Vibration Characteristics Research Articles

Geographically-Informed Modeling and Analysis of Platform Attitude Jitter in GF-7 Sub-Meter Stereo Mapping Satellite

The GF-7 satellite, China’s inaugural sub-meter-level stereoscopic mapping satellite, has been deployed for a wide range of applications, including natural resource investigation, environmental monitoring, fundamental surveying, and the development of global geospatial information resources. The satellite’s stable platform and reliable imaging systems are crucial for achieving high-quality imaging and precise attitude measurements. However, the satellite’s operation is affected by both internal and external factors, which induce vibrations in the satellite platform, thereby affecting image quality and mapping accuracy. To address this challenge, this paper proposes a novel method for constructing a satellite platform vibration model based on geographic location information. The model is developed by integrating composite data from star sensors and gyroscopes (gyro) with subsatellite point location data. The experimental methodology involves the composite processing of gyro data and star sensor optical axis angles, integration of the processed data through time-matching and normalization, and denoising of the integrated data, followed by trigonometric fitting to capture the periodic characteristics of platform vibrations. The positions of the satellite substellar points are determined from the satellite orbit data. A rigorous geometric imaging model is then used to construct a vibration model with geographic location correlation in combination with the satellite subsatellite point positions. The experimental results demonstrate the following: (1) Over the same temporal range, there is a significant convergence in the waveform similarities between the gyro data and the star sensor optical axis angles, indicating a strong correlation in the jitter information; (2) The platform vibration exhibits a robust correlation with the satellite’s geographic location along its orbit. Specifically, the model reveals that the GF-7 satellite experiences the maximum vibration amplitude between 5° S and 20° S latitude during its ascending phase, and the minimum vibration amplitude between 5° N and 20° N latitude during the descending phase. The model established in this study offers theoretical support for optimizing satellite attitude and mitigating platform vibrations.

Enhanced and rapid remediation of chlorpyrifos from aqueous phase by amine modified mesoporous silica SBA-15: A systematic investigation on sorption kinetics and mechanistic studies

Pesticides have become a necessary remedy of contemporary agricultural methods. However, the release of excess pesticides to the water bodies is a growing concern worldwide. Chlorpyrifos (CP), an organophosphate based pesticide used for nearly 50,000 tonnes per year globally, has significantly affected the ecosystem. Herein, we have reported that (3-Aminopropyl)triethoxysilane functionalized SBA-15 (ASBA-15) as an efficient adsorbent to remove CP from its aqueous solution to an extent of 1814 mg g−1 within 20 min. The uptake behavior was studied in detail as a function of adsorbent dosage, contact time, and concentration levels of CP. The adsorption findings were well-fitted into the Langmuir isotherm model and pseudo-second-order kinetics. The estimated values of ΔH0 and ΔS0 revealed the exothermic and spontaneous nature of the process. The XRD reflections between 2 θ = 0.90–1.8o, surface area in the ranges of 781–435 m2 g−1 and pore diameters between 7.2 and 6.0nm indicated the mesoporous as well as stable structure for SBA-15 and ASBA-15 materials at different stages of studies. FT IR studies evidenced the presence of the ‒NH group at 1541 cm−1 in ASBA-15. Thermogravimetric analysis results supported the grafting of the ‒NH group onto ASBA-15 as well as the efficient adsorption of CP. The appearance of characteristic vibration of CP at 1513 cm−1 in CP@ASBA supported the entrapment of CP within ASBA-15. The adsorption and desorption of CP by ASBA-15 were accomplished for five cycles without significant mass loss, which demonstrated the reusability, stability and reversible nature of the material.

Vibration characteristics of rolling bearing cage under speed variation conditions

Speed variation conditions will deteriorate the stress state of the rolling bearing internal components and aggravate the vibration of the cage, thereby affecting the service life and reliability of rolling bearings. In this paper, a nonlinear dynamic analysis model of the cylindrical roller bearing is established considering the rubbing effect and hydrodynamic contact between the cage and the guiding ring, as well as the sliding between the cage and other rolling elements. The vibration characteristics of the cage is discussed under the start-stop conditions and different fluctuations of rotation rate. The results show that the vibration of the cage mainly occurs at the middle and late stages of the acceleration process, and the impact mainly occurs at the middle stage of the deceleration process under the start-stop conditions. Moreover, the fluctuation of inner ring speed will enhance the unstable motion of the cage, among which the vibration and impact of the cage are most severe under the rectangular fluctuation of speed, followed by simple harmonic and triangular fluctuations. The findings can provide a theoretical guidance for improving the performance of rolling bearings and ensuring their safe and reliable operation.

