Research on the vibration model and vibration performance of cold orbital forging machines

2021 ◽  
pp. 095440542110450
Author(s):  
Lin Hua ◽  
Mingzhang Chen ◽  
Xinghui Han ◽  
Xuancheng Zhang ◽  
Fangyan Zheng ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Vertical Vibration ◽  
Absolute Difference ◽  
Equivalent Stiffness ◽  
External Excitation ◽  
Horizontal Vibration ◽  
Equivalent Damping ◽  
Vibration Model ◽  
Vibration Performance ◽  
Orbital Forging

The vibration of cold orbital forging (COF) machines is a major issue for the quality of forging parts. It is therefore necessary to investigate the vibration of COF machines and provide some effective methods for reducing the vibration. In this paper, horizontal and vertical dynamic models of COF machines are established. These dynamic models are then effectively verified by conducting experiments. By using dynamic models of the COF machine, the vibration performance of the COF machine is investigated. To investigate methods for reducing the vibration of the COF machine, the effects of some key parameters on the vibration of the COF machine are studied, which include the eccentricities and rotation angular speeds of the inner eccentricity ring and the outer eccentricity ring, the amplitude and frequency of external excitation, and the equivalent stiffness and equivalent damping between swing shaft and bearing. Investigative conclusions can be drawn: During the COF process, vertical vibration is more drastic than horizontal vibration. A larger absolute difference between the eccentricities of the inner eccentricity ring and the outer eccentricity ring contributes to reducing the horizontal vibration of the COF machine. A larger equivalent stiffness and a larger equivalent damping between the swing shaft and bearing, a smaller amplitude and a smaller frequency of the external excitation contribute to reducing the vertical vibration of the COF machine.

scholarly journals Vibration Modelling and the Difference Between Different Vibration Models for a Fewer-DOF Parallel Robot

2020 ◽  
Author(s):  
Shuai Fan ◽  
Shouwen Fan ◽  
Xin Zhang ◽  
Guangkui Song ◽  
Weibin Lan
Keyword(s):  
Design Process ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Parallel Robot ◽  
Machining Accuracy ◽  
Object A ◽  
Vibration Model ◽  
Kane’S Equation ◽  
Joint Clearances ◽  
Vibration Performance

Abstract The accuracy of the vibration model used in the design process directly affects the vibration performance of a parallel robot in practice, which determines the machining accuracy and the surface finish of the manufactured products. Considering a drilling parallel robot with a passive branch and few degrees of freedom as the implementation object, a vibration modelling method is proposed in which Kane’s equation is utilized, and various commonly ignored factors, such as the passive branch, the joint clearances and gravity, are considered. To explore the effects of the passive branch, which was considered ideal in previous studies, two dynamic models are derived in which the passive branch is rigid or flexible. To explore the effects of the joint clearances, which were ignored in previous studies, two stiffness models of branches are derived, in which the joint clearances are considered or ignored. Finally, numerical examples are presented for analysing the effects of these commonly ignored factors on the vibration performance of the drilling parallel robot. Regarding to the effects of these commonly ignored factors, the findings of this paper can serve as a reference for designers in simplifying the vibration model in the design process of parallel robot.

scholarly journals Estimation of Additional Equivalent Damping Ratio of the Damped Structure Based on Energy Dissipation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Xiuyan Hu ◽  
Qingjun Chen ◽  
Dagen Weng ◽  
Ruifu Zhang ◽  
Xiaosong Ren
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Theoretical Concept ◽  
Estimation Methods ◽  
External Excitation ◽  
Single Degree Of Freedom ◽  
Equivalent Damping ◽  
Seismic Motion ◽  
Practical Engineering ◽  
Energy Dissipation Capacity

In the design of damped structures, the additional equivalent damping ratio (EDR) is an important factor in the evaluation of the energy dissipation effect. However, previous additional EDR estimation methods are complicated and not easy to be applied in practical engineering. Therefore, in this study, a method based on energy dissipation is developed to simplify the estimation of the additional EDR. First, an energy governing equation is established to calculate the structural energy dissipation. By means of dynamic analysis, the ratio of the energy consumed by dampers to that consumed by structural inherent damping is obtained under external excitation. Because the energy dissipation capacity of the installed dampers is reflected by the additional EDR, the abovementioned ratio can be used to estimate the additional EDR of the damped structure. Energy dissipation varies with time, which indicates that the ratio is related to the duration of ground motion. Hence, the energy dissipation during the most intensive period in the entire seismic motion duration is used to calculate the additional EDR. Accordingly, the procedure of the proposed method is presented. The feasibility of this method is verified by using a single-degree-of-freedom system. Then, a benchmark structure with dampers is adopted to illustrate the usefulness of this method in practical engineering applications. In conclusion, the proposed method is not only explicit in the theoretical concept and convenient in application but also reflects the time-varying characteristic of additional EDR, which possesses the value in practical engineering.

