Low-amplitude Vibration Research Articles

Principal stress lines based design method of lightweight and low vibration amplitude gear web

<abstract> <p>A lightweight and low vibration amplitude web design method was investigated to reduce gear weight and noise. It was based upon the relationship between length and orthogonality that the principal stress lines were designed at the gear web. By constructing a vibration control model with gear design parameters, the optimal distance was calculated. By offsetting the principal stress lines at the optimal distance, the lightweight gear web with the low vibration amplitude was then generated. A vibration experimental platform was built to verify the novel gear vibration performances, and it was compared with other gears with the same web's porosity to verify loading performance. The experimental results indicated that compared with the solid gear, the novel gear is 20.50% lighter and with a 29.46% vibration amplitude reduction.</p> </abstract>

Dynamics of Carbon Nanotube Chains Residing on Flat Substrates

Stationary states of a single-walled carbon nanotube array lying on a flat substrate formed by the surface of a molecular crystal are investigated. Numerical modeling showed that in the case of weak interaction with the substrate it is more energetically favorable for nanotubes to get assembled into multilayer packing, while in the case of strong interaction (e.g., the interaction with the h–BN crystal surface) they form monolayer packing (i.e., a chain on the substrate surface). The dynamics of nanotube chains is modeled. We show that acoustic supersonic solitons can exist only in small-diameter nanotubes (D < 0.8 nm), and soliton motion is always accompanied by energy loss to excitation of internal vibrations in nanotubes. Low-amplitude vibrations are analyzed. For a finite nanotube chain residing on a flat substrate, it is shown that vibrations are confined to only the end nanotubes or a nanotube that forms a structural defect in the chain.

Dynamic Characteristics of Transport Structures

There exists a great need to increase the bearing capacity of soils when building high embankments on a weak foundation in seismically hazardous areas. The article considers two methods for testing soils under dynamic conditions: 1) cyclic triaxial compression, which is used to determine the dynamic strength of water-saturated soils by cyclic triaxial tests with controlled load, as well as shear modulus and damping coefficient; 2) low-amplitude dynamic vibrations (resonance column) to determine the shear wave velocity, shear modulus and soil damping coefficient in a small range of shear deformations, which can be widely used in engineering seismology. In laboratory tests using the cyclic triaxial compression method, data are obtained with a high degree of accuracy for high strain levels, the results of which can be used in the integral Fourier transform. Spetras are used in engineering seismology and as a basic tool for assessing the spectral composition of recorded ground motion or structure response, as well as for assessing ground motion from fundamental seismological parameters in regions where ground motion records are not available. After carrying out these tests and analyzing the amplitude Fourier spectra of accelerations, velocities and displacements, the calculation results will be obtained.

Собственные частоты изгибных колебаний углеродных нанотрубок

Using a molecular dynamics model with a reduced number of degrees of freedom, the natural frequencies of bending vibrations of carbon nanotubes (CNTs) of various diameters are calculated under plane strain conditions. It is shown that the theory of thin cylindrical shells provides high accuracy in estimating the frequencies of low-amplitude natural vibrations even for relatively small CNT diameters. It is shown that with an increase in the amplitude, the frequency of natural vibrations decreases, which is consistent with the data available in the literature. The results obtained are necessary for the design of terahertz resonators based on CNTs and high-precision mass and force nanosensors based on the effect of electromechanical coupling that CNTs exhibit.

Experimental research on the influence of ultrasonic vibrations on the laser cladding process of a disc laser

Disc lasers have a wide range of applications in laser cladding due to a series of advantages such as good beam quality. The cladding layer formed by the disc laser in laser cladding is prone to microcracks, pores and other microscopic defects, which seriously affects the promotion of this technology. Ultrasonic vibration can generate high-frequency and low-amplitude vibrations, which actively affect the formation of the microstructure during the solidification of the cladding layer. They can effectively reduce the formation of microscopic defects. This paper builds an ultrasonic-assisted laser cladding system platform based on a disc laser. We cladded 316L powder onto an ASTM 1045 steel substrate for multiple laser cladding experiments, and performed microscopic characterization and analysis of the cladding layer. The result shows that ultrasonic vibrations can effectively refine the bottom and top microstructures of the cladding layer, especially the morphology of the dendrite arms. The phase structure did not change under different ultrasonic amplitudes. Ultrasonic vibration changes the direction of heat flow inside the molten pool, causing the crystal orientation to change from a (220) crystal orientation to a (111) crystal orientation. This research will provide an important theoretical basis for the precise control and optimization of the cladding process and reduction of the formation of microscopic defects.

