Effect of temperature on the nonlinear dynamic behavior of two-lobe non-circular gas-lubricated micro-bearings

2021 ◽  
pp. 135065012199568
Author(s):  
Azizmohammad Gharanjik ◽  
Ardeshir Karami Mohammadi
Keyword(s):  
Dynamic Behavior ◽  
High Temperatures ◽  
Nonlinear Dynamic ◽  
Phase Portraits ◽  
Effect Of Temperature ◽  
Behavior Changes ◽  
Runge Kutta Method ◽  
Nonlinear Dynamic Behavior ◽  
Effects Of Temperature ◽  
Increasing Temperature

In this paper, the molecular gas lubrication model was used to analyze the nonlinear dynamic behavior of two-lobe non-circular gas-lubricated micro-bearings. The effects of temperature rise are taken into account. At high temperatures, in addition to gas rarefaction, its viscosity and friction will also change, and slip across boundaries will occur. The rarefaction of the lubricating gas film caused by the microscale effect at high temperatures was considered. The effects of temperature and rotation speed (with and without rarefaction effect) on the dynamic behavior of the non-circular micro gas bearing were studied. The nonlinear equation governing the gas behavior is discretized using the finite-element method and then solved simultaneously with the dynamic equations of rotor motion using the fourth-order Runge–Kutta method. Center orbit diagrams, phase portraits, Poincare maps, power spectrum, and bifurcation diagrams are used to investigate the dynamic behavior of two-lobe non-circular gas-lubricated micro-bearings. Some results show that with increasing temperature, the rotor behavior changes from T-periodic to quasi-periodic. It was also observed that at high temperatures, with increasing rotational speed, the behavior of the system changes from T-periodic to quasi-periodic, but if the gas is rarefied, this change occurs at a slower speed.

scholarly journals Nonlinear analysis of high accuracy and reliability in traffic flow prediction

2020 ◽  
Vol 9 (1) ◽  
pp. 290-298
Author(s):  
Liming Dai ◽  
Luyao Wang
Keyword(s):  
Traffic Flow ◽  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
High Accuracy ◽  
Kutta Method ◽  
Duffing System ◽  
Traffic Flow Prediction ◽  
Runge Kutta Method ◽  
Flow Prediction ◽  
Nonlinear Dynamic Behavior

AbstractFor quantitatively identifying the chaotic patterns in traffic flow prediction, certain types of Duffing systems can be used. The accuracy and reliability of numerical results of the system’s solution have significant influence on the traffic flow prediction. The nonlinear dynamic behavior of Duffing system used for the traffic flow prediction is investigated in this research. The solutions of the system are developed and solved numerically by using the P-T method. The regular and irregular responses of the system considered are graphically illustrated with the newly developed P-R method. Based on the results of the research, the frequency and amplitude of the external excitations applied on the system significantly affecting the nonlinear dynamic behavior therefore the traffic flow prediction in transferring the results by Wigner-Ville transform. Additionally, a comparison between the P-T and Runge-Kutta method is conducted in regarding the accuracy and reliability of the methods.

Effects of Temperature on Nonlinear Dynamic Behavior of Gas Journal Bearing-rotor Systems for Microengine

2016 ◽  
Vol 59 (5) ◽  
pp. 944-956 ◽  
Author(s):  
Xiao-Qing Zhang ◽  
Xiao-Li Wang ◽  
Li-Na Si ◽  
Yu-De Liu ◽  
Wen-Tian Shi ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
Journal Bearing ◽  
Rotor Systems ◽  
Nonlinear Dynamic Behavior ◽  
Effects Of Temperature ◽  
Gas Journal Bearing

Impact of blast and mechanical loads on the shear deformable stiffened sandwich plate with an auxetic core layer in thermal environment

2021 ◽  
pp. 109963622110219
Author(s):  
Vu Thi Thuy Anh ◽  
Vu Dinh Quang ◽  
Nguyen Dinh Duc ◽  
Pham Ngoc Thinh
Keyword(s):  
Dynamic Behavior ◽  
Elastic Foundation ◽  
Nonlinear Dynamic ◽  
Sandwich Plate ◽  
Thermal Environment ◽  
Core Layer ◽  
Mechanical Loads ◽  
Environment Temperature ◽  
Nonlinear Dynamic Behavior ◽  
Fgm Layer

By using the first order shear deformation theory (FSTD), this paper presents the results of the nonlinear dynamic behavior and natural frequencies of sandwich plate supported by elastic foundations in thermal environment and subjected to mechanical load and blast loading. This work takes advantage of the sandwich plate configuration with three layers: graphene platelet –reinforced composite (GPL) layer – auxetic layer – FGM layer, to analyze the dynamic and vibration problem, in which the auxetic core layer has a negative Poisson's ratios and the FGM layer is reinforced by stiffeners made of full metal or full ceramic depending on a situation of stiffeners at the metal-rich or ceramic-rich side of the plate respectively. Corresponding to the combination of material layers, the mechanical quantities of the problem are processed and calculated to suit the structure and reinforcement conditions. Numerical results are provided to explore the influences of geometrical parameters, elastic foundation parameters, GPL volume fraction, blast and mechanical loads on the nonlinear dynamic behavior and vibration of sandwich plate resting on elastic foundation and in thermal environment. In addition, the study is not only assumed that the material properties depend on environment temperature variation, but also considered the thermal stresses in the stiffeners, as well as considered the effect of imperfections in the original shape of the structure.

