High Frequency Vibration Research Articles

Stress Prediction Model of Super-High Arch Dams Based on EMD-PSO-GPR Model

In response to the challenge of limited model availability for predicting the lifespan of super-high arch dams, a hybrid model named EMD-PSO-GPR (EPR) is proposed in this study. The EPR model leverages Empirical Mode Decomposition (EMD), Gaussian Process Regression (GPR), and Particle Swarm Optimization (PSO) to provide an effective solution for super-high arch dam stress prediction. This research focuses on three strategically selected measurement points within the dam, characterized by complex stress conditions. The predicted results from the EPR are compared with those from GPR, Long Short-Term Memory (LSTM), and Support Vector Regression (SVR), using actual stress data measured at research points within a super-high arch dam in Southwest China. The findings reveal that the proposed EPR model attains a maximum mean absolute error (MAE) of 0.02916 and a maximum root mean square error (RMSE) of 0.03055, surpassing the compared models. As a result, the EPR model introduces an innovative computational framework for stress prediction in super-high arch dams, excelling in handling stress data characterized by high vibration frequencies and providing more accurate predictions.

Experimental and numerical studies on mechanical behavior of pre-stressed infilled rock joints subjected to horizontal vibration loading

Underground jointed rock masses are usually subjected to a coupled effect of static pre-stress and vibration disturbance from rock-cutting in Tunnel Boring Machines (TBMs) tunneling. To investigate the mechanical behavior of pre-stressed infilled rock joints disturbed by horizontal vibration loading, a series of laboratory and numerical experiments were conducted, based on the in-situ vibration characteristics during TBM rock-cutting. The P-wave velocity and direct shear test techniques are combined to quantitatively characterize the damage of infilled rock joints. The experimental results reveal that the damage degree of rock joints exhibits a nonlinear increase with the increase of vibration frequency and amplitude, and the decrease of static pre-stress. Low static pre-stress (below 0.5 MPa), high vibration frequency (above 70 Hz) and high vibration amplitude (above 0.3 mm/s) are adverse factors to the stability of rock joints. From the PFC2D simulation, the contact force chain and contact force field were analyzed to elucidate the failure mechanism of infilled rock joints. The failure mode of infilled rock joints is closely related to the level of parameters, consisting with the results in laboratory experiments. In addition, the comparison of vibration results for weakly and strongly filling material demonstrates that grouting reinforcement enhanced the vibration resistance of in-situ jointed rock masses.

Integrated transmission vibration reduction technology based on the “isolating-reducing-optimizing” method

Hydro-mechanical transmission devices that can transfer power from the engine to the action mechanism are widely used in heavy-duty vehicles. It has many components, and the operating conditions are complex and changeable. Multi-source excitations and load disturbances easily aggravate vehicle vibrations, which has an adverse impression on the running quality of the whole vehicle. Therefore, it is necessary to carry out research on the vibration problems caused by multiple excitation sources. Thus, in this paper, a new vibration reduction method of “isolating-reducing-optimizing” for hydro-mechanical transmission devices is proposed to optimize such devices in multiple dimensions to improve their dynamic responses. This novel method optimized the coupling stiffness to isolate the vibration caused by the engine fluctuating torque. Moreover, the vibration energy decoupling method and optimization method are used to decouple the rigid body vibration of the mounting system, and gear profile modification method based on a dynamic model is used to attenuate the internal high frequency vibration caused by the gear meshing excitation. Finally, the steady-state conditions and cycle conditions vibration tests of the transmission system before and after optimization are carried out. The time and frequency domain vibration responses of the transmission system before and after optimization are compared to verify the effectiveness of the optimization method.