Optimal Design of Vibration Absorber Systems Supported by Elastic Base

1991 ◽  
Author(s):  
Hashem Ashrafiuon
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Elastic Base ◽  
Design Parameters ◽  
Primary System ◽  
Vibration Absorbers ◽  
Equivalent Damping ◽  
System Equations ◽  
Different Levels

Abstract This paper presents the effect of foundation flexibility on the optimum design of vibration absorbers. Flexibility of the base is incorporated into the absorber system equations of motion through an equivalent damping ratio and stiffness value in the direction of motion at the connection point. The optimum values of the uncoupled natural frequency and damping ratio of the absorber are determined over a range of excitation frequencies and the primary system damping ratio. The design parameters are computed and compared for the rigid, static, and dynamic models of the base as well as different levels of base flexibility.

Stability Prediction of the Nuclear Turbine Blades During Wet Steam Nonequilibrium Condensation Process

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Bing Guo ◽  
Weixiao Tang
Keyword(s):  
Turbine Blades ◽  
Condensation Process ◽  
Equivalent Stiffness ◽  
Wet Steam ◽  
Two Phase ◽  
Equivalent Damping ◽  
Novel Method ◽  
Phase Temperature ◽  
Nonequilibrium Condensation ◽  
The Stability

Stability of the nuclear turbine blades is difficult to be accurately predicted because the wet steam load (WSL) as well as its induced equivalent damping and stiffness during nonequilibrium condensation process (NECP) is hard to be directly calculated. Generally, in design, NECP is assumed as equilibrium condensation process (ECP), of which the two-phase temperature difference (PTD) between gaseous and liquid is ignored. In this paper, a novel method to calculate the WSL-induced equivalent damping and equivalent stiffness during NECP based on the combined microperturbation method (MPM) and computational fluid dynamics method (CFDM) was proposed. Once the WSL-induced equivalent damping and equivalent stiffness are determined, the stability of the blade-WSL system, of which the blade was modeled by a pretwisted airfoil cantilever beam, can then be predicted based on the Lyapunov's first method. Besides, to estimate the effects of PTD, comparisons between the WSL-induced equivalent damping and equivalent stiffness as well as the unstable area during NECP and ECP were presented. Results show that the WSL-induced equivalent damping and equivalent stiffness during NECP are more sensitive to the inlet boundary due to the irreversible heat transfer caused by PTD during NECP. Accordingly, the unstable area during NECP is about three times larger than during ECP.

scholarly journals Experimental investigation on the correlation of pressure pulsation and vibration of axial flow pump

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988947
Author(s):  
Xiaohui Duan ◽  
Fangping Tang ◽  
Wenyong Duan ◽  
Wei Zhou ◽  
Lijian Shi
Keyword(s):  
Pressure Pulsation ◽  
Axial Flow ◽  
Domain Analysis ◽  
Vertical Vibration ◽  
High Flow ◽  
Design Flow ◽  
Flow Rates ◽  
Horizontal Vibration ◽  
Axial Flow Pump ◽  
Flow Pump

Pressure and vibration displacement value are relatively measured by 14 pressure sensors and 2 vibration sensors distributing inside the tank-type model axial flow pump device under different flow rates. By comparison, it is found that the pressure pulsation on the inlet of the impeller is the main cause of hydraulic induced vibration of the pump device, and it is found to have similar amplitude trend with the vertical vibration as the flow rates increases and large correlation coefficient with the horizontal vibration under high flow rates through time-domain analysis. By frequency-domain analysis, it is found that the main frequency of pressure pulsation is three multiplies of the shaft frequency, but it is one multiplies of vertical vibration, and it changes from one multiplies to three multiplies of horizontal vibration. Combining with the analysis of phase-flow rates characteristics of both pressure pulsation and vibration, it is concluded that, for the horizontal vibration, the frequency ingredient of one multiplies ranging from low to high flow rates and three multiplies removing from unstable and high flow rates zone are possibly induced by pressure pulsation on the inlet of impeller, while for the vertical vibration, the frequency ingredient of one multiplies under design flow rates and high flow rates are possibly induced by pressure pulsation on the inlet of impeller. Both the horizontal and vertical vibrations with frequency of two multiplies have little relationship with the pressure pulsation on the inlet of impeller.

