Papers by Keyword: Resonance

Abstract: By the developed applicative research we look for setting up a procedure for dynamically diagnosing the technological equipment proposed for remanufacturing. Actually, this paper presents some of the results of the research carried out for the establishment an analysis method of the non-functioning technological equipment structure, using the Finite Element Analysis, for stating the own vibration modes, thus based on the structure own frequencies to be stated the maximum critical rotation up to the new equipment would function in the imposed quality and safety conditions. With the proposed procedure we could exactly state the structure own frequencies that yet appear within the working frequencies band of the analyzed technological equipment, and thus we could find the revolutions at which the mechanic system could enter into resonance.

Abstract: Magnetorheological elastomers (MREs) belong to the group of so-called smart materials, which respond to an external stimulus by changing their viscoelastic properties.The vibration head will be modified with the MRE regulation system. The elastomer pillows will be enhanced with MRE and the regulation system (coils).The main idea of the modification is to increase an effectiveness of the vibrator work by the regulation that will stable the vibrations in the resonance frequency. It will be caused by the changeable stiffness of MRE elements under magnetic field.The aim of presented study is to research the influence of MREs cured under the magnetic fields on the strength properties of the elastomer pillow.

Abstract: Process of vertical vibrations of the weight suspended on a spring at harmonic kinematic excitation is examined. It is shown that the resonance tuning of a system can be done with the use of magnetic force which occurs if the coil turns while moving cross external magnetic field lines.

Abstract: This study performed 2D analysis for suspension bridge to predict the bridge superstructure oscillation induced by wind load. Previous studies exhibited that a large torsional mode can be generated by continuous vertical modes in suspension bridge. However, the previous studies did not consider torsional resistance of the superstructure and unrealistic results were shown as wind speeds increasing. Therefore, this study developed a new model considering torsional resistances and predicted responses of a suspension bridge. Analysis results exhibited that vertical oscillations were transformed to the torsional oscillations. With varying torsional resistances, vertical responses were stabilized over a time. However, the rotational response amplified at resonance points. Also, it was found that the resonance of the rotational mode depended on the torsional resistance.

Abstract: The paper is concerned with the frequency reliability sensitivity and related robust analysis problem for the random continuous vibration structure systems. Reliability analysis based on frequency is necessary for reliability problems of uncertain vibration structure systems. With the criterion that the absolute value of the difference between the natural frequency and forcing frequency, the reliability mode and the safety probability of the random systems are defined, and then The frequency sensitivity analysis method is quested by using the random perturbation technique, the reliability theory and sensitivity approach. Furthermore, the frequency reliability-based robust method of the random dynamic structural system was obtained by the robust and the optimization technology on the basis of frequency reliability and sensitivity design, which helped designers to establish acceptable parameter values and to determine the fluctuations of the parameters for the safe operations. Moreover, a numerical example is provided to demonstrate the effectiveness and accuracy of the proposed method. This study established theory basis for sensitivity and robust evaluation.

Abstract: The output response of the piezoelectric cantilever has excellent linearity over a very wide dynamic range. This paper demonstrates the potential of piezoelectric cantilever to be a self-powered accelerometer. Three different-sized piezoelectric cantilevers were tested under a vibration source at 50 Hz, 100 Hz, and 150 Hz. It is proven that the piezoelectric cantilevers can be used as an accelerometer since the output voltage generated by the cantilever is linear and proportional to the vibration acceleration level far before reaching its resonance. Three piezoelectric cantilevers with similar length of 28.6 mm, but different width of 3.2 mm, 6.3 mm and 12.7 mm were used in the experiment in order to observe the linearity of the output voltage from different-sized piezoelectric cantilevers with the same resonance frequency. The length of piezoelectric may affect the resonance frequency of the cantilever, while the width of the piezoelectric will not. Hence, cantilevers with different width are chosen as the subject of the experiment. The linearity of the experiment results show the maximum error percentage obtained is between 5 to 15% when excited at a vibration magnitude in the range of 1 to 5-g.

Abstract: For the low power wind turbine, the tower and the generator unit is easy to produce resonance, which will result in bigger amplitude. In this paper, as an example, the authors establish a finite element model for modal analysis by a 55kw direct-drive permanent-magnet generator, to confirm its inherent frequency and vibration mode. Horizontal amplitude on the top of the tower can be received under different external excitation frequency. The results correspond to the codes very well and can provide effective reference data for the design of the wind turbine tower.

Abstract: Under excitation of high-voltage pulse electric field, the deformation vibration of droplet in oil was very important to electro-dehydration of emulsified oil. So far, the theoretical calculation on vibration of droplet was scarcely studied. In order to calculate the vibration of droplet, the forces acted on a single droplet needed to be analyzed, and the vibration kinetic model of droplet needed to be established. The model was resolved by method of harmonious wave balance. It was found by analysis that the resonance of droplet might occur. In the experiment, the results approximated to that of model calculation. So it was verified that the model could efficiently calculate the vibration amplitude of droplet.

Abstract: As the environment and customer are sensitive to compressor noise from refrigeration air condition system, it’s necessary to reduce noise level for scroll compressor to compete with piston one in this field. In this paper, we studied one way to detect noise resource and reduce noise level for scroll compressor; analyzed its vibration and noise characteristics; got the sound intensity distribution on the surface of compressor; performed the model test of the main part by using hammer strike and gained their intrinsic frequents. At last, by comparing the scroll compressor noise test results, sound intensity distribution, and intrinsic frequents, it was confirmed that upper shell resonation is the root cause to increase the noise. Also we gave a specific method, adding additional weight to upper shell, to avoid resonation. It’s proved to be efficient after test check.

Abstract: In the paper steadiness of the compressed and twisted drill rod is examined. The rod is presented in the form of a circular cylindrical shell, which is circulated from the outer side by a supersonic stream of gas. The rod is affected by the uniformly distributed on its length axial force and the torque. The problem of stability is solved by means of reviewing of a small deviation from the periodic solution of the problem. Boundaries of instability zones of the mechanical system are defined with application of the method of harmonic balance.