ABSTRACT This study examines the influence of ultrasonic-assisted turning (UAT) on the surface finish of hardened Mo40 steel under various cutting speeds, feed rates, and ultrasonic excitation voltages (Vg) at 21 kHz. Compared to conventional turning (CT), UAT improves surface quality most effectively at lower cutting speeds and higher ultrasonic amplitudes. Increasing Vg enhances vibration-induced surface micro-disruptions, producing finer textures and reduced roughness. These benefits are maximized at low-to-moderate cutting speeds and feed rates. Above a critical cutting speed, UAT efficiency declines due to continuous tool contact, causing a slight roughness increase. Optimization identifies an ideal combination of feedrate (0.07 mm/rev), ultrasonic voltage (130 V), and cuttingspeed (27 m/min) for minimal surface roughness. Findings highlight ultrasonic excitation voltages (vibration amplitude) as a key factor in achieving superior surface finish and demonstrate UAT’s potential to enhance machining of hardened steels, offering improved precision and component longevity for industrial applications.

The combination of strong structural nonlinearity and flow-induced vibration can enhance energy harvesting efficiency while potentially triggering system instability; however, its specific mechanism remains obscure. Motivated by this, a sliding-type electromagnetic vortex-induced vibration harvester, designed for durable operation in flowing water by integrating nonlinear stiffness, frictional and fluid damping, and nonlinear electromechanical coupling, is investigated. A wake-oscillator model is used to capture the nonlinear features of the system and enable parametric studies; analyses based on coupled computational fluid dynamics/computational structural dynamics/electrical simulation elucidate the wake-mode reorganization and energy-transfer pathways, with water-tunnel tests with particle image velocimetry validating the simulations and revealing key flow features. Differences among linear, nonlinear hardening, and bistable configurations are observed and elucidated in terms of frequency lock-in, amplitude changes, and power output. The nonlinear hardening case exhibits widened bandwidth and increased overall output. In the bistable configuration, a barrier-crossing amplitude reset-and-build-up (BC-ARB) phenomenon is identified. The BC-ARB phenomenon features a delayed and stretched roll-up of shear layer, which reverses the lift-velocity phase relative to structural velocity, creating a negative-work interval that rapidly resets the vibration amplitude; the wake then shifts to a 2S (two single vortices per cycle) mode alongside a synchrony phase return and amplitude rebuilding within the potential well. The phenomenon is found to be sensitive to the mass ratio and, alongside chaos, reduces the harvested power in the bistable configuration. This work elucidates how structural nonlinearity reshapes wake modes and energy transfer, informing parameter optimization for hydrodynamic energy harvester design and vibration control.

As the shipping industry pursues sustainable alternatives, biofuel has emerged as a promising fuel but introduces risks like fuel dilution into lubricating oil, particularly threatening cylinder liner-piston ring (CLPR). In this study, marine lubricating oil was mixed with B24 biofuel according to different mass fractions, and their physicochemical properties were analyzed. The results show that with the increase of the dilution concentration of biodiesel, the viscosity decreases significantly. When the dilution concentration is 20%, the viscosity of the lubricating oil decreases by 18.97% (40°C) and 16.63% (100°C) respectively, and the thermal stability and oxidation resistance of the lubricating oil also decline. Tribological tests show that both the friction coefficient and wear quality of CLPR have increased. Specifically, under high-speed and heavy-load working conditions, compared with pure lubricating oil, the average friction coefficient increases by up to 19.4%, the wear mass increases by up to 26%, and the vibration amplitude during the test process also increases significantly. This study provides valuable insights into the long-term operational challenges brought about by the use of marine biofuel and determines 10 wt% as the dilution threshold for B24 biofuel, offering a scientific basis for optimizing the lubrication strategy of marine engines.

