Papers by Keyword: Dynamic Vibration Absorber

Abstract: Centrifugal pumps are widely used in industry and also domestically. It is commonly used for its robust design and its efficiency. Every machine has to be monitored periodically in order to maintain its efficiency and also to avoid unexpected failure which lead to loss of efficiency. So fault diagnosis is necessary to monitor the pump periodically for finding out the defects in pump and to replace it if necessary. Dismantling and assembling of pumps during fault diagnosis is a tedious process, vibration analysis can be helpful to monitor the performance of the pump system without dismantling. For the experimentation purpose mono-block centrifugal pumps have been used in this work. By using the Lab VIEW program and DAQ card as an interface, amplitude and frequency of vibration is obtained at different axes of the pump with the help of an accelerometer. Then the vibration spectrum is analyzed and defects are pointed out by identifying the frequency at which the amplitude of vibration is above the danger limit. The defects such as unbalance of impeller, bent shaft in pump, misalignment of shaft, hydraulic pulsation, cavitation and bearing defects are diagnosed using vibration data. The frequency at which different defects are occurring has been founded out by means of experimentation in the centrifugal pumps. Thus by diagnosing centrifugal pump using vibration data reduces cost and time for periodical maintenance. Shape memory alloy based ATDVA is used to control the amplitude of vibration due to hydraulic pulsation. Around 60% reduction in amplitude of vibration is evident for the varying excitation frequency between 336 Hz and 340 Hz due to hydraulic pulsation.

Abstract: Nowadays, absorbing energy from vibration is one of the most promising technologies. In general, the vibrations may be very large, such as the vibrations of tall buildings, large flexible bridges, and ocean platform and so on in some environmental loading. With the global concern on energy and environmental issues, energy absorbing from large-scale vibrations for structural health monitoring purposes is more attractive and becomes a research frontier. A type of damped dynamics vibration energy absorber, where two masses are connected in series with the energy transducer and spring, is built and analyzed in this paper. The relationships among electrical damping ratio, excitation frequency ratio and dimensionless power are analyzed in frequency domain. The optimal parameters for maximizing the power output are discussed in analytical form while taking the parasitic mechanical damping of the system into account. In addition, the numerical simulations in time domain are calculated. The results indicate that when the system is excited by the larger peak of local optimal excitation frequency, more power can be obtained. It is helpful for design of energy absorber device.

Abstract: The selection of absorber parameters is of utmost significance for structural vibration control by dynamic vibration absorbers. Based on the classical frequency tuning approach by Den Hartog, optimal damping ratio is derived in close form by equating the dynamic magnification factors of the structural motion at three particular frequencies of interest. In addition, by maximizing the two identical modal damping ratios through root locus in the first quadrant of complex plane, the corresponding absorber damping ratio is derived and proposed as the upper bound of the absorber damping ratio for practical applications.

Abstract: In order to improve working frequency band and damping effect of a dynamic vibration absorber, a new kind of dynamic vibration absorber is presented. Its resonant frequency could be real-time adjusted by adapting the stiffness of the spring. The vibration attenuation characteristics are analyzed theoretically and numerically. According to simulation analysis, effects of geometrical parameters are researched and optimum geometric parameters are determined. The damping effect was simulated in a flat structure, the results show that the working frequency band and damping effect of the DVA are both remarkable.

Abstract: In this paper the transverse vibration of a fixed-fixed end beam will be investigated by experimental measurement. This paper is concerned with the classical theory formula as well as the analysis and design of the dynamic vibration absorber (DVA) which is composed by a flexible beam with two masses symmetrically mounted at its both sides. The fixed end beam clamped to a static structure where dynamic vibration absorber then being attached onto it. One side of end of the beam is harmonically excited in transversal direction by an electric shaker. The structure equipped with accelerometer sensor to measure its vibration response amplitudes and natural frequencies. The dynamic vibration absorber arrangement located under motor near the beam end was then being vibrated and done in two conditions; before and after mounting dynamic vibration absorber. The comparison amplitudes before and after equipped dynamic vibration absorber were compared and discussed. From the experimental results, proved that the DVA has successfully absorbed the beam vibration hence reduced the vibration amplitude of the beam structure. The knowledge and result obtained from this study can help engineers control the vibration level of beam structure.

Abstract: The dynamic control equations are derived for the mechanical model with two degrees of freedom that the soften spring is considered in the dynamic vibration absorber. In order to facilitate the computation to the equations, through the integral of the dynamic control equations which became a four order ordinary differential equation. The amplitude frequency response curves of the primary structure excited by a harmonic force were drawn with harmonic balance method, the influence of the dynamic characteristics of primary structure about this kind of nonlinear dynamic vibration absorber was discussed.

Abstract: As cars become quieter the sound quality of components becomes more critical in the customer perception of car quality. Considering that middle frequency noise plays an important roll for internal noise, the noise signals in the range from200Hz to 500Hz are specially emphasized. Then the acoustic evaluation parameters, such as Sound Pressure Level, Acceleration have been evaluated. Judged from experiences and measuring results, an abnormal noise comes from engine mounts, through the use of dynamic vibration absorber on engine mounts, Vibration on engine mounts and Sound Pressure Level in interior vehicle were greatly improved. At the same time, subjective evaluation also indicated that there was no complaint any more in passenger compartment. Dynamic vibration absorber can properly solve the abnormal noise.

Abstract: Abstract: Unwanted vibration produced by production process of chemical enterprises is controlled by the vibration absorber. This design is low-cost, easy installation and monitoring. The control algorithm builds a dynamic absorber model to analyze attributes of damping characteristics, and completes detailed experimental work in simulated factory environment. The investigation results demonstrate the good performance of absorber, and experiment results are able to prove the theory.

Abstract: A new method for vibration control of aeronautical thin-walled workpiece in high-speed milling progress using a dynamic vibration absorber is presented. First, the theoretical model of the method is established and studied. Then the effectiveness of this method is testified via the simulation based on FEM. Finally, the feasibility of this method is discussed. The result shows that this method for vibration control of the aeronautic thin-walled workpiece in high-speed milling progress is effective and practical.

Abstract: Multiplexing the dynamic vibration absorber (DVA) has tried for improving the vibration absorption efficiency of the dynamic vibration absorber, and because there are several tuning vibration frequencies in the multi-mass dynamic vibration absorber system, the vibration absorption efficiency is more excellent than a conventional single-mass dynamic vibration absorber when they are in the same total mass ratio. In this paper, a two-series-mass dynamic vibration absorber was proposed, optimal parameters of the two-series-mass dynamic vibration absorber have been calculated and vibration absorption is analyzed with the simulation and experiment. The results show that the two-series-mss dynamic vibration absorber can improve vibration absorption, in the same total mass ratio, by about 20% above that of a conventional single-mass dynamic vibration absorber. Based on the above optimal results, the two-series-mass dynamic vibration was used for vibration control on high building, and the practical measure result shows its effectiveness.