Three-dimensional distributed acoustic sensing at the Sanford Underground Research Facility

Distributed acoustic sensing (DAS) is a valuable tool for monitoring seismic signals as it provides high spatial and temporal resolution strain sensing along the length of a fiber-optic cable. DAS records the seismic wavefields essentially synchronously at each sensing location (i.e., sensing channel with gauge lengths) because the interrogator senses the distributed strain at the speed of light in the fiber. Unlike traditional seismic sensors, DAS has an intrinsic directional sensitivity to the axial strain change along the fiber, leading to difficulties when using standard seismic analysis and interpretations that rely on 3D particle velocity sensing. In addition, cable deployments on the surface can be dominated by high-amplitude wind or urban noise, impeding the detection of low-amplitude distant seismic sources. Here we investigate the capabilities of a unique 3D array with spiral-like portions in the Sanford Underground Research Facility (SURF), the former Homestake Mine, between 1250 m (4100 ft) and 1488 m (4850 ft) in depth for detecting local, regional, and teleseismic sources of ground vibrations. Our pilot array finds that DAS records high frequency (above 5 Hz) vibration sources well, such as mine activities and local and regional blasting events. Furthermore, our deployment method (fiber resting on the surface with rocks placed every meter or so) may contribute to low-frequency noise that contaminates the interpretation of teleseismic waves, particularly lower frequency S-wave arrivals. Nevertheless, this 3D DAS array provides significant data for future analysis as well as the basis for improving and expanding the array in SURF.

Design of Kagome lattice composite sandwich metastructures with high load bearing and low frequency vibration reduction properties

Design of Kagome lattice composite sandwich metastructures with high load bearing and low frequency vibration reduction properties

Mechanical characteristics of a corset type structure with negative Poisson’s ratio

For mechanical metamaterials and their vibration isolation ability, a new corset type structure (CTS) is designed from the inward hexagonal steel structure by applying fillet at the inward corners. Ten CTS cells are born by using the different fillet radius. The fillet radius is 10 mm to 100 mm, but the cell mass remains constant when the plate has the same thickness. The static deformation, vibration modality and harmonic response of these NPR structures are analyzed in this paper. These CTS cells are modeled by using the finite element method (FEM) with a uniform grids. In static analysis, a surface load and a point load on the top plate are respectively considered to study the elastic deformation, the NPR and the stiffness of CTS cells with different fillet radii and thicknesses. These CTS cells have a greater NPR and a higher stiffness than the original inward hexagonal steel structure. In modal analysis, the natural frequency, the eigenmode and the fixed modality are numerically computed. These frequency values and displacement distributions of CTS cells show that these CTS cells have a higher vibration frequency than the origin inward hexagonal structure cell. In harmonic response analysis, the frequency domain is from 1 Hz to 1000 Hz, and the excitation force is on the top surface of the upper plate. All displacement responses of these CTS cells are analyzed. The harmonic response analysis result shows that the resonance magnitude can be significantly suppressed by these new CTS cells. The analysis result presents the characteristics of this new CTS, and it is beneficial for the vibration isolation in engineering application.

Elastic architected mechanical metamaterials with negative stiffness effect for high energy dissipation and low frequency vibration suppression

In this research, mechanical metamaterials with negative stiffness (NS) effect were architected and fabricated for high energy dissipation and low frequency vibration suppression. Periodic cellular metamaterials formed by connecting multiple NS elements in series exhibited hysteresis and lengthy sawtooth loading and unloading plateaus, which made them desirable for use in energy dissipation applications. And the key point was that the deformation of these metamaterials was completely reversible. To determine the underlying cause of hysteresis, the mechanical behavior with phase-transition characteristics was analyzed. Then, a finite element model was built, and the numerical simulation results were compared to the experimental test findings of the metamaterials, and the two were in good agreement, verifying the validity of the model. Furthermore, the influences of structural parameters on mechanical characteristics were systematically investigated and discussed utilizing the numerical models that had undergone experimental validation. The energy dissipation effect resulting from the phase transformation mechanisms could also be applied to the field of vibration control. Corresponding hammer tests were performed to explore the dynamic behavior of the NS metamaterials. The results show that the proposed metamaterials exhibit excellent vibration suppression performance, especially for low frequency vibration mitigation.

