Low-frequency Vibration Research Articles

Sonic vibration ameliorates inflammatory diseases via the up-regulation of IL-10

ABSTRACT Sonic vibration (SV), or vibroacoustic therapy, is applied to enhance local and systemic blood circulation and alleviate pain using low-frequency sine wave vibrations. However, there is limited scientific data on the mechanisms through which the benefits are achieved. In this study, we investigated the impact of SV on inflammatory responses by assessing cytokine secretion in both in vivo and in vitro models. After inducing inflammatory responses in mice and macrophages, we studied cytokine expression and the symptoms of inflammatory diseases in response to three frequencies (14, 45, or 90 Hz) of SV stimulation at 0.5 m/s2 of amplitude. The results showed that SV at 90 Hz significantly increased interelukin-10 (IL-10) secretion in mice who were administered lipopolysaccharides (LPS) and increased the expression of IL-10 transcripts in peritoneal exudate cells and macrophages. Furthermore, SV at 90 Hz improved LPS-induced lethality and alleviated symptoms in a colitis model. In conclusion, this study scientifically proves the anti-inflammatory effects of vibration therapy through its ability to increase IL-10 expression.

Probing Ion-Receptor Interactions in Halide Complexes of Octamethyl Calix[4]Pyrrole.

Ion receptors are molecular hosts that bind ionic guests, often with great selectivity. The interplay of solvation and ion binding in anion host-guest complexes in solution governs the binding efficiency and selectivity of such ion receptors. To gain molecular-level insight into the intrinsic binding properties of octamethyl calix[4]pyrrole (omC4P) host molecules with halide guest ions, we performed cryogenic ion vibrational spectroscopy (CIVS) of omC4P in complexes with fluoride, chloride, and bromide ions. We interpret the spectra using density functional theory, describing the infrared spectra of these complexes with both harmonic and anharmonic second-order vibrational perturbation theory (VPT2) calculations. The NH stretching modes of the pyrrole moieties serve as sensitive probes of the ion binding properties, as their frequencies encode the ion-receptor interactions. While scaled harmonic spectra reproduce the experimental NH stretching modes of the chloride and bromide complexes in broad strokes, the high proton affinity of fluoride introduces strong anharmonic effects. As a result, the spectrum of F-·omC4P is not even qualitatively captured by harmonic calculations, but it is recovered very well by VPT2 calculations. In addition, the VPT2 calculations recover the intricate coupling of the NH stretching modes with overtones and combination bands of CH stretching and NH bending modes and with low-frequency vibrations of the omC4P macrocycle, which are apparent for all of the halide ion complexes investigated here. A comparison of the CIVS spectra with infrared spectra of solutions of the same ion-receptor complexes in d3-acetonitrile and d6-acetone shows how ion solvation changes the ion-receptor interactions for the different halide ions.

A novel vibration barrier for low-frequency surface waves in the ground

As for certain engineering scenarios, such as open-air quarries and underground pipeline areas, vibration barriers are in urgent need. However, their design and construction face various challenges, especially for attenuating surface waves with low frequencies. Inspired by the topography of hills and periodic phononic crystal structures, a novel vibration barrier consisting of periodic soil strips is proposed. Firstly, utilizing the finite element method and the theory of periodic structures, the dispersion band diagram is calculated for the periodic soil strips. The corresponding band gap mechanisms are discussed by the displacement field of modes in the lower boundary of band gaps. Besides, a simplified model and a theoretical expression are proposed to analyze the minimum frequency of the band gaps. Through frequency domain analysis, the influence of the damping of soil strips on isolation effects is examined, and the dissipated energy is also quantified using a spatial Fast Fourier Transform. Finally, a comparison of the isolation effect between soil strip barriers and typical trench barriers is conducted. The results show that periodic soil strips can exhibit several band gaps, within which surface waves (SWs) can be effectively isolated. Soil strip barriers exhibit similar or even better vibration isolation effects compared to trench barriers, especially for isolating low-frequency vibrations. This study enhances our understanding of surface wave mitigation using periodic barriers and provides fresh insights for designing seismic metamaterials.

