Vibrational Transfer Research Articles

Effect of Soil Layering on Coupled Dynamic Response and Active Length of Piles Embedded in Layered Soil Using Cone Model

Dynamic analysis of single pile embedded in two-layered soil has been performed to study the influence of layering on the frequency dependent displacement response and active length under coupled horizontal and rocking vibration. Cone model has been used to determine the dynamic stiffness coefficient of pile. The soil and pile has been assumed to behave as elastic during dynamic loading. It has been also assumed that perfect bond exists between pile surface and surrounding soil medium. The wave generated due to pile vibration transfer to the soil through soil–pile interface and propagates to the infinity. The wave propagation has been modeled with cone model and soil–pile interaction has been incorporated through beam equation. The dynamic response of the pile obtained from the analysis has been plotted against non dimensional frequency to investigate the behavior of pile under such loading condition. The horizontal displacement profile along the depth of pile has been studied for different top layer thickness and homogeneous soil. The results showed that dynamic response is very sensitive to the thickness of the top layer and its properties. The active length of pile increases with the increase in top layer thickness.

Using the Fourier Transform in the Analysis of Vibration Load Tests of Heterogeneous Mechanical Systems

The aim of this study was to find possibilities of using the Fourier transform in the analysis of vibration load tests of heterogeneous mechanical systems, especially those of a biological nature. The study applied the idea that the dispersion of a stationary stochastic signal depends on its power spectral density. We have verified that a sophisticated reduction in the spectral power of the ergodic signal may be used to filter it effectively. The proposed procedure is suitable for the detection and separation of harmonic artefacts. We have created an algorithm in the MATLAB environment and tested its functionality when analysing the vibration transfer within the human axial system.

Reducing vibration transfer from power plants by active methods

The possibility of applying the methods of active damping of vibration and pressure pulsations for reducing their transfer from power plants into the environment, the seating, and the industrial premises are considered. The results of experimental works implemented by the authors on the active broadband damping of vibration and dynamic forces after shock-absorption up to 15 dB in the frequency band up to 150 Hz, of water pressure pulsations in the pipeline up to 20 dB in the frequency band up to 600 Hz, and of spatial low-frequency air noise indoors of a diesel generator at discrete frequency up to 20 dB are presented. It is shown that a reduction of vibration transfer through a vibration-isolating junction (expansion joints) of pipelines with liquid is the most complicated and has hardly been developed so far. This problem is essential for vibration isolation of power equipment from the seating and the environment through pipelines with water and steam in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. For improving efficiency, reducing the energy consumption, and decreasing the overall dimensions of equipment, it is advisable to combine the work of an active system with passive damping means, the use of which is not always sufficient. The executive component of the systems of active damping should be placed behind the vibration isolators (expansion joints). It is shown that the existence of working medium and connection of vibration with pressure pulsations in existing designs of pipeline expansion joints lead to growth of vibration stiffness of the expansion joint with the environment by two and more orders as compared with the static stiffness and makes difficulties for using the active methods. For active damping of vibration transfer through expansion joints of pipelines with a liquid, it is necessary to develop expansion joint structures with minimal connection of vibrations and pulsations and minimal vibration stiffness in the specified frequency range. The example of structure of such expansion joint and its test results are presented.

Exotic states in the strong-field control of dissociation dynamics: from exceptional points to zero-width resonances

is an ideal candidate for the detailed study of strong-field coherent control strategies inspired by basic mechanisms referring to some specific photodissociation resonances. Two of them are considered in this work, namely: zero-width resonances (ZWRs) and coalescing pairs of resonances at exceptional points (EPs). An adiabatic transport theory based on the Floquet Hamiltonian formalism is developed within the challenging context of multiphoton dynamics involving nuclear continua. It is shown that a rigorous treatment is only possible for ZWRs, whereas adiabatic transport mediated by EPs is subjected to restrictions. Numerical maps of resonance widths and non-adiabatic couplings in the laser parameter plane help in optimally shaping control pulses. Full time-dependent wavepacket dynamics shows the possibility of selective, robust filtration and vibrational population transfers, within experimentally feasible criteria.

