evaluate fault size and position, whereas vibrational detectors may detect local reinforcement and delamination more easily. These results highlight the importance of choosing the right detector according to the location, size, and specific modal characteristics of defects. Full article

Automotive NVH (Noise, Vibration, and Harshness) performance significantly impacts driving comfort and traffic safety. Vehicles exhibiting superior NVH characteristics are more likely to achieve consumer acceptance and enhance their competitiveness in the marketplace. In the development of automotive NVH performance, traditional vibration reduction methods have proven to be mature and widely implemented. However, due to constraints related to size and weight, these methods typically address only high-frequency vibration control. Consequently, they struggle to effectively mitigate vehicle body and component vibration noise at frequencies below 200 Hz. In recent years, acoustic metamaterials (AMMs) have emerged as a promising solution for suppressing low-frequency vibrations. This development offers a novel approach for low-frequency vibration control. Nevertheless, conventional design methodologies for AMMs predominantly rely on empirical knowledge and necessitate continuous parameter adjustments to achieve desired bandgap characteristics—an endeavor that entails extensive calculations and considerable time investment. With advancements in machine learning technology, more efficient design strategies have become feasible. This paper presents a tandem neural network (TNN) specifically developed for the design of AMMs. The trained neural network is capable of deriving both the bandgap characteristics from the design parameters of AMMs as well as deducing requisite design parameters based on specified bandgap targets. Focusing on addressing low-frequency vibrations in the back frame of automobile seats, this method facilitates the determination of necessary AMMs design parameters. Experimental results demonstrate that this approach can effectively guide AMMs designs with both speed and accuracy, and the designed AMMs achieved an impressive vibration attenuation rate of 63.6%. Full article

This research introduces an innovative passive vibration control methodology employing acoustic black hole (ABH) structures to mitigate vibration transmission in electric automotive steering machines—a prevalent issue adversely affecting driving comfort and vehicle safety. Leveraging the inherent bending wave manipulation properties of ABH configurations, we conceive an integrated vibration suppression framework synergizing advanced computational modeling with intelligent optimization algorithms. A high-fidelity finite element (FEM) model integrating ABH-attached steering machine system was developed and subjected to experimental validation via rigorous modal testing. To address computational challenges in design optimization, a hybrid modeling strategy integrating parametric design (using Latin Hypercube Sampling, LHS) with Kriging surrogate modeling is proposed. Systematic parameterization of ABH geometry and damping layer dimensions generated 40 training datasets and 12 validation datasets. Surrogate model verification confirms the model’s precise mapping of vibration characteristics across the design space. Subsequent multi-objective genetic algorithm optimization targeting RMS velocity suppression achieved substantial vibration attenuation (29.2%) compared to baseline parameters. The developed methodology provides automotive researchers and engineers with an efficient suitable design tool for vibration-sensitive automotive component design. Full article

With the global transition towards renewable energy, pumped storage has become a pivotal technology for large-scale energy storage, playing an essential role in peak load regulation, frequency control, and ensuring the stability of modern power systems. As the core equipment of pumped storage power stations, pump-turbines operate under complex and frequently changing conditions. These units are required to switch repeatedly between pumping, generating, and transitional modes, giving rise to significant fluid–structure interactions (FSIs). Such interactions have a profound impact on the operational performance and stability of the units. This review provides a comprehensive summary of current research on FSIs in pump-turbines, encompassing both experimental investigations and numerical simulations. Key topics discussed include internal flow dynamics, vibration and acoustic characteristics, and structural responses such as runner deformation and stress distribution. Various numerical coupling strategies for FSI modeling are also examined in detail. Despite progress in this field, several challenges remain, including the complexity of multidisciplinary coupling, the difficulty in developing and solving accurate models, and limitations in predictive capabilities. This review highlights the critical requirements for advancing FSI research in pump-turbines and identifies gaps in the current literature that warrant further investigation. Full article

This study presents a comprehensive investigation of acoustic emission (AE) characteristics for condition monitoring of rolling bearings in passenger ropeway systems. Through controlled laboratory experiments and field validation across multiple operational ropeways, we establish an optimized AE-based diagnostic framework. Key findings demonstrate that resonant VS150-RIC sensors outperform broadband sensors in defect detection, showing greater energy response at characteristic frequencies for inner race defects. The RMS parameter emerges as a robust diagnostic indicator, with defective bearings exhibiting periodic peaks and higher mean RMS values. Field tests reveal progressive RMS escalation preceding visible damage, enabling predictive maintenance. Furthermore, we develop a novel Paligemma LLM model for automated wear detection using AE time-domain images. The research validates the AE technology’s superiority over conventional vibration methods for low-speed bearing monitoring, providing a scientifically grounded approach for safety-critical ropeway maintenance. Full article

