385,810 research outputs found
Vibration-based damage detection in plates by using time series analysis
This paper deals with the problem for vibration health monitoring (VHM) in structures with nonlinear dynamic behaviour. It aims to introduce two viable VHM methods that use large amplitude vibrations and are based on nonlinear time series analysis. The methods suggested explore some changes in the state space geometry/distribution of structural dynamic response with damage and their use for damage detection purposes. One of the methods uses the statistical distribution of state space points on the attractor of a vibrating structure, while the other one is based on the Poincaré map of the state space projected dynamic response. In this paper both methods are developed and demonstrated for a thin vibrating plate. The investigation is based on finite element modelling of the plate vibration response. The results obtained demonstrate the influence of damage on the local dynamic attractor of the plate state space and the applicability of the proposed strategies for damage assessment. The approach taken in this study and the suggested VHM methods are rather generic and permit development and applications for other more complex nonlinear structures
Nonlinear vibration absorber optimal design via asymptotic approach
This paper tackles the classical problem of Vibration Absorbers (VAs) operating in the nonlinear dynamic regime. Since traditional
linear VAs suffer from the drawback of a narrow bandwith and numerous structures exhibit nonlinear behavior, nonlinear absorbers
are of practical interest. The resonant dynamic behavior of a nonlinear hysteretic VA attached to a damped nonlinear structure is
investigated analytically via asymptotics and numerically via path following. The response of the reduced-order model, obtained
by projecting the dynamics of the primary structure onto the mode to control, is evaluated using the method of multiple scales up
to the first nonlinear order beyond the resonance. Here, the asymptotic response of the two-degree-of-freedom system with a 1:1
internal resonance is shown to be in very close agreement with the results of path following analyses. The asymptotic solution
lends itself to a versatile optimization based on differential evolutionary
A two-step hybrid approach for modeling the nonlinear dynamic response of piezoelectric energy harvesters
An effective hybrid computational framework is described here in order to assess the nonlinear dynamic response of piezoelectric energy harvesting devices. The proposed strategy basically consists of two steps. First, fully coupled multiphysics finite element (FE) analyses are performed to evaluate the nonlinear static response of the device. An enhanced reduced-order model is then derived, where the global dynamic response is formulated in the state-space using lumped coefficients enriched with the information derived from the FE simulations. The electromechanical response of piezoelectric beams under forced vibrations is studied by means of the proposed approach, which is also validated by comparing numerical predictions with some experimental results. Such numerical and experimental investigations have been carried out with the main aim of studying the influence of material and geometrical parameters on the global nonlinear response. The advantage of the presented approach is that the overall computational and experimental efforts are significantly reduced while preserving a satisfactory accuracy in the assessment of the global behavior
Weakly Nonlinear AC Response: Theory and Application
We report a microscopic and general theoretical formalism for electrical
response which is appropriate for both DC and AC weakly nonlinear quantum
transport. The formalism emphasizes the electron-electron interaction and
maintains current conservation and gauge invariance. It makes a formal
connection between linear response and scattering matrix theory at the weakly
nonlinear level. We derive the dynamic conductance and predict the
nonlinear-nonequilibrium charge distribution. The definition of a nonlinear
capacitance leads to a remarkable scaling relation which can be measured to
give microscopic information about a conductor
High-impact dynamic-response analysis of nonlinear structures
Program predicts expected deformations and stresses in nonlinear simple geometric structures subjected to high-impact loading. Technique is based on node-wise predictor-corrector approach and requires moderate computer storage and run time for most problems. Program extends to include physical and geometrical nonlinearities
Dynamic nonlinear (cubic) susceptibility in quantum Ising spin glass
Dynamic nonlinear (cubic) susceptibility in quantum d-dimensional Ising spin
glass with short-range interactions is investigated on the basis of quantum
droplet model and quantum-mechanical nonlinear response theory. Nonlinear
response depends on the tunneling rate for a droplet which regulates the
strength of quantum fluctuations. It shows a strong dependence on the
distribution of droplet free energies and on the droplet length scale average.
Comparison with recent experiments on quantum spin glasses like disordered
dipolar quantum Ising magnet is discussed.Comment: 15 pages, 3 figure
Chaos in Small-World Networks
A nonlinear small-world network model has been presented to investigate the
effect of nonlinear interaction and time delay on the dynamic properties of
small-world networks. Both numerical simulations and analytical analysis for
networks with time delay and nonlinear interaction show chaotic features in the
system response when nonlinear interaction is strong enough or the length scale
is large enough. In addition, the small-world system may behave very
differently on different scales. Time-delay parameter also has a very strong
effect on properties such as the critical length and response time of
small-world networks
Development of a reduced basis technique for transient thermal analysis
A technique to reduce the degrees of freedom in static and dynamic problems, the reduced basis method, is described. The method combines the classical Rayleigh-Ritz approximation with contemporary finite element methods to retain modeling versatility as the degrees of freedom are reduced. Applications to a nonlinear dynamic response problem are discussed efforts to apply the method to nonlinear transient thermal response problems are summarized. The selection of basis vectors for reducing the system of equations is addressed
Nonlinear structural vibrations by the linear acceleration method
Numerical integration method for calculating dynamic response of nonlinear elastic structure
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