Frequency Mechanical Vibration Research Articles

Vibration and acoustic frequency spectra for industrial process modeling using selective fusion multi-condition samples and multi-source features

Abstract Frequency spectral data of mechanical vibration and acoustic signals relate to difficult-to-measure production quality and quantity parameters of complex industrial processes. A selective ensemble (SEN) algorithm can be used to build a soft sensor model of these process parameters by fusing valued information selectively from different perspectives. However, a combination of several optimized ensemble sub-models with SEN cannot guarantee the best prediction model. In this study, we use several techniques to construct mechanical vibration and acoustic frequency spectra of a data-driven industrial process parameter model based on selective fusion multi-condition samples and multi-source features. Multi-layer SEN (MLSEN) strategy is used to simulate the domain expert cognitive process. Genetic algorithm and kernel partial least squares are used to construct the inside-layer SEN sub-model based on each mechanical vibration and acoustic frequency spectral feature subset. Branch-and-bound and adaptive weighted fusion algorithms are integrated to select and combine outputs of the inside-layer SEN sub-models. Then, the outside-layer SEN is constructed. Thus, “sub-sampling training examples”-based and “manipulating input features”-based ensemble construction methods are integrated, thereby realizing the selective information fusion process based on multi-condition history samples and multi-source input features. This novel approach is applied to a laboratory-scale ball mill grinding process. A comparison with other methods indicates that the proposed MLSEN approach effectively models mechanical vibration and acoustic signals.

Low-frequency, broadband vibration energy harvester using coupled oscillators and frequency up-conversion by mechanical stoppers

The frequencies of ambient vibrations are often low (below 30 Hz). A broadband (3 dB bandwidth is larger than 10 Hz at an acceleration amplitude of 9.81 m s−2) vibration based energy harvester is proposed for transducing mechanical energy at such low frequencies into electrical energy. The mechanical setup converts low frequency mechanical vibrations into high frequency resonance oscillations of the transducer. This conversion is done by mechanical impacts on two mechanical stoppers. The originality of the presented design is that both low-frequency and high-frequency oscillators are permanently mechanically coupled. In the equivalent mechanical circuit, this coupling is achieved by connecting the ends of the stiff spring to both seismic masses, whereas one seismic mass (collison member) is also attached to the soft spring used as the constitutive element of a low-frequency oscillator. Further, both mechanical oscillators are not realized as conventional cantilever beams. In particular, the high frequency oscillator with the natural frequency of 340 Hz is a disc-shaped diaphragm with attached piezoelectric elements and a seismic mass. It is shown that it is possible to convert mechanical vibrations with acceleration amplitude of 9.81 m s−2 in the region between approximately 7 and 25 Hz into electrical power larger than 0.1 mW with the maximum value of 0.8 mW. A simplified mathematical model based on piecewise linear coupled oscillators shows good agreement with experimental results. The ways to enhance the performance of the harvester and improve agreement with experiments are discussed.

Low-resistive vibratory penetration in granular media.

Non-cohesive materials such as sand, dry snow or cereals are encountered in various common circumstances, from everyday situations to industry. The process of digging into these materials remains a challenge to most animals and machines. Within the animal kingdom, different strategies are employed to overcome this issue, including excavation methods used by ants, the two-anchor strategy employed by soft burrowers such as razor-clams, and undulatory motions exhibited by sandfish lizards. Despite the development of technology to mimic these techniques in diggers and robots, the limitations of animals and machines may differ, and mimicry of natural processes is not necessarily the most efficient technological strategy. This study presents evidence that the resisting force for the penetration of an intruder into a dry granular media can be reduced by one order of magnitude with small amplitude (A ≃ 10 μm) and low frequency (f = 50 − 200 Hz) mechanical vibrations. This observed result is attributed to the local fluidization of the granular bed which induces the rupture of force chains. The drop in resistive force on entering dry granular materials may be relevant in technological development in order to increase the efficiency of diggers and robots.