Characteristic Analysis of Passenger Car Door Vibration Transfer Function

In order to study the vibration transfer characteristics of passenger car door, modal and vibration transfer function of passenger car door are simulated by using HyperMesh and Nastran synthetically. The accuracy of the finite element model is verified through modal analysis. According to the first two modes, the position of transfer function response points is confirmed. The vibration transfer functions are simulated and the accuracy of the simulation is verified by test. The research shows that the natural frequency of a passenger car door is not necessarily a pole of the passenger car door transfer function. On the contrary, a pole of transfer function is bound to be a natural frequency of the passenger car door, which is of directive significance to study the NVH characteristics of the passenger car door structure.

Analysis of vibration transfer characteristics of vehicle suspension system employing inerter

In this paper, the force transfer mechanism of three mechanical elements “inerter, spring and damper” is analyzed based on the “force-current” analogy theory. The vibration isolation performance of the two types of simple three-element vehicle suspensions S1 (inerter is in parallel with damper) and S2 (inerter is in series with damper) are studied. The dual- -mass system model of the suspensions is built by means of using the mechanical impedance method. The influence of parameters variation on vibration transfer characteristics is also investigated.

Vibration transfer function of in-plane rigid–elastic-coupled tire model for heavy-loaded radial tire

The modeling and vibration transfer function of in-plane rigid–elastic-coupled tire model is put forward for researching the heavy-loaded radial tire with the feather of larger radial length and wi...

Two-mass linear vibratory conveyor with reduced vibration transmission to the ground

Linear vibratory conveyors are common equipment to convey goods. They are used in different industries such as for example the building, mining and food industry. The systems are mainly used for the supply of bulk goods into further processing operations. The goods to be conveyed, typically requesting a heavy-duty design of the conveyor and eccentric excitation drives with relatively high torque. A supply of strong vibrations to the floor is an effect, which often is caused by vibratory conveyors. The target of this article is to determine a dynamic model, based on a two-mass absorber system, helping to avoid the transfer of vibrations to the ground. An optimum supply of goods by the same time should be ensured.

Advanced electron transfer-induced heat transport theory that considers vibrational heat transfer

Theoretical chemists offer novel theory on transfer-induced heat transport and vibrational heat transfer during electron transfer.

Spectral negentropy based sidebands and demodulation analysis for planet bearing fault diagnosis

Planet bearing vibration signals are highly complex due to intricate kinematics (involving both revolution and spinning) and strong multiple modulations (including not only the fault induced amplitude modulation and frequency modulation, but also additional amplitude modulations due to load zone passing, time-varying vibration transfer path, and time-varying angle between the gear pair mesh lines of action and fault impact force vector), leading to difficulty in fault feature extraction. Rolling element bearing fault diagnosis essentially relies on detection of fault induced repetitive impulses carried by resonance vibration, but they are usually contaminated by noise and therefor are hard to be detected. This further adds complexity to planet bearing diagnostics. Spectral negentropy is able to reveal the frequency distribution of repetitive transients, thus providing an approach to identify the optimal frequency band of a filter for separating repetitive impulses. In this paper, we find the informative frequency band (including the center frequency and bandwidth) of bearing fault induced repetitive impulses using the spectral negentropy based infogram. In Fourier spectrum, we identify planet bearing faults according to sideband characteristics around the center frequency. For demodulation analysis, we filter out the sensitive component based on the informative frequency band revealed by the infogram. In amplitude demodulated spectrum (squared envelope spectrum) of the sensitive component, we diagnose planet bearing faults by matching the present peaks with the theoretical fault characteristic frequencies. We further decompose the sensitive component into mono-component intrinsic mode functions (IMFs) to estimate their instantaneous frequencies, and select a sensitive IMF with an instantaneous frequency fluctuating around the center frequency for frequency demodulation analysis. In the frequency demodulated spectrum (Fourier spectrum of instantaneous frequency) of selected IMF, we discern planet bearing fault reasons according to the present peaks. The proposed spectral negentropy infogram based spectrum and demodulation analysis method is illustrated via a numerical simulated signal analysis. Considering the unique load bearing feature of planet bearings, experimental validations under both no-load and loading conditions are done to verify the derived fault symptoms and the proposed method. The localized faults on outer race, rolling element and inner race are successfully diagnosed.

