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The paper describes experimental investigations of vibrations caused by train passages in the shallow underground tunnel (in Warsaw, Poland) in comparison to the results of measurements of vibrations from ground surface transporta...
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The paper describes experimental investigations of vibrations caused by train passages in the shallow underground tunnel (in Warsaw, Poland) in comparison to the results of measurements of vibrations from ground surface transportation (trams and buses). Propagation of surface ground vibrations from underground tunnel is presented. The problem of dynamic response of a building and influence of vibrations caused by underground on people residing in a building is discussed as well. The dynamic response of the building to underground vibrations is essentially different from the response of a building excited by surface sources of transport vibrations. Also the distribution of influence of the transport vibrations on people in the building is significantly different in both cases.
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This paper deals with the vibration control device that simultaneously generates electricity by using absorbed vibration energy. This device is composed of a generator and a Hula-Hoop that is fixed on the shaft of the generator. A...
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This paper deals with the vibration control device that simultaneously generates electricity by using absorbed vibration energy. This device is composed of a generator and a Hula-Hoop that is fixed on the shaft of the generator. As the conditions which have some effect on the vibration control performance and electric power, power of D.C. motor that is the substitute of generator, weight of Hula-Hoop, distance between the center of rotation and center of gravity, external frequency, and initial condition are examined.
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Due to the development of modem technologies, the number of sources initiating vibrations and noises has significantly increased. A variety of techniques are used to eliminate the negative impact of extraneous noise and vibrations...
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Due to the development of modem technologies, the number of sources initiating vibrations and noises has significantly increased. A variety of techniques are used to eliminate the negative impact of extraneous noise and vibrations. The article presents the concept of vibration protection, the options and mechanism for selecting coatings, and an overview of the global market for vibration-proof materials. The most common methods of vibration protection are vibration isolation and vibration damping, implemented by using materials with appropriate properties. Vibration isolation of vehicles is carried out by surface treatment with special mastics or coating with substrates as well as with the usage of hydraulic vibration supports. To minimize the impact of vibrations on buildings and structures, special fastenings and suspensions, vibration isolators, supports, soft rolled and sheet materials ,are used. For vibration isolation of machine tools and precision equipment, separate supports, a layer of elastic material placed between the machine and the foundation, a floating floor on an elastic base are used. The article presents a brief analysis of metal, rubber and rubber-metal vibration isolation supports in the budget, medium and premium price segments. Vibration damping is performed using special plates, which are available on the market in the form of rolled materials and multilayer plates. Vibration-absorbing composite polymer coatings based on thermosetting polymers have become widespread. The industry of Russia and foreign countries has established the production of vibration-absorbing reinforced sheet materials. Russian scientists are also actively developing new types of coatings: gradient polymer composite materials, thermoplastic extrusion films, laminated fiberglass polymers, etc.
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In this paper, a test for investigating the vibrational hazards occurred in a modernized hospital was carried out, in which a lot of power equipment such as chilled water pumps and freezers, etc. were installed in the ground floor...
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In this paper, a test for investigating the vibrational hazards occurred in a modernized hospital was carried out, in which a lot of power equipment such as chilled water pumps and freezers, etc. were installed in the ground floor. The generated vibrations could be experienced on the upper floors including some medical precision room. Next, solation and active control strategies were proposed, and evidently the active control could improve the suppression a lot. This study illustrated that the great vibrational hazards could not be ignored anymore, and the followed resolution strategies for eliminating these vibrations seemed to be urgent. In tradition, the vibration isolations would not be involved in initial design for civil structures, but in fact this might lead to a severe problem to be addressed in the future, and this study could give inspiration for green building.
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To enhance the stability of a harmonic vibration synchronous conveyer, this paper establishes a nonlinear dynamical model for this kind of vibration machine, and the effects and compensation function on the stability produced by t...
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To enhance the stability of a harmonic vibration synchronous conveyer, this paper establishes a nonlinear dynamical model for this kind of vibration machine, and the effects and compensation function on the stability produced by the nonlinearity of a master vibration spring have been analyzed. A small parameter perturbation method has been used to analyze the effects of a nonlinear force on the conveyer when a fluctuating impact was loaded onto the machine. The reaction between motion stability of the vibration conveyer and the synchronization of the two motors was also investigated. The results of experiments and practical applications demonstrated the correctness of the motion stability analysis of this nonlinear vibration conveyer and its application validity. In conclusion, significant reference values for design, dynamic analysis, testing, and application of the nonlinear vibration conveyer, with harmonic synchronous vibration, actuated by two motors have been achieved.
