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With the rapid development of wind power generation in recent years, the demand for detecting weak signals of wind turbine faults has become more urgent. This paper introduces a novel memristor chaotic circuit constructed based on third-order magnetically memristors. The Melnikov chaotic condition of this circuit is analyzed, and its dynamical characteristics are studied through phase trajectory diagrams, bifurcation diagrams, Lyapunov exponent spectra, and Poincaré maps. Leveraging the initial value sensitivity and noise immunity of chaotic systems, the memristor chaotic circuit is employed for the detection of weak signals in wind turbine faults. Using the chaotic system state transition method, we find the threshold for the circuit state to transition from chaotic state to large-scale periodic state, adjust the parameters to make the system in a critical state, input the wind turbine fault vibration signal, and detect the fault signal based on its state transition. Subsequently, the chaotic resonance method is employed, introducing the signal under test, which contains high-intensity chaotic noise, into this novel memristive circuit. This results in chaotic resonance, causing the noise components to be concentrated toward the frequency region where the weak signal under test is located, thereby enhancing the fault signal and facilitating fault identification. The results indicate that this novel memristor chaotic circuit possesses advantages such as high accuracy, strong noise immunity, straightforward operation, and clear judgment in the field of weak signal detection. This circuit shows promising applications in the field of weak signal detection.

As a high-temperature resistant damping material, reducing vibration by coating with M-shape metal rubber (MMR) in a pipeline system is a promising solution due to its energy dissipation induced by micro dry friction between metallic wires. The main challenge for dynamic calculation and performance evaluation of elastic-porous metal rubber (MR) is derived from the intricate spatial network structure. In this work, the dynamic properties including acceleration admittance and insertion loss of the MMR-coated pipeline system were conducted by numerical simulation and experimental analysis. The constitutive models used to characterize hysteresis phenomena, including Yeoh and Bergström–Boyce models, were identified with different density parameters and adopted for steady-state dynamic numerical analysis. The sine sweep frequency test was conducted to verify the accuracy of the developed numerical model. The results indicate that the maximum error of stress–strain curve between numerical prediction and experimental measurement is 10.7%. In the frequency range of 0–1 500Hz, the insertion loss of the MMR-coated pipeline system is positively correlated with the density of MMR, as opposed to the coating distance of pipeline clamps and the influence of excitation force is minimal. Furthermore, the error of dynamic response of the pipeline system in low frequency between the experiment and simulation is 4.7%, indicating that the accuracy of the hysteresis model in predicting the dynamic characteristic of MR materials is effective.

As a flexible component in high-pressure vessels and pipeline systems, bellows experience significant fluid–structure interaction effects under high-speed internal fluids and external vibrations. Nevertheless, their dynamic response mechanisms coupled with fluid–structure interaction mentioned below have not yet been clarified so far. In this work, a novel pressure-balanced metal bellow (PBMB) for low-stiffness and high-pressure resistance is firstly proposed. Several fluid–structure interaction models were considered to study the dynamic response characteristics of the PBMB. An experimental platform associated with fluid–structure interaction was established to validate the effectiveness of its vibration attenuation performance. The results indicate that the PBMB has an obvious vibration attenuation effect in the range of 5–90Hz, and super-harmonic and sub-harmonic resonance phenomena occur in the range of 90–200Hz. Under constant fluid conditions, fluid density, viscosity, flow velocity, and pressure are positively correlated with the response amplitude of the PBMB. The response of the PBMB oscillates at the fluid entry point due to both pulsating flow velocity and pulsating pressure. After several cycles, the response caused by pulsating flow velocity gradually decays and stabilizes. Thus, the impact of pulsating frequency on the stability of the response of bellows is insignificant during the initial cycles.

