Vibration Research Articles

Generalized bond polarizability model for more accurate atomistic modeling of Raman spectra.

Raman spectroscopy is an important tool for studying molecules, liquids and solids. While Raman spectra can be obtained theoretically from molecular dynamics (MD) simulations, this requires the calculation of electronic polarizability along the simulation trajectory. First-principles calculations of electronic polarizability are computationally expensive, motivating the development of atomistic models for the evaluation of the changes in the electronic polarizability with the changes in the atomic coordinates of the system. The bond polarizability model (BPM) is one of the oldest and simplest such atomistic models but cannot reproduce the effects of angular vibrations, leading to inaccurate modeling of Raman spectra. Here, we demonstrate that the generalization of BPM through the inclusion of terms for atom pairs that are traditionally considered to be not involved in bonding dramatically improves the accuracy of polarizability modeling and Raman spectra calculations. The generalized BPM (GBPM) reproduces the abinitio polarizability and Raman spectra for a range of tested molecules (SO2, H2S, H2O, NH3, CH4, CH3OH, and CH3CH2OH) with high accuracy and also shows significantly improved agreement with abinitio results for the more complex ferroelectric BaTiO3 systems. For liquid water, the anisotropic Raman spectrum derived from atomistic MD simulations using the GBPM evaluation of polarizability shows significantly improved agreement with the experimental spectrum compared to the spectrum derived using the BPM. Thus, the GBPM can be used for the modeling of Raman spectra using large-scale molecular dynamics and provides a good basis for the further development of atomistic polarizability models.

IFD-BiC: A Class-incremental Continual Learning Method for Diesel Engine Fault Diagnosis

Abstract In recent years, deep learning-based fault diagnosis methods for diesel engines have been developed assuming that a comprehensive dataset is available for one-time learning. However, in reality, it is impractical to obtain a complete dataset all at once. Instead, new data is gradually acquired over time. To address this issue, this paper proposes an incremental fault diagnosis method with bias correction (IFD-BiC). When receiving incremental fault data, the IFD-BiC model incorporates new classifier nodes and updates network parameters using a combination of distillation loss and cross-entropy. During the update process, old samples saved in the exemplar set are replayed, and a bias correction layer is used to correct the prediction bias caused by the imbalance between new and old samples. This enables the model to learn new fault tasks without experiencing catastrophic forgetting. To ensure the applicability of the method to various operating conditions of diesel engines, cyclic angular vibration with consistent length at different speeds is used as the model input. Through experimental validation across a pair of distinct diesel engine models, the proposed method achieves highly accurate fault diagnosis on stream format training data. Moreover, an evaluation against leading incremental learning techniques affirms the proposed method’s advantage. 

Tool Condition Monitoring Model Based on DAE–SVR

Cutting tools are executive components in metal processing, and tool wear directly affects the quality of the workpiece and processing efficiency; monitoring the change in its state is crucial to avoid accidents and ensure the safety of workers. The traditional monitoring model cannot compress a large amount of cutting data effectively, failing to obtain reliable feature data, and there are some defects in generalization ability and monitoring accuracy. For this purpose, this article takes milling cutters as the research object, and it integrates signals from force sensors, vibration sensors, and acoustic emission sensors, combining the advantages of the denoising autoencoder (DAE) model in data compression and the high monitoring accuracy of the support vector regression (SVR) model, to establish a tool wear monitoring model based on DAE–SVR. The results show that compared with traditional DAE and SVR models in multiple datasets, the maximum improvement in monitoring performance (MAE) is 43.58%.