Identification of stiffness variations in supporting substances of a human canine tooth with a bracket-beam-piezoelectric sensor and its electromechanical impedance

In this paper, an experimental method is described to identify the stiffness variations produced by drillings done in different supporting substances of a human canine tooth. To measure the supporting substances parameters through of a canine, a sensor-actuator system was developed. The sensor-actuator device was composed of a stainless steel bracket bonded to a steel wire attached to two piezoelectric transducers, with a concentrated mass attached to the end of the wire. To excite the device, high frequency voltage (between 5 and 10 KHz) was applied through the piezo-transducers, which affects the tooth by means of the vibration of the wire. High frequency mechanical vibrations allowed the appraisal of the mechanical response from the supporting substances. Mechanical responses associated with the stiffness of the support were quantified with the electrical impedance of the piezo-transducers. The device was coupled to the crown of a canine tooth simulating a condition of fixing as in the bone, the tooth was fastened by the root portion inside the supporting substance. Four supporting substances were characterized for the tests. After establishing base values of the stiffness of each supporting substance, the stiffness variations were assessed in two stages (two drillings); these were made perpendicularly to the longitudinal axis of the tooth, Results show that it is possible to assess stiffness variations with the proposed methodology as well as to quantify the stiffness differences, by means of variation indexes.

Utility of RF MEMS miniature switched capacitors in phase shifting applications

This paper demonstrates research carried out towards the development of switched capacitors having miniature dimensions. Such devices are based on the Radio Frequency Micro Electro Mechanical Systems (RF MEMS) technique which has gained prominence in implementing a wide variety of microwave and millimetre devices till date. Switched capacitors having standard or conventional dimensions are prone to several limitations which are addressed by scaling down the standard dimensions by 150× times (in terms of area requirement). Such switched capacitors are employed to develop phase shifters working in K-band (22GHz) frequency range to yield appreciable performance both in terms of electromechanical and RF characterizations. Such switched capacitors are utilized to develop phase shifters which find immense applications in the design of Phased Array RADARs. Switched capacitors fabricated on 500µm thick quartz substrates, result in 30° phase shift (0.66mm×1mm in dimension) with associated minimum −0.18dB insertion loss and better than −21dB reflection coefficient at 22GHz frequency. Electromechanical characterization reports an actuation voltage of 14.6V, mechanical vibration frequency of 2.5MHz and a switching time of 620ns respectively. Demonstrations showing complete realization of 180° phase shifter (4mm×1mm) employing a cascaded arrangement of six similar 30° unit cells are also included in this paper.

Determination of Maximum Damping Efficiency based on Electric Drive Vibrations of Elastic Mechanisms

The main factors that determine maximum values of elastic mechanical vibrations of operating machines with an electric drive were detected. The efficiency of different ways of vibrations passive damping of elastic mechanisms was reviewed. The conditions were determined and recommendations about the choice of parameters of electric drives ensuring minimum dynamic efforts in springy elements of mechanical gears were given. It was found that damping of vibrations in the elastic mechanisms caused by changing of disturbing effort by the electric drive is the most effective if the resonant frequency of mechanical vibrations is in the range of frequencies of electric drive dropping. The estimation of marginal efficiency by the electric drive of vibrations in elastic mechanical gears has been performed, the areas of reasonable application of damping devices and the electric drive for the reduction of dynamic efforts in springy elements of mechanical gears were defined. The practical implementation of the proposed recommendations has been carried out for the MP100 type balanced manipulator.

Stable single-layer structure of group-V elements

In addition to stable single-layer buckled honeycomb and washboard structures of group-V elements (or pnictogens P, As, Sb, and Bi) we show that these elements can also form two-dimensional, single-layer structures consisting of buckled square and octagon rings. An extensive analysis comprising the calculation of mechanical properties, vibration frequencies, and finite-temperature ab initio molecular dynamics confirms that these structures are dynamically and thermally stable and suitable for applications at room temperature and above. All these structures are semiconductors with a fundamental band gap, which is wide for P but decreases with increasing row number. The effect of the spin-orbit coupling decreases the band gap and is found to be crucial for Sb and Bi. These results are obtained from first-principles calculations based on density functional theory.

