 Subjects -> ASTRONOMY (Total: 94 journals)
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- Performance review of locking alleviation methods for continuum ANCF beam
elements-
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Abstract: Abstract The absolute nodal coordinate formulation (ANCF) is a nonlinear finite element approach proposed for the large deformation dynamics analysis of beam- and plate/shell-type structures. In the ANCF approach, elastic forces can be defined using three-dimensional elasticity-based continuum mechanics. This approach is often straightforward, and it makes it possible to use advanced material models in the ANCF framework. However, it has been pointed out in several studies that continuum ANCF-based elements with a full three-dimensional elasticity description can suffer from locking phenomena. In this study, a comparison between various combinations of locking alleviation techniques and their applicability to different ANCF beam variants is studied using numerical examples. Furthermore, the enhanced deformation gradient (EDG) technique, which has been proposed recently in finite element literature, is demonstrated for high-order ANCF beam elements. Based on the numerical tests, none of the currently available techniques are suitable for all types of ANCF elements. The paper also shows that the efficiency and accuracy of the techniques are case-dependent. For the ANCF beam element involving higher-order terms with respect to trapezoidal mode, however, the EDG-based techniques are preferable to reduce locking phenomena.
PubDate: 2022-05-19
- Nonlinear dynamics of dry friction oscillator subjected to combined
harmonic and random excitations-
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Abstract: Abstract The dynamics of a nonlinear single degree freedom oscillator on a moving belt subjected to combined harmonic and random excitations is numerically investigated. The dynamics is described by differential equations with discontinuities due to dry friction between the mass and the belt. The discontinuous oscillator is modelled as a Filippov system. Discontinuity induced bifurcations such as the adding sliding bifurcations due to harmonic excitation and stochastic bifurcations like the P and D bifurcations are investigated by numerically integrating the equations of motion using an adaptive time stepping method. A bisection approach is used to accurately determine the discontinuity point, and a Brownian tree approach is used to follow the correct Brownian path. The associated Fokker–Planck (FP) equation is solved by the finite element method. The largest Lyapunov exponent is computed by using the Müller jump matrix and the Wedig algorithm. The effects of the system parameters on the dynamics of the system are investigated.
PubDate: 2022-05-18
- Degeneration of solitons for a (2+1)-dimensional BBMB equation in
nonlinear dispersive media-
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Abstract: Abstract A (2+1)-dimensional nonlinear evolution equation describing the propagation of bore and small-amplitude long waves in nonlinear dispersive media, namely Benjamin–Bona–Mahony–Burgers (BBMB) equation is seriously investigated via different approaches. We will attain classic N-soliton solutions by taking advantage of Hirota bilinear form and symbolic computation. Meanwhile, Y-type solitons are found out via adding a novel restrictive condition to N-soliton solutions. Applying complexification method to N-soliton solutions, T-breathers ( \(T=1,2,3,\ldots \) ) are constructed. During the degeneration of breathers, rogue waves will be discovered by taking the parameter limit method. Besides, combining long wave limit approach and the complexification method to N-soliton solutions, M-lump ( \(M=1,2,3,\ldots \) ) solutions and hybrid solutions composed of soliton, breather and lump can be derived, it means that hybrid solutions could emerge through the partial degeneration of N-soliton process. To detect the dynamical behaviors of these solutions vividly, the corresponding numerical simulations are presented in several figures.
PubDate: 2022-05-18
- Online identification of time-variant structural parameters under unknown
inputs basing on extended Kalman filter-
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Abstract: Abstract To date, many parameter identification methods have been developed for the purpose of structural health monitoring and vibration control. Among them, the extended Kalman filter series methods are attractive in view of the efficient unbiased estimation in recursive manner. However, most of these methods are performed on the premise that the parameters are time-invariant and/or the loadings are known. To circumvent the aforementioned limitations, an online extended Kalman filter with unknown input approach is proposed in this paper for the identification of time-varying parameters and the unknown excitation. A revised observation equation is obtained with the aid of projection matrix. To capture the changes of structural parameters in real time, an online tracking matrix associated with the time-varying parameters is introduced and determined via an optimization procedure. Then, based on the principle of extended Kalman filter, the recursive solution of structural states including the time-variant parameters can be analytically derived. Finally, using the estimated structural states, the unknown inputs are identified by means of least-squares estimation at the same time step. The effectiveness of the proposed approach is validated via linear and nonlinear numerical examples with the consideration of parameters being varied abruptly.