Design of Piezoelectric Energy Harvester Single Cantilever Beam for IoT applications and Micro-electronic devices

A few years back the power requirement of electronic devices was very high. But with the technological developments in the field of internet-based systems, the design of low-powered microelectronic devices, WSN and IoT devices became necessary. In these systems the size and the power requirement are low and in most situations the replacement of batteries is challenging. For these microelectronic and IoT devices the abundant energy harvester is very useful. Among different abundant energy resources, vibrational energy harvesting with piezoelectric cantilever beam energy harvesters is of interest. This research work presents the design and analysis of an energy harvester (EH) which contains a single piezoelectric cantilever beam that captures the vibrational energy of the suspension bridge. This approach ties the two things together by framing piezoelectric energy harvesting as a solution to the power challenges faced by low-powered devices, making the transition feel more natural and connected. The main challenge in the design was matching the resonance frequency of the bridge with a piezo EH which is around 2.5Hz to extract maximum power. To overcome this problem Eigen frequency analysis in COMSOL Multiphysics is done. The 3D geometry of single beam piezo EH is designed and analyzed in COMSOL Multiphysics solid works. In this research work a relationship is established between the geometrical parameters of the single beam piezo EH and Eigen frequency based on the first six Eigen frequency analyses in COMSOL Multiphysics. For fi nite element analysis(FEA) a piezo single beam harvester is vibrated by application of force which is equal to the vibrational force (0.98m/s<sup>2</sup>) in the suspension bridge. The force of (0.98 m/s²) is chosen because it avoids resonating with critical system components. The output from the harvester is achieved at a resonance frequency of 2.5Hz. The output from the piezo is very low 800 milli volts at 2.5Hz. The output results of piezo EH are also compared with a cantilever beam with a single-branch structure.

Weight Effects on Vertical Transverse Vibration of a Beam with a Nonlinear Energy Sink

Reductions in the vibration of a continuum system via a nonlinear energy sink have been widely investigated. It is usually assumed that weight effects can be ignored if the vibration is measured from the static equilibrium configuration. The present investigation reveals the dynamic effects of weight on the vertical transverse vibrations of a Euler–Bernoulli beam coupled with a nonlinear energy sink. The governing equations considering and neglecting weights were derived. The equations were discretized with some numerical support. The discretized equations were analytically solved via the harmonic balance method. The harmonic balance solutions were compared with the numerical solution via the Runge–Kutta method. Finite element simulations were performed via ANSYS software (version number:2.2.1). Free and forced vibrations, predicted by equations considering or neglecting the weights, were compared with the finite element solutions. For the forced vibrations, the amplitude–frequency responses determined by the harmonic balance method agree well with those calculated by the Runge–Kutta method. The free and forced vibration responses predicted by the equations considering the weights are closer to those computed by the finite element method than the responses predicted by the equation neglecting the weights. The assumption that weights can be balanced by static deflections leads to errors in the analysis of the vertical transverse vibrations of a Euler–Bernoulli beam with a nonlinear energy sink.

Free and forced vibration analysis of three-phase composite sandwich plate with magneto-electro-elastic facesheets

Free and forced vibration analysis of three-phase composite sandwich plate with magneto-electro-elastic facesheets

Design and Analysis of Combined Vibration Absorbers for Ship Propulsion Shaft Systems

The vibration of a ship’s propulsion shaft system directly affects the ship’s lifespan, and many studies have designed vibration absorbers only for one of the natural frequencies of a ship’s propulsion shaft system without considering the influence of multiple low-order resonance frequencies. In this paper, a vibration absorber combined with a magnetorheological elastomer vibration absorber and a rubber vibration absorber in series is designed, and it can cover two torsional natural frequency band ranges to achieve better vibration reduction performances in multiple different torsional natural frequencies. The torsional natural frequency of the propulsion shafting of a 45 m fishing vessel is determined based on a multiple-degrees-of-freedom equivalent discretization model. Two natural frequencies, 22.4 Hz and 131.4 Hz, of a ship propulsion shaft system are selected as the design goal parameters of the combined vibration absorber. The magnetic field is simulated to ensure that the magnetic field generated by an energized coil can meet requirements. Then, a dynamic simulation of the ship propulsion shaft system with a combined vibration absorber is conducted via co-simulation. Afterward, the device is installed on the intermediate shaft of the ship propulsion shaft system for simulation, and the vibration reduction effect of the device is analyzed at different frequencies by controlling the current. When the device is controlled to operate at the optimal frequency point, the results show that the angular acceleration vibration amplitude reduction around the first and third torsional natural frequencies of the propulsion shaft system reaches 90% and 18%, respectively. This study provides new ideas for the intelligent and controllable vibration damping of ship propulsion shaft systems, especially for the development trend of intelligent ship equipment under complex working conditions.