Wettability of a surface subjected to high frequency mechanical vibrations

Ultrasonic radiation can modify some physical properties in liquid/solid interactions, such as wettability. The dependence of solid surface wettability on its vibrational state was studied. Experiments with an interface formed by distilled water deposited on a titanium alloy and surrounded by air were carried out.It is shown that it is possible to control the apparent wettability of a given liquid/solid/gas system by applying sonic-ultrasonic vibrations of controlled amplitude at the interface.The system studied is composed of a drop of distilled water deposited on a flat titanium surface in air. The contact angle was used as an indicator of apparent wettability.It is shown that the apparent wettability of a surface is linearly dependent on the peak vibration velocity and independent of the vibration frequency. Higher vibration speed lowers the contact angle and therefore causes greater surface wettability.

Influence of peripheral vibrations and traveling magnetic fields on VGF growth of Sb-doped Ge crystals

We performed 3D numerical and experimental studies to assess the potential of peripheral low frequency mechanical vibrations for improving the homogeneity of Sb-doped 4″ Ge crystals grown by vertical gradient freeze (VGF). For this study, a novel bell-shaped graphite vibrator was developed for the generation of the axial vibrations in the direction of three-phase junction. Melt stirring by downward traveling magnetic field (TMF) was used as a benchmark.The results showed superiority of peripheral vibrations to TMF stirring concerning radial and longitudinal doping distribution and initial stirring rate. Experimentally observed standing free surface waves in Ge were caused by shielding effect of the vibrator on TMF.

Investigation of Ti-6Al-4V alloy acoustic softening

High power ultrasonic vibration is widely used for improving manufacturing processes such as machining and metal forming. High frequency mechanical vibration affects material properties and friction forces in contacting surfaces. Flow stress reduction under superimposed ultrasonic vibration is called as acoustic softening. The amount of this parameter should be determined for ultrasonic assisted metal forming processes. For determination of this parameter for workhorse Ti-6Al-4V alloy, experimental setup was designed and fabricated. Then tensile test under longitudinal ultrasonic vibration was performed for different ultrasonic powers. Results show that ultrasonic vibration has considerable effect on plastic behavior of the alloy and decreases flow stress. Also, increasing ultrasonic power leads to higher acoustic softening. Yield stress reduction up to 9.52%, ultimate stress reduction up to 4.55% and elongation up to 13% were obtained at 340W ultrasonic power. After applying ultrasonic vibrations and its termination, hardness of specimens were measured in which increase up to 9% was observed.

Investigation of High Frequency Mechanical Vibrations in PMN-32%PT Crystals by Laser Interferometry

Lead magnesium niobate-lead titanate (PMN-PT) single crystal has first been successfully grown in 1990 by the Bridgman method using PbO as a flux. These single crystals have excellent piezoelectric properties. The PMN-PT crystals with different vibration modes may be used for development of novel high efficiency ultrasonic transducers due to high piezoelectric properties.

Efficient Piezoelectric Energy Harvesters Utilizing (001) Textured Bimorph PZT Films on Flexible Metal Foils

Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self‐powering for sensors and wearables. The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application. In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O3 (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration. In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO3 seed layers on HfO2 buffer layers. The performance of PCM with an active area of 5.2 cm2 is explored for various excitation accelerations (0.02–0.16 g [g = 9.8 m s−2]) around 6 Hz. The PCM device provides a power level of 3.9 mW cm−2 g2 and 65% mode shape efficiencies.

Evaluating vibration assisted vacuum infusion processing of hexagonal boron nitride sheet modified carbon fabric/epoxy composites in terms of interlaminar shear strength and void content

The results of an investigation of the effect of voids on the interlaminar shear strength (ILSS) of carbon fabric/epoxy composites consolidated from fabric preforms containing hexagonal boron nitride sheets (h-BNSs) were presented. To produce the preforms, h-BNSs were first dissolved in ethanol through sonication and the solution obtained was then used for through-the-thickness impregnation of carbon fabrics. The composites with h-BNSs were produced by membrane added vacuum infusion process (MAVIP) with application of mechanical vibrations at various different low frequencies, including 10, 25 and 60 Hz. For the sake of property comparison, identical static samples were also produced. A facile thermogravimetric analysis (TGA) based methodology was utilized for composite fiber volume fraction and void content measurements. Analysis was carried out on specimen-by-specimen basis, and the findings obtained were correlated with the ILSS of the composites. It was determined that the composites produced at 10 Hz exhibited the lowest void content, whereas the highest one was obtained from the composites produced at 25 Hz. The highest fiber volume fraction, density, and ILSS values were obtained from the composites that were produced at 60 Hz. The findings obtained were discussed, placing particular emphasis on the interrelationships among ILSS, mechanical vibration frequency, and composite fiber volume fraction and void content.

