Effect Of External Excitation Research Articles

Chaos and resonance of nonlinear FG shallow shells reinforced by oblique stiffeners

This paper presents an analysis of the nonlinear dynamics of functionally graded (FG) shallow shells that are simply supported, reinforced with oblique stiffeners, and subjected to external excitation. The properties of these oblique stiffened functionally graded (OSFG) shallow shells vary across their thickness, following a power law distribution based on the volume fractions. Employing the first-order shear deformation theory (FSDT) coupled with the von Kármán nonlinear strain-displacement relations, the derivation of the nonlinear equations of motion is accomplished through the application of Hamilton's principle. The model of FG shallow shells reinforced with oblique two-series stiffeners is developed, allowing for the angles of the two stiffeners to be similar or different from each other. In this context, the employment of the first-order shear deformation theory (FSDT) results in the enhancement of the complexity in modeling the oblique stiffeners. Galerkin's method is applied to discretize the given equations, converting them into a nonlinear dynamical system with two degrees of freedom. This system incorporates both quadratic and cubic nonlinearities and considers the effects of external excitation. The analysis of this research particularly focuses on the resonant scenario involving principal resonance and 1:1 internal resonance. Through the asymptotic perturbation method, a four-dimensional nonlinear averaged equation is obtained. For the first time, a numerical investigation of the research reveals critical insights into the behavior of the system, such as waveforms, phase diagrams, and Poincaré maps, highlighting the effects of different angles of the stiffeners and variations of material parameters on the nonlinear dynamics of these shells.

Torque effect on vibration behavior of high-speed train gearbox under internal and external excitations

AbstractThe high-speed train transmission system, experiencing both the internal excitation originating from gear meshing and the external excitation originating from the wheel–rail interaction, exhibits complex dynamic behavior in the actual service environment. This paper focuses on the gearbox in the high-speed train to carry out the bench test, in which various operating conditions (torques and rotation speeds) were set up and the excitation condition covering both internal and external was created. Acceleration responses on multiple positions of the gearbox were acquired in the test and the vibration behavior of the gearbox was studied. Meanwhile, a stochastic excitation modal test was also carried out on the test bench under different torques, and the modal parameter of the gearbox was identified. Finally, the sweep frequency response of the gearbox under gear meshing excitation was analyzed through dynamic modeling. The results showed that the torque has an attenuating effect on the amplitude of gear meshing frequency on the gearbox, and the effect of external excitation on the gearbox vibration cannot be ignored, especially under the rated operating condition. It was also found that the torque affects the modal parameter of the gearbox significantly. The torque has a great effect on both the gear meshing stiffness and the bearing stiffness in the transmission system, which is the inherent reason for the changed modal characteristics observed in the modal test and affects the vibration behavior of the gearbox consequently.

Research on performance of solid-liquid triboelectric nanogenerators based on anti-rolling tank

In this article, we present an anti-rolling tank solid-liquid triboelectric nanogenerators (ART-SL-TENGs) harvesting dissipated kinetic energy from the ocean in ship stabilizer to tackle the electric energy replenishment problem. The harvester mainly consists of several L-damping plates and U-tank equipped with TENGs. This paper investigates the dynamic processes of water within the tank and the potential distribution of TENGs using parameterized modeling, simulations, and experiments. The effects of external excitation, tank's initial water level, and TENG layout on the performance of ART-SL-TENGs are analyzed. During the roll motion of the tank, the water hits the outer side wall and rebounds towards the inner side wall upon collision. Due to a larger water-TENG contact area, the outer side wall generates more charges transfer than the inner side wall, resulting in a higher open-circuit voltage and a higher power. Under low-frequency excitation, the dynamic processes of water make it easier to have sufficient contact with the TENGs, exchange charges, and generate a higher voltage. The results show that the harvester generates maximum average output voltage of about 39.26 V and instantaneous power 6.49 μW under the excitation of 0.7 Hz and 90 mm amplitude at 30 mm initial water level. The ART-SL-TENGs take into account both anti-rolling characteristics and the electric energy replenishment, providing significantly a reference for the design of self-powered marine equipment in ship stabilizer.