Digital control of cable vibration with time delay

A simplified model for active control of vibration of a suspended cable is proposed. The model is constructed so that it considers the dynamic characteristics of the cable at the location where a vibration absorber is attached together with the absorber itself. The control is applicable for attenuating high-frequency, low-amplitude cable vibration due to periodic excitation that may model the wind effect. The methodology to choose control parameters is based on the dynamics of the vibration absorber and the stability analysis of the controlled system. The model takes into account the time delay that is always present in digital control due to sampling. Results reveal that the application of active control reduces vibration amplitude significantly provided that samples are taken in short time intervals. Increasing time delay reduces the effects of control and above a critical value, the vibration amplitude becomes even greater than without control. The importance of time delay grows with increasing excitation frequency, which means a limitation of the application of the control methodology developed. This limitation concerns the highest excitation frequencies.

Management of the dynamic properties of a base modified by deep soil mixing technology

Conversion of building properties is performed primarily to reduce the compressibility of the base and increase strength. However, in addition to changing the static properties of soils, it is necessary to take into account changes in dynamic properties, such as dynamic shear modulus, damping coefficient, velocity of elastic shear and longitudinal waves. Thus, it is possible to control the dynamic properties of the base by converting the construction properties of soils. In this paper, we consider the change in the velocity of shear waves in a base transformed by the technology of deep soil mixing (DSM). In the work, the influence of additional vertical stresses on the dynamic properties of the bases transformed using deep soil mixing technology was evaluated. As a parameter that allowed us to evaluate the dynamic properties, the propagation velocity of elastic shear waves was chosen. Shear wave velocity was estimated based on the results of triaxial tests using the method of low-amplitude torsional vibrations in a resonant column. The research results showed that at small values of axial strains, there is no significant increase in the velocity of shear waves, an increase in the speed of shear waves by two times with an increase in stress by 0.6 MPa.

The Influence of the Motor Traction Vibration on Fatigue Life of the Bogie Frame of the Metro Vehicle

During the service life of metro vehicles, the cracks frequently appear at the root of motor seats. This indicates the previous antifatigue designs are unable to cover the actual operating environment. Some individual loads, such as motor vibration, have been ignored or wrongly understood, which leads to the occurrence of local insufficient fatigue life of the frame. To illustrate the influence of the motor vibration on the fatigue life of the bogie frame, a metro vehicle was taken as an example: first, the precise finite element model of the frame was established, and its correctness was verified; then, the vibration characteristics of the frame were analyzed by sweep frequency calculation; and finally, considering the vibration acceleration signal of the motor measured on a metro line as the excitation, the influence of the random vibration on the fatigue life of the frame under traction and idle running conditions was compared and analyzed by solving the power spectral density of the dynamic stress response at the weak fatigue nodes of the structure. The results show that the energy of the vibration in the frame is mainly concentrated in modes 6 and 7, which are excited by the motor transverse and vertical vibration, respectively, and contribute a lot to the fatigue damage of the frame; the fatigue life of the vital positions of the frame under the traction condition significantly reduces compared to the idle running condition; and the contribution of the low-amplitude vibration above 300 Hz to the fatigue damage can be ignored. At last, the importance of the influence of the motor traction vibration on the fatigue life should be fully considered in the metro vehicle design was proposed.

Highly sensitive multicore fiber accelerometer for low frequency vibration sensing

We report on a compact, highly sensitive all-fiber accelerometer suitable for low frequency and low amplitude vibration sensing. The sensing elements in the device are two short segments of strongly coupled asymmetric multicore fiber (MCF) fusion spliced at 180° with respect to each other. Such segments of MCF are sandwiched between standard single mode fibers. The reflection spectrum of the device exhibits a narrow spectrum whose height and position in wavelength changes when it is subjected to vibrations. The interrogation of the accelerometer was carried out by a spectrometer and a photodetector to measure simultaneously wavelength shift and light power variations. The device was subjected to a wide range of vibration frequencies, from 1 mHz to 30 Hz, and accelerations from 0.76 mg to 29.64 mg, and performed linearly, with a sensitivity of 2.213 nW/mg. Therefore, we believe the accelerometer reported here may represent an alternative to existing electronic and optical accelerometers, especially for low frequency and amplitude vibrations, thanks to its compactness, simplicity, cost-effectiveness, implementation easiness and high sensitivity.

Biology, sounds and vibratory signals of hooded katydids (Orthoptera: Tettigoniidae: Phyllophorinae).