Improved vehicle interior structure-borne noise induced by the powertrain using parallel dry friction damper

Because of the higher requirements for vehicle comfort and people’s increasing ecological consciousness, research on the interior noise in a vehicle has received wide attention, among which structure-borne noise is hard to diagnose. To solve the problem, the transfer path analysis method of powertrain structure-borne noise has been systematically analyzed. By introduction of the powertrain source-path-receiver model, this method enables the researchers to estimate and study the noise, vibration, and harshness transfer functions and their operational forces. The aim is to further improve noise, vibration, and harshness with minimal negative impact on other vehicle attributes, such as ride comfort, handling, drivability, durability, etc. In this article, a parallel dry friction damper was added to the vehicle nearside powertrain mount, which is the most significant one to the receiver of passenger vehicle for improving its interior structure-borne noise induced by the engine. The test vehicle was a midsize executive vehicle. Since the structure-borne noise is composed of multiple paths, then the transfer path analysis test of the vehicle was carried out, and the transfer function and operational data at speed range started from 20 to 100 km/h were obtained. On the basis of the transfer path analysis results and the above principle, the friction damper on the body side of the nearside mount is improved by combination of the experimental transfer path analysis and the final measurements. The results indicate that a significant reduction for the A-weighted sound pressure level of the interior noise has been gained when the frictional damper was added to conventional mount.

Constrained-layer Damping Applied to DCJ Vibration Isolation Design

A dual piezoelectric cooling jet (DCJ) is an innovative cooling device that uses piezoelectric materials to generate high-speed vibrations, thereby causing changes in the flow field to achieve heat exchange. Despite its high cooling efficiency, a DCJ transfers vibrations through its supporting base to its peripheral devices. To attenuate vibrations from DCJs, this study employed constrained-layer damping (CLD)-a technique for suppressing vibrations-to develop a base for cooling devices and to propose a C-DCJ model. ANSYS simulation of the vibrations of a DCJ and the C-DCJ suggested that, under the same vibration conditions and with the same levels of cooling efficiency, the amplitude and acceleration of the base on the C-DCJ were 30%–50% lower than that on the DCJ. Thus, the proposed C-DCJ effectively isolated vibration transfer.

Torsional vibration signal analysis as a diagnostic tool for planetary gear fault detection

Abstract This paper aims to investigate the effectiveness of using the torsional vibration signal as a diagnostic tool for planetary gearbox faults detection. The traditional approach for condition monitoring of the planetary gear uses a stationary transducer mounted on the ring gear casing to measure all the vibration data when the planet gears pass by with the rotation of the carrier arm. However, the time variant vibration transfer paths between the stationary transducer and the rotating planet gear modulate the resultant vibration spectra and make it complex. Torsional vibration signals are theoretically free from this modulation effect and therefore, it is expected to be much easier and more effective to diagnose planetary gear faults using the fault diagnostic information extracted from the torsional vibration. In this paper, a 20 degree of freedom planetary gear lumped-parameter model was developed to obtain the gear dynamic response. In the model, the gear mesh stiffness variations are the main internal vibration generation mechanism and the finite element models were developed for calculation of the sun-planet and ring-planet gear mesh stiffnesses. Gear faults on different components were created in the finite element models to calculate the resultant gear mesh stiffnesses, which were incorporated into the planetary gear model later on to obtain the faulted vibration signal. Some advanced signal processing techniques were utilized to analyses the fault diagnostic results from the torsional vibration. It was found that the planetary gear torsional vibration not only successfully detected the gear fault, but also had the potential to indicate the location of the gear fault. As a result, the planetary gear torsional vibration can be considered an effective alternative approach for planetary gear condition monitoring.

