scholarly journals Rub-Impact Detection in Rotor Systems with Pedestal Looseness Using a Nonlinearity Evaluation

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Mian Jiang ◽  
Yingwei Kuang ◽  
Jigang Wu ◽  
Xuejun Li
Keyword(s):  
Piecewise Linear ◽  
Rotor Systems ◽  
Nonlinear Fitting ◽  
Impact Detection ◽  
Impact Forces ◽  
Fitting Method ◽  
Nonlinear Mathematical Models ◽  
Vibration Responses ◽  
Stiffness And Damping ◽  
Piecewise Linear Stiffness

In this paper, a nonlinearity evaluation is proposed in order to identify the rub-impact in rotor systems with pedestal looseness. Nonlinear mathematical models have been established for bearing-rotor systems with single pedestal looseness and pedestal looseness coupled with rub-impact. Piecewise linear stiffness and damping are considered regarding the position of pedestal looseness, while radial impact forces are defined using the Colulomb type of frictional relationship during rub-impact. The nonlinearity evaluation is employed to quantify the nonlinearity of the dynamics of bearing-rotor systems, which are calculated at different looseness clearances. The experiments for rotor systems with pure pedestal looseness and pedestal looseness coupled with rub-impact are conducted respectively to collect the vibration signals on different looseness clearances. Two different curves are obtained using the nonlinear fitting method for the values of nonlinearity evaluation. The rub-impact within rotor systems with pedestal looseness can then be identified by comparing the curves that denote the trend of nonlinearity evaluation for the measured vibration responses.

scholarly journals Analysis on Influences of Squeeze Film Damper on Vibrations of Rotor System in Aeroengine

2022 ◽  
Vol 12 (2) ◽  
pp. 615
Author(s):  
Haobo Wang ◽  
Yulai Zhao ◽  
Zhong Luo ◽  
Qingkai Han
Keyword(s):  
High Speed ◽  
Vibration Suppression ◽  
Rotor System ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Lumped Mass ◽  
Squeeze Film Damper ◽  
Rotor Systems ◽  
Vibration Responses ◽  
Stiffness And Damping

Squeeze film damper (SFD) is widely used in the vibration suppression of aeroengine rotor systems, but will cause complex motions of the rotor system under specific operating conditions. In this paper, a lumped-mass dynamic model of the high-pressure rotor system in an aeroengine is established, and the nonlinear stiffness and damping formula of SFD are introduced into the above model. The vibration responses of the rotor system under different rotating speeds and with different unbalances are investigated numerically, and the influence of SFD on the rotor system vibration and the change of suppression ability are compared and analyzed. The results show that in the case of high speed, together with a small unbalance, the rotor system will perform a complex vibration or a bistable vibration due to SFD. If the unbalance is properly increased under the same case of high speed, the vibration of the rotor becomes single-harmonic and the bistable vibration disappears. The research results can provide a helpful reference for analyzing complex vibration mechanisms of the rotor system with SFD and achieving an effective vibration suppression through unbalance regulation.

Frequency Response Analysis of Damped Dual Mass Flywheel

2015 ◽  
Vol 724 ◽  
pp. 271-274 ◽  
Author(s):  
Rong Zeng ◽  
Zheng Feng Jiang ◽  
Xing Wan
Keyword(s):  
Frequency Response ◽  
Piecewise Linear ◽  
Vibration Damping ◽  
Torsional Stiffness ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Power Train ◽  
Detail Design ◽  
Stiffness And Damping ◽  
Sinusoidal Excitation

s:Aiming at circumferential arc spring dual mass flywheel (CSDMF), this paper carries out analysis on the piecewise linear model and calculates the frequency response of damped model under sinusoidal excitation. Being combined with the calculate results, the research respectively analyzes the value of inertia ratio, torsional stiffness and damping parameters. The analysis results show that the greater the damping, inertia ratio of primary and secondary flywheels are, the torsional stiffness, the more obvious vibration damping of the dual mass flywheel would be. To meet the vibration damping requirements, the detail design of the three parameters need to be combined with power train and the torsion characteristic of CSDMF.