The tettigoniid subfamily Phyllophorinae, distributed in Southeast Asia and Australia, is poorly known. Our study of the biology of Giant Katydid Siliquofera grandis (Blanchard, 1853) from a laboratory culture has shown that these insects mate more than once, the females lay a total of up to 400 eggs during their life, and these hatch after 2-2.5 months. The life cycle from egg to death takes longer than one year. In the laboratory, the insects fed mainly on leaves of various Rosaceae, Ficus, and lettuce, and on fruits. It is known that the males of hooded katydids lack the tegminal stridulatory apparatus typical for Tettigoniidae, but are capable of producing protest sounds using their coxosternal sound-producing organs for stridulation. Here, protest stridulation of the males and females and the sound-producing organs used to produce it have been analyzed in Phyllophorina kotoshoensis Shiraki, 1930 and S. grandis. In addition, nymphal protest sounds produced by friction of the metafemur against the edge of the pronotum and adult protest signals produced with the wings are described. In S. grandis, vibratory signals have been described and studied for the first time: territorial, protest, drumming and rhythmic low-amplitude vibrations emitted by adults and nymphs and pre- and postcopulatory vibrations of the males and females. The territorial signals not accompanied with visible movements of the body may be produced by contracting the antagonist muscles of the thorax and possibly of the legs. Using their coxosternal sound-producing organs males of S. grandis produced also an audible courtship song lasting for several seconds. Acoustic signals may thus both regulate intrapopulation relations and serve for interspecific communication (protest signals). The acoustic communication in Phyllophorinae is probably especially important during mating behavior.

Fuzzy PD hybrid control of low frequency vibration of annular antenna

The annular antenna is a typical large flexible space truss structure featured by small damping and low modal frequencies. The external disturbances, e.g. impulse load resulting from satellite attitude adjusting, may induce the low frequency large amplitude vibrations of annular antenna for a long time and thus reduce working precision and cause even its damage. The active control of vibration of annular antenna under impulse excitation is investigated in the paper. The voice coil actuator instead of piezoelectric stack actuator is used in order to meet the demand of large output displacement. The governing equation of active vibration control system is established by use of finite element method. The proportional differential (PD) control and fuzzy control algorithms are firstly studied in the active control. The results show that the fuzzy control exhibits worse control performance than PD control due to weak control function near structural equilibrium position. To circumvent the drawback of fuzzy control, a fuzzy PD hybrid control strategy is proposed which can combine the merits of both control methods. The simulated and experimental results show that the fuzzy PD hybrid control can yield the best control effect under impulse excitation comparing with the PD control and ordinary fuzzy control. The work provides a promising control way for active control of low frequency and large displacement vibration of annular antenna in satellite engineering.

Analysis of the statistical characteristics of the discrete breater in CuPt7 crystal by the method of molecular dynamics by GPU-calculations

The article uses the molecular-dynamic method to calculate the statistical characteristics of a quasi-breather in a CuPt7 model crystal. In the calculations, a high-performance computing complex based on a GPU accelerator was used, which provided the necessary speed and accuracy of calculations. The phonon spectrum of this model crystal was calculated, and the dependences of the standard deviation, coefficient of variation, and average frequency of the model quasi-breather on its lifetime were revealed. The analysis of statistical data allows concluding that in the model under consideration, using the interatomic interaction potential obtained by the immersed atom (EAM) method, the quasi-breather model solution does not differ significantly from the corresponding exact breather. Moreover, the final destruction of the quasi-breather occurs at a time when the standard deviation of the frequencies exceeds the difference between the average frequency of the quasi-breather and the upper boundary of the phonon spectrum of the crystal. At this moment, the delocalization of vibrations and the dissipation of energy through the crystal in the form of low-amplitude thermal vibrations of the lattice occur. This may indicate the stability of the obtained discrete breather and the possibility of excitation in real alloys of the considered composition.