Longitudinal wave propagation analysis in Entangled metallic wire materials using an improved wave and finite element method

This paper proposes a novel concept and methodology to study longitudinal wave propagation in entangled metallic wire material (EMWM), a porous structural network consisting of spatial helix wires. The numerical model of EMWM is constructed using representative volume elements (RVE) obtained through X-ray tomography and skeletonization of a standard specimen. By increasing the approximate periodic boundary, the improved wave and finite ele-ment method (WFE) is employed to model EMWM as approximately periodic structures, allowing for numerical simulations of wave propagation characteristics. Frequency bands and resonance modes of EMWM are calculated to analyze the characteristics of one-dimensional wave propagation. The numerical results show that EMWM exhibits unique frequency band characteristics compared to typical periodic porous materials. In the frequency range of 15 to n n 35 kHz, the first pass band corresponds to the tensile-compressive motion of the entire specimen, while the higher pass bands correspond to localized vibrations within the spatial wires. Additionally, the frequency bands can be adjusted across a wide range based on the relative density of EMWM specimens. The improved WFE method and obtained numerical data can facilitate the application of EMWM on high frequency vibration isolation.

PWM harmonics reduction for dual-branch three-phase PMSMs using interleaving topology

High-frequency pulse width modulation (PWM) acoustic noise is generated by PWM switching harmonics in the dual-branch three-phase permanent magnet synchronous motor (PMSM) systems during the switching process of the drivers. Because of the special winding structure of the double branch motor, the sum of the current of the two branches reflects the high frequency vibration of the motor. This paper proposes a method using four voltage source inverters and coupled inductors with a special connection method to eliminate the carrier frequency as well as its twice, triple noise for dual-branch three-phase PMSMs. Carrier-phase-shift technique is used to change the direction of the current harmonics. Compared with the conventional method, four paralleled VSIs can be saved. The simulation results verify the effectiveness of the method.

An Optimal Periodic Carrier Frequency PWM Scheme for Suppressing High-Frequency Vibrations of Permanent Magnet Synchronous Motors

High-frequency vibration caused by pulse width modulation (PWM) is a critical problem of permanent magnet synchronous motor (PMSM) drives for low-noise applications. Periodic carrier frequency PWM (PCFPWM) can effectively reduce high-frequency vibrations by dispersing concentrated harmonics over a wider frequency band. However, the resulting vibration spectra are normally far from ideal and still contain several local peaks because the uneven vibration frequency response of the motor is not taken into account. To address this problem, this paper proposes an optimal PCFPWM scheme that minimizes vibration spectral peaks of the motor by considering its vibration frequency response function (VFRF). A time series of PWM carrier frequency is carefully devised such that the amplitude of the induced electromagnetic (EM) force is inversely related to the VFRF of the motor, thereby shaving peaks in the vibration spectra. Finally, the optimal PCFPWM scheme is experimentally verified and demonstrates improved vibration suppressing performance.

Sonomechanobiology: High frequency cell mechanostimulation

It is well known that cells respond in many different ways to various forms of mechanical cues. To date, however, mechanostimulation has typically been carried out statically or at relatively low frequencies (several Hz), characteristic of the frequencies associated with the motion experienced by cells in their local environment, for example, in the human body (e.g., walking and running). Where higher frequency vibrational mechanotransduction pathways have been investigated, these have primarily been limited to kHz order, and it has generally been suggested that there is no significant advantage in utilising higher frequencies. In a similar manner to observations of new and often nonlinear discoveries when we couple high frequency (10–30 MHz) vibration in the form of surface and hybrid acoustic waves into fluids as well as crystalline materials, we however observe unique and novel phenomena when similar MHz-order vibrational stimuli are transmitted into cells. These include modulation of various ion and piezo channels, and transient, yet reversible, permeabilization of the cell membrane, which have implications for efficient intracellular cytosol delivery, exosome biogenesis, cytoskeletal reorganization and stem cell differentiation, at the same time maintaining very high levels (>95%) in cellular viability.