Methodology for Designing Vibration Devices with Asymmetric Oscillations and a Given Value of the Asymmetry of the Driving Force

In mechanical engineering, the building industry, and many other branches of industry, vibration machines are widely used, in which circular and directed oscillations predominate in the form of movement of the working equipment. This article examines methods for generating asymmetric oscillations, which are estimated by a numerical parameter, namely by the coefficient of asymmetry of the magnitude of the driving force when changing the direction of action in a directed motion within each period of oscillations. It is shown that for generating asymmetric mechanical vibrations, vibration devices are used, consisting of vibrators of directed vibrations, called stages. These stages form the total asymmetric driving force. The behavior of the total driving force of asymmetric vibrations and the working equipment of the vibration machine are described by analytical equations, which represent certain laws of motion of the mechanical system. This article presents a numerical analysis of methods for obtaining laws of motion for a two-stage, three-stage, and four-stage vibration device with asymmetric oscillations. An analysis of the methodology for obtaining a generalized law of motion for a vibration device with asymmetric oscillations is performed based on the application of polyharmonic oscillation synthesis methods. It is shown that the method of forming the total driving force of a vibration device based on the coefficients of the terms of the Fourier series has limited capabilities. This article develops, substantiates, and presents a generalized method for calculating and designing a vibration device with asymmetric oscillations by the value of the total driving force and a given value of the asymmetry coefficient in a wide range of rational designs of vibration machines. The proposed method is accompanied by a numerical example for a vibration device with an asymmetry coefficient of the total driving force equal to 10.

Investigating slope stability of multiple stopes prone to instability in the Ziluoyi iron ore mining site

The ore mining sites commonly experience slope instability, which is causing concern for the workers’ safety and the operation’s stability. Considering the Ziluoyi iron ore mining site as a case study, uniaxial compression strength and shear tests are performed on the lower disk peripheral rock, ore body, and upper disk peripheral rock, leading to the extraction of compressive strength and elastic modulus (lower disk: 77.7 MPa–9.093 GPa; ore body: 19.6 MPa–4.619 GPa; upper disk: 55.47 MPa–5.573 GPa). Further, using the Hoek–Brown criterion in conjunction with the Moher–Columb criterion, the cohesion and internal friction angle of various samples are appropriately determined (lower disk: 21.124 MPa–35.614°; ore body: 21.66 MPa–26.5°; upper disk: 42.916 MPa–25.743°). By employing an appropriate rock mass reduction model, its constants (m and s) and RMR score for the consisting layers (schist layer and ore body) of the three understudy slopes (Slope#1–Slope#3) are evaluated. An effective algorithm based on the Morgenstern–Price method is employed and its effectiveness is also proved by comparing its factor of safety results with those of Geo-Slope for various slope structures subjected to different loads. Subsequently, the stability analyses of various slopes are methodically examined by predicting the factor of safety values under multiple types of loading (i.e., self-weight + groundwater, slope self-weight + groundwater + blasting vibration force, and self-weight + groundwater + seismic force). The factor of safety values of the slopes pertinent to Slope#1/Slope#2/Slope#3 subjected to the above loading conditions are obtained as 1.354/1.273/1.188, 1.326/1.239/1.169, and 1.321/1.232/1.162, respectively. Upon comparing these results with those of a valid homeland specification, it becomes clear that the results are able to meet safety standards and ensure efficient mine operation.