By using a computational procedure of three-dimensional aerostatic and aerodynamic stability analysis of long-span bridges, the dynamic characteristics, structural stability including the aerostatic stability and aerodynamic stability are first analyzed for a three-tower cable-stayed suspension bridge with main spans of 1400m, then the parametric analysis is conducted, and finally a structural optimization scheme of the example bridge is proposed and confirmed numerically. The results show that the three-tower cable-stayed bridge has significant flexibility with less vertical and especially horizontal stiffness, and is sensitive to the transverse wind action; the three-tower cable-stayed bridge exhibits a coupled aerostatic instability pattern of vertical bending and torsion; the aerodynamic stability is worse than the aerostatic stability, the flutter critical wind speed is significantly reduced due to the static wind action, and thus the aerostatic effect must be involved in the aerodynamic stability analysis; the best wind stability is obtained for the example bridge as 2 auxiliary piers are set in each side span, the cable sag-to-span ratio is 1/6, the suspension-to-span ratio is 0.23, three pairs of cross hangers are set at the transition regions of the cable-stayed and suspension systems, and the girder depth is 4.5m.

Dynamic characteristics of a room play a significant role in its acoustic performance. Among other dynamic parameters, the resonance frequency and modal damping are two most important factors in a room’s acoustic behavior and the efficiency of the active/passive absorbers used to control that behavior. In this paper, the experimental modal analysis (EMA) techniques will be exploited for the purpose of identification of the resonance and modal damping of a listening room, using different excitation sources and various room configurations and the accuracy of the results will be examined.

In this study, dynamic impact analysis for the passenger air-bag(PAB) module has been carried out by using FEM to predict the dynamic characteristics of vehicle ride safety against head impact. To carry out the dynamic analysis of head impact test of the PAB module assembly of automobile, the FE models, which are consist of instrument panel, PAB Module, and head part, are combined to the whole module system. Then, impact analysis is carried out by the explicit solution procedure with assembled FE model. And the dynamic characteristics of the head impact are observed to prove the effectiveness of the proposed method by comparing with the experimental results. As a result, the better optimized impact characteristics are proposed by changing the tie bracket's width and thickness of module. The proposed approach of impact analysis will provides an efficient vehicle to improve the design quality and reduce the design period and cost.

The local extinction and the nonlinear behavior of a premixed methane/air flame under acoustic excitation are investigated experimentally. High-speed photography and high-speed schlieren imaging are used to investigate the oscillation characteristics of the premixed methane/air flame. The flame structure shows a periodic fluctuation when the acoustic excitation is performed to the flame. The local flame extinction can be observed during the flame evolution process. During the local flame extinction process, the flame is found to be cut into two components, then the downstream one extinguishes shortly. The Particle Image Velocimetry (PIV) results suggest that the lower velocity at the separation point is one of the reasons for the flame local extinction. The flame without the acoustic excitation oscillates with a dominant frequency of 18 Hz, which is shown by the schlieren images to be related to the evolution of the hot gas around the flame driven by the buoyant force. When the acoustic excitation frequency is 100 Hz, the structure of the hot gas is destroyed, meanwhile the amplitude of the nature frequency decreases significantly. The hot gas structure appears regularly with the increasing excitation frequency. As a result, the amplitude of the nature frequency also increases gradually. Proper Orthogonal Decomposition (POD) analysis shows that the dominant frequency of the flame without the acoustic excitation is mainly caused by the evolution of the production zone of the flame and the fluctuation of the flame tip. The evolution of the production zone is driven by the buoyant force, which indicates that the result from POD method is consistent with the conclusion obtained from the high-speed schlieren images. Two dominant modes are obtained when the excitation frequencies are 100 and 200 Hz. The two modes are mainly caused by the process of the local flame extinction and the increasing flame length.