Nonlinear Dynamic Study on Effects of Rub-Impact Caused by Oil-Rupture in a Multi-Shafts Turbine With a Squeeze Film Damper

2014 ◽  
Author(s):  
T. N. Shiau ◽  
C. R. Wang ◽  
D. S. Liu ◽  
W. C. Hsu ◽  
T. H. Young
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
Equations Of Motion ◽  
Rotor System ◽  
Squeeze Film ◽  
Speed Ratio ◽  
Frequency Spectra ◽  
Squeeze Film Damper ◽  
Assumed Mode Method ◽  
Nonlinear Dynamic Behavior

An investigation is carried out the analysis of nonlinear dynamic behavior on effects of rub-impact caused by oil-rupture in a multi-shafts turbine system with a squeeze film damper. Main components of a multi-shafts turbine system includes an outer shaft, an inner shaft, an impeller shaft, ball bearings and a squeeze film damper. In the squeeze film damper, oil forces can be derived from the short bearing approximation and cavitated film assumption. The system equations of motion are formulated by the global assumed mode method (GAMM) and Lagrange’s approach. The nonlinear behavior of a multi-shafts turbine system which includes the trajectories in time domain, frequency spectra, Poincaré maps, and bifurcation diagrams are investigated. Numerical results show that large vibration amplitude is observed in steady state at rotating speed ratio adjacent to the first natural frequency when there is no squeeze film damper. The nonlinear dynamic behavior of a multi-shafts turbine system goes in its way into aperiodic motion due to oil-rupture and it is unlike the usual way (1T = >2T = >4T = >8T etc) as compared to one shaft rotor system. The typical routes of bifurcation to aperiodic motion are observed in a multi-shafts turbine rotor system and they suddenly turn into aperiodic motion from the periodic motion without any transition. Consequently, the increasing of geometric or oil parameters such as clearance or lubricant viscosity will improve the performance of SFD bearing.

Nonlinear Dynamic Behavior of a Rotor Bearing System With Nonlinear Viscous Damping Suspension

2017 ◽  
Author(s):  
Shuai Yan ◽  
Bin Lin ◽  
Jixiong Fei ◽  
Pengfei Liu
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
Vibration Isolation ◽  
Lubricating Oil ◽  
Viscous Damping ◽  
Oil Viscosity ◽  
Speed Range ◽  
Rotor Bearing ◽  
Nonlinear Dynamic Behavior ◽  
Bearing System

Nonlinear damping suspension has gained attention owing to its excellent vibration isolation performance. In this paper, a cubic nonlinear viscous damping suspension was introduced to a rotor bearing system for vibration isolation between the bearing and environment. The nonlinear dynamic response of the rotor bearing system was investigated thoroughly. First, the nonlinear oil film force was solved based short bearing approximation and half Sommerfeld boundary condition. Then the motion equations of the system was built considering the cubic nonlinear viscous damping. A computational method was used to solve the equations of motion, and the bifurcation diagrams were used to display the motions. The influences of rotor-bearing system parameters were discussed from the results of numerical calculation, including the eccentricity, mass, stiffness, damping and lubricating oil viscosity. The results showed that: (1) medium eccentricity shows a wider stable speed range; (2) rotor damping has little effect to the stability of the system; (3) lower mass ratio produces a stable response; (4) medium suspension/journal stiffness ratio contributes to a wider stable speed range; (5) a higher viscosity shows a wider stable speed range than lower viscosity. From the above results, the rotor bearing system shows complex nonlinear dynamic behavior with nonlinear viscous damping. These results will be helpful to carrying out the optimal design of the rotor bearing system.

scholarly journals Nonlinear Model and Dynamic Behavior of Photovoltaic Grid-Connected Inverter

2020 ◽  
Vol 10 (6) ◽  
pp. 2120 ◽  
Author(s):  
Zhi-Xian Liao ◽  
Dan Luo ◽  
Xiao-Shu Luo ◽  
Hai-Sheng Li ◽  
Qin-Qin Xiang ◽  
...  
Keyword(s):  
Bifurcation Diagram ◽  
Dynamic Behavior ◽  
Nonlinear Model ◽  
Nonlinear Dynamic ◽  
Optimization Design ◽  
Stable Operation ◽  
Control Parameters ◽  
Nonlinear Dynamic Behavior ◽  
Predictive Controller ◽  
Grid Connected Inverter

A photovoltaic grid-connected inverter is a strongly nonlinear system. A model predictive control method can improve control accuracy and dynamic performance. Methods to accurately model and optimize control parameters are key to ensuring the stable operation of a photovoltaic grid-connected inverter. Based on the nonlinear characteristics of photovoltaic arrays and switching devices, we established a nonlinear model of photovoltaic grid-connected inverters using the state space method and solved its model predictive controller. Then, using the phase diagram, folded diagram, and bifurcation diagram methods, we studied the nonlinear dynamic behavior under the influence of control parameters on both fast and slow scales. Finally, we investigated the methods of parameter selection based on the characteristics of nonlinear dynamic behavior. Our research shows that the predictive controller parameters are closely related to the bifurcation and chaos behaviors of the grid-connected photovoltaic inverter. The three-dimensional bifurcation diagram can be used to observe the periodic motion region of the control parameters. After selecting the optimization target, the bifurcation diagram can be used to guide the selection of control parameters for inverter design. The research results can be used to guide the modeling, stability analysis, and optimization design of photovoltaic grid-connected inverters.

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