PubDate: 2022-05-18
- Integrable (3+1)-dimensional Ito equation: variety of lump solutions and
multiple-soliton solutions-
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Abstract: Abstract In this work, we study an extended integrable (3+1)-dimensional Ito equation, where its complete integrability is justified via Painlevé analysis. The simplified Hirota’s method is used to formally derive multiple-soliton solutions. Moreover, we obtain a general class of lump solutions by using symbolic computation with Maple. Lump solutions are furnished for specific cases of the parameters.
PubDate: 2022-05-18
- Study on impact characteristics of electric powertrain in regenerative
braking process-
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Abstract: Abstract Electromagnetic torque reversal may lead to gear impact during regenerative braking of electric vehicles. To simulate the dynamic response of gear transmission during impact, an electromechanical non-smooth model is established by combining the permanent magnet synchronous motor model with the gear transmission model. In this model, the coast-side mesh stiffness and impact damping are further coupled based on considering the drive-side mesh stiffness, meshing damping, and electromagnetic characteristics. The theoretical model is validated against an experimental platform. The mechanism of gear impact is revealed through the analysis of the gear contact force. Furthermore, the effects of driving status and internal excitations on the impact characteristics are studied. The results show that the initial braking speed and regenerative braking torque greatly influence the impact times and impact force. The impact times for various backlashes change little. Changing rotor inertia and torsional damping can effectively improve impact characteristics. The research provides theoretical support for dynamic load study and life prediction of the electric powertrain.
PubDate: 2022-05-18
- Correction to: Structural and electrical dynamics of a grating-patterned
triboelectric energy harvester with stick–slip oscillation and magnetic
bistability-
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PubDate: 2022-05-17
- Bifurcation analysis and $$\pmb {H_{\infty }}$$ H ∞ control of a
stochastic competition model with time delay and harvesting-
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Abstract: Abstract In this paper, a stochastic competition model with time delay and harvesting is investigated. By means of the stochastic center manifold reduction principle and stochastic averaging method, the model is simplified to a one-dimensional Markov diffusing process. The singular boundary theory and invariant measure are applied in analyzing the stochastic stability and bifurcation. The T-S fuzzy model of the system is constructed, and the \(H_{\infty }\) state feedback controller is designed to eliminate the instability phenomenon by using a linear matrix inequality approach. Finally, numerical simulations are given to demonstrate our results.
PubDate: 2022-05-17
- Correction to: Dynamic behavior analysis of tethered satellite system
based on Floquet theory-
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PubDate: 2022-05-16
- Analysis of lumps, single-stripe, breather-wave, and two-wave solutions to
the generalized perturbed-KdV equation by means of Hirota’s bilinear
method-
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Abstract: In this paper, we implement the Hirota’s bilinear method to extract diverse wave profiles to the generalized perturbed-KdV equation when the test function approaches are taken into consideration. Several novel solutions such as lump-soliton, lump-periodic, single-stripe soliton, breather waves, and two-wave solutions are obtained to the proposed model. We conduct some graphical analysis including 2D and 3D plots to show the physical structures of the recovery solutions. On the other hand, this work contains a correction of previous published results for a special case of the perturbed KdV. Moreover, we investigate the significance of the nonlinearity, perturbation, and dispersion parameters being acting on the propagation of the perturbed KdV. Finally, our obtained solutions are verified by inserting them into the governing equation.
PubDate: 2022-05-16
- Novel bursting dynamics and the mechanism analysis in a mechanical
oscillator-
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Abstract: The complex bursting dynamics of a mechanical oscillator under parametric and external forced excitations are investigated. When the frequencies of the forcing terms are much smaller than the natural frequency of the oscillator, excitations can be expressed as slow-varying variables and the oscillator is regarded as a smooth autonomous system. A new route to bursting dynamics called the pulse-shaped explosion (PSE) is then proposed. PSE is represented by a sharp change in the number of pulse-shaped signals corresponding to the transformation of system parameters. Four PSE-type bursting dynamics are analyzed based on the slow-fast analysis method: bursting dynamics of “supHopf/supHopf” form via “PSE/PSE” hysteresis loop, bursting dynamics of “supHopf/supHopf-PSE/supHopf” form via “PSE/PSE” hysteresis loop, bursting dynamics of “supHopf/supHopf-PSE/PSE” form via “PSE/PSE” hysteresis loop and bursting dynamics of “PSE/PSE-PSE/PSE” form via “PSE/PSE” hysteresis loop. In addition, two non-PSE-type bursting dynamics are also investigated: bursting dynamics of “supHopf/supHopf” form and bursting dynamics of “supHopf/supHopf-supHopf/supHopf” form. Our results strengthen the understanding of the PSE-type bursting oscillations and enrich the possible routes to complex bursting behaviors.