The vibration noise of plate structures in engineering is strongly related to the modal resonance, and modal design is the key to improve the dynamic characteristics of plate structures and avoid structural resonance. This paper investigates the dynamic and mode characteristics for an edge periodic acoustic black hole plate structure to provide a new approach to vibration and sound attenuation in plate structures. Firstly, based on the principles of symmetry and periodicity, this work presents the geometrical modeling and mathematical description of a rectangular plate with symmetrical periodic acoustic black holes at its edge. Then, it presents the dynamic modeling of a rectangular plate with periodic acoustic black holes at its edge via the “remove-and-fill” substitution method, which reveals the effects of the structural parameters and period distribution, etc., on the modal characteristics of vibration. The study indicates that the power law index, radius, number and configuration (e.g., semicircular, rectangular block shape) of the edge periodic acoustic black holes significantly affect the modal frequency of the rectangular plate, and increasing the radius of the acoustic black holes or the number of the black holes results in a decrease in the modal frequency of the rectangular plate. Moreover, the four-side symmetric layout achieves broader modal frequency modulation, while semicircular acoustic black holes can achieve a lower modal frequency compared with the rectangular wedge-shaped acoustic black hole. The theoretical model is verified by finite element simulation (FEM) and experiments, in which the errors of the first six modal frequencies are within 2%. The research in this paper provides a theoretical basis for the realization of modal frequency control in plate structures and the suppression of structural resonance through the design of edge periodic acoustic black hole structures. Full article

During prolonged deployment, deep-sea acoustic submerged buoys may undergo displacement and torsional deformation of their main floating body under turbulent flows, which degrades the quality of acquired sensor data and introduces vibration-induced noise that interferes with acoustic measurements. This paper presents a novel structural design for acoustic buoy main bodies based on hydrodynamic principles. We performed fluid-structure interaction (FSI) simulations to evaluate the dynamic response characteristics of the structure in deep-sea conditions, including computational analysis of velocity and pressure field distributions surrounding the buoy. Leveraging pressure data derived from computational fluid dynamics (CFD) simulations, we developed an innovative vibration noise quantification methodology. This approach employs plane wave excitation with equivalent pressure magnitude to simulate hydrodynamic loading effects while incorporating tripartite coupling mechanisms among fluid, structural, and acoustic domains. The simulated vibration noise profiles establish environmental baseline noise levels for onboard acoustic monitoring instruments, thereby enhancing measurement fidelity. Full article

The application of double-layer shell structure is very common in some situations that require complex loads and vibrations, such as key components such as the shell and wings of aerospace engines, and the shell of underwater vehicles. Many authors have conducted research on the vibration and acoustic radiation characteristics of double-layer cylindrical shells. By adding reinforcement and ribs between the double-layer cylindrical shells and optimizing structural design, passive vibration control techniques can effectively solve high frequency vibration problems, but the impact on mid to low frequency vibrations is still limited. Therefore, this article conducts theoretical research on a novel active vibration control method that inserts an active actuator between a double-layer cylindrical shell to achieve better mid low frequency vibration control effects. Firstly, the substructure admittance method is applied to analytically and dynamically model a double-layer cylindrical thin shell structure with active support, and the vibration power flow of the system is theoretically derived to evaluate the vibration reduction effect. Then, numerical simulation analysis was conducted on the influence of different configurations of six feedback control parameters, time delays, and other factors on the vibration power flow. Finally, based on the image, the conclusion is drawn that all six feedback control parameters can improve the vibration control effect of the coupled system to a certain extent, but not every feedback control parameter has a prominent effect, and the effective range of some parameters is relatively narrow. Full article

High-frequency injection (HFI) is widely adopted for the sensorless control of permanent magnet synchronous motors (PMSMs) at low speeds. However, conventional HFI strategies relying on fixed-frequency carrier modulation and square-wave injection concentrate current harmonic energy within narrow spectral bands, thereby inducing pronounced high-frequency motor vibrations and noise. To mitigate this issue, this paper proposes a noise suppression strategy based on synchronized periodic frequency modulation (PFM) of both the carrier and high-frequency square-wave signals. By innovatively synchronizing the periodic modulation of the triangular carrier in space vector pulse width modulation (SVPWM) with the injected high-frequency square wave, harmonic energy dispersion and noise reduction are achieved, substantially lowering peak acoustic emissions. First, the harmonic characteristics of the voltage-source inverter output under symmetric triangular carrier SVPWM are analyzed within a sawtooth-wave PFM framework. Concurrently, a harmonic current model is developed for the high-frequency square-wave injection method, enabling the precise derivation of harmonic components. A frequency-synchronized modulation strategy between the carrier and injection signals is proposed, with a rigorous analysis of its harmonic suppression mechanism. The rotor position is then estimated via high-frequency signal extraction and a normalized phase-locked loop (PLL). Comparative simulations and experiments confirm significant noise peak attenuation compared to conventional methods, while position estimation accuracy remains unaffected. This work provides both theoretical and practical advancements for noise-sensitive sensorless motor control applications. Full article