Dynamic analysis of viscoelastic functionally graded nanoplate

In this article, the dynamic behavior of nanoplates under time-dependent load is investigated, focusing on functionally graded viscoelastic materials and nanoscale effects. Eringen’s nonlocal elasticity theory is utilized to examine mechanical response of the nanoplate. Hamilton’s principle is utilized to derive the equations of motion, taking into account both kinetic and potential energy aspects. The obtained complex partial differential equations are then solved employing Navier method and provides an efficient way to obtain analytical solutions. The study initially performed a free vibration analysis for functionally graded nanoplate, comparing the obtained results with those available in the literature to validate the developed method. Following this validation, a parametric analysis was conducted to examine the influence of both nonlocal parameter, which accounts for nanoscale effects, and power law exponent governing material gradation on free vibration behavior of functionally graded nanoplate. Finally, as the original contribution of this study, a damped forced vibration analysis was carried out within the scope of the parametric study, investigating the effects of power law exponents, viscoelastic parameters, nonlocal parameters, and various geometric properties on functionally graded viscoelastic nanoplates’ the displacement-time relationship and maximum displacements.

Free and forced vibrations of circular plates made of functionally graded graphene origami-enabled auxetic metamaterials

Presented herein is a numerical investigation into the free and forced vibrational characteristics of circular plates made of functionally graded graphene origami-enabled auxetic metamaterials (FG-GOEAMs). The material properties of FG-GOEAM are estimated using genetic programing-assisted micromechanical models considering two graphene content distribution patterns. The effects of graphene content, size and folding degree on the material properties are taken into account by the models. The formulation of the paper is in the context of first-order shear deformation plate theory, and the governing equations of motion are achieved utilizing Hamilton’s principle. In the solution approach, the variational differential quadrature (VDQ) method is employed by which the variational statement of problem is directly derived and discretized using matrix differential and integral operators. Selected numerical results are presented to study the effects of graphene origami (GOri) content, folding degree, and distribution pattern on the free and forced vibration responses of FG-GOEAM circular plates with clamped and hinged boundary conditions.

High-frequency jetting through axial forced vibration of jet tube

On-demand droplet jetting can be achieved through the axial reciprocating motion of the jet tube, which is a novel technology. However, its feasibility for high-frequency jetting has not been explored. In this study, it is found that when high-frequency driving signals are applied to the piezoelectric ceramic, the tube undergoes forced vibration, which enables repeatable jetting at frequencies of up to 10 kHz. This paper also investigates the effects of the vibration amplitude and frequency of the tube on the jetting behavior and reveals a linear relationship between the jet velocity and the tube vibration velocity amplitude.

Vortex-induced vibration characteristics of twin-box girder section in long-span bridge: A numerical evaluation method

The vortex-induced vibration (VIV) characteristics of twin-box girders are critical in the design of long-span bridges. This study aims to investigate the VIV behavior of a twin-box girder section and to deepen the understanding of the mechanisms underlying VIV. A numerical approach that integrates both free and forced vibration analyses is developed to predict VIV performance. The VIV amplitude is evaluated using the free vibration method within the wind speed range identified by the forced vibration method. Comparisons with wind tunnel test results demonstrate the feasibility of this approach. Meanwhile, flow structure and aerodynamic characteristics of the twin-box girder were analyzed in relation to the VIV mechanism. The results show that flow restrictor plate could effectively suppress vertical VIV at a wind attack angle 0° and reduce the VIV amplitude by 50% at +3°wind attack angle. The central opening slot is identified as a significant factor in inducing VIV, as the upper and lower vortices interact with the airflow passing through the respective sections of the slot. The flow restrictor plates positioned at the upper section of the opening slot cause most upper vortices to shift downstream at wind attack angles of 0° and +3°. This shift results in minimal airflow reflux at the slot, which is crucial for optimizing VIV performance. At a wind attack angle of +3°, the vortices at the lower part of the slot persist, albeit with reduced size. These changes in vortex behavior underscore the sensitivity of vortex formation to variations in wind attack angles.