PubDate: 2022-05-16
- Nonlinear vibration analysis of a generally restrained double-beam
structure coupled via an elastic connector of cubic nonlinearity-
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Abstract: Double-beam structures are frequently encountered in various engineering applications. Their vibration behavior is attracting more and more research attention. The majority of the existing studies are mainly limited to double-beam structures coupled via linear connectors. Additionally, the rotational boundary restraints of double-beam structures are usually neglected, limiting the dynamic analysis of double-beam structures in engineering applications. To study the potential application of the elastic cubic nonlinearity on double-beam structures, the dynamic analysis model of a generally restrained double-beam structure coupled via a flexible connector of cubic nonlinearity is modeled in this study. The Galerkin truncated method (GTM) is employed to solve the nonlinear governing equations of the double-beam structure. Mode functions of beam structures without any nonlinearity and damping are selected as the trail and weight functions. The Galerkin condition is applied to discretize the nonlinear governing equations. Then, residual equations of the double-beam structure are established and arranged into a matrix form. The Runge–Kutta method is utilized to solve the corresponding matrix. The finite difference method (FDM) is applied to verify the correctness and reliability of the current model. Based on the model established, the influence of the coupling nonlinearity on the dynamic behavior of the double-beam structure is studied and discussed. The research found that the variation of nonlinear stiffness, coupling viscous damping, and coupling position can effectively transform vibration states of the double-beam structure. For the determined boundary conditions and structural parameters, a suitable combination of coupling nonlinear stiffness, coupling position, and coupling viscous damping has a beneficial effect on the vibration suppression of the double-beam structure.
PubDate: 2022-05-16
- Theoretical analysis and verification of particles moving along the
arc-shaped surface in vibration machinery-
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Abstract: Vibration machinery with an arc-shaped surface as the main working surface widely exists. The experimental phenomenon shows that the bulk material particles exhibit regular sliding motion and throwing motion along the arc-shaped surface under the alternating load of the exciting system. It is essential to systematically investigate the motion theory of particles considering the interactions between the vibration body and the particles. In this paper, firstly, the interaction mechanism between the vibration body and the particles under different motion states is analyzed, and the particle’s kinematics equation is established based on the nonlinear force analysis of sliding motion and throwing motion. After that, the differential equation of the vibration body movement considering the interaction forces is given. Then, the discrete element method (DEM) is used to verify the feasibility of using a small number of particles to study the whole motion law of particle flow. Meanwhile, the correctness of the mechanical model established in this paper and the numerical solution of the vibration system solved by the Newmark-β method are also verified by DEM. Finally, the particle’s motion state intervals are given, and the Sommerfeld effect’s influence on the system’s motion stability is further discussed. In addition, the effects of the nonlinear force, particle mass, friction coefficient, exciting force, and installation angle on the system’s frequency-domain response, conveying efficiency, and throwing index are discussed emphatically. The theoretical basis and experimental method in designing this kind of mechanical equipment are provided for reference.
PubDate: 2022-05-16
- Diverse excitations of two-component rogue waves for a nonautonomous
coupled partially nonlocal nonlinear Schrödinger model under a parabolic
potential-
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Abstract: Vector similar structures for solutions with similar expressions of nonlinear models are paid attention in the previous literature. However, the demand of different localized structures of two components for the same system to describe the practical problems is increasing. We take into account a (2+1)-dimensional nonautonomous coupled partially nonlocal nonlinear Schrödinger model under a parabolic potential and erect a projecting expression reducing this nonautonomous equation into an autonomous one. Uniting these solutions of the autonomous equation into the projecting expression, we demonstrate explicit two-component solutions with different forms, including two-component bright–dark Peregrine-type rogue waves and rogue wave doublets. In order to illustrate special properties of these two-component solutions, we study their diverse excitations, such as excitations of two-component rogue waves and rogue wave doublets to full shape, tail-dragged shape, crest-maintaining shape and nascent shape.