Analysis of annoying shocks transferred from tractor seat using vibration signals and statistical methods

In many developing countries, agricultural tractors are employed for different field operations and transportation along rural roads where the operator is exposed to high levels of harmful vibrations from the tractor seat. In case of the vibrations transferred to the operator’s body, the vibration signal form and the number and type of the shocks have been neglected in related literature. This article is focused on modern approaches to analyze tractor and car seats vibrations which have been ignored in many standards guidelines. For this purpose, examining a case study, kurtosis and skewness approaches were used to evaluate the vibration signals generated by a tractor seat. Further, an innovative model was developed to evaluate the effect of the vibrations, in terms of vibration intensity and signal form, on the operator. Average percentage of vibration transfer from the engine to feet platform was estimated at 31%. It could be concluded that, ground roughness generates vibrations within the frequency range of 0–30Hz, while the engine causes vibrations at some frequency ranging within 50–200Hz. Kurtosis could better present the difference between the two signals. The results indicated that, when considered independently, the values of RMS, VDV and kurtosis cannot well represent differences in vibration signals parametrically. However, the novel approach, when used as a benchmark for comparison, showed the differences between the signals at high accuracy.

Planetary Gearbox Fault diagnosis via Joint Amplitude and Frequency Demodulation Analysis Based on Variational Mode Decomposition

Planetary gearbox vibration signals have strong modulation features due to the amplitude modulation and frequency modulation (AM-FM) effect of gear faults, as well as the amplitude modulation (AM) effect of time-varying vibration transfer paths, on gear meshing vibrations. This results in an involute sidebands structure in Fourier spectrum, possibly misleading fault diagnosis. The modulating frequency of both amplitude modulation (AM) and frequency modulation (FM) parts is closely related to the gear fault characteristic frequency. This inspires the idea of joint amplitude and frequency demodulation analysis, thus addressing the complex sidebands issue inherent in Fourier spectrum. Demodulation analysis requires mono-component signals for accurate estimation of instantaneous frequency, and proper selection of an AM-FM component sensitive to gear fault. To this end, we firstly decompose the complex signal into intrinsic mode functions (IMFs) via variational mode decomposition (VMD), by exploiting its capability in decomposing complex modulated signal into constituent AM-FM components. For effective application of VMD in complex planetary gearbox signal analysis, we propose a method to determine a key parameter in VMD, i.e. the number of IMFs to be separated. For accurate instantaneous frequency estimation, we decompose IMFs via empirical AM-FM decomposition, to remove the influence of AM on instantaneous frequency estimation. Then, we select the sensitive IMF that contains the main gear fault information for further demodulation analysis. In order to properly select the sensitive IMF, we propose a criterion based on the gear vibration characteristics and the VMD properties. Finally, we obtain the amplitude and frequency demodulated spectra by applying Fourier transform to the amplitude envelope and instantaneous frequency of the selected sensitive IMF. According to the characteristics exhibited in the demodulated spectra, we can detect planetary gearbox fault. The proposed method is illustrated via a numerical simulated planetary gearbox vibration signal, and is further validated using lab experimental vibration signals of a planetary gearbox. Faults on all the three types of gear (sun, planet and ring) are successfully identified.

Reliability analysis of random vibration transmission path systems

The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Therefore, the uncertainty of path parameters influences the system reliability greatly. In order to avoid the resonance failure, the transmission reliability analysis and the reliability sensitivity analysis are both very important. Based on the reliability theory, the absolute value difference of natural frequency and excitation frequency of random vibration transmission path system was limited and the reliability pattern of the resonance problem was defined in this paper. Applying the generalized second moment technique of vector-valued functions and the stochastic finite element theory, the theoretical analysis method of the transmission reliability and reliability sensitivity was presented. The corresponding vibration transmission path system with uncertain path parameters including mass, stiffness and path position was analyzed theoretically and computed numerically, and then the correlated mathematical expressions were obtained. Thus, in practical project, most of uncertain factors in the vibration systems can be analyzed so that the effective way can be given to avoid resonance failure.