Effect of external excitation on the isolated and collective dynamics of a generic FitzHugh–Rinzel neuron

Effect of external excitation on the isolated and collective dynamics of a generic FitzHugh–Rinzel neuron

Effect of external excitation on synchronization behavior in a network of neuron models

Effect of external excitation on synchronization behavior in a network of neuron models

On the primary resonance of laminated moderately-thick plates containing of heterogeneous nanocomposite layers considering nonlinearity

In this study, the primary resonance of laminated plates consisting of heterogeneous nanocomposite layers is investigated comparatively within first order shear deformation theory (FSDT) and classical lamination plate theory (CLPT). One of the features of the work is the generalization of the FSDT for homogeneous anisotropic laminated plates to laminated functionally graded anisotropic nanocomposite plates. The mechanical properties of the matrix reinforced with carbon nanotube (CNT), and fundamental relations of laminated moderately thick plates consisting of heterogeneous anisotropic nanocomposite layers are modeled theoretically within FSDT using von Kármán type nonlinear theory. It then derives equations of motion in the form of nonlinear partial differential equations (NL-PDEs) within FSDT. NL-PDEs equations are transformed into nonlinear ordinary differential equations (NL-ODEs) by Galerkin method and are solved by multi-scale method. The nonlinear forced vibration frequency as the function of amplitude at primary resonance within both theories are obtained for the first time. In addition, backbone curve and nonlinear frequency/linear frequency ratio are found. The reliability and accuracy of the proposed formulation is verified by comparing with the results in the literature. Finally, the effects of external excitation, non-linearity, and variation of CNT patterns on the forced vibration frequencies are examined.

Nonlinear vibration analysis for bolted CFRC plates based on displacement-dependent surface spring-damping model of bolted joint

Under the effect of external excitation, bolted structures are prone to stiffness weakening and damping energy dissipation at the bolted joint, which makes the structures show nonlinear vibration behavior. In this paper, the displacement-dependent surface springs and tangential surface damping expressed by the S-curve model are proposed to simulate the nonlinear mechanical properties of the bolted joint. The non-uniform distribution of the mechanical parameters for the bolted joint is given to simulate the actual joint interface pressure distribution. Based on these, a nonlinear semi-analytical model for bolted carbon fiber reinforced composites (CFRC) plates considering the nonlinear mechanical characteristics of the bolted joint is established. Combined with the experimental results for a bolted CFRC beam, the specific S-curve expressions for the relevant mechanical parameters of the bolted joint are obtained by the inverse identification technology and numerical fitting method. After that, the bolted joint model is transplanted to the dynamic model of a bolted CFRC plate for numerical calculation. The comparison with the corresponding measured results shows that the proposed modeling method can well reproduce the soft nonlinear vibration of the actual bolted CFRC plate, which verifies the correctness and applicability of the proposed modeling method.

On the Stability of the van der Pol-Mathieu-Duffing Oscillator under the Effect of Fast Harmonic Excitation

This paper aims to examine the nonlinear dynamics of a van der Pol-Mathieu-Duffing oscillator under the effect of fast harmonic excitation. The governing equations of motion describing the harmonically forced oscillations of the van der-Pol-Mathieu-Duffing oscillator are expressed in terms of the second-order nonhomogeneous nonlinear ordinary differential equation with suitable initial conditions. This paper uses Krylov-Bogoliubov averaging technique for the stability analysis of the system. The frequency response curves under the effect of external excitation, damping, and nonlinearity are obtained at various resonances. Additionally, the stable and unstable regions were identified. It turns out that the damping reduces the amplitude of oscillations and squeezes the instability regions, whereas the stability region grew with the increase in the amplitude of external excitation.

An analytical nonlinear dynamic model for linear guide with carriage flexibility

Accurate estimation of vibration characteristics of linear guide is imperative for sophisticated structural performance of linear motion equipment. It has been illustrated that flexible model considering carriage deformation is a more precise description of realistic system. However, few dynamic model of carriage flexibility is found for vibration analysis when complex external load is applied. This paper proposes an analytical model to analyze the nonlinear vibration behavior of flexible linear guide system under multidirectional harmonic excitations. The outward deformation of flexible carriage skirt region is calculated by the classical deformation formula of vertical loaded cantilever beam. A lumped dynamic model accounting for segmented restoring force is proposed by coupling the vertical, lateral and rolling displacement and outward deformation. Dynamic responses of rigid and flexible models are compared, and the condition that neglects carriage flexibility is obtained. Numerical simulation exhibits abundant and fascinating nonlinear phenomena when the effects of external excitation, preload and carriage weight are discussed. Additionally, excitation experiments are performed to verify the proposed model. The developed theoretical model is promising for structure optimization of linear guide.