PubDate: 2022-05-15
- Nonlinear aeroelastic analysis of a damped elastica-aerofoil system
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Abstract: This work formulates a comprehensive model of a nonlinear aeroelastic system developed for the analysis of complex aeroelastic phenomena related to structural and aerodynamic nonlinearities. The system is formulated as a two-dimensional cantilevered elastica with a rigid airfoil section firmly attached at its tip undergoing large displacements in the crosswind conditions. The system can demonstrate a wide range of domain specific as well as coupled nonlinear phenomena. The structural model is developed by means of the Rayleigh–Ritz approach, with shape functions discretizing both vertical and horizontal displacements and Lagrangian multipliers enforcing inextensibility. Damping is modeled based on a non-local strain-based mechanism in the Kelvin–Voigt arrangement. The resulting structural model is examined through studying the behavior under a follower load and with a tip-attached tendon under tension to study the shape convergence properties and the alignment of the results with known characteristics in the literature. The ONERA dynamic stall model is used to model the aerodynamics of the problem to accurately capture post-stall behavior at large deformations. The LCO responses of the aeroelastic problem are evaluated through time-marched simulations, and the combined airspeed–damping interactions are studied in this manner.
PubDate: 2022-05-14
- Novel dynamical behaviors in fractional-order conservative hyperchaotic
system and DSP implementation-
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Abstract: In this paper, a novel fractional-order conservative system is constructed. The new system has rich dynamical behaviors by the consequence of the data simulation findings. The change of a certain parameter value can make system produce a range of conservative flows with varying topologies, and modifying further parameters the conservative flows can exhibit extension, expansion, and rotational tendencies. The initial offset behavior, extreme multi-stability, as well as multiple transient transition phenomena, can be observed. It is worth noting that two special phenomena are discovered in the paper: one is the discovery of hyperchaos in this system, which has never been reported before in the study of fractional-order conservative systems; the other is the existence of dissipation in this conservative system, which can be manifested by altering the order or parameter. These phenomena are analyzed in detail by utilizing phase diagram, bifurcation diagram, the Lyapunov exponent spectra and time series diagram. Over and above, we also analyze the feasibility of the system being used as a pseudo-random sequence generator. At last, the hardware implementation of the system is carried out on the DSP experimental platform to verify the correctness of theoretical analysis. The results show that this system has potential practical application value.
PubDate: 2022-05-14
- Nonlinear superposition between lump and other waves of the
(2+1)-dimensional generalized Caudrey-Dodd-Gibbon-Kotera-Sawada equation
in fluid dynamics-
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Abstract: With the premise that N-soliton solutions are acquired, this paper will focus on the nonlinear superposition between one lump and other types of localised waves of the (2+1)-dimensional generalized Caudrey-Dodd-Gibbon-Kotera-Sawada(gCDGKS) equation. By introducing a novel constraint, combining the long wave limit method and mode resonance method, it is guaranteed that there is no interaction between one lump (local waves that remain wave form invariant in space) and line solitons (analytic solutions in exponential form in both space and time), breather waves and resonant Y-type solitons ever or that one lump is always situated on at least one of line solitons, breather waves (shape is similar to the rise and fall of the breath) and resonant Y-type solitons (similar to the letter Y in spatial structure). In addition, by defining novel velocity resonance constraints, it is ensured that lump and line waves, lump and breather waves, breather and line wave have exactly the same velocity magnitude and direction, which means that they form new molecularly bound states. Remarkably, we find that one line and one breather wave can be transformed into two breather waves. In general, lump wave interact with other types of localised waves in three stages: before, during and after the interaction, but the results obtained in this paper break this perception and provide some references for the explanation of certain nonlinear phenomena occurring in fields such as shallow water waves, solitons and fluid mechanics.