The uncertainty in stiffness and damping of an automotive vehicle’s trim-structure mounts and its effect on the variability of the vibration transfer function

A large number of plastic clips are used in an automotive vehicle to connect the trim to the structure. These are small clips with very small masses compared to the structural elements that they connect together; however, the uncertainty in their properties can affect the dynamic response. The uncertainty arises out of their material and manufacturing tolerances and more importantly the boundary conditions. A test rig has been developed that can model the mounting condition of the clips. This allows measurement of the range of their effective stiffness and damping. Initially, the boundary condition at the structure side is replicated. The variability is found to be 7% for stiffness and 8% for damping. In order to simulate the connection of the trim side, a mount is built using a 3D printer. The variability due to the boundary condition on both sides was as large as 40% for stiffness and 36% for damping. A Monte Carlo simulation is used in order to assess the effect of the uncertainty of the clips’ properties on the vibration transfer functions of a door assembly. A simplified connection model is used in this study where only the axial degree of freedom is considered in connecting the trim to the door structure. The uncertainty in the clip stiffness and damping results in a variability in the vibration transfer function which is frequency dependent and can be as high as 10% at the resonant peaks with higher values at some other frequencies. It is shown that the effect of the uncertainty in the clips effective damping is negligible and the variability in the dynamic response is mainly due to the uncertainty in the clip’s stiffness. Furthermore, it is shown that the variability would reduce either by increasing or decreasing the effective stiffness of the clips.

Effect of the static compressive load on vibration propagation in multistory buildings and resulting heavyweight floor impact sounds.

Experiments were performed to identify the mechanism of heavyweight floor impact sound transmission through floors in a high-rise apartment building. Vibration and sound levels on each floor of the multistory building were measured. The vibration generated at a given floor was transferred to multiple adjacent floors with decreasing amplitudes proportional to the distance from the excited floor. This vibration transfer introduced significant sound transmissions. The structural static load varied depending on the floor location due to differences in the weight of the structure above the floor, especially for wall construction buildings. The static load at the wall of the bottom floor was the largest among the different floors. The influence of this static load on the impact sound generation was investigated through tests in the actual building and the scale model, respectively. The results were numerically analyzed using the spectral element method. With the increasing static load, the resonance frequencies of the floor increased due to the change in the vibration modes of the structure. The modulated sound generation from the floor vibrations transmitted to multiple layers with larger magnitudes due to this static load.

Investigation of the vibration transfer process to a stuck drill string

Investigation of the vibration transfer process to a stuck drill string

Rabi-like vibrational coherence transfer in a hydrogen-bonded charge transfer material

We report ultrafast spectroscopic measurements of intersite charge transfer in a single crystal of the hydrogen-bonded material quinhydrone showing anticorrelated dynamics of vibrational coherences at 172 and $216\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. To explain these coherent dynamics we derive a density matrix model in the presence of higher order electron-vibration coupling. Given the symmetry of vibrations calculated using density functional theory, the Huang-Rhys parameter of the Raman-active vibration found from spontaneous resonance light scattering measurements, and previously reported nonresonant impulsive stimulated Raman scattering measurements on quinhydrone, we restrict the density matrix model to three levels in the excited state of this material to simulate the observed dynamics with a density matrix approach. The close agreement between the experiment and our theoretical treatment leads us to conclude that the measured behavior corresponds to intermolecular Rabi-like oscillatory coherence transfer. These results provide foundational knowledge into the capability of functional organic materials to support quantum coherent transport of charge and energy as well as shed light on recent experimental and theoretical investigations of room temperature organic ferroelectrics.