Concurrent 3D acquisition of diffusion tensor imaging and magnetic resonance elastography displacement data (DTI-MRE): Theory and in vivo application.

To introduce a newly developed technique (DTI-MRE) for the simultaneous acquisition of diffusion tensor imaging (DTI) and 3D-vector field magnetic resonance elastography (MRE) data, and to demonstrate its feasibility when applied in vivo to the mouse brain. In DTI-MRE, simultaneous encoding is achieved by using a series of diffusion/motion-sensitizing gradients (dMSGs) with specific timing and directions. By adjusting the duration of the dMSGs with the diffusion time and with the mechanical vibration frequency, the shear wave motion and diffusion are encoded into the MR phase and MR magnitude signals, respectively. The dMSGs are applied in a noncollinear and noncoplanar manner that optimizes the capture of both the DTI signal attenuation and the three-dimensional MRE displacements. In this work, the feasibility of the DTI-MRE technique was demonstrated on in vivo mouse brains (n=3) using a 9.4T animal MRI scanner. The DTI-MRE derived parameters (MD, mean diffusivity; FA, fractional anisotropy; MRE displacement fields; and shear modulus |G|) were compared with those acquired using conventional, separate MRE and diffusion methods. The averaged (MD, FA, and |G|) values for three mice are (0.580 ± 0.050 µm2 /ms, 0.43 ± 0.02, and 4.80 ± 0.06 kPa) and (0.583 ± 0.035 µm2 /ms, 0.46 ± 0.02, and 4.91 ± 0.19 kPa) for DTI-MRE, and conventional DTI and 3D-vector field MRE measurements, respectively. All derived parameters (MD, FA, |G|, and displacement) obtained using the combined DTI-MRE method and conventional methods were significantly correlated with P < 0.05. Simultaneous acquisition of DTI and 3D-vector field MRE is feasible in vivo and reduces the scan time by up to 50% compared with conventional, separate acquisitions, while providing an immediate co-registration of maps of diffusion properties and stiffness. Magn Reson Med 77:273-284, 2017. © 2016 Wiley Periodicals, Inc.

Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study.

Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies.

Influence of the Copper-Containing SBA-15 Silica Fillers on the Mechanical Properties of High Density Polyethylene

The paper concerns the mechanical properties of the high density polyethylene (HDPE) with the copper-containing SBA-15 silica filler. The considered filler is the SBA-15 mesoporous silica containing copper ions bounded inside channels via propyl-phosphonate anchoring groups. With its help, we can impart the biocidal properties to this plastic. Research covered mechanical properties, thermal analysis, colour, shine, and nanomolecular structure. Dynamical properties of the samples like modulusE′changes and mechanical core loss angle tangenttgδversus temperature and vibration frequency were tested using DMTA method. Level of crystallinity was tested using DSC method while their structure was observed with going through light by optical microscope. Hardness and toughness of obtained samples were also defined. Colour and shine changes of the samples were observed for PE-HD with filler contents 0.5% and 1%. Modulus value changes versus temperature and frequency were notified for the samples with modifier. There were no differences in modulus changes versus temperature for samples with and without filler and frequencies 1 and 10 Hz. It was detected that melting enthalpy of the samples with the modifier decreases. Moreover, some influence of the samples with filler on colour and shine was observed.