Damage detection of bridge structures under unknown seismic excitations using support vector machine based on transmissibility function and wavelet packet energy

Since it may be hard to obtain the exact external load in practice, damage identification of bridge structures using only structural responses under unknown seismic excitations is an important but challenging task. Since structural responses are determined by both structural properties and seismic excitation, it is necessary to remove the effects of external excitation and only retain the structural information for structural damage identification. In this paper, a data-driven approach using structural responses only is proposed for structural damage alarming and localization of bridge structures. The transmissibility functions (TF) of structural responses are used to eliminate the influence of unknown seismic excitations. Moreover, the inverse Fourier transform of TFs and wavelet packet transform are used to reduce the influence of frequency bands and to extract the damagesensitive feature, respectively. Based on Support vector machines (SVM), structural responses under ambient excitations are used for training SVM. Then, structural responses under unknown seismic excitations are also processed accordingly and used for damage alarming and localization by the trained SMV. The numerical simulation examples of beam-type bridge and a cablestayed bridge under unknown seismic excitations are studied to illustrate the performance of the proposed approach.

Coupled Vibration Behavior of Hot Rolling Mill Rolls under Multinonlinear Effects

A coupled vibration model of hot rolling mill rolls under multiple nonlinear effects is established by considering the nonlinear spring force produced by the hydraulic cylinder, the nonlinear friction between the work rolls, the dynamic variation of rolling force, and the effect of external excitation as well as according to the structural constraints of a four-high hot rolling mill in the vertical and horizontal directions. The amplitude-frequency response equation of rolling mill rolls is determined by using a multiple-scale approximation method. Furthermore, use of actual data for simulation indicates that the internal resonance is the main cause of coupling vibration of the rolling mill rolls. In addition, changes in the movement displacement of the hydraulic cylinder and the coupling parameters strongly affect the coupling system of the rolling mill rolls. Finally, the study of the dynamic bifurcation characteristics of the rolling mill rolls indicates that, with varying external excitation amplitude, the vibration of rolls alternates between periodic motion, period-doubling motion, and chaotic motion in both vertical and horizontal directions. This is one of the reasons for the appearance of periodic light and dark stripes on the strip surface. Furthermore, the range of the external excitation amplitude (F0) at which the rolling mill roll system vibrates violently, that is, 5.68e5 N < F0 < 5.84e5 N and F0 > 6.12e5 N, must be avoided. The research results can provide a theoretical reference for further exploration of the coupling vibration mechanism of hot rolling mills.

Nonlinear vibrations of fluid-conveying FG cylindrical shells with piezoelectric actuator layer and subjected to external and piezoelectric parametric excitations

Nonlinear vibrations of a fluid-conveying functionally graded (FG) cylindrical shell with piezoelectric actuator layer and subjected to external excitation and piezoelectric parametric excitation are analyzed theoretically. Considering the electric-thermo-fluid-structure interaction effect, a nonlinear dynamic model of fluid-conveying FG cylindrical shell with piezoelectric actuator layer is developed based on Hamilton’s principle and von-Karman geometrical nonlinearity. The inviscid, incompressible, isentropic and irrotational fluid is coupled into governing equations using the linearized potential theory. The nonlinear coupled differential governing equations of system are obtained by using Galerkin’s method with two modes. The developed coupled model is validated by comparing with the prior data and good agreements are observed. Multiple scales method is used to obtain nonlinear dynamic behaviors of the coupled system in case of 1:2 internal resonance, primary parametric resonance and 1/2 subharmonic resonance. The effects of three coupling cases between two modes on the dynamic behaviors of system are explored. Considering strongly coupled effect between two modes, the effect of external excitation, damping coefficient, piezoelectric harmonic voltage, fluid flow velocity, temperature and volume fraction exponent of FG cylindrical shell on the frequency-response curves are investigated. The influence of detuning parameters on force-amplitude response and voltage-amplitude response of system are also discussed.

Dynamic characteristics and reliability analysis of ball screw feed system on a lathe

For ball screw feed system on a lathe, the randomness of geometric parameters deriving from the inevitable manufacturing and assembly errors significantly affected the system dynamic characteristics and turning accuracy. In this study, a novel lumped dynamic model accounting for the analytical piecewise restoring force function involving the overall axial deformation is proposed. The equivalent mechanical model of bearing joints including the change of nominal contact angle is made a reasonable simplification to facilitate acquisition of the system analytical equation of motion. Additionally, the approximate analytical solution of the proposed equation is obtained by the modified Lindstedt–Poincaré method (MLP). The advanced first order second moment method (AFOSM) is employed to evaluate the reliability of dynamic response error. Furthermore, the numerical simulation aims to demonstrate the capabilities of the MLP and AFOSM method in the practical applications. Eventually, the effects of external excitation, sliding platform position, and nominal contact angles on the dynamic response are discussed and the reliability and sensitivity analysis in accordance with actual turning accuracy level is presented.

