Generation Of Mechanical Vibrations Research Articles

Installation for Producing Mechanical Vibrations used in the Finishing of the Welded Joints Structure

Abstract The paper presents a constructive version of a mechanical vibration generator designed to be used at stress relieving of welded joints. This installation can be used on all brands of steels and welded joints, whether they have magnetic properties or not. In the generator construction a DC motor was used, in order to be able to adjust the speed more easily. The speed adjustment is made with a potentiometer, and the speed measurement is made with a tachometer. The tachometer measures the speeds based on the pulses given by a four-pointed cam rotating between the plates of a capacitor. The vibration system also contains a piezoelectric accelerograph, which is attached to the welded part subjected to vibration, in order to measure the level of vibration and the parameters of the vibration wave.

Energy Analysis of the Propulsion Shaft Fatigue Process in a Rotating Mechanical System Part II Identification Studies – Developing the Fatigue Durability Model of a Drive Shaft

Abstract The article presents a continuation of research carried out concerning identification of energy consequences of mechanical fatigue within a propeller shaft in a rotating mechanical system, while working under conditions of the loss of the required alignment of shaft lines. Experimental research was carried out on a physical model reflecting a full-sized real object: i.e., the propulsion system of the ship. It is proven, by means of an active experiment, that changes in propeller shaft deflection are reflected in the amount of dissipated kinetic energy of masses in rotational motion and the accumulated internal energy in its construction material. Adoption of a high-cycle fatigue syndrome, consisting of diagnostic symptoms determined from the action of the propeller shaft associated with the transformation of mechanical energy into work and heat, as well as with the generation of mechanical vibrations and elastic waves of acoustic emission, is proposed. To assess the diagnostic information quantity brought about by the defined features of propeller shaft fatigue, an experimental research program was developed and implemented, in which two statistical hypotheses are verified: the significance of the impact of the values enforcing the fatigue process, presented in the first part of the article, and the adequacy of the regression equation describing the fatigue durability of the propeller shaft in the energy aspect, constituting the second part of the article. This finally gives us the opportunity, after the appropriate translation of the model test results into full-sized real objects, to develop a methodology to diagnose marine propeller shaft fatigue in operating conditions. The third part of the article is devoted to this issue

Cooling of mechanical vibrations by heat flow

We theoretically consider a nanomechanical link between two metallic leads subject to a temperature drop. It is shown that mechanical dynamics of such system can be strongly affected by a heat flow through it via the position dependent electron-electron interaction, even though the electronic transport between leads is blocked. In particular, it is demonstrated that, under certain conditions, the stationary distribution of the excitations in the mechanical subsystem has a Boltzmann form with an effective temperature, which is much lower than the temperature of the environment; this seems rather counterintuitive. We also find that a change in the direction of the temperature gradient can result in the generation of mechanical vibrations rather than the heating of the mechanical subsystem.

Experimental study on the effects of mechanical vibration on the heat transfer characteristics of tubular laminar flow

In this study, experiments were performed to investigate the effects of sinusoidal vibrations on the heat transfer characteristics of internal flow in a circular heated tube. Water was used as the working fluid with inlet Reynolds numbers varying between 512 and 2047. The frequencies of the mechanical vibration generator varied from 158 to 3000Hz, and the vibration accelerations were 1.0g, 3.0g, and 5.0g. The time domain acceleration signal was obtained using a vibration accelerometer and then transferred to the frequency domain using the fast Fourier transform method in the experiments. The results demonstrated that mechanical force vibration significantly influences the heat transfer in a heated pipe flow. The Nusselt number increases indistinctively with the vibration acceleration augmentation, while the enhancement in the Nusselt number is weakened as the inlet velocity increases. The Nusselt number increases rapidly when the vibration frequency increases to the resonance frequency value of 400Hz and then decreases sharply and levels off at the frequency of 1500Hz. Finally, a new correlation was derived using the key parameters of vibration frequency, vibration acceleration, and Reynolds number.

Generation of mechanical vibrations in metal samples by the use of the pinch effect

The article presents the recent research in electrodynamic processes for metal samples exposed to current pulses. The pinch effect and the skin effect cause the vibration of the metal rods. The results of these studies show how current and magnetic field interact with material samples of gold, silver and copper. The analysis allowed establishing the dependences of peak acceleration on current density and conductor diameter. The dependencies can be used in metal workings and for nondestructive testing.

${\rm{IP}}^{2}{\rm C}$ Sensor Modeling

A model of a new class of total polymeric sensors known as ionic polymer–polymer composite <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$({\rm IP}^{2}{\rm C})$</tex></formula> has been developed. Starting from a previous model, new experimental investigations have been performed in order to increase the significance of the sensor model. The device uses Clevios P HC V4 electrodes and a conducting polymer, produced and distributed by Heraeus. The sensing behavior of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm IP}^{2}{\rm Cs}$</tex> </formula> has been modeled by applying a suitable set of deforming signals and using a data-driven identification procedure. The sensor model has been investigated in a suitable range of working frequencies by using an ad hoc realized setup. Also, Young's modulus of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm IP}^{2}{\rm Cs}$</tex></formula> has been measured by means of the dynamic mechanical analysis and the results have been used in the identification of the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm IP}^{2}{\rm Cs}$</tex></formula> sensor model. The model identification and validation have been performed by using a programmable mechanical vibration generator system, and experimental evidence of the suitability of the proposed model is given in this paper.