PubDate: 2022-05-14
- Theoretical modeling and experimental evaluation of a magnetostrictive
actuator with radial-nested stacked configuration-
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Abstract: Stacked magnetostrictive actuator (SMA) has the advantages of high energy density and high bandwidth, but the output stroke is relatively small and accompanied by strong hysteresis nonlinearity. Introducing the radial-nested stacked configuration, the stroke of a SMA can be increased without deteriorating its bandwidth. However, this configuration consists of three magnetostrictive rods of different shapes which brings more serious asymmetric hysteresis nonlinearity and poses a great challenge on the theoretical modeling of the actuator. In this paper, a magnetic equivalent circuit (MEC) model is established to describe the magnetic characteristic of radial-nested stack. Then, a nonlinear dynamic magnetization model is proposed with the combination of the MEC model and the Jiles-Atherton model. Finally, by considering the multi-degree-of-freedom (MDOF) mechanical dynamic system, a multiphysics comprehensive dynamic (MCD) model is established. What’s more, a prototype of radial-nested stacked Terfenol-D actuator (RSTA) is fabricated, a series of simulations and experiments are conducted to evaluate the proposed models. The parameters that cannot be calculated or measured in the model are identified by employing the multi-island genetic algorithm. Results show that: (a) the MEC model can accurately calculate the magnetic distribution of the RSTA with an error less than 0.2% compared with a finite element model; (b) the MCD model can accurately describe the RSTA output hysteresis nonlinearity under different operating frequencies and amplitudes with a root-mean-square (RMS) error less than 1.1 \(\upmu \hbox {m}\) (1.76%).
PubDate: 2022-05-13
- Experimental verification of dynamic behavior for multi-link press
mechanism with 2D revolute joint considering dry friction clearances and
lubricated clearances-
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Abstract: The existence of clearance joints seriously affect the kinematic accuracy and service life of precision mechanisms. So as to ensure the kinematic accuracy reliability of mechanism, it is imperative to accurately predict the dynamic behavior of precision mechanism considering clearances. At present, the studies often focus on theoretical analysis and simulation verification of mechanism with clearances, while the studies verified by experiment are relatively few and often focus on simple mechanism. Moreover, most of studies centered on simple mechanism with dry friction clearance, while the studies on complex mechanism with multiple lubricated clearances are less. In this paper, the impact of multiple clearances on dynamic behavior of 2-DOF 9-bar precision press mechanism is analyzed. Firstly, the mathematical models of dry friction clearance and lubricated clearance are established and embedded into the Lagrange dynamic equation, respectively. Then, the impact of clearance values, the material of clearance-shaft and crank driving speeds on dynamic behavior of mechanism are researched. Finally, the simplified experimental platform of 2-DOF 9-bar press mechanism considering 2D revolute joint clearances is established, and the correctness of the theoretical model is proved by experimental verification. This study not only offers theoretical guidance for the layout and life prediction of multi-link press mechanism, but also provides reference for the dynamic behavior analysis and prediction of other mechanisms.
PubDate: 2022-05-13
- On occurrence of mixed-torus bursting oscillations induced by
non-smoothness-
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Abstract: The paper devotes to the slow–fast behaviors of a higher-dimensional non-smooth system with the coupling of two scales. Some novel bursting attractors and interesting phenomena are presented, especially the so-called mixed-torus bursting oscillations, in which the trajectory moves along different tori in turn, though the bursting attractor still behaves in quasi-periodic form. Based on a 4-D hyper-chaotic model with two scrolls, a modified non-smooth slow–fast version is established. Upon the smooth and non-smooth bifurcations analysis, the coexisted attractors with the variation of the slow-varying parameter are derived. With the increase in the exciting amplitude, bursting oscillations may change from periodic to quasi-periodic attractor, the mechanism of which is obtained by employing the overlap of the transformed phase portrait and coexisted attractors as well as the bifurcations. Sliding along the boundary on the trajectory can be observed on the bursting attractor, the mechanism of which can be accounted for by employing the non-smooth theory or by the in-turn influence of two pseudo-attractors in different regions. Super-cone defined by an unstable focus may lead to the period-adding or period-decreasing phenomena in the spiking oscillations, while fold limit cycle bifurcation may result in the dramatical change of the spiking amplitude. Different limit cycles may involve the full vector field, resulting in the so-called mixed-torus bursting oscillations, in which the quiescent states seem to be pivots of the oscillations.
PubDate: 2022-05-13
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