Spectroscopic properties under vibrational strong coupling in disordered matter from path-integral Monte Carlo simulations.

Vibrational strong coupling (VSC), the strong coupling between a Fabry-Perrot cavity and molecular vibrations at mid-infrared frequencies, has received important attention in the last years due to its capacity of modifying both vibrational spectra and chemical reactivity. VSC is a collective effect, and in this work, we introduce Path Integral Monte Carlo (PIMC) simulations that not only take into account the quantum character of the molecular vibrations and of the optical resonance of the cavity but also reproduce this collective behavior by considering multiple replicas of the molecular system. Moreover, we show that it is possible to extract from the PIMC simulations the decomposition of the hybrid optical and molecular states in terms of the bare molecular modes. On a model system of an ensemble of disordered Morse oscillators coupled to a single cavity through the Pauli-Fierz Hamiltonian, PIMC can retrieve known features obtained from analytical modes such as the Tavis-Cummings model and obtain a very close agreement with exact diagonalization for a small number of Morse oscillators. We also find that notwithstanding the anhamonic character of the Morse oscillators, the collective mode coupled to the cavity behaves as a harmonic oscillator, following the quantum central limit theorem.

Optimizing vortex-induced vibration suppression in π-shaped girders using wind tunnel testing and CFD analysis

This investigation meticulously explores the vortex-induced vibration (VIV) characteristics in Π-shaped girders within long-span cable-stayed bridges, presenting novel VIV mitigation techniques. Employing detailed wind tunnel evaluations of a 1:50 scale model alongside computational fluid dynamics (CFD) analyses to model the two-dimensional flow around the girder, this study reveals the formation and shedding of vortices behind the railings and main steel girder, which significantly contribute to VIV in such structures. The introduction of horizontal splitter plates, one m in width, in conjunction with two-m-wide V-shaped guide vanes, was found to substantially reduce the VIV amplitude of the Π-shaped girder, minimizing vortex generation on the deck’s sides and dramatically reducing the maximum vertical VIV amplitude from 208.75 mm to only 5.56 mm. CFD simulations confirm the effectiveness of these measures in suppressing Karman vortex street formation, thereby significantly improving downstream airflow characteristics. These findings offer pivotal insights for the advancement of bridge design and the proactive management of VIV, showcasing the potential of integrated aerodynamic modifications to enhance structural resilience and performance.

Electromechanical coupling vibration characteristics of high-speed train transmission system considering gear eccentricity and running resistance

Electromechanical coupling vibration characteristics of high-speed train transmission system considering gear eccentricity and running resistance

Free vibration of sandwich beams with graphene nanoplatelets reinforced piezoelectric face sheets

Owing to its exceptional physical properties, graphene is considered as an excellent reinforcement for composite materials. However, the existing higher-order models encounter significant hurdles when attempting to accurately predict the natural frequencies of sandwich beams with graphene nanoplatelets reinforced composite (GNPRC) piezoelectric face sheets. If transverse shear deformations are not accurately modeled, the dynamic behavior of piezoelectric sandwich beams will be noticeably influenced by the disparities of material properties at the interfaces of adjacent layers, as well as the inherent electromechanical coupling characteristic. To overcome these challenges, an advanced electro-mechanical coupling theory will be introduced for the vibration analysis of sandwich beams featuring GNPRC piezoelectric face sheets. Compared to previous higher-order models, the proposed beam model introduces an enhanced interlaminar shear stress field incorporating electromechanical properties. This improved stress field can be involved in the equations of motion based on the Hamilton principle, significantly enhancing the precision in analyzing the free vibration behavior of piezoelectric sandwich beams. Furthermore, a simplification of finite element implementation can be achieved by removing the second-order derivatives of in-plane displacements from the transverse shear stress field. Consequently, a C0-type three-node beam element is constructed for the dynamic analysis of sandwich beams with GNPRC piezoelectric face sheets. To validate the performance of the proposed theory, the 3D elasticity solutions and results obtained from alternative theoretical frameworks are used. Numerical results demonstrate that the present model offers superior accuracy over the existing higher-order theories. Additionally, a comprehensive parametric investigation is conducted to explore the influence of key parameters on the free vibration characteristics of piezoelectric sandwich beams.

