Modeling and Simulation of Nonlinear Combination Disc-Spring Vibration Isolator for High-Speed Press

2011 ◽  
Vol 211-212 ◽  
pp. 40-47 ◽  
Author(s):  
En Lai Zheng ◽  
Fang Jia ◽  
Zhi Sheng Zhang ◽  
Jin Fei Shi
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Variable Stiffness ◽  
Harmonic Excitation ◽  
Adaptive Performance ◽  
Vibration Isolator ◽  
Different Types ◽  
Solid Foundation ◽  
The Mathematical Model ◽  
Disc Spring

With its variable stiffness, capability to provide friction damping by itself, and space-based adaptive performance, the disc spring, by replacing the cylindrical helical spring extensively, has found wide application in fields like aerospace, metallurgy, architecture, machinery and so on. For the nonlinear combination disc-spring vibration isolator, the mathematical model is established in this study on the basis of classical disc spring theories. The simulation results of the combination vibration isolator under simple harmonic excitation and the effects of damping ratio and different types of load on the vibration isolator are explored in depth, the findings of which help to lay a solid foundation for parameterization and serialization of the nonlinear combination disc-spring vibration isolator.

scholarly journals Suppression of Ground Borne Vibration Induced by High-Speed Lines

2018 ◽  
Vol 152 ◽  
pp. 02001
Author(s):  
Ali Mohamed Rathiu ◽  
Mohammad Hosseini Fouladi ◽  
Satesh Narayana Namasivayam ◽  
Hasina Mamtaz
Keyword(s):  
Mathematical Model ◽  
Analytical Model ◽  
High Speed ◽  
Moving Load ◽  
Ground Vibration ◽  
Harmonic Excitation ◽  
Vibration Response ◽  
Vibration Velocity ◽  
Velocity Response ◽  
The Mathematical Model

Vibration of high-speed lines leads to annoyance of public and lowering real estate values near the railway lines. This hinders the development of railway infrastructures in urbanised areas. This paper investigates the vibration response of an isolated rail embankment system and modifies the component to better attenuate ground vibration. Mainly velocity response is used to compare the responses and the applied force is of 20 kN at excitation frequencies of 5.6 Hz and 8.3 Hz. Focus was made on ground-borne vibration and between the frequency range of 0 and 250 Hz. 3D Numerical model was made using SolidWork software and frequency response was produced using Harmonic Analysis module from ANSYS Workbench software. For analytical modelling MATLAB was used along with Simulink to verify the mathematical model. This paper also compares the vibration velocity decibels (VdB) of analytical two-degree of freedom model mathematical model with literature data. Harmonic excitation is used on the track to simulate the moving load of train. The results showed that modified analytical model gives the velocity response of 75 VdB at the maximum peak. Changes brought to the mass and spacing of the sleeper and to the thickness and the corresponding stiffness for the ballast does not result in significant vibration response. Limitations of two-degree analytical model is suspected to be the cause of this inactivity. But resonance vibration can be reduced with the aid of damping coefficient of rail pad. Statistical analysis methods t-test and ANOVA single factor test was used verify the values with 95% confidence.

Development of a Variable Stiffness and Damping Tunable Vibration Isolator

2005 ◽  
Vol 11 (3) ◽  
pp. 381-396 ◽  
Author(s):  
Johan M. Cronjé ◽  
P. Stephan Heyns ◽  
Nico J. Theron ◽  
Philip W. Loveday
Keyword(s):  
Damping Ratio ◽  
Variable Stiffness ◽  
Leaf Spring ◽  
Vibration Isolator ◽  
Flow Losses ◽  
Isolation Frequency ◽  
Hot Air ◽  
At Resonance ◽  
Air Gun ◽  
Stiffness And Damping