Analysis of steady-state dynamics and stability of particle dampers considering the friction effect

This study analyzes the steady-state dynamics and stability of a structure with a particle damper considering the friction effect between the particle and container, with a focus on whether the system can maintain stable-state motion for an extended period. The determination of friction’s contribution and the maximum allowable gap clearance for steady-state motion is demonstrated through the solution of motion of the primary structure with a particle damper subjected to low-frequency vibration conditions. Additionally, stability analysis is conducted to assess if initial disturbances cause deviations from the original stable state and identify necessary parameters for stability when the system parameters are uncertain. Analytical descriptions for the stability of the system are derived. The effects of friction on the dynamics and stability regions of the particle dampers are systematically revealed, where the theoretical and numerical models are mutually verified and supported by the cases of previous studies. Results show that the inclusion of the rolling friction effect will disrupt the steady-state motion as gap clearance approaches the optimal value. As the coefficient of rolling friction increases, the stability region’s area gradually decreases with a notable leftward shift of its right boundary. This shift ultimately leads to a leftward shift in the optimal vibration reduction curve. In the range of gap clearance variation allowing for steady-state motion with two symmetrical impacts per cycle, the relative velocity of the particle is more effective and intuitive to reveal the vibration reduction mechanism of particle dampers than other perspectives such as momentum, energy, and phase.

Optimal Design and Performance Evaluation of HMDV Inertial Suspension Based on Generalized Skyhook Control

The hub motor driven vehicle (HMDV), due to the increase in unsprung mass and the influence of uneven electromagnetic radial forces from road excitations, results in the deterioration of body acceleration, significantly impacting ride comfort. This seriously impacts ride comfort. However, the inerter proves effective in reducing low-frequency vibrations in body acceleration, and skyhook control significantly enhances ride comfort. To fully exploit the benefits of the inerter, comprehensively elevate skyhook control performance, and effectively counteract the worsening of body acceleration caused by the hub motor, this study integrates skyhook control with an inertial suspension system. This integration markedly improves the suspension’s low-frequency isolation performance, thereby substantially enhancing vehicle ride comfort. Firstly, establish a quarter-vehicle dynamics suspension model based on the Switched Reluctance Motor (SRM) driven wheel motor system. Subsequently, confirm the constraints of two different generalized skyhook inertial suspension structures separately and optimize their parameters to determine the most suitable parameters for each structure. Finally, analyze the impact of these two suspension types on body acceleration to derive the optimal structure. Simulation results demonstrate that, compared to traditional suspensions, the optimized generalized skyhook inertial suspensions reduce the Root Mean Square (RMS) values of body acceleration and suspension working space by 18.8% and 22%, respectively. This reduction is particularly significant in the 0[Formula: see text]2[Formula: see text]Hz frequency range, effectively enhancing ride comfort. It also adequately validates the effective utilization of the advantages of inertial suspensions and skyhook control.

Micro-crack localization for steel strands using nonlinear vibro-acoustic modulation based on modified signal bispectrum analysis

Under continuous environmental erosion and long-time high tension, fatigue micro-cracks of bridge cables appear frequently to challenge the reliability of cables. The vibro-acoustic modulation analysis is adopted because of its sensitivity to contact-type defects, especially fatigue cracks. In this paper, using multiple sets of low-frequency vibration and high-frequency ultrasonic excitation, the propagation of the ultrasonic wave in the steel strands is studied. Then, the modulated signal bispectrum is proposed to improve the detection reliability of nonlinear modulation components in the nonlinear vibro-acoustic modulation signal of the contact-type defect. The numerical simulations and laboratory tests of straight wire, helical wire, and multi-wire strands are carried out for micro-crack detection to verify the robustness of the proposed method. Compared with the traditional method, the modulated signal bispectrum can still produce clearer peak detection under high noise conditions. The results show that it provides a promising, dynamic and rapid cable defect detection technique.