Mechanical properties and vibration characteristics of multiaxial carbon/glass hybrid fiber composites

AbstractIn this paper, the mechanical properties and vibration characteristics of Carbon‐Glass Hybrid Fiber Composites (CGHFC) are experimentally investigated with varying axial directions and blending ratios. The experimental results demonstrate a significant increase in the tensile strength of the CGHFC with an increasing content of carbon fibers. The biaxially CGHFC exhibits a maximum static tensile strength of 413.27 MPa in the 0° direction and 466.33 MPa in the 90° direction, surpassing both the quadratic and uniaxial directions. Notably, compared to biaxially oriented glass fiber material, the tensile strength of CGHFC is enhanced by 44.36%, thereby significantly improving its overall performance, making them particularly suitable for blade structures subjected to simultaneous tensile and vibratory loads. By optimizing the fiber orientation and blend ratio, the CGHFC provides good vibration control and fatigue resistance while ensuring high strength, thus maximizing the overall performance and service life of the blades. The results of this paper provide important data and theoretical support for the selection and design of wind turbine blade materials and help to promote the development of composite materials in wind turbine blade structure and design.Highlights CGHFCs show enhanced tensile strength with more carbon fibers. Biaxial CGHFCs have max tensile strength at 0° and 90° directions. CGHFCs' strength improves by 44.36% over glass fiber materials. Optimized CGHFCs offer superior vibration control and fatigue resistance. Research supports wind turbine blade material innovation.

New method for predicting the free vibration characteristics of composite laminates based on generalized cell and spectral‐Tchebychev methods

AbstractThis paper presents a new method for analyzing the free vibration characteristics of composite laminates under arbitrary boundary conditions by integrating the generalized method of cells (GMC) and the Two‐Dimensional Spectral‐Tchebychev (2D‐ST) method. First, a meso‐macro correlation matrix is constructed based on the GMC, and the macroscopic performance parameters of the composite laminates are predicted. Then, virtual boundary springs are introduced to simulate the arbitrary boundary conditions, and the energy equation of the laminate is derived based on the first‐order shear deformation theory (FSDT) and Hamilton's principle. Furthermore, an approximate displacement function of the laminate is derived by using the 2D‐ST Tchebychev polynomials, and the Gauss‐Lobatto points are selected for meshless discretization of the structure to obtain the discretized characteristic equation, which is solved to obtain the free vibration frequency of the laminate. Based on Matlab programming, the free vibration frequencies of the laminate under different conditions are calculated, and the convergence, accuracy and computational efficiency of the calculation method are discussed, and the effects of boundary conditions, stacking angle, geometrical parameters, and material parameters on the free vibration frequencies of the laminate are analyzed. The numerical results show that the method has the advantages of fast convergence, high accuracy and high efficiency, and the method can be convenient and fast for parametric studies.Highlights The free vibration characteristics of composite laminates are studied. Combining generalized cell method with spectral‐Tchebychev method. The method has the characteristics of fast convergence, high accuracy and high efficiency. A parametric study is conducted on the free vibration of laminated panels.

A unified Jacobi-Ritz-spectral BEM for vibro-acoustic behavior of spherical shell

In order to solve the vibration and acoustic characteristics of spherical shell in light fluid environment, based on Jacobi-Ritz-spectral BEM, a unified analysis formula for acoustic vibration of spherical shell under arbitrary boundary conditions is established. Based on the First-order shear deformation theory (FSDT) and domain decomposition method (DDM), the theoretical model of spherical shell structure is established. The improved Jacobi polynomial is innovatively used to construct the displacement tolerance function of the spherical shell. Based on the spectral Kirchhoff-Helmholtz integral formula, the theoretical model of the acoustic fluid outside the spherical shell is established. The special form of Jacobi polynomial Chebyshev polynomial is used to describe the excitation sound pressure on the spherical shell segment, so as to ensure that the generalized coordinates of the structure can be perfectly matched with the acoustic boundary element nodes. In addition, the integration along the meridian of the shell is used to control the movement of the fluid, which simplifies the surface integration. The CHIEF method is used to solve the problem of non-unique solution of acoustic variables of rotary structure. Compared with the published literature, numerical simulation results and experimental results, the proposed method has higher calculation accuracy. In addition, based on this method, the influence of boundary conditions, geometric dimensions and other factors on the acoustic and vibration characteristics of spherical shells is discussed, which accumulates data for analyzing the acoustic and vibration behavior of spherical shells.

Characterization of PbMo0.3W0.7O4 Crystal: A Potential Material for Photocatalysis and Optoelectronic Applications

AbstractPbMo0.3W0.7O4 semiconductor crystal, which contains the balanced ratios of Mo and W, is grown for the first time by Czochralski method. The structural and optical properties of the crystal are investigated in detail in the present study. Structural analysis shows that crystal has tetragonal structure like PbMoO4 and PbWO4 compounds. The optical characteristics are studied by transmission, Raman, FTIR and photoluminescence methods. The bandgap energy is found to be 3.18 eV, and the positions of the conduction and valence bands are determined. The vibrational characteristics are studied by means of Raman and FTIR spectroscopy techniques. Photoluminescence spectrum presents three peaks around 486, 529, and 544 nm which fall into the green emission spectral range. Taking into account the properties of the compound, it is stated that PbMo0.3W0.7O4 (or Pb(MoO4)0.3(WO4)0.7) has the potential to be used in water splitting applications and optoelectronic devices that emit green light.