Abstract Squeeze film dampers (SFDs) utilize a thin oil film between a nonrotating journal and stationary housing to reduce vibrational amplitudes while crossing critical speeds and improve stability. SFDs may experience air ingestion with certain end seal designs and motion amplitudes, leading to a reduction in damping coefficients. Most research into SFDs focuses on circular, centered orbits (CCOs), meaning the applied excitation consists of one frequency component; however, turbomachines frequently experience excitations containing both synchronous and subsynchronous frequency components. These experiments use a dual-frequency excitation with the smaller frequency varying from 9 to 42 Hz and being labeled as “subsynchronous.” A higher frequency is held constant at 100 Hz and is labeled “synchronous.” One test condition holds the subsynchronous amplitude constant with an amplitude to clearance ratio (r/c) equal to 5%, and the synchronous amplitude ranging from r/c = 5–60%. A second test condition sets both amplitudes to equal values ranging from r/c = 5–30%. Preliminary CCO tests are performed using the synchronous amplitude range outlined above and a frequency range of 10–100 Hz. The 100 Hz tests are used for evaluating the dynamic pressure. All testing is performed using an open-end configuration with a relatively large radial clearance of 279 μm (11 mils). Additional analysis is provided by calculating the average squeeze velocity due to both frequency components and plotting against damping coefficients. The results show a large increase in subsynchronous damping as synchronous amplitude increases, despite the onset of air ingestion. Synchronous amplitude provides the most significant contribution to the squeeze velocity, and the results show that subsynchronous damping increases with significant increases in squeeze velocity.

Abstract Ionic wind thrusters are emerging electrohydrodynamic propulsion devices that have drawn significant interest owing to their simple structure, silent operation, and potential applications in microaerial vehicles. A high-voltage electrode is a crucial component that directly impacts the corona discharge efficiency and the resultant ionic wind thrust. In this study, significant mechanical vibrations were observed in a high-voltage tungsten wire electrode under alternating current (AC) excitation in a wire-to-cylinder ionic wind thruster operating under atmospheric conditions. The experiments were conducted at a fixed AC frequency of 10 kHz, with voltages ranging from 5 kV to 9 kV. The electrode vibrations were measured using a 3D high-speed video extensometer, and the waveforms and frequency spectra were analyzed. The results reveal that the vibration amplitude increases significantly with voltage. The spectrum reveals harmonic responses at 120 Hz and its multiples (240 Hz and 360 Hz), indicating strong nonlinear vibration behavior. The periodic Coulomb force induced by the AC electric field was confirmed to be the primary excitation source.

Extensive research has been conducted in recent years to mitigate damages caused by undesired vibrations in motor vehicles used for transportation. Vibrations occurring in highly active moving components of vehicles not only lead to discomfort in driving comfort but also reduce the material’s service life, causing fatigue and structural damage. Rotating elements in vehicles, such as the shaft (cardan shaft), crankshaft, and gears, can be sources of problems. In this study, vibrations resulting from an imbalance problem in the vehicle shaft were experimentally investigated, and the effects of balancing on the vehicle shaft were evaluated. For this purpose, vibration data were measured at three different points on a vehicle. Vibrations generated by the shaft under different road conditions and vehicle speeds were recorded and compared before and after balancing. The results of the study demonstrated a one-third reduction in vibration amplitude at the point beneath the driver's seat, which is directly associated with the comfort of both driver and passengers. Specifically, under the most demanding conditions (80 km·h⁻¹ speed and an uneven road surface), the vibration amplitude induced by the unbalanced driveshaft reached a high value of 2198 µm; after balancing, a reduction of approximately 65–70% in this amplitude was achieved at the measurement point under the driver's seat. In contrast, no significant difference was observed in the vibrations measured at the engine block and the luggage compartment. The findings indicate that vibrations originating from the vehicle driveshaft can be substantially mitigated through proper balancing.