Investigation of post weld heat treatment on mechanical properties of low frequency vibration assisted SMAW mild steel welded joints

Investigation of post weld heat treatment on mechanical properties of low frequency vibration assisted SMAW mild steel welded joints

Temperature sensing and energy harvesting with A MEMS parametric coupling device under low frequency vibrations

The frequency-based self-powered sensor has an important place in the era of the Internet of Things. In existing reports, the resonator is used either as an energy harvester or a sensor, yet it cannot undertake both demands simultaneously in a single structure. A parametric coupling device (abbreviated as PCD), capable of both temperature sensing and energy harvesting, is proposed with a common wings-inspired structure. Under one low frequency vibration excitation, the vibration energy can be potentially converted to electric energy, while the output frequency is observed to have a linear relationship with the temperature. The wings-inspired structure is comprised of three parts bonded in series, two side beams for collecting vibration energy one of them synchronously for temperature sensing, and a middle flexible beam for achieving parametric coupling. Once the heat is applied to the sensing one, the internal thermal stress is generated in the beam, while the reaction force acts on the anchor end of the beam to create compressive stress, for which the stiffness is decreased to cause frequency shifts and turn the working frequency domain. The parametric coupling is designed to improve the PCD performance, which is supported by theoretical analysis and experimental verification. With a manufactured MEMS PCD prototype, under a harmonic vibration excitation, when the temperature varies from 35.85 °C to 48.35 °C, both frequency shifts for sensing and working frequency domain for harvesting are 13.7 Hz which is 3.5 times larger than those of a non-parametric coupling device (abbreviated as NPCD). The sensing sensitivity of PCD is measured as 2.91 times higher than that of NPCD under a harmonic vibration excitation, while that of PCD is analyzed as 1.69 times higher than that of NPCD under a random one. Theoretical analysis shows the maximum temperature detection range is from 33.32 °C to 84.07 °C and can be further enlarged from 33.32 °C to 108.54 °C by adjusting the length of the sensing beam. The proposed PCD has the potential to be applied to temperature compensation systems or to maintain the operating environments of sensing nodes in self-powered wireless sensing networks (WSN).

Study on vibration attenuation of three-component local resonant pile with low-frequency attenuation zone

The paper explores the increasing concern over environmental vibrations resulting from machine operation and rail transit. Notably, low-frequency vibrations generate surface waves with characteristics like significant energy carrying capacity, long-distance propagation, and slow attenuation. The primary challenge in ground vibration attenuation lies in addressing low-frequency vibrations. The study employs the finite element method to investigate the vibration attenuation of a three-component local resonance pile in three-dimensional space. The analysis delves into the impact of the unit cell structure’s geometry size on bandgaps, and the influences of the period number on the Attenuation Zones (AZs) are also discussed. Furthermore, a comparison is made regarding the vibration attenuation performance of a two-component local resonance pile. The findings reveal that the appropriate design of a three-component local resonance pile can generate low-frequency complete bandgap. The concrete radius, rubber layer thickness, and buried depth of the pile significantly affect Rayleigh wave bandgap. Frequency domain analysis indicates that an increase in period number expands AZs into the bandgap range. Time domain analysis demonstrates a noticeable decrease in ground acceleration amplitude within the bandgap range. The research results presented in this paper offer a novel approach to address the low-frequency vibration attenuation.

Consideration of the issue of regulating low-frequency vibrations of the drill string when drilling with a downhole motor

The object of research is the dynamic processes that occur in the drill string during the deepening of the hole in deep wells. The work is aimed at solving the problem for an idealized system in the form of rod systems while preserving its main oscillatory properties. The nature of oscillatory processes that occur in the drill string during drilling with downhole motors is considered, in some cases it turns out to be very complicated. In the general case, the dynamic process changes according to an aperiodic law, which is superimposed by processes of an oscillating nature with an increasing (damping) nature of the amplitudes of different frequencies. The influence of the torque characteristics of the downhole motor and bit on the development of oscillatory processes in the drill string during well drilling has been theoretically determined. The results of theoretical and experimental studies of oscillatory processes and their interaction with the use of proposed models of hole deepening in the future make it possible to create a simulation model. This model would include taking into account the mode parameters of drilling, the mechanical properties of the rocks to be drilled and the layout of the drill string bottom (DSB). The obtained research results can be applied in practice in the process of designing the structure of the drill string bottom (DSB) with the use of downhole motors, in particular, screw motors, the use of which leads to energy stress, the complication of work processes and structural schemes. As a result, the nature of vibrations changes and the vibration loads on parts of the downhole motor, bits and elements of the drill string are reduced. In the future, it is necessary to take into account the hydrodynamics and the type, as well as the design and parameters of the applied downhole elements for the development of their dynamic models.