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The method suggested makes it possible to determine maximum amplitudes of standing vibration waves, slopes of the conductor with respect to horizontal, bending moments, and cutting forces in any cross section of the conductor and ...
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The method suggested makes it possible to determine maximum amplitudes of standing vibration waves, slopes of the conductor with respect to horizontal, bending moments, and cutting forces in any cross section of the conductor and of the flexible element of the vibration damper with the help of "SVT — Conductor with Vibration Damper" software for any grade of conductor, earth wire, or vibration damper (GPG). Comparative evaluation of parameters at the places of exit of the conductor from the supporting clamp and from the clamp of the vibration damper is performed.
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The determination of the vibration characteristics of Gofasa wood (vitexcofassus) can be carried out through bending tests, compression tests, and excitation tests. The beams used for the excitation test were fixed with the unsupp...
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The determination of the vibration characteristics of Gofasa wood (vitexcofassus) can be carried out through bending tests, compression tests, and excitation tests. The beams used for the excitation test were fixed with the unsupported ends. Four measurement points were determined on the radial and tangential direction of the grain of the wood to obtain the vibration parameter values. The measurement points were subjected to movements in order to obtain the vibration transmission characteristics. The analysis was carried out by using the non-destructive evaluation method (impact test), and to obtain the Poisson ratiota mechanical test was carried out, by using polynomial regression. The abtained results showed that the dynamic stiffness value of the tangential direction of the grain was higherthan the radialdirection of the grain k_T>k_R.The Poisson ratio of the grain radial direction had a higher value, and the natural frequency of thegrain radial direction showed a difference of 1 Hz, higher than the tangential direction of the grain. This research is to demonstrate that the vibration transmission characteristics have a damping ratio value less than √2. The transmission ratio TR<1 which means that the system requires damping.
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In this work, vibration reduction in randomly forced systems is considered using a new vibration absorber setup. In the new setup, the absorber consists of a mass spring and damper, and is attached such that it separates the prima...
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In this work, vibration reduction in randomly forced systems is considered using a new vibration absorber setup. In the new setup, the absorber consists of a mass spring and damper, and is attached such that it separates the primary system from the fixed support. White noise excitation is assumed and the objective function is the mean square value of the primary system response function. For given damping and mass ratios of the system, the optimal stiffness and damping ratios of the absorber are determined. The optimal parameters are obtained in an analytical closed form when the primary system is undamped, and calculated numerically for damped primary systems. It is shown that an optimal mass ratio exists, unlike the case of classical absorbers where performance increases with increasing absorber mass. The optimal parameters associated with the optimal mass ratio are calculated and tabulated for a range of primary system damping ratios. The efficiency of the proposed absorber is discussed and compared to that of the classical absorber.
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A method and corresponding equipment are proposed for exciting powerful resonant acoustic rotary waves in a gas or liquid flow within an annular zone between the rotor and stator. Such waves may be used for vibrational machining. ...
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A method and corresponding equipment are proposed for exciting powerful resonant acoustic rotary waves in a gas or liquid flow within an annular zone between the rotor and stator. Such waves may be used for vibrational machining. The application of acoustic vibration in dispersion and homogenization significantly improves product quality. For example, the fuel-air mixture produced by vibration for internal combustion engines is saturated with oxygen at the molecular level.
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The processing of materials with a hardness greater than 55 HRC has always required the use of unconventional or grinding methods in order to obtain the quality and precision required by the technical conditions. For these reasons...
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The processing of materials with a hardness greater than 55 HRC has always required the use of unconventional or grinding methods in order to obtain the quality and precision required by the technical conditions. For these reasons, the researches of the last decades have developed an unconventional method of processing, with great precision and precision, by assisting the classic processing techniques, with forced, unamortized, low amplitude ultrasonic vibrations. The present paper presents the results of some researches regarding the processing of extradural materials, by the assisted realization of the non-cushioned, low amplitude ultrasonic vibrations. It is demonstrated that this method of processing can obtain very fine surfaces, sometimes being able to replace the grinding, with much lower costs, in terms of energy consumption and tool wear.
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