Resonance Damping Research Articles

Analytical solutions for thermo-elastic damping of rotational ring resonators incorporating thermal relaxations and elastic small scales

At the micro and nanoscales, thermo-elastic damping is regarded as one of the most crucial factors for promoting energy dissipation in vibrating structures. The thermo-elastic damping of a thin rotational ring resonator is explored in this paper based on three phase lag heat conduction model for thermal relaxations and nonclassical elasticity for small scale effects. Solving the heat conduction equation for radial direction heat flow and zero heat flux boundary conditions yields the temperature spread across ring cross-section. The equation takes into account only the rotating narrow ring’s in-plane vibrations. For the frequency dependent thermo-elastic damping, the combined nonlocal thermo-elasto-dynamic equations are solved. The present model is validated with the experimental and finite element data. The thermo-elastic damping of rotating rings has been found to be over predicted by classical elasticity. For a particular small scale factor, as rotational speed rises by 80%, the equivalent thermo-elastic damping of the ring resonator reduces by 43%. In addition, the effects of cross-sectional shape, nonlocal scale factor, rotating speed, modenumber, ambient temperature, and substance on thermo-elastic damping are thoroughly explored in this work. The results presented here are useful to build and construct future nanoscale resonant sensors and radio-frequency devices.

Vibration filtering effect of a novel three-dimensional isolation bearing on metro vibration isolation

Three-dimensional (3D) isolation bearings are effective means to reduce the adverse effects of metro vibrations on structures. The current research focuses on the relationship between the vertical stiffness and metro vibration isolation performance of bearings, but neglects the vibration filtering effect resulting from the inherent resonance and material damping effect of them. In this study, a novel 3D isolation bearing was proposed, composed of spring bearings (SBs) and laminated nature rubber bearings (LNR) vertically in series (denoted as 3DSL), and not only its vertical stiffness but also vibration filtering effect on metro-induced vibration isolation performance were fully studied. The design principle and vibration isolation mechanism of the 3DSL were described, followed by the design and test of three specimens. After that, a case study was conducted to investigate the influence of the 3DSL's filtering effect on metro vibration isolation. The results indicated that the 3DSL exhibited high vertical loading capacity and low vertical stiffness. Furthermore, it was found that the vibration amplitude was slightly amplified in the low-frequency range (1–50 Hz), while significantly reduced in the high-frequency range (50–200 Hz) due to the vibration filtering effect of the 3DSL. Altogether, these results demonstrated that the excellent metro vibration isolation performance of the 3DSL was attributed to the low vertical stiffness and vibration filtering effect. It is recommended to consider both the reduction of vertical stiffness and vibration filtering effect of 3D isolation bearings when designing isolation systems for metro vibrations.

Seeded growth synthesis, reshaping, and damping of the localized surface plasmon resonance in Au@Fe2O3 nanoparticles

Core@shell Au@Fe2O3 nanoparticles with different iron oxide content were synthesized by a seeded-growth approach. The morphology and structural analysis were carried out by transmission electron microscopy (TEM and HR-TEM) and X-ray diffraction (XRD). The oxidation state of the iron was determined through cyclic voltammetry measurements. The plasmonic resonance modes were investigated by Infrared (IR) and UV–vis spectroscopy. The morphology analysis of Au nanowires (AuNW’s) shows a modification from NW’s (seeds) to faceted nanoparticles, while spectroscopic studies show a disappearance of the Propagation Surface Plasmon Resonance (PSPR) due to this change. Localized Surface Plasmon Resonance (LSPR) is damped due to the aggregation of the iron oxide layer.

Damping of 3D-printed polymer microbeam resonators

The emerging high-resolution 3D printing technique called two-photon polymerization (2PP) enables to print devices bottom-up rapidly, contrary to the top–down lithography-based fabrication methods. In this work, various polymer microbeams are 3D printed and their resonant characteristics are analyzed to understand the origin of damping. The 2PP printed polymer resonators have shown less damping than other polymer devices reported earlier, with tensile-stressed clamped–clamped beams reaching a record quality factor of 1819. The resonant energy loss was dominant by bulk friction damping. These results pave the path towards using 3D printed microresonators as mass sensors with improved design and fabrication flexibility.