Dual straight-wing FBG accelerometer for low-frequency vibration measurement

Fiber optic accelerometers have a wide range of applications in low-frequency vibration measurement, such as in earthquake monitoring, disaster early warning, underground resource exploration, and anti-seismic monitoring projects for critical structures like dams and bridges. In response to the current issues of Fiber Bragg Gratings (FBG) accelerometers being insensitive to low-frequency vibration signals and challenging to apply in engineering, a dual straight-wing FBG accelerometer for low-frequency vibration measurement is proposed. Firstly, a sensor model is established and theoretically analyzed. Secondly, the impact of the sensor's main structural parameters on sensitivity and natural frequency is analyzed, and the sensor is simulated using ANSYS. Finally, a prototype of the sensor is developed, and a low-frequency vibration testing system is set up to test the sensor's performance. Experimental results show that the accelerometer has a natural frequency of 39.1 Hz, operates in the 5–22 Hz frequency band, and has a sensitivity of 171.7 p.m./g, a dynamic range of 69.82 dB, and a transverse interference resistance of less than 9.5%. This research provides a new reference for the development of similar sensors.

Band gap characteristics of bionic acoustic metamaterials based on spider web

For the purpose of low-frequency vibration isolation and noise reduction, combined with the nested mode of spider web, a new concave star bionic acoustic metamaterial was proposed in this paper. Based on the finite element method (FEM) and Bloch theory, the effects of vertex connection mode, nesting level (n), and rotation angle (α) on the band gap distribution, transmission spectrum, and isofrequency line of concave star structure were discussed. The results showed that the two-dimensional (2D) concave star structure had the lowest opening frequency of the first band gap when the vertices coincide and n = 3; when α = 45°, the three-dimensional (3D) concave star structure had the widest band gap distribution and the lowest first band gap in the frequency range within 1000 Hz. The correctness of the simulation results was verified by experiments. These findings can provide a new idea for low-frequency vibration isolation and noise reduction.

Alterations in Step Width and Reaction Times in Walking Subjects Exposed to Mediolateral Foot-Transmitted Vibration

This study explores how low-frequency foot-transmitted vibration (FTV) affects both gait parameters and cognitive performance. Twenty healthy male participants experienced harmonic mediolateral FTV (1.25 Hz, 1 m/s2) while either standing or walking on a treadmill. We assessed participants’ reaction times to visual stimuli using a psychomotor vigilance task (PVT) test under five conditions, including (i) baseline (standing still without vibration), (ii) vibration (standing still with vibration), (iii) walking (walking without vibration), (iv) walking with vibration, and (v) post-test (standing still without vibration after the tests). Additionally, the step width (SW) was measured with a camera system in conditions (iii) and (iv), i.e., when participants were walking with and without vibration and during PVT execution. The results showed that the average vigilance decreased, and the step width increased while walking and/or with vibration exposure. These findings suggest a potential connection between decreased vigilance, increased step width, and the need for enhanced stability, focusing on balance maintenance and a wider base of support. Implications for future standard revisions are presented and discussed.

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl2–NaCl and ZrF4–LiF

AbstractDensity functional theory (DFT) calculations were performed to examine the impact of exchange–correlation (XC) functionals and van der Waals corrections (specifically the D3 method) on the structural and vibrational properties of the SrCl2–NaCl and ZrF4–LiF salt systems. Multiple XC functionals, including the local density approximation (LDA), the generalized gradient approximation using the Perdew–Burke–Ernzerhof (PBE) model, and its modified form suitable for solids (PBEsol), the dispersion‐corrected PBE‐D3 and PBEsol‐D3, were considered. Of these functionals, LDA was found to exhibit the highest degree of error, while PBEsol and PBE‐D3 displayed the least error. Underestimated lattice parameters compared with experimental values were observed to result in higher force constants, leading to an overprediction of vibrational frequencies. Conversely, an overestimation of lattice parameters was associated with lower vibrational frequencies. The methodology presented in this study yielded results that are in good agreement with experiment, irrespective of the method (finite differences vs. density functional perturbation theory) employed for calculating infrared and Raman spectra. It was further demonstrated that for alkali halides with weak Raman scattering, utilizing a supercell constructed from primitive cells better predicts Raman features than does the use of conventional cells.