Sound pressure recordings at different positions at the head such as ear canal, nasal cavity, or on the skin are effective tools to verify, fit, or follow up the output of bone conduction devices (BCDs) intra- and post-operatively. Here, we investigated the possibility of using a surface microphone (SM) as a non-invasive alternative to laser Doppler vibrometry (LDV) measuring cochlear promontory (CP) vibrations in human heads. A percutaneous BCD (Ponto system) was implanted at the standard position in five human (four males/one female) cadaver heads (ten ears). CP vibration was measured using LDV in response to the BCD stimulation. Simultaneously, the sound pressure level (SPL) emitted by the skin was measured by the SM attached to the forehead of the specimens. A linear regression model estimated the vibration amplitudes based on the measured SPL. A frequency-independent linear regression between recorded SM SPL and CP velocity showed a significant correlation (slope = 1.012; r2 = 0.535, p < 0.001). An enforced fixed slope (constant = 166.7 dB) of one resulted in a mean absolute error of MAE = 7.7 ± 2.7 dB across frequencies. Although the initial linear model with a fixed slope of one showed frequency-dependent deviations, applying a frequency-specific correction significantly improved the prediction accuracy (r2 = 0.557, MAE = 6.5 ± 1.5 dB). Microphone-based recording of acoustic surface emissions offers a non-invasive alternative to LDV to assess BCD output.

Abstract The dynamic interaction among multiple defective rollers in cylindrical roller bearings (CRBs) would lead to the complex vibrations of bearings and slip behavior of rollers. Compared with raceway defects, roller defects involve a more intricate contact process, which has often been oversimplified in previous studies. However, the characteristics of roller defects contacting with raceways are closely related to both the motion behavior of the rollers and the geometric features of the defects. To accurately capture the complex dynamic interactions between the defective regions of the rollers and the raceways, a dynamic model for CRBs with multiple defective rollers under elastohydrodynamic lubrication (EHL) conditions is developed by introducing a time-varying displacement excitation function. Furthermore, accounting for both the number and relative position of defective rollers, a comprehensive dynamic model is proposed to investigate the vibration mechanisms in various multi-defect scenarios. Experimental results confirm the simulated response of roller bearings. The influence of the number and relative positions of defective rollers on bearing vibration characteristics and slipping behavior are studied in further, as well as their effects on the motion of the cage and healthy rollers. The results indicate that with increasing quantity of defective rollers, the vibration amplitude and cage slip ratio of the bearing would increase correspondingly. Moreover, reducing the spacing between defective rollers intensifies the vibration and slipping behavior of the bearing.

Despite progress in research, the mechanobiological mechanisms behind adverse vascular remodeling and failure in arteriovenous fistulae (AVF) for hemodialysis remain unclear. The aim of this investigation is to assess the association between flow-induced vascular wall vibrations and adverse vascular remodeling in AVFs. Six end-stage kidney disease patients with native distal radio-cephalic AVF were monitored for 1 year with magnetic resonance imaging and Doppler ultrasound examinations. Patients were divided based on AVF outcomes: two maintained proper AVF patency and four developed complications (two venous stenoses and two excessive dilatations). Patient-specific fluid-structure interaction simulations were performed at different time points. Before vascular remodeling, stenotic AVFs exhibited two dominant frequency bands, between 45 and 100 Hz, while excessively dilated AVFs exhibited a single band at 50 Hz. Before the onset of remodeling, patients with complications exhibited significantly higher vibration amplitude (22.5 ± 5.8 μm vs. 6.6 ± 2.0 μm, p < 0.01) and high-pass strain ((1.30 ± 0.35)∙10-3 vs. (0.30 ± 0.10)∙10-3, p < 0.01) than those with proper patency. Significant differences in vibration amplitude and high-pass strain were observed between patients with proper patency and those with stenosis (p < 0.001 and p < 0.01, respectively), and in high-pass strain between patients with preserved patency and those with excessive dilatation (p < 0.01). Specific vibration frequencies and amplitude levels appear to be associated with distinct types of vascular remodeling, indicating they could potentially be biomarkers for AVF surveillance.