In this paper, a boost converter emulator with a memristive load instead of a resistive load is proposed, and a fractional-order model of the memristive boost converter is created. Firstly, the fractional-order models of the memristor and the memristive boost converter are established respectively, and then based on different switching states, the circuit equations of the fractional-order memristive boost converter operating in continuous conduction mode are derived. Secondly, the dynamic characteristics of the fractional-order system are analyzed by numerical simulations and are compared with the integer-order memristive boost converter. Furthermore, the effects of the memristive load on the system is studied by comparing it to the traditional boost converter with resistive load. The results indicate that the fractional-order memristive boost converter can exhibit rich dynamic behavior by adjusting bifurcation parameters, and the fractional-order circuit system expands the stable working regions of the integer-order circuit system. Meanwhile, the addition of the memristive load significantly widens the normal working regions. Finally, simulations of the fractional-order system circuit based on PSIM further verify the correctness of the theoretical analysis.

Robust Design is an important method for improving product quality, manufacturability, and reliability at low cost. Most research in robust design has been focused on problems with static responses. This paper deals with the robust design problems with dynamic responses. The objective of the paper is to investigate and compare three modeling approaches: the loss model, the response function model, and the response model approaches. Taguchi¹⁶ proposes the loss model approach which models the loss measures as functions of the control factor effects. Miller and Wu¹⁰ propose the response function model approach which models the loss measures as functions of the effects of both control and noise factors. Tsui¹⁸ proposes the response model approach which directly models the response as a function of the effects of control, noise, and signal factors. In this paper, we identify and derive the relationships between the effect estimates of the three approaches and show that the loss model approach creates unnecessary biases for the factorial effect estimates and may lead to non-optimal solutions. The three modeling approaches are compared in a real example.

This paper is concerned with the dynamic characteristics of composite beams with partial shear connections. The governing equations of motion for partial composite beams are derived from the one-dimensional partial composite beam theory. By solving the corresponding characteristic equation, the natural frequencies and modal shapes for simple partial composite beams are obtained. The orthogonality condition between the natural modes is utilized to decouple the equations of motion. Closed-form solution for the simple partial composite beam subjected to a moving load is derived by the modal superposition method. Key parameters that govern the fundamental frequency and deflection impact factor of simple partial composite beams are identified. Numerical results show that the former is controlled by the composite connection and section combination parameters, and the latter by the fundamental frequency ratio. It was observed that the time-history response of a partial composite beam may differ significantly from that of a full composite beam in terms of amplitude, period, and overall shape, depending on the composition connection.

Key parameters on the dynamic characteristics of triply coupled pretwisted rotor blades are investigated. The issues of concern include the combined flap-wise bending, chord-wise bending, and torsion vibrations of the pretwisted rotor blade, considering the centrifugal force and Coriolis effects. The governing differential equations of motion presented by Houbolt and Brooks for the rotor blade are used as the basis of study, which contain many factors previously ignored. The differential quadrature method is adopted as the method of solution for its ease in implementation, accuracy, and fast convergence. The dynamic responses of the rotor blade are obtained for different cases of coupling and geometries, which agree well with existing results. The dynamic responses of the rotor blades are plotted against parameters such as angular velocity, pretwisting angle, and hub radius in proper curves and discussed in details.

For the analysis of dynamic characteristics of fluid-conveying pipes with piecewise linear support, a fluid–structure coupling dynamic model based on the finite element method is proposed. A user-defined pipe element based on Euler–Bernoulli beam is developed for modeling the pipes, considering the dynamic flow conditions. A nonlinear spring element is utilized to model the clamp between the pipe and the base. The dynamic responses of the system are obtained through the direct time integration. The stiffness of the clamp support is investigated by the analytical method and the experimental method, in which it is found that the clamp stiffness is piecewise linear. For different pipe geometries the user-defined element model, analytical model and measurement data are compared. The results show high quality of the element developed in this paper. Finally, the dynamic characteristics of the pipe system with piecewise linear support subjected to base harmonic excitation are calculated and the effects of the system parameters on pipe behaviors have also been studied. As a consequence, the model proposed in this paper can represent the piecewise linear nonlinearity of the clamp support and be used conveniently to investigate the effects of the fluid–structure coupling on the system behaviors.

