Non-Linear Coupled Dynamics of a Flexible Propeller-Shaft System Supported by Water Film Bearings

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Chang-Gang Lin ◽  
Ming-Song Zou ◽  
Can Sima ◽  
Li-Bo Qi ◽  
Yue Yu
Keyword(s):  
Nonlinear Vibration ◽  
Damping Ratio ◽  
Water Film ◽  
Vibration Characteristics ◽  
Superposition Method ◽  
Propeller Shaft ◽  
Chaotic Motions ◽  
Mode Superposition Method ◽  
Shaft System ◽  
Slice Method

Abstract A slice method to determine the boundary conditions between the stern bearing and shaft by dividing the journal in the stern bearing into several slice elements along the axial direction is proposed for the first time. A comprehensive finite element model considering the nonlinear force of the water film and the flexibility of the propeller blade is established for a propeller-shaft system. The long bearing approximation is adopted to calculate the pressure distribution around each journal element in the stern bearing. The mode superposition method is employed. The nonlinear equation of motion is solved iteratively using the Newmark method. A parametric study is implemented to analyze the nonlinear vibration characteristics of the system. It is shown that the real motion state of the journal in the stern bearing can be simulated more precisely by the slice method proposed. The responses of the system alternate among period-one, quasi-periodic, multi-periodic, and chaotic motions as the rotating speed increases. The damping ratio has a significant effect on the dynamic characteristics of the propeller-shaft system. The motion of the system is unstable when the damping ratio is very small. At this time, the modes of the flexible propeller blades can be excited readily. The slice method, which can also be extensively used in similar rotor-bearing systems in the engineering field, is very simple and efficient to analyze the nonlinear vibration characteristics of a flexible propeller-shaft system supported by water film bearings.

Study on vibration characteristics of hydraulic planetary transmission considering engine and torque converter excitation

2021 ◽  
pp. 095440702110477
Author(s):  
Wen Liu ◽  
Chunji Ren ◽  
Tengjiao Lin ◽  
Yanjun Zhang
Keyword(s):  
Calculation Method ◽  
Torque Converter ◽  
Vibration Characteristics ◽  
Vibration Response ◽  
Working Environment ◽  
Superposition Method ◽  
External Excitation ◽  
Mode Superposition Method ◽  
Planetary Transmission ◽  
Force Calculation

Large-size vehicle loaders are mainly used in various construction projects with complex working environment, which has a serious impact on the internal vibration of the whole system. In this study, the vibration characteristics of hydraulic planetary transmission of vehicle loader considering the influence of the external excitation are evaluated theoretically and experimentally. The output torque of the four-stroke six-cylinder diesel engine is obtained by force calculation of crank and connecting rod mechanism. The equivalent stiffness and damping of the torque converter are solved according to the torsional dynamic equation of the torque converter. The trapped oil area, oil pressure, and flow rate of gear meshing part are extracted to obtain the trapped oil pressure of variable-speed pump. Then, the multi-degree-of-freedom gear system dynamic model is established to calculate the meshing force, which is applied to vibration response analysis model by using mode superposition method. Lastly, the vibration response test is performed on the experimental prototype to verify the calculation method. The conclusion shows that the generation principle of external excitation and its calculation method in this paper are feasible in the analysis of dynamic characteristics of hydraulic planetary torque converter.

Nonlinear Vibration Characteristics With Large Unbalance of Turbogenerators Rotor Systems

1995 ◽  
Author(s):  
Songyuan Lu ◽  
Gao Wei
Keyword(s):  
Nonlinear Vibration ◽  
Power Plants ◽  
Vibration Characteristics ◽  
Accident Analysis ◽  
Operation Condition ◽  
Rotor Systems ◽  
Shaft System ◽  
Time Marching ◽  
Made In China ◽  
Made In

Abstract Some catastrophic vibration failures of turbogenerators shaft system have occurred in China and abroad. But, since the researches on nonlinear vibration characteristics of real engineering rotor-bearing system were not thoroughgoing in the past years, so the accurate and quantity analysis on particular accidents is still impossible. However, to understand the nonlinear vibration characteristics with large unbalance is engineering important for accident analysis, investigation and for precautions against the failures. This paper employed a new transfer matrix-time marching approach, and made researches on calculation for nonlinear vibration caused by large vibration at the generator rotor and low pressure rotor of 200MW turbogenerators made in China. By this study, some new and important conclusions concerned transient process while much mass escaped from turbogenerators rotor at operation condition have been obtained. They can provide valuable suggestions to the accident analysis, the design of large turbogenerators shaft and operation technology of the power plants, and these conclusions will be the foundation for the further researches on the destruction mechanism of turbogenerators forced by nonlinear vibration.

scholarly journals Transient Response of Bridge Piers to Structure Separation under Near-Fault Vertical Earthquake

2021 ◽  
Vol 11 (9) ◽  
pp. 4068
Author(s):  
Wenjun An ◽  
Guquan Song
Keyword(s):  
Large Scale ◽  
Bending Moment ◽  
Relative Displacement ◽  
Superposition Method ◽  
Longitudinal Displacement ◽  
Transient Wave ◽  
Vibration Period ◽  
Vertical Excitation ◽  
Mode Superposition Method ◽  
Main Girder

Given the possible separation problem caused by the double-span continuous beam bridge under the action of the vertical earthquake, considering the wave effect, the transient wave characteristic function method and the indirect mode superposition method are used to solve the response theory of the bridge structure during the earthquake. Through the example analysis, the pier bending moment changes under different vertical excitation periods and excitation amplitudes are calculated. Calculations prove that: (1) When the seismic excitation period is close to the vertical natural vibration period of the bridge, the main girder and the bridge pier may be separated; (2) When the pier has a high height, the separation has a more significant impact on the longitudinal displacement of the bridge, but the maximum relative displacement caused by the separation is random; (3) Large-scale vertical excitation will increase the number of partitions of the structure, and at the same time increase the vertical collision force between the main girder and the pier, but the effect on the longitudinal displacement of the form is uncertain; (4) When V/H exceeds a specific value, the pier will not only be damaged by bending, but will also be damaged by axial compression.