A study of the axle box ASD spectrum of high-speed rail vehicles based on field test measurements in China

The axle box ASD (Acceleration Spectral Density) spectrum serves as the main resource of high frequency vibration for rail vehicles, which is usually taken as a critical load spectrum for the evaluation of vibration fatigue of rail vehicle sub-assemblies. However, the continuous in-service failures occurring in a plenty of rail vehicles invariably suggested a low reliability for the ASD defined in IEC 61373 standard for some scenarios. This paper thus investigated on the characteristics of axle box ASD spectrum through measurements acquired from a number of high speed rail vehicles in China, so as to develop a more realistic vibration spectrum for the considered operation condition. Firstly, a brief review for typical fatigue failures of rail vehicles was conducted to understand fatigue failure modes caused by the high frequency vibration of wheel/rail system. Subsequently, the definition of axle box ASD spectra in IEC 61373 was analyzed and further compared with the ASD spectra of axle box obtained from measurements to demonstrate the reliability of standard vibration level. The results suggest that the ASD spectrum given in IEC 61373 underestimates the vibration level in high frequency ranges, especially the frequency band above 500 Hz. Finally, a modified ASD spectrum profile of axle box considering the characteristic frequency bands of wheel/rail system was proposed to better representation of vibration characteristics of axle box, especially for those arising from the wheel/track vibration modes. This is expected to better characterize the vibration characteristics of axle box for rail vehicles, and improve the estimation accuracy of fatigue lifetime for the components subjected to the axle box vibration.

Design and correlation analysis of quasi-zero stiffness passive vibration isolation air spring

Vibration isolation systems are widely used in high-end automobile manufacturing, precision instrument processing, building and bridge seismic resistance, ship machinery noise reduction and other engineering fields, with good development prospects. At present, the existing vibration isolation systems on the market are mainly divided into active and passive vibration isolation systems. Passive vibration isolation does not require external energy input. Its structure is simple and the control scheme is easy to implement. However, passive vibration isolation performs well in high frequency vibration but not in low frequency. As a new nonlinear low-frequency vibration isolation technology, the quasi-zero stiffness vibration isolation system has changed the traditional concept of linear system vibration isolation. In addition, compared with traditional spring, air spring as a new type of elastic vibration isolation mechanism has many excellent performances, such as high fatigue resistance and high stiffness. Therefore, this paper uses air spring to design a passive vibration isolation quasi-zero stiffness air spring structure with good vibration isolation effect, simple structure and low cost in both low-frequency and high-frequency vibration.

Propagation characteristics analysis of high-frequency vibration in pumped storage power station based on a 1D fluid-solid coupling model

High-frequency pressure fluctuation is a common hydraulic phenomenon in pumped storage power station (PSPS), which is caused by the rotor-stator interaction in the pumped turbine. The propagation of the high-frequency vibration (HFV) could transmit the vibration energy to the upstream headrace tunnel, inducing severe environmental vibration and noise pollution. This study aims to establish an applicable numerical model to investigate the propagation characteristics of HFV, and evaluate the vibration magnitude of both solid and fluid in the headrace tunnel of the PSPS. In this study, a one-dimensional (1D) numerical model is established for the fluid solid interaction (FSI) behavior of the pipe, where the equations of solid and fluid are solved intuitively in the time domain by the Finite Difference Method (FDM) and Method of Characteristics (MOC), respectively. Detailed discretization schemes and solution procedures are deduced and presented in this study. Four validation cases are carried out to examine the established model. The results demonstrate that the established mode is applicable for predicting the vibration in the fluid-filled pipe (FFP). The non-reflect boundary conditions are proposed to eliminate the influence of the reflected wave from the boundary. The propagation characteristics of the high-frequency vibration (HFV) in FFP are comprehensively analyzed and summarized based on a real PSPS. And magnitude distributions of the pressure fluctuation, axial and radial vibration along the pipeline axis are presented and discussed.

Novel Isomer of Volleyballene Sc20C60.

The Stone-Wales defect is a well-known and significant defective structure in carbon materials, impacting their mechanical, chemical, and electronic properties. Recently, a novel metal-carbon nanomaterial named Volleyballene was discovered, characterized by a C-C bond bridging two carbon pentagons. Using first-principles calculations, a stable Stone-Wales-defective counterpart of Volleyballene, exhibiting Th symmetry, has been proposed by rotating the C-C bond by 90°. Although its binding energy per atom is slightly higher than that of Volleyballene (ΔEb = 0.009 eV/atom), implying marginally lower structural stability, it can maintain its bond structure until the effective temperature reaches about 1500 K, indicating greater thermodynamic stability. Additionally, its highest vibration frequency is 1346.2 cm-1, indicating a strong chemical bond strength. A theoretical analysis of the Sc20C60 + Sc20C60 binary systems highlights that the stable building block may be applied in potential nanoassemblies.