This study investigates a piezoelectric energy harvester with three hinged springs, in which bistable or quad-stable potential wells are configured by adjusting spring assembly distances under equivalent potential barrier constraints. Static bifurcation analysis reveals the formation mechanisms of multistable topologies, while dynamic analysis characterizes intra-well and inter-well resonant responses. A multiobjective framework integrating Root Mean Square (RMS) voltage, effective bandwidth, and Basin of Attraction (BA) area is established to quantify the performance of the bistable and quad-stable energy harvesting systems. Numerical simulations using the cell-mapping approach with fourth-order Runge–Kutta integration demonstrate the superior practical performance of the bistable configuration under low-to-moderate base vibration amplitudes, resulting from its significantly larger BAs that ensure reliable high-energy responses. Conversely, a reversal in performance dominance occurs at higher amplitudes, where the quad-stable system prevails due to its broader BAs that enable robust inter-well oscillations. The core innovation of this work lies in establishing a direct link between the geometrically parameterized potential wells of the system and the resulting amplitude-dependent basin stability, offering a deterministic design principle for selecting and optimizing nonlinear energy harvesters according to anticipated environmental vibrations.

Mass concrete foundations are widely used to support low-frequency rotary machines due to their ability to provide adequate mass, stiffness, and vibration control. However, traditional design approaches are largely empirical and may lead to inefficient material usage or inadequate vibration performance. This research review critically evaluates existing studies on the optimization of mass concrete foundations through material modification and geometric refinement. Particular attention is given to the application of rubberized concrete, where partial replacement of mineral aggregates with recycled rubber has been shown to improve damping characteristics and energy dissipation under dynamic loading. The effects of foundation geometry, including rectangular and trapezoidal configurations, on natural frequency, vibration amplitudes, and soil–structure interaction are also examined. Numerical investigations based on Finite Element Analysis dominate the recent literature and provide valuable insight into stress distribution, resonance avoidance, and dynamic response prediction. The review identifies a lack of comprehensive studies combining material and geometric optimization within a unified framework for low-frequency machines. Design implications and future research needs are discussed to support the development of performance-oriented and sustainable machine foundation systems.

ABSTRACT This study examines the synergistic effects of plasma-assisted heating and ultrasonic vibration on the hard turning of 34CrNiMo6 steel, aiming to minimize tool flank wear. While cubic boron nitride (CBN) and tungsten carbide tools were evaluated, CBN demonstrated superior wear resistance, with statistical analysis confirming that the tool material was the most significant factor influencing wear. A hybrid machining approach was developed, integrating a plasma system for localized workpiece softening and ultrasonic vibration to reduce cutting forces through intermittent tool-workpiece contact. Using Taguchi-designed experiments, the optimal parameters for minimal flank wear were identified: CBN tools operating at reduced cutting conditions (0.50 mm depth of cut, 0.08 mm/rev feed, 40 m/min speed) combined with controlled plasma current (25 A) and maximum vibration amplitude (10 µm). Results revealed a dual-phase plasma current effect, initial force reduction followed by thermal wear at excessive current, and demonstrated that vibration amplitude significantly lowers wear.

In recent years, power-split Hybrid Electric Vehicles (HEVs) have attracted widespread attention for their superior fuel efficiency and performance. However, the planetary gear sets that mechanically couple the engine and drivetrain often induce undesirable torsional vibrations, degrading drivability and component durability. To mitigate this, an efficient multi-channel Active Vibration Control (AVC) strategy is proposed, utilizing a notch Filtered-x Least-Mean-Square (FxLMS) algorithm to leverage motor torque for compensating engine torque fluctuations. First, the system’s torsional vibration responses are analyzed to identify the input and output shafts as critical control targets. Second, a Back Propagation Neural Network (BPNN) is employed to model the secondary paths, which improves estimation accuracy and reduces errors by 65%–95% compared to the traditional Finite Impulse Response (FIR) filtering method. Third, a multi-channel AVC strategy is developed based on a modified notch FxLMS algorithm featuring variable step sizes. The proposed AVC strategy is then incorporated into the vehicle’s energy management system, forming an integrated control framework (ICF) for coordinated vibration suppression and energy optimization. Simulation and experimental results under various operation conditions verify that the proposed strategy effectively reduces torsional vibration amplitudes and improves powertrain smoothness, thereby enhancing overall drivability and comfort.