Study on vibration characteristics of the shaft system for a dredging pump based on FEM

2012 ◽  
Vol 15 (4) ◽  
pp. 042002
Author(s):  
L M Zhai ◽  
L Qin ◽  
C Y Liu ◽  
X Liu ◽  
L Y He ◽  
...  
Keyword(s):  
Vibration Characteristics ◽  
Shaft System

scholarly journals Identification of Acoustic-Vibratory System by Acoustic Measurement

1996 ◽  
Vol 3 (1) ◽  
pp. 27-37
Author(s):  
Takuzo Iwatsubo ◽  
Shozo Kawamura ◽  
Masahito Kamada
Keyword(s):  
Inverse Analysis ◽  
Coefficient Matrix ◽  
Superposition Method ◽  
Vibration Modes ◽  
Identification Problems ◽  
Mathematical Property ◽  
Vibratory System ◽  
Stochastic Error ◽  
Mode Superposition Method ◽  
Ill Conditioning

A new method for reducing ill-conditioning in a class of identification problems is proposed. The key point of the method is that the identified vibration of the sound source is expressed as a superposition of vibration modes. The mathematical property of the coefficient matrix, the practical error expanding ratio, and the stochastic error expanding ratio are investigated in a numerical example. The mode-superposition method is shown to be an effective tool for acoustic-vibratory inverse analysis.

scholarly journals Dynamic Impact Factor Determination of an Existing Pre-stressed Concrete I-Girder Bridge Using Vehicle-Bridge Interaction Modelling

2021 ◽  
Vol 10 (3) ◽  
pp. 163-176
Author(s):  
Shuvrodeb Adhikary ◽  
Shohel Rana ◽  
Jerin Tasnim ◽  
Nazrul Islam
Keyword(s):  
Impact Factor ◽  
Dynamic Model ◽  
Superposition Method ◽  
Dynamic Impact ◽  
Mode Superposition Method ◽  
Road Roughness ◽  
Girder Bridge ◽  
Dynamic Impact Factor ◽  
Interaction Problem

The dynamic Impact Factor (IM) of a bridge is influenced by many factors, including Vehicle-Bridge Interaction (VBI), vehicle speed and road roughness. This paper represents the dynamic effects of moving vehicles and the determination of IM of an existing Pre-stressed concrete I-girder bridge utilizing VBI modeling. Evaluation of the IM is expected to provide valuable information for condition assessment and management of the existing bridge. The interaction problem between the vehicle and the bridge includes a dynamic model for the bridge structure subsystem, a dynamic model for the vehicle subsystem, interaction constraints, road roughness modelling and numerical solution techniques for the dynamic systems. The Half-car model is utilized for modelling of the vehicle dynamics and the bridge dynamic model is idealized according to Finite Element Method (FEM). Then FEM along with the mode superposition method are utilized for determining the Equation of Motion (EOM) for the bridge subsystem. D’Alembert’s principle is used for developing EOM for the vehicle subsystem. The interaction between vehicle vibration and bridge vibration is established through the contact forces between the wheels and the bridge by employing the compatibility relationship between the contact points and by applying the static equilibrium condition. Lastly, Newmark’s-β method is used for solving the coupled mathematical model of the vehicle and bridge interaction problem to determine the responses of the two sub-systems. The whole procedure is then performed for different vehicle speeds and various bridge deck surface roughness conditions to determine the dynamic impact on the existing I-girder bridge named Teesta Bridge located in Bangladesh.

scholarly journals Evaluation of bearing capacity of reinforced concrete box ribbed arch bridge based on dynamic load test

2021 ◽  
Vol 233 ◽  
pp. 01047
Author(s):  
Mao He ◽  
Xin Fu ◽  
Shunchao Chen
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Load ◽  
Damping Ratio ◽  
Vibration Characteristics ◽  
Load Test ◽  
Driving Safety ◽  
Original Material ◽  
Arch Bridge ◽  
Dynamic Load Test ◽  
And Function

Dynamic load test is to measure the natural vibration characteristics of the bridge structure or the forced vibration characteristics under dynamic load, and to evaluate the driving performance, driving safety and comfort of the bridge through dynamic load test. In order to evaluate the stress state and working performance of a reinforced concrete box-ribbed arch bridge, the load test of the bridge is carried out. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. Through the experiment with the key parts of the stress (strain) and displacement load and other important data, through analysis and study, the comprehensive analysis of the phenomenon of calculation and test, a comprehensive performance evaluation structure and function whether meet the design requirements, to provide technical basis for the safety of the bridge operation, and provide the original material for the bridge maintenance and management in the future.

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