Instability analysis of vibrated thermo-convection in Casson nanofluid suspension

This work is motivated by the importance of vertical vibration in nanofluids suspension, because of its wide applications in heat exchangers from one fluid to another, controlling the mixing in microvolumes, pharmaceutical industry, and engineering. The current study analyzes the effects of high-frequency vertical vibration on a horizontal Casson nanofluid layer heated from below saturated between rigid-rigid, rigid-free, and free-free boundary conditions. Field equations are derived by using time-average method, which describes the vibrational thermo-convection. These field equations are solved by utilizing linear stability analysis and Galerkin technique to obtain the thermal stability curve. By using this curve, the impacts of vertical vibration and physical governing factors on temperature profile are discussed. High-frequency vertical vibration is observed to have a stabilizing effect on Casson nanofluid suspension, thereby reducing thermo-convective heat transfer from one fluid to another. Stability threshold of vibrated suspension is increased approximately as [Formula: see text] and [Formula: see text] when [Formula: see text] and [Formula: see text], respectively. The significance of Brownian motion and thermophoretic force on convective heat transfer with vertical vibration is discussed. The resisting nature of Casson nanofluid on vibrational convective heat transfer is also tabulated.

Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V

The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.

A High Frequency Vibration Compensation Approach for Ultra-High Resolution SAR Imaging Based on Sinusoidal Frequency Modulation Fourier-Bessel Transform

A High Frequency Vibration Compensation Approach for Ultra-High Resolution SAR Imaging Based on Sinusoidal Frequency Modulation Fourier-Bessel Transform

Theoretical analysis of the attenuation characteristics of high-frequency pressure vibration in pumped storage power station

High-frequency vibration is a common hydraulic phenomenon in pumped storage power station. In this study, a theoretical model for analyzing the high-frequency vibration in fluid-pipe-surrounding support coupling system is established. The discontinuity characteristics between the pipe wall and surrounding medium are modeled by the linear spring model, where axial and radial spring constants represent the bounding degree of the pipe and surrounding support. The relation between the wave speed and attenuation characteristics of the high-frequency vibration could be derived from the established theoretical model. And a strategy for estimating the attenuation rate of the high-frequency vibration is proposed. According to the theoretical analysis results, the connection and transition of the vibration energy through the pipe and surrounding support mainly rely on radial bounding. With decreasing in the compressibility of the pipe wall and the surrounding medium, the attenuation rate of high-frequency decreases. One of the reasons why the high-frequency pressure vibration could propagate over long distances in the pumped storage power station may be attributed to the little compressibility of the solid structures in the headrace tunnel.

The Effects and Mechanisms of Periodic-Carrier-Frequency PWM on Vibrations of Multiphase Permanent Magnet Synchronous Motors

High-frequency vibration and noise induced by pulse width modulation (PWM) deteriorate the acoustic performance of permanent magnet synchronous motor (PMSM) drives. Periodic-carrier-frequency PWM (PCFPWM) is an effective method that can disperse the high-frequency harmonics to a wider frequency band, thereby suppressing the peak harmonic. This paper presents a detailed study on how exactly PCFPWM affects both the low-frequency and high-frequency vibrations of PMSMs. It is revealed that PCFPWM actually deteriorates low-frequency vibrations of the motor, due to unwanted side effect of additional AC components in d- and q-axis currents and thus increased torque pulsations. But this can be remedied by quasi-proportional resonant control of corresponding current harmonics. For high-frequency vibrations, the paper thoroughly studies the effects of PCFPWM on current harmonics and the zero-order electromagnetic (EM) force acting on motor stator teeth. Compared with the experimental vibration results, it is found that high-frequency zero-order EM force is the direct and major cause of EM vibrations induced by PCFPWM. This paper provides the theoretical basis for future optimization of PCFPWM based on the zero-order EM force as a direct vibration metric.