As a novel energy-saving and maneuvering device for ships, the gate rudder system (GRS) functions similarly to an accelerating duct. While providing additional thrust, its independently controllable rudder blades on either side of the propeller also enhance ship maneuverability. The GRS was first fully implemented on a container ship in Japan, demonstrating improved propulsion efficiency, fuel savings, and excellent performance in maneuvering, noise, and vibration reduction. In recent years, extensive research has been conducted on the hydrodynamic performance, acoustic characteristics, and energy-saving effects of the GRS. However, certain gaps remain in the research, such as a lack of systematic studies on optimal GRS design in the publicly available literature. Only Ahmet Yusuf Gurkan has investigated the sensitivity of propulsion performance to parameters such as rudder angle, rudder X-shift, rudder tip skewness, and blade tip chord ratio. Therefore, this study employs the JBC benchmark vessel and adopts a coupled CFD-CAESES approach to develop a matching optimization design for the GRS. The influence of geometric parameters—including GRS airfoil camber, maximum camber position, chord length, thickness, distance from the leading edge to the propeller plane, and the gap between the GRS and propeller blades—on ship propulsion performance is investigated. The sensitivity of these design variables to propulsion performance is analyzed, and the optimal GRS design is selected to predict and evaluate its energy-saving effects. This research establishes a rapid and comprehensive CFD-based optimization methodology for GRS matching design. The findings indicate that the gap between the GRS and propeller, the distance from the GRS to the stern, and the airfoil camber of the GRS significantly contribute to various performance responses. After GRS installation, the viscous pressure resistance of the JBC ship decreases, resulting in an 8.05% energy-saving effect at the designated speed. Full article

For relaxor ferroelectric single crystal (1 − x)Pb(Mg_1/3Nb_2/3)O₃ − xPbTiO₃ (PMN-PT), through reasonable component regulation and electric field polarization, an orthogonal mm² point group structure can be obtained, which has high piezoelectric constants and is, therefore, a desired substrate material for lateral-field-excited (LFE) bulk acoustic wave (BAW) devices. In this work, acoustic wave resonance characteristics of (zxt) 45° PMN-PT BAW devices with LFE are investigated. Firstly, Mindlin first-order plate theory is used to obtain vibration governing equations of orthorhombic crystals excited by a lateral electric field. By analyzing the electrically forced vibrations of the finite plate, the basic vibration characteristics, such as motional capacitance, resonant frequency, and mode shape are obtained, and influences of different electrode parameters on resonance characteristics of the device are investigated. In addition, the effects of the structure parameters on the mass sensitivity of the devices are analyzed and further verified by FEM simulations. The model presented in this study can be conveniently used to optimize the structural parameters of LFE bulk acoustic wave devices based on orthorhombic crystals, which is crucial to obtain good resonance characteristics. The results provide an important basis for the design of LFE bulk acoustic wave resonators and sensors by using PMN-PT orthorhombic crystals. Full article

During geomagnetic storms, a geomagnetically induced current (GIC) flows into grounding transformers, potentially causing anomalous vibrations and audible noise in internal components. This study establishes an electromagnetic–mechanical–acoustic coupling (EMAC) model to characterize the multi-physics interactions in transformers under GIC interference. Based on the measured data, the GIC is classified into fluctuating and constant components according to its fluctuation characteristics. A propagation-path-based coupling model is proposed to investigate the correlated interactions among physical fields, extracting critical parameters, including winding current, magnetic flux, electromagnetic force, vibration, and noise. Comparative simulations reveal that the fluctuating component induces more complex multi-physics variations, generating significantly higher vibration amplitudes and noise levels compared to those of the constant component. A dynamic experimental platform is built to obtain multi-physics field information in different modes, and the effectiveness of the model and the correctness of the conclusions are verified through virtual–physical consistency validation. On this basis, multimodal feature information domains are established to delineate the operational state intervals of the transformer under GIC interference. Stability threshold criteria are subsequently developed, providing a critical quantitative basis for the condition monitoring of power transformers. Full article

The noise generated by combine harvesters during operation has drawn growing attention, particularly that of the conveying trough shell, whose noise generation mechanism remains unclear. This study investigated the vibration radiation noise characteristics of conveying troughs by analyzing a chain system with 83 links using numerical simulation and experimental validation. A dynamic model of the conveyor chain system was developed, and the time domain reaction force at the bearing support was used as excitation for the trough shell’s finite element model. Modal and harmonic response analyses were performed to obtain the vibration response, which served as an acoustic boundary input for the LMS Virtual Lab. The indirect boundary element method was used to compute the radiated noise, achieving coupled modeling of chain system vibration and trough shell noise. Simulation results revealed that the maximum radiated noise occurred at approximately 112 Hz, closely matching experimental data. Comparative analysis of transmitted noise at 500 Hz and 700 Hz showed acoustic power levels of 98.4 dB and 109.52 dB, respectively. Results indicate that transmitted noise dominates over structural radiation in energy contribution, highlighting it as the primary noise path. This work offers a validated prediction model and supports noise control design for combine harvester conveying troughs. Full article