This paper focuses on the dynamic characteristics of reflectors considering the effects of assembly of gores. A model is established to properly predict the assembled shape of planar gores, and nonlinear finite element method and subspace iteration method are adopted to analyze the dynamic characteristics of reflectors. A comparative study is carried out based on the dynamic analysis with ideal reflector and assembled reflector to illustrate the impacts of assembly on mode shapes and natural frequencies of the reflectors. The results show that the presence of assembly of gores and seaming tapes has significant effects on mode shapes and natural frequencies of reflectors, which will influence the shape control of reflectors.

A method is proposed to obtain the exact solution for the dynamic analysis of functionally graded porous (FGP) curved beams with general boundary conditions and variable curvatures. First, the model of a curved beam of variable curvature is constructed, and then the beam is divided into a number of free beam segments via a multi-segment segmentation (MSS) strategy. Second, the first-order shear deformation theory (FSDT) is adopted to obtain the displacement fields of each segment, and then the kinetic energy and potential energy of the structure are expressed by the displacement field. Finally, the exact solution is obtained by the Hamilton principle. Using the springs to simulate various boundary conditions, the frequency parameters, modal shapes and forced vibration responses of the structure with elastic boundary conditions are calculated, with the convergence and correctness verified. Finally, effects of the FGP curved beams, such as porosity distribution types, porosity ratios, boundary condition types, geometry parameters and load types, are investigated in detail.

The plate-type structures are classical configurations in many engineering applications. A comprehensive understanding of the structural dynamic mechanisms is of great significance. An analytical modeling approach is established and applied to investigate the dynamic characteristics of a plate system. The model encompasses two parallel elastically restrained rectangular plates coupled through mechanical links. The linear stiffness parameters are used to simulate various structural boundary conditions and mechanical links. The wave propagation of the plate structure is considered based on the improved Fourier series method. And the theoretical formulations for the dynamic performance of the plate system are obtained by employing the energy principle and Rayleigh–Ritz method. The stability and efficiency of the proposed model are firstly validated for the plate system with classical boundary conditions by comparing the results obtained from FEM software. Subsequently, the boundary restraining parameters are analyzed to figure out their effects on the modal characteristics of the plate system. In addition, the influence of mechanical link distributions on the forced response properties of the plate system is presented and discussed. Numerical results show that the importance of both the boundary conditions and the mechanical link distributions on the dynamic behavior of the plate system. The obtained results of the dynamic investigation and parametric analysis of the plate system can be useful for the further work of vibration and noise control technology of engineering applications.

Large-displacement corner deformation often occurs at the joints of towering structures and long-span space structures subjected to strong earthquake. In order to improve the energy dissipation capacity of structural joints, the Nitrile Butadiene Rubber/High Abrasion Furnace Black (NBR/HAF) high damping composite was fabricated by formulation optimization in this paper, where a nonlinear large-deformation viscoelastic joint damper was proposed. The damper consists of five layers of restrained steel plates and four layers of shear energy dissipating material, which can reach 60mm shear displacement. In this paper, dynamic mechanical performance tests and static mechanical tests were firstly conducted on the core energy dissipating media of the damper. The loss factor of NBR/HAF composite reached a peak of 1.51 at about 8.2°C, while its wide damping temperature range was 27°C. Second, the accuracy of the simulation method was verified by comparing the simulated and experimental hysteresis curves. Then, the refined numerical simulation of this damper was carried out using ABAQUS finite element software with the high damping material as its core energy dissipating media. Finally, the magnitude and type of energy dissipation of each part of the viscoelastic joint damper under different loads were investigated. It was found that the large-deformation viscoelastic joint damper based on the composite had good damping capacity. Its dynamic characteristics were affected by the displacement amplitude and excitation frequency, which exhibited hardening nonlinear characteristics. As the frequency and load amplitude increased, the peak displacement in the loading direction gradually decreased, whereas the total energy input to the damper and the energy dissipated by the viscoelastic material increased monotonically. The input energy was only dissipated by the viscoelastic material, and no plastic loss occurred in the steel plate during the entire loading stage. Under high frequency and large loads, the damper can also have good energy dissipation characteristics. Because of the negative strain energy caused by plastic dilatancy, the energy dissipated by the material was gradually greater than the input energy with the load increasing.