In this paper we report on the development of a variable stiffness and damping Liquid Inertia Vibration Eliminator (LIVE) vibration isolator. The result is the ability to shift the isolation frequency of the isolator and also to change the amplification at resonance. A practical variable stiffness spring was developed by using a compound leaf spring with circular spring elements. A wax actuator, controlled by a hot-air gun with a closed-loop displacement and velocity feedback control system, was used to separate the springs at the center. An experimental isolator was constructed and tested. The isolation frequency was shifted from 22.8 to 36.2 Hz by changing the stiffness of the spring by 270%. A transmissibility of less than 10% was achieved over the whole range. The viscous damping ratio was changed from 0.001 to 0.033 by increasing the flow losses in the system.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

scholarly journals Research on aerodynamic characteristics of two-stage axial micro air turbine spindle for small parts machining

2020 ◽  
Vol 12 (12) ◽  
pp. 168781402098437
Author(s):  
Liu Jiang ◽  
Guo Zhiping ◽  
Miao Shujing ◽  
He Xiangxin ◽  
Zhu Xinyu
Keyword(s):  
High Speed ◽  
Aerodynamic Characteristics ◽  
Maximum Efficiency ◽  
Two Stage ◽  
Output Torque ◽  
Air Turbine ◽  
Solid Foundation ◽  
Computational Fluid Dynamics Cfd ◽  
Micro Machine ◽  
Small Parts

In order to meet the requirements of output torque, efficiency and compact shape of micro-spindles for small parts machining, a two-stage axial micro air turbine spindle with an axial inlet and outlet is proposed. Based on the k-ω turbulence model of SST, the flow field and operation characteristics of the two-stage axial micro air turbine spindle were studied using computational fluid dynamics (CFD) combined with an experimental study. We obtained the air turbine spindle under different working conditions of the loss and torque characteristics. When the inlet pressure was 300 KPa, the output speed of the two-stage turbine was 100,000 rpm, 9% higher than that of a single-stage turbine output torque. The total torque reached 6.39 N·mm, and the maximum efficiency of the turbine and the spindle were 42.2% and 32.3%, respectively. Through the research on the innovative structure of the two-stage axial micro air turbine spindle, the overall performance of the principle prototype has been significantly improved and the problems of insufficient output torque and low working efficiency in high-speed micro-machining can be solved practically, which laid a solid foundation for improving the machining efficiency of small parts and reducing the size of micro machine tool.

scholarly journals Does the Opening of High-Speed Railway Lines Reduce the Carbon Intensity of China’s Resource-Based Cities?

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4648
Author(s):  
Zhipeng Tang ◽  
Ziao Mei ◽  
Jialing Zou
Keyword(s):  
High Speed ◽  
National Average ◽  
Carbon Intensity ◽  
Time Varying ◽  
Low Carbon ◽  
High Speed Railway ◽  
Different Types ◽  
Endogenous Selection ◽  
Mode Of Development ◽  
The Impact

The carbon intensity of China’s resource-based cities (RBCs) is much higher than the national average due to their relatively intensive mode of development. Low carbon transformation of RBCs is an important way to achieve the goal of reaching the carbon emissions peak in 2030. Based on the panel data from 116 RBCs in China from 2003 to 2018, this study takes the opening of high-speed railway (HSR) lines as a quasi-experiment, using a time-varying difference-in-difference (DID) model to empirically evaluate the impact of an HSR line on reducing the carbon intensity of RBCs. The results show that the opening of an HSR line can reduce the carbon intensity of RBCs, and this was still true after considering the possibility of problems with endogenous selection bias and after applying the relevant robustness tests. The opening of an HSR line is found to have a significant reducing effect on the carbon intensity of different types of RBC, and the decline in the carbon intensity of coal-based cities is found to be the greatest. Promoting migration of RBCs with HSR lines is found to be an effective intermediary way of reducing their carbon intensity.

scholarly journals Melatonin in Cancer Treatment: Current Knowledge and Future Opportunities