Research on targeted modulation of elastic wave bandgap in cantilever-structured piezoelectric Phononic crystals

Piezoelectric phononic crystals (PPCs) have the advantages of simplicity and efficiency in controlling elastic wave bandgaps, which can be utilized to solve NVH problems with varying frequency features, such as the low-frequency vibrations caused by the time-varying power source (i.e., motor) in the subframe and underbody of new energy vehicles. However, most of the previous studies on PPCs bandgap control are qualitative, lacking the knowledge of bandgap targeted modulation. This paper analyzes the locally resonant (LR) bandgap characteristics of PPCs with shunting circuits, and aims to achieve precise control of bandgap position by circuit parameters. A theoretical research model of cantilever-structured PPCs is established firstly, and its accuracy is verified through finite element analysis and experiments. Subsequently, the formation mechanism of the LR bandgap is analyzed, and a bandgap characteristic frequency estimation method is proposed, along with an analysis of the influence of electrical parameters using this method. Finally, from the perspective of bandgap practicality, the variable capacitance method is proposed, which can quickly calculate the capacitance value through an estimation formula under the arbitrary designation of target bandgap in the low-frequency range of 200 Hz∼500 Hz. The results show that the actual bandgap position is very close to the target bandgap position, and the bandgap always keeps enough bandwidth and attenuation amount. This method has broad prospects in the field of vibration attenuation where frequency characteristics are variable.

Chiral phononic crystal-inspired railway track for low-frequency vibration suppression

Chiral phononic crystals (CPCs) offer an advanced approach to vibration isolation by exploiting inertial amplification, establishing broad band gaps at low frequencies and outperforming conventional phononic designs. This study pioneers a CPC-inspired railway track that significantly enhances low-frequency vibration isolation through an orthogonal polarization coupling mechanism of the chiral subunit cell. Mechanical modeling and simulations have validated the causes of the enhanced performance and the tunability of crucial physical parameters across characteristic dimensions. Incorporating this structure within a coupled vehicle-floating slab track (FST)-tunnel system facilitates a comparative analysis against conventional steel spring FSTs. The CPC-inspired track system demonstrates enhanced isolation, significantly reducing vibrations within the 200 Hz range for both slab and tunnel structures, achieving a maximum insertion loss of 7.19 dB for the slab and 5.69 dB for the tunnel. Further evaluation of rail and slab displacements, alongside the wheel load reduction rate, underscores the operational safety of trains with the CPC-inspired system implemented. This pioneering exploration of CPC-inspired structures showcases the potential to significantly advance vibration control in urban rail infrastructure, providing a foundational reference for future research.

Mechanical characteristics analysis of high dimensional vibration isolation systems based on high-static-low-dynamic stiffness technology

Large floating raft vibration isolation systems (FRVISs) based on high-static-low-dynamic stiffness (HSLDS) technology offer excellent low frequency vibration isolation performance with broad application prospects. However, the design process for these complex high-dimensional coupled nonlinear systems remains poorly developed, particularly when applied for ocean-going vessels that experience rolling and pitching motions. The present work addresses this issue by establishing a six-degree-of-freedom HSLDS vibration isolation model for FRVISs composed of eight isolators, and the model is applied to fully analyze the swing stability and multidimensional vibration isolation performance of these systems. The influence of nonlinearity on the mechanical properties of the vibration isolators is analyzed more clearly by assuming that each vibration isolator realizes nonlinear HSLDS characteristics in the z direction and linear characteristics in the x and y directions. The results demonstrate that the swing displacement responses of the system are greatly reduced under weak nonlinearity, which reflects the high static stiffness and high static stability characteristics of an HSLDS system. The multidimensional vibration isolation performance of the system is evaluated according to the impacts of nonlinearity, the installation height Hz of the isolators, and the relative position Dr of the two middle isolators. The results of analysis demonstrate that applying a value of Hz = 0 produces the best vibration isolation performance overall under strong nonlinearity by avoiding unnecessary secondary peaks in the force transmission rate under harmonic mechanical excitation and ensuring a maximum high-frequency vibration isolation effect. However, applying a weak nonlinearity is better than a strong nonlinearity if Hz is not zero. In contrast, Dr has little effect on the vibration isolation effect of the raft in the x, y, and z directions. Therefore, an equidistant installation with Dr = 0.5 would be considered ideal from the standpoint of installation stability.