An analytical method for the vibration characteristics of double panel structures with uniform elastic boundary supports

ABSTRACT In this paper, the methods for solving the free vibration and forced vibration of double panel structures under arbitrary boundaries are studied. Based on the Mindlin plate theory, the natural boundary between plates and plates is constrained by artificial springs, and the theoretical model of the structure is derived. The displacement function of in-plane vibration and bending vibration is expressed by a modified Fourier series expansion. The effectiveness and reliability of this method are verified by a series of numerical calculations and comparison with those of the finite element method. Through the parameter analysis, it can be seen that the vibration isolation effect can be increased by properly increasing the coupling height or making the connecting plate closer to the boundary of the bottom plate. The method presented in this paper can be used in vibration absorption and structural design of such structures.

Research on Radial Vibration Model and Low-Frequency Vibration Suppression Method in PMSM by Injecting Multiple Symmetric Harmonic Currents

Driven by frequency conversion, the windings of a three-phase permanent magnet synchronous motor (PMSM) contain both odd and even harmonic currents. Due to the motor’s pole–slot conductance modulation, the interaction between the magnetic fields generated by these harmonic currents and the permanent magnet field results in harmonic radial vibrations of the motor. This paper analyzes the three-phase currents of the prototype and derives the radial magnetomotive force (MMF) spatiotemporal models for symmetric harmonic currents. By integrating Maxwell’s magnetic force formula and vibration response formula, the radial vibration models for symmetric harmonic currents are developed. The characteristics of vibrations caused by odd and even harmonic currents, as well as positive sequence and negative sequence harmonic currents, are analyzed separately. A cyclic sequence, low-frequency vibration suppression control method incorporating multiple harmonic current injections was designed. Experimental results of this method are compared with those obtained using an ideal sinusoidal current. Except for the second harmonic vibration, all other vibrations are significantly suppressed, with a maximum suppression rate of 92.28%. The total vibration level is reduced by 12.7619 dB, and the average torque is reduced by 0.67% with the total harmonic distortion of the current at 2.89%. The experimental results show that the vibration method in this paper has little influence on the average torque of the motor, the current distortion rate is small, and the vibration suppression effect is good.

The role of ion beam in modification of CuO@NiO@ZnO/GO electrode for supercapacitor application

Recently, mixed transition metals oxides became emerging electrode materials for energy storage devices such as supercapacitors, batteries, etc. due to their high electrochemical performances. In this study, mixed transition metals including Copper oxide (CuO), Nickel oxide (NiO) and Zinc oxide (ZnO) in conjunction with graphene oxide (GO) were used to fabricate electrode materials for the supercapacitor applications adopting hydrothermal process. The features of the as-fabricated electrodes were further modified by irradiating them with 5.0 MeV C++ ions with varying fluence rates. Monte Carlo-based Stopping and Range of Ions in Matter (SRIM) simulation code was utilized to analyze the ion implantation-induced processes inside the target electrode. Electrodes' crystal features, morphologies, elemental compositions, and vibrational and optical characteristics were examined employing X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and UV–visible spectroscopy, respectively. Electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD), and cyclic voltammetry (CV) were among various techniques engaged to analyze the electrochemical properties of the pristine and post-implanted electrode materials. The electrochemical findings from CV and GCD for the electrode implanted with 5.0 × 1015 ionscm−2, which offered the best result presented enhanced specific capacitances of 1250 and 1350 Fg−1 at a scan rate 1.0 mVs−1 and current density 0.5 Ag−1 respectively. This study revealed that carbon ion implantation at a fluence 5.0 × 1015 ionscm−2 could prompt the enhancement of the electrochemical properties of this fabricated electrode material.

Effect of SFD on rubbing-induced vibration characteristics in dual-rotor-blade-casing system

Effect of SFD on rubbing-induced vibration characteristics in dual-rotor-blade-casing system

Influence of Distributor Structure on Through-Sea Valve Vibration Characteristics and Improvement Design

To address the issue of excessive transient noise during the opening and closing of a sea valve, a method for reducing pressure fluctuations during the opening of the electromagnetic hydraulic distributor has been proposed by analyzing the structure and working principle of the distributor. Based on theoretical calculation and simulation analysis, the size and shape of the buffer slot of the flow hole are determined under the condition that the stable working flow rate remains unchanged. An improved electromagnetic hydraulic distributor is developed and tested. The results indicate that this method can effectively control the opening and closing transient noise of the sea valve.