Output-Only Damage-Detection Method for Concrete Frame Structure Using the Phase Space Reconstruction Method

Abstract Vibration-based techniques for structural health monitoring have garnered increasing attention in recent years, particularly in the context of numerous existing concrete frame structures. However, the detection of minor damages remains a challenging endeavor. Diverging from conventional methods reliant on time, frequency, or time-frequency domains for identification, this study proposes and evaluates an output-only phase space–based algorithms for structural damage detection, which involves reconstructing the dynamic system in phase space. Key to this approach is the introduction of the attractor distance, which is derived from attractor geometry, as a defining feature. Although impact force or ambient vibration typically serve as external excitations, this study employs chaotic excitation to induce vibrations in structures. Numerical and experimental investigations are conducted to assess the efficacy of the proposed phase space reconstruction method in detecting damage. A frame structure modeled as a lumped mass model is simulated and analyzed, exploring various degrees of damage and their effects on identification results. Furthermore, the influence of delay time and Gaussian distributed noise on damage-detection results is scrutinized. Validation experiments on a four-story frame structure subjected to chaotic excitation confirm the utility of the reconstructed attractor for damage detection, particularly in scenarios involving minor damage, with an approximately 5 % reduction in stiffness. The findings suggest that combining trajectory analysis with attractor distance facilitates efficient diagnosis of minor damage. The proposed methodology holds promise for damage identification in more intricate and large-scale concrete frame structures.

Sedimentation stability of fuel slurries under influence of vibration and centrifugal forces

Sedimentation stability of fuel slurries under influence of vibration and centrifugal forces

Studying a droplet impaction on a vibrating porous medium

This study investigates the influence of vibration on droplet dynamics when a droplet impacts a three-dimensional (3D) structured porous medium, focusing on intrinsic properties such as porosity and wettability, along with the effect of vibration phase angle. Using an Allen-Cahn equation-based lattice Boltzmann method (A-C LBM), the research analyzes multiphase flow dynamics. The results compare droplet spreading and penetration on vibrating versus non-vibrating porous media. Without vibration, droplets get trapped within the pores, reaching equilibrium due to adhesive, viscous, and capillary forces. However, sufficient vibrational forces can overcome surface adhesion, allowing droplets to pass through the porous medium. This phenomenon is influenced by the droplet's contact angle and initial impact inertia. The study finds that hydrophobic surfaces, characterised by higher contact angles, significantly reduce liquid infiltration into the medium under both vibrational and non-vibrational conditions. This reduction is due to dominant surface tension and repellent forces, which, in combination with vibrational forces, minimise droplet spreading and penetration, even in highly porous media. Conversely, on hydrophilic surfaces, adhesive and capillary forces enhance the droplet's inertia, causing sudden penetration into the porous medium. Further, the study reveals that the phase angle of vibration critically affects the droplet's behaviour. With sinusoidal vibration, lower phase angles cause the porous medium to move in the opposite direction to the droplet, enhancing the synergy between vibration and inertia forces, leading to rapid infiltration. Higher phase angles, aligning the medium's movement with the droplet's impact path, result in reduced infiltration. Overall, this research provides crucial insights into how porosity, wettability, and vibration phase angle collectively influence droplet dynamics on structured porous media, offering valuable implications for applications involving fluid transport and filtration in porous structures.

ANALYSIS OF VIBRATIONS OF AN ELASTIC PLATE ON A VISCOELASTIC BASE VIA THE FRACTIONAL DERIVATIVE KELVIN-VOIGT MODEL

In the present paper, free and forced vibrations of an elastic Kirchhoff-Love plate on a viscoelastic foundation of the Fuss-Winkler type are studied, the damping properties of which are described using the Kelvin-Voigt model with a fractional derivative. The integral Laplace transform method with further expansion of the sought functions into a series of eigenfunctions of the problem is used as the method for solving the problem of non-stationary vibrations of linear elastic plates on a viscoelastic foundation. The solution is obtained as the sum of two terms, one of which controls the drift of the equilibrium position of the system and is determined by the quasi-static creep processes occurring in the system, and the other term describes the damping of oscillations around the equilibrium position and is determined by the inertia and energy dissipation of the system.