A novel adjustable magnetorheological fluid gradient material of low frequency vibration isolation: a theoretical and experimental study

In this paper, a novel adjustable magnetorheological fluid (MRF) gradient material for low-frequency control is proposed, and the vibration isolation performance of this gradient material is investigated theoretically and experimentally. The gradient material has an excellent ability to control the sound waves and vibrations. However, the currently prepared gradient material does not have the parameter adjustability. At the same time, the MRF can change its material parameters according to the external magnetic field. After applying the traveling magnetic field (TMF) to the MRF with continuously varying and adjustable magnetic induction strength, its material parameters will also be continuously varying and adjustable to constitute an adjustable gradient material. In order to investigate the vibration transfer characteristics of this adjustable gradient material, this paper establishes a micro-mechanical model of MRF and theoretically investigates and numerically calculates the mechanical impedance and vibration transfer characteristics of the adjustable gradient material through the machine-electric analogy theory. At the same time, experimental research was conducted by building an experimental platform to conduct experiments. The results show that the novel adjustable gradient material composed of a TMF and MRF has a good vibration suppression effect in the low-frequency range (10 ∼ 60 Hz) with the vibration level difference of up to 30 dB or more, which has a broad application prospect in the field of vibration control.

Effectiveness of low frequency vibration on the rate of canine retraction: a randomized controlled clinical trial

To investigate the effectiveness of AcceleDent Aura vibrating device on the rate of canine retraction. Thirty-two patients requiring extraction of upper first premolars and canine retraction were randomly allocated with a 1:1 ratio into either no-appliance group or the AcceleDent Aura appliance group. Canine retraction was done applying 150gm of retraction force using NiTi coil springs on 16 × 22 stainless steel archwires. The duration of the study was 4 months. Models were collected and digitized directly after extraction of upper first premolars and at monthly intervals during canine retraction for recording the monthly as well as the total distance moved by the canine. Digitized models were superimposed on the initial model and data were statistically analyzed. Anchorage loss, rotation, tipping, torque and root condition were evaluated using cone beam computed tomography imaging. Pain was evaluated by visual analog scale. No patients were dropped-out during this study. There was no statistically significant difference between both groups regarding the total distance travelled by the canine (P = 0.436), as well as the rate of canine retraction per month (P = 0.17). Root condition was the same for the two groups. Regarding the pain level, there was no statistically significant difference between the two groups at day 0 (P = 0.721), after 24 h (P = 0.882), after 72 h (P = 0.378) and after 7 days (P = 0.964). AcceleDent Aura was not able to accelerate orthodontic tooth movement. Pain level couldn’t be reduced by vibrational force with an AcceleDent device during orthodontic treatment. Root condition was not affected by the vibrational forces.

Low-frequency vibration and noise control in sandwiched composite locally resonant metamaterials-embedded plate structures

This study proposes a sandwiched composite locally resonant metamaterial (SLRM) system and SLRM-embedded plate structure (SLRMeP) to effectively control low-frequency vibrations and sound radiation. The wave control mechanism and configuration of the proposed system are more suitable and realistic to address practical low-frequency vibro-acoustic problems. A numerical model was proposed based on the material properties, unit dimensions, and mass ratios to determine the local resonance characteristics and bandgap formation. The experimental results on a full-scale SLRMeP measuring 3000 × 4200 × 210 mm confirmed the efficacy of the local resonance bandgap for controlling vibrations and sound radiation, achieving a 94.08% reduction in the acceleration response and a 15.13 dB reduction in the sound pressure level. Additionally, variations in mass ratio, achieved by altering the mass density or dimensions, yield distinct bandgap behaviors, offering strategies to enhance vibro-acoustic performance.