Vibration analysis of a multifunctional hybrid composite honeycomb sandwich plate

2018 ◽  
Vol 22 (8) ◽  
pp. 2818-2860 ◽  
Author(s):  
Paul Praveen A ◽  
Vasudevan Rajamohan ◽  
Ananda Babu Arumugam ◽  
Arun Tom Mathew
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Hybrid Composite ◽  
Sandwich Plate ◽  
Core Material ◽  
Sandwich Plates ◽  
Composite Sandwich ◽  
Honeycomb Sandwich ◽  
Vibration Responses ◽  
Stiffness And Damping

In the present study, the free and forced vibration responses of the composite sandwich plate with carbon nanotube reinforced honeycomb as the core material and laminated composite plates as the top and bottom face sheets are investigated. The governing equations of motion of hybrid composite honeycomb sandwich plates are derived using higher order shear deformation theory and solved numerically using a four-noded rectangular finite element with nine degrees of freedom at each node. Further, various elastic properties of honeycomb core materials with and without reinforcement of carbon nanotube and face materials are evaluated experimentally using the alternative dynamic approach. The effectiveness of the finite element formulation is demonstrated by performing the results evaluated experimentally on a prototype composite sandwich plate with and without carbon nanotube reinforcement in core material. Various parametric studies are performed numerically to study the effects of carbon nanotube wt% in core material, core thickness, ply orientations, and various boundary conditions on the dynamic properties of composite honeycomb sandwich plate. Further, the transverse vibration responses of hybrid composite sandwich plates under harmonic force excitation are analyzed at various wt% of carbon nanotubes and the results are compared with those obtained without addition of carbon nanotubes to demonstrate the effectiveness of carbon nanotube reinforcement in enhancing the stiffness and damping characteristics of the structures. The study provides the guidelines for the designer on enhancing both the stiffness and damping properties of sandwich structures through carbon nanotube reinforcement in core materials.

scholarly journals A Novel Adaptive Non-Local Means-Based Nonlinear Fitting for Visibility Improving

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 741
Author(s):  
Hongtao Wu ◽  
Lei Jia ◽  
Ying Meng ◽  
Xiao Liu ◽  
Jinhui Lan
Keyword(s):  
Filter Design ◽  
Trade Off ◽  
Nonlinear Fitting ◽  
Local Means ◽  
Fitting Method ◽  
Central Pixel ◽  
Smooth Plane ◽  
Non Local ◽  
Geometric Surface ◽  
Weight Coefficients

The spatial-based method has become the most widely used method in improving the visibility of images. The visibility improving is mainly to remove the noise in the image, in order to trade off denoising and detail maintaining. A novel adaptive non-local means-based nonlinear fitting method is proposed in this paper. Firstly, according to the smoothness of the intensity around the central pixel, eight kinds of templates with different precision are exploited to approximate the central pixel through a novel adaptive non-local means filter design; the approximate weight coefficients of templates are derived from the approximation credibility. Subsequently, the fractal correction is used to smooth the denoising results. Eventually, the Rockafellar multiplier method is employed to generalize the smooth plane fitting to any geometric surface, thus yielding the optimal fitting of the center pixel approximation. Through a large number of experiments, it is clearly elucidated that compared with the classical spatial iteration-based methods and the recent denoising algorithms, the proposed algorithm is more robust and has better effect on denoising, while keeping more original details during denoising.

scholarly journals Lateral vibration control of a shafting-hull coupled system with electromagnetic bearings

2018 ◽  
Vol 38 (1) ◽  
pp. 154-167 ◽  
Author(s):  
Hui Qin ◽  
Hongbo Zheng ◽  
Wenyuan Qin ◽  
Zhiyi Zhang
Keyword(s):  
Frequency Response ◽  
Acoustic Radiation ◽  
Synthesis Method ◽  
Coupled System ◽  
Lateral Vibration ◽  
Vibration Transmission ◽  
Lateral Vibrations ◽  
System A ◽  
Vibration Responses ◽  
Stiffness And Damping

In order to suppress lateral vibration transmission and reduce acoustic radiation of a shafting-hull coupled system, a new approach using electromagnetic bearings in the shafting system is proposed. The dynamic characteristics of the electromagnetic bearings, especially the equivalent stiffness and damping as well as the applicable scope of linearization of the electromagnetic bearings, are analysed at first. With the equivalent parameters, a dynamic model of the shafting-hull coupled system is established subsequently by using the frequency response synthesis method to derive frequency response functions associated with the lateral vibrations. Finally, the influence of the control parameters of the electromagnetic bearings on vibration transmission in the shafting-hull system is studied. Analysis results indicate that lateral vibration responses are suppressed significantly when electromagnetic bearings are introduced into the shafting-hull system, and as a result, sound radiation of the system is reduced, which demonstrates that the proposed approach is effective in controlling vibration transmission in the shafting system.

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