Experimental and theoretical study on a novel multi-dimensional vibration isolation and mitigation device for large-scale pipeline structure

The pipeline structure is prone to multi-dimensional vibration under the effect of external excitation, fluid pulsation and water hammer, which influences transportation efficiency and leads to accidents. In this paper, the multi-dimensional vibration isolation and mitigation device (MVIMD) is developed, which controls the vibration of the pipeline structure from two aspects simultaneously: isolating vibration and mitigating vibration. The device which consists of viscoelastic (VE) bearing, VE dampers and U-shaped springs, has energy dissipation capacities both in horizontal and vertical vibration due to employing VE material with high energy dissipation capacity. In order to investigate the mechanical properties of the device in the horizontal and vertical directions, the characterization tests under different frequencies and amplitudes are carried out. To accurately describe the nonlinear characteristics of the device caused by the complex viscoelasticity, the mathematical model for MVIMD is proposed for considering the effects of frequency and displacement amplitude based on the equivalent standard solid model. Finally, the numerical results are compared with the experimental data. It can be shown from comparison results that the proposed model can describe the properties of MVIMD precisely.

Scattering by an Electrically Large Slot in a Rectangular Cavity

This paper presents a new approach to describe the scattering of an electrically large slot aperture between half-space and a rectangular cavity. The developed method generalizes known theories for the scattering of electrically small apertures and presents a general and understandable formalism for correctly calculating the induced scattering moments. The theory is first developed and validated for the electrically long thin wire in free space. Then, it is applied to describe the scattering of an electrically large thin slot in an infinite screen and backed by a rectangular cavity. The results can be used to determine the effects of external excitation, e.g., a high-power and wideband electromagnetic pulse, on the internal and external fields caused by the scattering slot. The external fields can also be analyzed for the internal resonances of the cavity.

Finite Difference Method for Simulating Transverse Forced Vibration of Vertical Rope with Multi-Rope Winding Hoister

During the high speed of the mine hoisting system, external excitation will produce large transverse vibrations on the vertical rope, which may eventually lead to dynamic instability. In this paper, the Hamiltonian principle is used to establish the partial differential equations transverse vibration of the vertical rope. By using the Finite Difference Method, the differential vibration control equation under lateral excitation is discretized and solved, and the transverse vibration characteristics of the vertical rope are improved. Taking the multi-cable winding hoisting system as an example, the effect of external excitation on the transverse vibration of the vertical rope was simulated and analysed. The simulation results show that the solution of vertical rope vibration equations based on the Finite Difference Method can improve the vibration results of the system.

Reduced-order model for robust aeroelastic control

The objective of aeroelastic control, i.e., aeroservoelasticity, is either suppression of instability, such as flutter, or impeding the effect of external excitation, e.g., due to a gust. In the present work, a robust active feedback controller for a NACA64A010 airfoil model under sub- and transonic flow conditions is designed to impede flutter. The airfoilmodel has an elastic heave and pitch suspension and is equipped with an active aerodynamic control surface. The control design is based on linear reduced-order models (ROM) derived from a coupled computational fluid dynamics (CFD)-computational structural mechanics (CSM) simulation environment. Because the control design should be robust across a range of flow conditions, a collection of ROMs, which span the desired operational envelope, is considered. For each condition, the stability region for a three-term controller is determined with a parameter space approach. Building the intersection area for certain flow regimes allows determining the area of robust stability. The possibility of shifting the flutter boundary with a robust controller compared to adaptive control designs is discussed. To determine finally a set of control parameters chosen from within the stabilizing area, an optimization approach is used. Comparisons of the response of the investigated airfoil model under control between ROM and CFD–CSM shows that the linear ROM is able to predict the response very accurately, despite nonlinearities due to shocks in the flow field.

外界激励对生物类溶致液晶的影响

外界激励对生物类溶致液晶的影响

Effect of external excitation on dynamic characteristics of vibration isolating table

Effect of external excitation on dynamic characteristics of vibration isolating table

Effect of External Excitation on Dynamic Characteristics of Vibro-Isolating Table

Performance of optical table with pneumatic vibration isolators is analyzed within 2–50 Hz frequency range. Specific vibrational excitation platform with a vibrator of the frequency range of 1–50 Hz in one of three directions were tested.The following pneumatic vibration isolator dynamic parameters were identified:transmissibility of vertical oscillation characteristics at 50 Hz frequency range;resonant frequency (vertical direction);damping efficiency at 5 Hz to 10 Hz for excitation frequencies.