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2506
Author(s):  
Wamidh H. Talib ◽  
Ahmad Riyad Alsayed ◽  
Alaa Abuawad ◽  
Safa Daoud ◽  
Asma Ismail Mahmod
Keyword(s):  
Clinical Trials ◽  
Current Knowledge ◽  
Biological Activities ◽  
Experimental Studies ◽  
Therapeutic Effects ◽  
Cell Proliferation Inhibition ◽  
Different Types ◽  
Solid Foundation

Melatonin is a pleotropic molecule with numerous biological activities. Epidemiological and experimental studies have documented that melatonin could inhibit different types of cancer in vitro and in vivo. Results showed the involvement of melatonin in different anticancer mechanisms including apoptosis induction, cell proliferation inhibition, reduction in tumor growth and metastases, reduction in the side effects associated with chemotherapy and radiotherapy, decreasing drug resistance in cancer therapy, and augmentation of the therapeutic effects of conventional anticancer therapies. Clinical trials revealed that melatonin is an effective adjuvant drug to all conventional therapies. This review summarized melatonin biosynthesis, availability from natural sources, metabolism, bioavailability, anticancer mechanisms of melatonin, its use in clinical trials, and pharmaceutical formulation. Studies discussed in this review will provide a solid foundation for researchers and physicians to design and develop new therapies to treat and prevent cancer using melatonin.

Rotordynamic Performance of Flexure Pivot Hydrostatic Gas Bearings for Oil-Free Turbomachinery

2007 ◽  
Vol 129 (4) ◽  
pp. 1020-1027 ◽  
Author(s):  
Xuehua Zhu ◽  
Luis San Andrés
Keyword(s):  
High Speed ◽  
Low Cost ◽  
Damping Ratio ◽  
Extreme Temperature ◽  
Gas Bearings ◽  
Speed Increase ◽  
Feed Pressure ◽  
Motor Test ◽  
Direct Stiffness ◽  
Commercial Applications

Micro-turbomachinery demands gas bearings to ensure compactness, light weight, and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. Presently, tests conducted on a small rotor supported on flexure pivot hydrostatic pad gas bearings (FPTPBs) demonstrate stable rotordynamic responses up to 100,000rpm (limit of the drive motor). Test rotor responses show the feed pressure raises the system critical speed (increase in bearing direct stiffness) while the viscous damping ratio decreases. Predictions correlate favorably with experimentally identified (synchronous) direct stiffness bearing force coefficients. Identified experimental gas bearing synchronous damping coefficients are 50% or less of the predicted magnitudes, though remaining relatively constant as the rotor speed increases. Tests without feed pressure show the rotor becomes unstable at ∼81krpm with a whirl frequency ratio of 20%. FPTPBs are mechanically complex and more expensive than cylindrical plain bearings. However, their enhanced stability characteristics and predictable rotordynamic performance makes them desirable for the envisioned oil-free applications in high speed micro-turbomachinery.

Research on the Performance Simulation of the Transmission System of Loader with Secondary Regulating Technique

2010 ◽  
Vol 426-427 ◽  
pp. 299-302
Author(s):  
Fa Ye Zang
Keyword(s):  
Mathematical Model ◽  
Fuzzy Control ◽  
Energy Saving ◽  
High Speed ◽  
Transmission System ◽  
Performance Simulation ◽  
Constant Torque ◽  
Braking Torque ◽  
The Mathematical Model ◽  
Inertial Energy

Based on deeply analyzing the working principles and energy-saving theory of loader secondary regulating transmission system, regenerating the transmission system’s inertial energy by controlling constant torque was put forward. Considering large changes of the parameters of the transmission system and its non-linearity, a fuzzy control was adopted to control the transmission system, and the mathematical model of the system was established, then the simulations of the performance of the transmission system has been conducted. The conclusion was made that the inertial energy can be reclaimed and reused in the system by the application of the secondary regulation technology, and braking by controlling constant torque is stable, it can ensure the security of braking at high speed and also permits changing the efficiency of recovery by changing the braking torque. The system’s power has been reduced and energy saving has been achieved.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

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