Investigation on the characteristics of flow-induced vibration and noise of acoustic window with embedded compound acoustic black holes

In recent decades, acoustic black hole (ABH) structures have shown significant potential for suppressing structural vibrations and noise radiation. However, the ABH structure has not been applied to panel–cavity noise control under heavy fluid loading. In this study, a hybrid numerical approach was used to analyse the vibro-acoustic response suppression mechanism of a compound acoustic black hole (CABH) acoustic window under turbulent boundary layer (TBL) excitation. Both sides of the acoustic window interact with the water. The results show that the local vibration modes of the CABH lead to a strong interaction between the structure and damping material. The amplitude of the high-order modal wavenumber spectra of the CABH was small, which weakened the spatial coupling between the TBL pressure and the structure. The coupling strength between the CABH acoustic window and the internal sound field was reduced, causing noise suppression inside the cavity. To further examine the noise reduction performance of the CABH panel cavity system, a flow-induced experiment with a large-scale CABH acoustic window was carried out in a large cavitation channel, and the results showed significant hydrodynamic self-noise reduction.

Analysis of FGM-type porous sandwich plates subjected to free vibration using Student Order Theory

This research adopts a high-order shear deformation theory to explore the free vibration characteristics of square porous sandwich plates constructed from functionally graded materials (FGMs). This theory effectively addresses shear deformation effects without necessitating a shear correction factor. The material properties of the FGMs change continuously throughout the plate's thickness, following a power-law distribution (P-FGM) based on the volume fractions of the component materials. The outer layers are metal, while a uniform ceramic layer constitutes the core. The governing equations are derived from the principle of virtual displacements. This study examines three different porosity distributions. By utilizing Hamilton's principle, the equations of motion were formulated. The numerical analysis demonstrates how the distribution of materials, geometry, and porosity affect the free vibration responses of FGM sandwich plates. The validity of the present theory is studied by comparing certain results obtained with other results published in the literature.

Reducing the diameter of the atomized particles by coating polymer membrane on the inner wall of micro-tapered holes of the ultrasonic mesh atomizers

Atomized inhalation therapy with its rapid efficacy, low side effects and high medicine utilization, has become a crucial method for treating respiratory diseases. The depth of atomized particles deposition in the respiratory tract mainly depends on the particle diameter, making the reducing of the atomized particle size crucial for medicine deposit in lung. In the existing literatures, for the widely used dynamic mesh atomizer, the majority of the researches focused on the mechanical structure and the vibration characteristics of the atomizers. However, there is little researches on the micro-tapered holes of the metal sheet of the atomizer, despite the fact that the diameter of these tapered holes determines the size of the atomized particles. Due to the processing technology, the diameter of the micro-tapered holes cannot be further reduced, which greatly limits the development of the dynamic mesh atomizer in inhalation therapy. In this study, we consider the use of polymer coating on the inner wall of the micro-tapered holes to eliminate burrs, reduce the diameter of the holes, and ultimately reduce the size of the atomized particles. A theoretical model of the initial thickness of the coating polymer membrane and the rupture depth under the uniform air pressure applied to a single tapered hole was established. The metal sheets with different initial coating thicknesses were processed to verify the theoretical model by observing the quality of the inner surface and measuring the diameter of the holes. The particle size measurement experiment results show that when the initial coating thickness was 3 μm and 4.5 μm, the average particle sizes were reduced by 12.5 % and 23.2 %, respectively. Therefore, the proposed method can effectively reduce the atomized particles size, which helps to efficiently deposit atomized drugs in the lungs.

Analysis of the vibration behaviour of a gas turbine during operation

The vibratory behaviour of the gas turbine during operation is analysed in this article. The modern method consists of studying the state of a machine during its operation, to intervene only when the parameters allow it. However, experience has shown that vibration analysis is the most widely used technique to make a reliable diagnosis and to detect the appearance and evolution of most mechanical and hydraulic defects. In our study, we applied the method of vibration analysis of the gas turbine line using monitoring methods to diagnose mechanical defects in shaft bearings. In this sense, the experimental was carried out by measuring and monitoring the level of vibration produced by the turbine, an indicator on its condition was obtained. Should the rise in vibration levels of the machine facilitate the identification of a fault, the subsequent analysis of the machine's vibration characteristics will enable the source of the fault to be determined. It is then possible to determine with accuracy the time before the situation becomes critical.