Forced Response Prediction of Blades With Loosely Assembled Dovetail Attachment by HBM

2009 ◽  
Author(s):  
Shangguan Bo ◽  
Zili Xu ◽  
Qilin Wu ◽  
XianDing Zhou ◽  
ShouHong Cao
Keyword(s):  
Friction Force ◽  
Centrifugal Force ◽  
Dry Friction ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Balance Method ◽  
Force Model ◽  
Equivalent Stiffness ◽  
Equivalent Damping

To understand the mechanism of interfacial damping of axial loosely assembled dovetail to suppress blade vibration, a dry friction force model is presented by the Coulomb friction law and the macroslip model, and the mathematical expression of the friction force is derived. The nonlinear friction force is linearized as an equivalent stiffness and an equivalent damping through the one-term harmonic balance method. The effect of centrifugal force on the equivalent stiffness and the equivalent damping is studied. The forced response of one simplified blade with loosely assembled dovetail attachment is predicted by the harmonic balance method, in which the blade is described by the lumped mass and spring model, and the friction contact joints is simplified as a ideal friction damper. The results show that the equivalent stiffness of loosely assembled dovetail attachment increases with blade centrifugal force, gradually reaches a certain value, and there exists the maximum value for the equivalent stiffness. The equivalent damping increases at the beginning and then decreases with blade centrifugal force increasing, there exists a maximum too. The resonant frequency of blade rises with blade centrifugal force, but it no longer increases when the centrifugal force exceed a certain value. There exists a special centrifugal force on which the effect of dry friction damping is the best.

Comparison of Vertical Model and Spatial Model for Vehicle-Track-Bridge Coupling Vibration System

2011 ◽  
Vol 243-249 ◽  
pp. 4307-4310
Author(s):  
Yuan Zhang ◽  
Wei Lin ◽  
Ze Ming Wang
Keyword(s):  
Vertical Vibration ◽  
Coupling Vibration ◽  
Spatial Coupling ◽  
Advantages And Disadvantages ◽  
Vibration Model ◽  
Spectrum Density ◽  
Exciting Source ◽  
Vibration Responses ◽  
Track Bridge ◽  
Bridge System

In this paper, models for vertical and spatial coupling vibration of vehicle-track-bridge system are established separately. The track vertical irregularity sample in time domain is established by power spectrum density and taken as the exciting source to analyze the coupling vibration of vehicle-track-bridge system of two models. The advantages and disadvantages and applicability of the vertical vibration model and the spatial vibration model are analyzed by comparing the vertical vibration responses of the two models under excitation with same level of track vertical irregularity.

Stiffness and Damping Analysis of a Single EHL Contact Between the Rolling Element and Raceways Under Wider Load and Speed Ranges

2012 ◽  
Author(s):  
Yuyan Zhang ◽  
Xiaoli Wang
Keyword(s):  
Viscosity Coefficient ◽  
Equivalent Stiffness ◽  
Solution Convergence ◽  
Vibration Model ◽  
Rolling Element ◽  
Inlet Length ◽  
Motion Characteristics ◽  
Stiffness And Damping ◽  
Increasing Load ◽  
Ehl Contact

The numerical analysis for the equivalent stiffness and damping of a single EHL contact between the rolling element and raceways under wider load and speed ranges is presented. The unsteady EHL model and free vibration model are applied to describe the motion characteristics of the rolling element. The inlet length and dimensionless natural frequency are determined according to the corresponding working load and speed. The DC-FFT method is implemented in order to increase the computational efficiency associated with elastic deformations and the semi-system approach is applied to ensure solution convergence under severe conditions which makes the analysis of stiffness and damping in the larger ranges of load and speed possible. The numerical results demonstrate that the stiffness increases with the increasing load and decreases with speed. However, the changes of the damping are complex, which are different in various load and speed ranges, especially under heavier load and higher speed. It is also indicated that the stiffness and damping increases with the increase in ambient viscosity and the decrease in pressure-viscosity coefficient.

VERTICAL VIBRATION CHARACTERISTICS OF A HIGH-TEMPERATURE SUPERCONDUCTING MAGLEV VEHICLE SYSTEM

2013 ◽  
Vol 27 (15) ◽  
pp. 1362022 ◽  
Author(s):  
JING JIANG ◽  
KE CAI LI ◽  
LI FENG ZHAO ◽  
JIA QING MA ◽  
YONG ZHANG ◽  
...  
Keyword(s):  
High Temperature ◽  
Vibration Frequency ◽  
Excitation Frequency ◽  
Vertical Vibration ◽  
External Excitation ◽  
Maglev Vehicle ◽  
Vehicle System ◽  
High Temperature Superconducting Maglev ◽  
External Excitation Frequency ◽  
Maglev Vehicle System

The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0–100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

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