Practical background modification fermented beverage technology for the formation of defined functional properties

The problem of provision of population with dairy products is escalating due to the fact that today, throughout the world, particularly in Russia, there is a shortage of milk as raw material, increasing every year. In the future, the consumption of milk and dairy products will continue to outpace growth in milk production is solid. To solve this problem, domestic producers need to find new ways to increase production of raw milk and improve the consumer and functional properties of fermented dairy products. The work was proposed the use of acoustic effects of ultrasound, triggered by the ultrasound, the technological model UTA ABOUT, 4/22 OM (frequency mechanical vibrations 22 ± 1,65 kHz). The main factors determining consumer characteristics, were taken physico-chemical parameters, structural and mechanical characteristics and the accumulation of minor biologically active substances – kefiran. In the study was obtained results confirming the necessity of using ultrasonic impact (RAS) in the production technology of dairy products.

A MEMS PPA Based Active Vibration Isolator - STUDENT AWARD 3RD PLACE $500

Several types of micro-devices are adversely affected by high frequency mechanical vibrations present in the operating environment. Examples include MEMS vibratory gyroscopes and resonators, and micro-optics. Various types of MEMS vibration isolators have been developed for use in the packaging of these vibration sensitive devices. Passive isolators consist of a spring-mass-damper MEMS device and usually have a very high mechanical quality factor, which makes them susceptible to ringing at the isolator's resonant frequency. Active isolators have been realized by using state sensing of the proof mass motion and feeding one or more of these states back through an actuator to adjust the frequency response of the isolator. For example, the technique known as skyhook damping uses velocity feedback to adjust, and typically increase, the damping of the isolator. Although these technique are doable, they require state sensing or state estimation, with feedback electronics to drive the actuator. A simpler MEMS active vibration isolator architecture employs only a parallel plate actuator (PPA) with the MEMS spring-mass-damper structure. The PPA driven with a DC voltage, in its stable operating range, displaces the proof mass, which results in a change in the effective system spring constant due to the electrostatic spring softening effect. This results in a change in the resonant frequency and the quality factor of the isolator. However, due to the nonlinearities inherent in this type of device, the stable operating range is reduced as the PPA voltage is increased. Furthermore, even when the isolator is stable in steady-state, a sufficiently large transient response can also drive it into the unstable regime, resulting in the electrodes snapping into contact. In this study, the PPA based active vibrator isolator is developed and its performance is evaluated. The characteristics of the transient instability are investigated and its stable range of operation is specified, for booth external disturbances and rapid application of the control voltage. This MEMS PPA based active vibration isolator can improve performance compared to passive isolators, while being much simpler than state feedback active isolators.

Resilience to Vibration of a Tuning Fork MEMS Gyroscope

This paper investigates the resilience to mechanical vibration of tuning fork MEMS gyroscopes and presents the limitations of this device. We focus our study on mechanical vibrations near the first three resonance frequencies corresponding to the in-phase and anti-phase drive modes and the sense mode. This original work quantifies the rejection capability of the anti-phase mode to external vibrations in comparison to the in-phase mode resulting in a ratio of 390. In-phase frequency mechanical vibrations can result in mechanical non-linearities visible in the gyroscope response. This paper demonstrates also the strong impact of the in-phase mode on the gyroscope operation leading to failure when it is excited simultaneously with the anti-phase mode. This issue is common to tuning fork gyroscopes and only phase mode control or shift to higher frequencies can preserve normal gyroscope operation at the bandwidth 0 – 50 kHz.

Механизм воздействия модулированного высокочастотного сигнала на неидеальный диэлектрик. Радиозвук

The article is related to the electromagnetic compatibility. Microwave auditory effect was analyzed as the observed phenomenon of high-frequency radio signals transformation into acoustic oscillations. This phenomenon was called a radio hearing effect. This sensory-acoustic effect is a natural phenomenon associated with the conversion of electromagnetic energy in the lowfrequency mechanical vibrations on the way to the receptor system by bone conduction. The physical interaction mechanisms of amplitude-modulated high-frequency electrical signal with a perfect nonconductor were considered, leading to a transformation in the low frequency mechanical vibrations or acoustic harmonics of the modulated signal. In the paper studies of the possible effects of direct exposure to high-frequency field in medical practice, or physical therapy are presented. The mechanisms of interaction of the modulated RF signal with a weakly absorbing material with goal to detect electro-acoustic effect were presented. The presence of inertial nonlinear conversion effect of a modulated RF signal into low frequency sound is confirmed.