Study of Radial Vibration Impact on Friction and Torque of Rotary Drill String

During extended-reach well drilling, the torque of a rotary drill string is too large in the horizontal section, which results in the failure of the drill string. The effect of radial vibration on the friction and torque of the rotary drill string is unclear. In this work, first, the principle of the impact of radial vibration on the friction and torque of the rotary drill string in the horizontal section is analysed. Then, joints with an elliptical outer edge of the section are designed, which can generate low-amplitude vibration as the drill string rotates owing to the interaction with the wellbore wall. The radial vibration characteristics can be tuned by changing the major to minor radius ratio of the ellipse. A self-developed experimental device was designed to test the performance of tools with reduced friction and torque. The drill string torque with different penetration rates, rotation speeds, and ratios of the major radius to minor radius of the ellipse were systematically studied. The experimental results show that the average and the maximum amplitudes of the torque fluctuation first decrease to the lowest value and then increase with the increase of the ratio. When the ratio reaches 1.065, the average and the maximum amplitudes of the torque fluctuation evidently reduce; therefore, a joint with a ratio of 1.065 can effectively reduce frictional torque. The average torque reduces when the penetration rate and rotation speed decrease. At rotation speeds of 45 and 60 r/min, the maximum amplitude of torque fluctuation increases first and then decreases with an increase in penetration rate, and it reaches a maximum value at a penetration rate of 22.5 m/h. The fundamental frequency of torque fluctuation is almost linearly related to rotation speed, which is irrelevant to the penetration rate and the ratio of major to minor radius of the ellipse.

Heat flux correlation models for spray evaporative cooling of vibrating surfaces in the nucleate boiling region

New empirical correlation models are constructed to characterise heat transfer associated with spray evaporative cooling of vibrating surfaces - a process involving complex two-phase physics well beyond current numerical simulation capabilities. The proposed correlation models, which account for dynamic, rather than just static surface conditions as in existing models, are constructed using dimensional analysis involving the Generalized Buckingham Π-Theorem. Experimentally-measured spray evaporative cooling data is used to fit the model using the Vibrational Reynolds number and a dimensionless acceleration number which better correlate the influence of surface frequency and amplitude in the nucleate boiling regime. Different coolant flow-rates through a full-cone spray nozzle are used to cool a flat circular test-piece acting as a horizontal surface. The test-piece surface is excited by a shaker through a range of low and high vibration frequencies and amplitudes. The results show that surface dynamic effects certainly influence nucleate boiling, but they also show that surface vibration does not have the same effect for all excess temperatures - dynamic effects can either increase or decrease heat transfer depending on the heat transfer mechanism. These new models are important for thermal management in several areas, particularly involving batteries, power electronics, and electrical machines in automotive and aerospace applications.

Multi‐output modal identification of landmark suspension bridges with distributed smartphone data: Golden Gate Bridge

Bridge infrastructure assets possess ultimate value for safe, resilient, and sustainable transportation networks. Monitoring of bridge structural characteristics is an essential process to minimize damage-associated risk but requires expensive sensor instrumentation, manpower, and expert intervention. Besides, certain bridges' vitality exceeds practical needs due to their landmark identity with symbolic value. In this study, an economical and consumer-grade-distributed sensor array is utilized to determine dynamic characteristics of the Golden Gate Bridge, the most prominent landmark suspension bridge in the United States. The bridge is instrumented with multiple smartphones throughout the main and the side spans to collect vibration data without obstructing pedestrian or vehicle traffic. The accelerometer data collected under clock distribution are processed to retrieve modal frequencies and mode shapes of the bridge. Asynchronous and sampling-deficient sensing approaches are adopted to extract the bridge modal characteristics despite the low vibration frequency and amplitude of the long-span suspension bridge combined with limited sensing and acquisition quality of the smartphones. The findings show significant correlation with high-fidelity reference instrumentations and present the largest-scale civil infrastructure monitoring example utilizing smartphone technology.

Resonance behavior in coupled Van der Pol harmonic oscillators with controllers and delayed feedback

It has been revealed in the proposed work that a pair of delay positive position feedback control can lessen the vibration response of double Van der Pol oscillators with external forces. We also studied the effects of both the control and the delayed feedback signal gains to illustrate the low vibration amplitudes. The averaging perturbation process has been used to consider the frequency-response equations of amplitudes and modulation phases at the primary resonance and one-to-one internal resonances. According to the perturbation solutions for the four-degrees-of-freedom system, we presented the frequency response curves that were periodic in the time delays. The stability analysis presented in this study has shown optimum stable ranges. If the time delays increase, the steady-state amplitudes of the oscillator’s system will periodically result in few stable regions and more unstable ones. The numerical simulation has been introduced to check the analytical approximation. It was also found to be almost identical after presenting the comparison of the results.

