Data-based Identification of nonlinear restoring force under spatially incomplete excitations with power series polynomial model

2011 ◽  
Vol 67 (3) ◽  
pp. 2063-2080 ◽  
Author(s):  
Bin Xu ◽  
Jia He ◽  
Sami F. Masri
Keyword(s):  
Power Series ◽  
Polynomial Model ◽  
Restoring Force ◽  
Nonlinear Restoring Force

Nonparametric nonlinear restoring force and excitation identification with Legendre polynomial model and data fusion

2021 ◽  
pp. 147592172199474
Author(s):  
Bin Xu ◽  
Ye Zhao ◽  
Baichuan Deng ◽  
Yibang Du ◽  
Chen Wang ◽  
...  
Keyword(s):  
Data Fusion ◽  
Legendre Polynomial ◽  
Structural Parameters ◽  
Polynomial Model ◽  
Magnetorheological Damper ◽  
Dynamic Responses ◽  
Identification Accuracy ◽  
Restoring Force ◽  
Nonlinear Restoring Force ◽  
Dynamic Loadings

Identification of nonlinear restoring force and dynamic loadings provides critical information for post-event damage diagnosis of structures. Due to high complexity and individuality of structural nonlinearities, it is difficult to provide an exact parametric mathematical model in advance to describe the nonlinear behavior of a structural member or a substructure under strong dynamic loadings in practice. Moreover, external dynamic loading applied to an engineering structure is usually unknown and only acceleration responses at limited degrees of freedom of the structure are available for identification. In this study, a nonparametric nonlinear restoring force and excitation identification approach combining the Legendre polynomial model and extended Kalman filter with unknown input is proposed using limited acceleration measurements fused with limited displacement measurements. Then, the performance of the proposed approach is first illustrated via numerical simulation with multi-degree-of-freedom frame structures equipped with magnetorheological dampers mimicking nonlinearity under direct dynamic excitation or base excitation using noise-polluted measurements. Finally, a dynamic experimental study on a four-story steel frame model equipped with a magnetorheological damper is carried out and dynamic response measurement is employed to validate the effectiveness of the proposed method by comparing the identified dynamic responses, nonlinear restoring force, and excitation force with the test measurements. The convergence and the effect of initial estimation errors of structural parameters on the final identification results are investigated. The effect of data fusion on improving the identification accuracy is also investigated.

Soft X-ray emission from an anharmonic collisional nanoplasma by a laser–nanocluster interaction

2021 ◽  
Vol 87 (3) ◽  
Author(s):  
R. Nemati Siahmazgi ◽  
S. Jafari
Keyword(s):  
Electric Field ◽  
Laser Beam ◽  
Resonant Frequency ◽  
Restoring Force ◽  
Cluster Radius ◽  
X Ray ◽  
Nonlinear Restoring Force ◽  
Cluster Temperature ◽  
Argon Clusters ◽  
Helium Neon

The purpose of the present paper is to investigate the generation of soft X-ray emission from an anharmonic collisional nanoplasma by a laser–nanocluster interaction. The electric field of the laser beam interacts with the nanocluster and leads to ionization of the cluster atoms, which then produces a nanoplasma. Because of the nonlinear restoring force in an anharmonic nanoplasma, the fluctuations and heating rate of, as well as the power radiated by, the electrons in the nanocluster plasma will be notably different from those arising from a linear restoring force. By comparing the nonlinear restoring force state (which arises from an anharmonic cluster) with that of the linear restoring force (in harmonic clusters), the cluster temperature specifically changes at the resonant frequency relative to the linear restoring force, while the variation of the anharmonic cluster radius is almost identical to that of the harmonic cluster radius. In addition, it is revealed that a sharp peak of X-ray emission arises after some picoseconds in deuterium, helium, neon and argon clusters.

Harmonic Oscillations of Nonlinear Two-Degree-of-Freedom Systems

1955 ◽  
Vol 22 (1) ◽  
pp. 107-110
Author(s):  
T. C. Huang
Keyword(s):  
Nonlinear System ◽  
Degrees Of Freedom ◽  
Forced Oscillations ◽  
Viscous Damping ◽  
Free Oscillations ◽  
Response Curves ◽  
Harmonic Oscillations ◽  
Restoring Force ◽  
Nonlinear Restoring Force ◽  
Two Degree Of Freedom

Abstract In this paper an investigation is made of equations governing the oscillations of a nonlinear system in two degrees of freedom. Analyses of harmonic oscillations are illustrated for the cases of (1) the forced oscillations with nonlinear restoring force, damping neglected; (2) the free oscillations with nonlinear restoring force, damping neglected; and (3) the forced oscillations with nonlinear restoring force, small viscous damping considered. Amplitudes of oscillations and frequency equations are derived based on the mathematically justified perturbation method. Response curves are then plotted.

scholarly journals A new autogenous mobile system driven by vibration without impacts, excited by an impulse periodic force

2018 ◽  
Vol 148 ◽  
pp. 04005 ◽  
Author(s):  
The-Hung Duong ◽  
Van-Du Nguyen ◽  
Ngoc-Tuan La
Keyword(s):  
Duffing Oscillator ◽  
Mobile Systems ◽  
Main Body ◽  
Rectilinear Motion ◽  
Mobile System ◽  
Restoring Force ◽  
Periodic Force ◽  
Nonlinear Restoring Force ◽  
Novel Structure ◽  
Excitation Force

This report describes a new proposed design for autogenous mobile systems which can move without any external mechanisms such as legs or wheels. A Duffing oscillator with a cubic spring, which is excited by an impulse periodic force, is utilized to drive the whole system. The rectilinear motion of the system is performed employing the periodically oscillation of the internal mass interacting without collisions with the main body. Utilizing the nonlinear restoring force of the cubic spring, the system can move in desired directions. When the ratio between the excitation force and the friction force is smaller than 2.5, backward or forward motion can be easily achieved by applying an excitation force in the same desired direction. Different from other vibro-impact drifting devices, no impact needed to drive the new proposed system. This novel structure allows to miniaturize the device as well as to simplify the control algorithm thus can significantly expand applicability of the proposed system.

139 Torsional Vibration Suppression of Driveshaft with Magnetic Nonlinear Restoring Force

2008 ◽  
Vol 2008 (0) ◽  
pp. _139-1_-_139-6_
Author(s):  
Shingo NISHIDA ◽  
Hiroshi MATSUHISA ◽  
Hideo UTSUNO ◽  
Keisuke YAMADA ◽  
Katsutoshi SAWADA
Keyword(s):  
Torsional Vibration ◽  
Vibration Suppression ◽  
Restoring Force ◽  
Nonlinear Restoring Force

Effects of Symmetrical Nonlinear Bearing Flexibility on Shaft Whirl

1966 ◽  
Vol 8 (2) ◽  
pp. 234-242 ◽  
Author(s):  
R. A. Billett
Keyword(s):  
Viscous Friction ◽  
Rotor System ◽  
Restoring Force ◽  
Nonlinear Restoring Force

A shaft-rotor system which has a symmetrical nonlinear restoring force exerted on the rotor when it is radially displaced is analysed. Solutions which predict harmonic whirl are obtained and their stability is investigated. The effect of viscous friction in the rotating members is considered and, as a result of the nonlinearity, a whirl is shown to occur at frequencies which correspond to the free undamped vibrations of the system rather than at the synchronous speed.

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