Effect of forced vibrations of brake pads on the thermal performance of the disc: A numerical perspective

In this work we numerically investigate the thermal behaviour of automobile brake discs when the brake pads are subjected to horizontal vibrations. To determine the influence of these vibrations on the performance of the disc, the partial differential equation (PDE) of conductive heat transfer in the disc is solved numerically using the finite element method. The outer surfaces of the disc and pad are exposed to convective and radiant heat flows. We determine the influence of the amplitude and frequency of vibrations of the plate on the isotherms’ distribution, maximum temperature, average temperature, and dissipation energy. As per the results, this study shows that adding a vibration force can reduce the heat dissipated in the disc and, therefore, improve the performance of the automobile braking system.

Low-frequency vibration monitoring system measuring the fringe shift by using linear Fresnel zone plates for shiny surfaces

This paper presents a vibration monitoring system that measures the fringe shift from the Fresnel diffraction pattern for noncontact measurement of translational and angular vibrations. Conventional vibration systems have some major limitations in practical applications. For example, a laser Doppler vibrometer (LDV) fails to accurately measure large-amplitude vibrations of a mirrored object undergoing dynamic tilts or rotations. Additionally, achieving the accuracy required for micro/nanomeasurement in precision machines when measuring low-frequency vibrations (LFV) remains a significant challenge. In this study, the vibration measurement system utilizes a linear Fresnel zone plate with parallel strip lines to create the diffraction pattern. Surface vibrations cause shifts in these lines, and the resulting fringe pattern on the vibrating surface carries information about the local vibrational amplitude and frequency. To achieve this, the linear vibration and displacement of the object are accurately verified using a linear motion platform and a rotation stage, with accuracies of approximately 20 nm and 0.002°, respectively. Rotational vibration measurements utilize tracking beam deflection through the image fringe shift measurement method, while out-of-plane displacement is determined both from this method and from changes in the period density of diffraction patterns, which depend on the position of the patterns and the local spatial frequency. A CCD camera captures sequences of images of the deflected fringes due to vibrating object. The system can detect linear vibrations with frequencies above 251.91 µHz and has a displacement uncertainty of approximately 5.8 µm, achieving an angular resolution of 37.67 µrad. Compared to conventional LDV vibrometers and eddy current sensors, the proposed method offers an effective and accurate technique for measuring LFVs of shiny surfaces. Furthermore, it provides a significantly extended measurement range for both translation and rotational angles of objects in engineering applications.

Flexural Wave Bandgap Characteristics Analysis of Periodic Double-Span Beam Based on Spectral Geometry Method: A Unified Formulation

The bandgap characteristics of periodic double-span beams are analyzed using spectral geometry methods in this paper. The displacement function of the beam structure is represented in a unified form, supplemented by sine series in addition to Fourier cosine series to avoid discontinuities in displacement at the boundary positions. The introduction of artificial spring technology satisfies the strong coupling connection conditions between beams. Combining it with Bloch’s theorem allows the separation of boundary conditions and displacement functions, ensuring the convergence and accuracy of the method. The energy functional of the double-span beam under periodic boundary conditions is established. The bandgap characteristics of the double-span beam can be obtained using the Rayleigh–Ritz method. The bandgap characteristics calculated based on the proposed method are in good agreement with those obtained from the transfer matrix method, and the bandgap frequency range matches well with the vibration attenuation range obtained from the test results. The effectiveness of forced vibration analysis for finite periodic double-span beams is also validated through the finite element method. Additionally, the influence of material properties, geometric parameters and lattice constants on the bandgap characteristics of periodic double-span beams is presented, providing insights into the mechanisms for tuning bandgap characteristics.