This paper proposed a novel amplifying damping transfer system (ADTS) as a new damping enhancement solution for high-rise structures like wind turbines. The proposed ADTS can transfer the upper rotation of turbine tower to its bottom with damping amplification mechanism. Hence, viscous damper can be installed on wind turbines in a very convenient and efficient way. The dynamic characteristics of wind turbines equipped with ADTS were parametrically investigated concerning the influence of the damping, stiffness, and position of the ADTS based on complex frequency analysis. It was found that each mode has a maximum damping ratio, which is affected by the ADTS stiffness and position. The optimal ADTS position of the first mode is about 0.7 H (turbine height), and the optimal positions of the second mode are at 0.3 H and 0.86 H. The proposed ADTS considerably attenuated both drift and acceleration responses of wind turbines caused by winds and earthquakes. For example, as compared to the optimized tuned mass damper, ADTS further decreases the displacement (acceleration) of wind turbine tower by about 22% (38%).

Although various vibration energy harvesters have been designed over the past few decades, efforts to develop efficient, broadband energy harvesters continue. This work provides a detailed insight into a bistable vibration harvester subjected to correlated Gaussian white noise, with the friction between the rack and pinion described by the slip-stick model. Using the harmonic balance method, the frequency response curve of the amplitude under different mass ratios is discussed. The system response will be enhanced with an increased mass ratio for sinusoidal excitation, but not in the case of random excitation. By employing the stochastic average of the energy envelope, the dynamical governing equation of the harvester is solved, and the probability density functions (PDFs) under different damping coefficients, nonlinear stiffness of the restoring force, and excitation intensities are derived. The results are compared with those from Monte Carlo simulations (MCS) and show good accuracy. The results reveal the presence of P-bifurcations. When the nonlinear stiffness and damping coefficient vary, the number of peaks in the PDFs of system displacement and velocity changes. By adjusting the system parameters, the motion of the system can be significantly enhanced.

Structural parameters are important factors that affect the dynamic performance of the electrical spindle of high-speed grinder. In this study, the influences of the electric spindle's major structural parameters on its dynamic characteristics are investigated. Based on the transfer-matrix method and taking into consideration the gyroscopic couple, the shear, the variable cross-section, and other influential factors, a dynamic model is established for the multidisk rotor of the rotor-bearing system of the electric spindle. The critical speeds of first three orders, the modes of variation, and other dynamic characteristic parameters of the electric spindle are programmed and calculated. The influences of the axial pre-tightening force of the bearing, the span of the fulcrum bearing as well as the changes in the front and rear overhangs on the critical speed of the rotor-bearing system on the electric spindle and their pattern of changes are analyzed. The results show that the span of the fulcrum bearing and the overhang have significant influences on the critical speed within a certain range, and the study provide the basis and guidance for the structural design and performance optimization of the electric spindle.

In this paper, the dynamic interaction of human body and structure is studied The shaking table experiment with a person standing on a rigid table supported by springs is firstly carried out to determine the dynamic characteristics of the coupled system. It is shown that the body mainly contributes only one degree of freedom to the human-structure coupled system. Then, the two-degree-of-freedom (TDOF) coupled model of the human-structure system is developed through the energy variation by considering the standing human body as an elastic bar of two segments with distributed mass, stiffness and damping. Based on the experiment data, the dynamic parameters of the TDOF coupled system are determined by using the least square method (LSM). The mechanical parameters such as the damping ratio and the distributions of mass and stiffness of the human body model of two segments are identified by adopting the inversing technique Finally, the determined body model is applied to analyze the free vibration of beams and plates occupied by standing persons. The governing differential equations of the human-beam system and the human-plate system are, respectively, derived out. The dynamic characteristics of the human-structure interaction are obtained by the use of the complex mode theory. The results are compared with the experimental ones and those from the finite element simulations. Good agreement is observed for all cases.