Spintronics-based mesoscopic heat engine

We consider a nanowire suspended between two spin-polarized leads and subjected to a nonuniform magnetic field. We show that a temperature drop between the leads can significantly affect the nanowire dynamics. In particular, it is demonstrated that, under certain conditions, the stationary distribution of the mechanical subsystem has a Boltzmann form with an effective temperature, which is lower than the temperature of the ``cold'' lead; this seems rather counterintuitive. We also find that a change in the direction of the temperature gradient can result in the generation of mechanical vibrations rather than the heating of the mechanical subsystem.

Magnetomotive instability and generation of mechanical vibrations in suspended semiconducting carbon nanotubes

We investigate the electromechanics of a freely suspended semiconducting carbon nanotube subjected to a magnetic field H in the current-biased regime and show that self-excitation of mechanical nanotube vibrations can occur if H exceeds a critical value Hc of the order of 10–100 mT. The effect can be detected by measuring the magnetic field dependence of the time-averaged voltage drop across the nanotube, which has a singularity at H=Hc. We discuss the applications of the device as an active, tuneable radiofrequency oscillator.

Theory of the generation of mechanical vibrations by laser radiation in solids containing internal stresses on the basis of the thermoelastic effect

The behavior of the nonsteady deformations in solids containing internal stresses under irradiation by temporally modulated laser radiation is analyzed. In the framework of the nonlinear theory of thermoelasticity a model is proposed for the excitation of mechanical vibrations with allowance for the dependence of the thermoelastic coupling parameter on the initial deformation. For the case of a piezoelectric method of detecting the mechanical vibrations in a uniformly deformed sample, an analytical expression is obtained for the electrical signal taken off from the piezoelement. The behavior of the piezoelectric signal under various conditions is investigated, and the results are compared with the available experimental data and found to be in qualitative agreement.

Theory of the thermoelastic generation of mechanical vibrations in internally stressed solids by laser radiation

An investigation was made of the behavior of transient deformations in solids with internal stresses exposed to time-modulated laser radiation. The nonlinear theory of thermoelasticity is used to propose a model for the excitation of mechanical stresses which takes account of the stress dependence of the thermoelastic coupling parameter. An expression is derived for the electric signal recorded by a piezoelement when mechanical vibrations are generated in a uniformly deformed sample. The results are compared with existing experimental data and show qualitative agreement.

Application of piezoelectricity for marine fouling prevention in oceanographic sensors

Abstract For all marine experiments, a real problem concerns the protection of oceanographic sensors against fouling. It appears that one of the more efficient techniques to reduce marine fouling remains the surface generation of mechanical vibrations, even if the conditions of exposure are not optimal. Studies concerning prevention against marine fouling have proved the remarkable efficiency of transverse vibrations. In the considered spectral frequency ranges it appears that the excitation of high modes produces the best response for the modal amplitude. In the present work, we develop a two-dimensional theory to study the dynamic component of glass structures activated by piezoelectric actuators, perfectly bonded to the surface to be protected.

PVdF: An electronically-active polymer for industry

A review is given of the properties and applications of poly(vinylidene fluoride) (PVdF), a strong, chemically-inert but electronically-active polymer. It is only recently that poled, electroded film, suitable for electronic devices, has been manufactured in quantity within the UK. The piezoelectric and pyroelectric responses of PVdF rival those of ceramics. Its polymeric nature also confers advantages over ceramics; for example, lower cost, large area, flexibility, low acoustic impedance, and high-frequency operation. There are many possible applications of PVdF in sensing (heat and vibration) and in the generation of mechanical vibrations. Possible fields of use include underwater sound detection, surveillance by infrared, ultrasonic test probes, vibrators and consumer electronics.

Magnetomechanische Verstärkung und Erzeugung mechanischer Schwingungen

A torsional pendulum with a Nickel-rod as torsional spring element can oscillate in its eigenfrequency when the rod is magnetized in its axial direction by an ac magnetic field. Investigating this effect, which was not understood until now, a mechanism of parametric amplification and generation of mechanical vibrations is derived. It is based on the effect of Joule's magnetostriction and its inverse. The calculations presented enable us to understand the experimental results of the corresponding oscillation measurements.

Generation of mechanical vibrations by penetrating particles: Beron, B.L., Hofstadten, R., physical review letters (28 July 1969) (1870)

Generation of mechanical vibrations by penetrating particles: Beron, B.L., Hofstadten, R., physical review letters (28 July 1969) (1870)

Generation of Mechanical Vibrations by Penetrating Particles

Mechanical oscillations of lead-zirconate-titanate piezoelectric disks have been observed when penetrating high-energy (1.0-BeV) beams of electrons impinge on the disks. Radial and compressional modes of vibration have been observed in the frequency range 40-158 kHz. Possible applications of this observation to particle detection at very high energies are discussed. The observed phenomenon also has a possible connection with measurements of gravitational waves.