ABSTRACT This study employs a fluid-structure interaction (FSI) method with an overlap grid technique to investigate the effects of U-shaped groove width on the vortex-induced vibration (VIV) characteristics of a cylinder. Numerical simulations were conducted on cylinders with three groove widths (W = 0.1D, 0.2D, 0.3D) at two arrangement angles (45° and 90°), analyzing their effects on vibration amplitude, frequency, lift and drag coefficients, and wake vortex shedding patterns. Results show that increasing groove width effectively reduces transverse vibration amplitude compared to a smooth cylinder, with a widening suppression range. At low reduced velocities (U* = 2.0-8.0), lift and drag amplitudes significantly decrease with wider grooves, whereas they slightly increase at high reduced velocities (U* = 9.0-14.0). Distinct from the smooth cylinder, the wake vortex shedding patterns of the U-shaped groove cylinder include not only the SS, 2S, 2T and 2P modes, but also the 2C and P + S modes.

This study examines the nonlinear free vibration of higher-order shear deformable porous orthotropic laminated beams resting on orthotropic Pasternak foundations. A unified analytical model is developed by combining higher-order shear deformation theory with von Kármán geometric nonlinearity to capture coupled effects of porosity, lamination, and anisotropic foundation support. The governing nonlinear equations are reduced via Galerkin’s method to obtain explicit frequency–amplitude relations and are validated against analytical benchmarks and finite element results. The results show that both Winkler and orthotropic Pasternak foundations increase nonlinear frequencies, with the Pasternak shear layer providing a stronger stiffening effect. Increasing vibration amplitude induces a hardening-type response in all configurations, and higher in-plane orthotropy ratios ( E ort ) further amplify nonlinear frequencies, particularly with foundation support. Increasing porosity decreases frequencies due to stiffness loss; however, the PDP pattern consistently yields the highest frequencies, and foundation support mitigates porosity-induced reductions. Increasing fiber orientation ( β ) and foundation orthotropy angle ( α ) generally reduces frequencies, especially at low amplitudes and in foundation-free cases. Larger slenderness ratios ( L / h ) increase frequencies and diminish the sensitivity to lamination sequence, while the 0 ° layup remains stiffer than the 0 ° / 90 ° / 0 ° configuration. These findings provide practical guidance for vibration-sensitive lightweight structures supported by anisotropic media.

Canal bed configurations caused by vibrations of suspended pipelines crossing the watercourse.

Distributed fiber-optic sensing has become an indispensable tool for large-scale structural and environmental monitoring, where spectral interrogation of backscattering light enables high-precision quantitative measurement of external perturbations. Conventional spectral analysis methods, typically based on frequency-domain serial interrogation or time-to-frequency mapping, face inherent trade-offs between measurement speed, dynamic strain measurement range, and system complexity. Here, we present a distributed frequency comb enabled spectrum-correlation reflectometry as a universal spectral analysis framework that leverages optical frequency comb for parallel multi-frequency interrogation, which is experimentally demonstrated in a phase-sensitive optical time-domain reflectometry (φ-OTDR) system. This method eliminates the need for large frequency scans, achieving more than tenfold improvement in measurement speed over the state-of-the-art spectral analysis methods. Compared to existing phase-demodulated φ-OTDR systems, this method enables vibration amplitude monitoring with a dynamic strain measurement range expanded by more than an order of magnitude, while intrinsically circumventing phase unwrapping issues and interference fading. This work establishes a new paradigm for distributed spectral analysis, providing a flexible and robust platform for a wide range of sensing technologies, including Rayleigh and Brillouin-based schemes, which may have significant impact for geophysics, seismology, civil engineering, and other fields.

Stochastic resonance represents one of the mechanisms that trigger protein ligand unbinding.

A novel multi-field interaction cutting model for ultrasonically activated surgical devices.

Effect of ultrasonic vibration amplitude on the microstructure, residual stress, and tensile properties of HR-2 austenitic stainless steel