Effect of broad-band phase-based motion magnification on modal parameter estimation

In this paper, broad-band phase-based motion magnification (BPMM) is used to improve the modal parameter estimation from high-speed video of a structure undergoing low amplitude vibration. The authors use a novel application of the phase-based motion magnification technique to obtain improved results in the presence of image noise. A numerical simulation is performed to demonstrate and quantify the effect of broad-band motion magnification. A clear correlation is found between the magnification factor and the error in the motion obtained from 2-dimensional point tracking (2DPT). In a laboratory experiment, operational modal analysis is performed on a metallic nozzle with a 5.3 in exit diameter and a constant wall thickness of 0.03 inches. Fluorescent markers are painted on the nozzle lip. The nozzle is attached to a test stand and excited by pressurized air. The induced vibrations are captured by a single high-speed camera, which takes images of the nozzle lip. Using a 2DPT algorithm, the displacement history of the markers in the nozzle exit plane is extracted. As is typical for small and stiff structures, the resonant frequencies are quite high and the resulting vibration amplitudes are fairly low. This leads to low signal-to-noise ratio in the higher frequencies, which makes the following operational modal analysis much harder. By using BPMM as a preprocessor, the authors demonstrate that the outcome of modal analysis is greatly improved. Comparison with Finite Element analysis shows that the mode shapes agree much better with the experimental results when motion magnification is used. The modal parameters of the first six modes are found in the frequency range 0–1400 Hz using the new methodology, whereas without motion magnification only the first five modes are found.

Analysis of power split vibration absorber performance in heavy-duty truck powertrains

The current development of more efficient combustion engines leads to an increase in engine torsional vibrations; therefore, new technology is needed for reducing the vibrations transmitted from the engine to the driveline. In this article, the concept of power split vibration absorber is evaluated. A mathematical model of the power split vibration absorber is presented, and an analytical study shows how different design parameters affect the power split vibration absorber performance. Numerical simulations with models representing typical heavy-duty truck powertrains are used in the evaluations. It is concluded that for a low level of damping, the power split vibration absorber can provide significantly lower vibration amplitudes than a corresponding dual mass flywheel within a limited speed range. If the power split vibration absorber is optimised for the critical low engine speeds, an overall decrease in the level of vibration can be obtained, but a larger installation space than with a conventional dual mass flywheel would probably be required.

A Self-adaptive and Self-Sufficient Energy Harvesting System.

Self-adaptive vibration energy harvesters convert the kinetic energy from vibration sources into electrical energy and continuously adapt their resonance frequency to the vibration frequency. Only when the two frequencies match can the system harvest energy efficiently. The harvesting of vibration sources with a time-variant frequency therefore requires self-adaptive vibration harvesting systems without human intervention. This work presents a self-adaptive energy harvesting system that works completely self-sufficiently. Using magnetic forces, the axial load on a bending beam is changed and thus the resonance frequency is set. The system achieves a relative tuning range of 23% at a center frequency of 36.4 Hz. Within this range, the resonance frequency of the harvester can be set continuously and precisely. With a novel optimized method for frequency measurement and with customized electronics, the system only needs 22 µW to monitor the external vibration frequency and is therefore also suitable for environments with low vibration amplitudes. The system was verified on a vibrational test bench and can easily be tailored to a specific vibration source.

Vibration acceleration promotes endochondral formation during fracture healing through cellular chondrogenic differentiation.

Vibration acceleration through whole body vibration has been reported to promote fracture healing. However, the mechanism responsible for this effect remains unclear. Purpose of this study was to determine whether vibration acceleration directly affects cells around the fracture site and promotes endochondral ossification. Four-week-old female Wistar Hannover rats were divided into two groups (vibration [V group] and control [C group]). The eighth ribs on both sides were cut vertically using scissors. From postoperative day 3 to 11, vibration acceleration using Power Plate® (30 Hz, low amplitude [30-Low], 10 min/day) was applied in the V group. Mature calluses appeared earlier in the V group than in the C group by histological analysis. The GAG content in the fracture callus on day 6 was significantly higher in the V group than in the C group. The mRNA expressions of SOX-9, aggrecan, and Col-II in the fracture callus on day 6 and Col-X on day 9 were significantly higher in the V group than in the C group. For in vitro analysis, four different conditions of vibration acceleration (30 or 50 Hz with low or high amplitude [30-Low, 30-High, 50-Low, and 50-High], 10 min/day) were applied to a prechondrogenic cell (ATDC5) and an undifferentiated cell (C3H10T1/2). There was no significant difference in cell proliferation between the control and any of the four vibration conditions for both cell lines. For both cell lines, alcian blue staining was greater under 30-Low and 50-Low conditions than under control as well as 30-High and 50-High conditions on days 7 and 14. Vibration acceleration under 30-L condition upregulated chondrogenic gene expressions of SOX-9, aggrecan, Col-II, and Col-X. Low-amplitude vibration acceleration can promote endochondral ossification in the fracture healing in vivo and chondrogenic differentiation in vitro.