Grid‐tied PEMFC power conditioning system based on capacitor voltage thorough feedback procedure in a weak and harmonics‐polluted network

AbstractProton exchange membrane fuel cells (PEMFC) have been noticed by researchers due to their high efficiency, low pollution, and high‐power density in distributed generation systems. In this paper, an LCL‐type grid‐tied PEMFC fuel cell power conditioning system is evaluated in a harmonics‐polluted low‐voltage grid. The LCL‐filters can lead to resonance and instability despite their capability to attenuate harmonics. In this research, a transformer has been used to connect the fuel cell inverter to the grid. The grid‐side inductor of LCL‐filter is realized by the leakage inductance of the transformer. In addition, for more effective resonance damping and attenuation of current ripples caused by the grid voltage harmonics, a capacitor voltage comprehensive feedback control has been designed and investigated. The comprehensive feedback control of the capacitor voltage contains proportional, first and second‐order derivative terms. In the proposed control scheme, the capacitor‐current‐feedback is opposed by the capacitor voltage derivative term due to reverse loop gain, which leads to deleting both of these loop gains. As a result, there is no need to utilize a current sensor in this control method. Consequently, the proportional and second‐order derivative terms of the capacitor voltage attenuate the LCL‐filter resonance. A low‐pass filter is also considered in the second‐order derivative loop in the controllable frequency range to ensure system stability. The simulation results of the PEMFC power conditioning system in different conditions confirm the proper attenuation of LCL resonance of grid‐tied inverter, high‐quality current injection to the harmonics polluted grid, the suitable stability, and the appropriate dynamic response for the proposed system. Under the proposed control scheme, the fuel cell power conditioning system demonstrates satisfactory stability. Even when reducing the LCL filter values by 5%–20%, the system maintains its stability effectively. Moreover, the THD of the injected current into the grid, employing the proposed control strategy, has been successfully reduced to an impressive value of 1.97% in a weak and harmonical grid.

Lightweight sound insulation optimization of simply supported locally resonant plate

A theoretical model of the normal sound insulation of a rectangular locally resonant (LR) plate with simply supported boundary conditions is established. The accuracy of the model is verified through comparison with finite element simulation results. Considering a 1-m2 aluminum plate as the research object, a non-dominated genetic algorithm is introduced. The algorithm optimizes the lightweight sound insulation of an LR finite plate with a center frequency band of 20–800 Hz as the optimization objective of maximum average sound insulation and minimum mass. The optimization parameters are substrate thickness and local resonance parameters (including resonator target frequency (fobj), number of resonators, additional mass ratio, and resonator damping). Optimization results indicate that the average sound insulation fluctuates at approximately 2 dB due to changes in fobj. The results also provide an optimal solution to the algorithm. The optimal sound insulation value curve of LR plates corresponding to different surface densities of intermediate improved cases is fitted and compared with the sound insulation value of an equal-mass bare plate. Under lightweight optimization, the resonators are deemed capable of improving the local frequency band sound insulation. In contrast, the wideband average sound insulation can approximate but not surpass the insulation provided by the equal-mass bare plate. In practical applications, an LR plate that can improve the local frequency band sound insulation and ensure the overall lightweight sound insulation performance of the wide frequency band can be obtained. This can be achieved by analyzing the frequency spectrum of optimal points in the lightweight sound insulation optimization process. Relevant research can provide a basis for the evaluation and design of the low-frequency sound insulation of plates for transportation equipment, such as airplanes, high-speed trains, and cars.

A new mechanism for internal kink stabilization by plasma flow and anisotropic thermal transport

Stability of the internal kink (IK) mode is numerically investigated with inclusion of the anisotropic thermal transport effect and the toroidal plasma flow. It is found that anisotropic thermal transport, in combination with plasma flow, stabilizes the IK in two ways. One is direct stabilization of the mode synergistically with plasma flow. The other, indirect stabilization involves generation of a finite mode frequency in static plasmas by thermal transport, which in turn invokes wave-wave resonance damping of the mode via interaction with stable shear Alfvén waves. This second IK stabilization mechanism is further corroborated by examining the eigenmode structure, which peaks at the radial locations where the mode frequency matches that of the shear Alfvén wave. Finally, two branches of unstable IK are identified, with mode conversion occurring at certain plasma flow speed and thermal transport level. These findings provide new physics insights in the IK stability in tokamak fusion plasmas.

Resonant Damping Analysis of Output Filter of Grid-Connected Inverters

Resonant Damping Analysis of Output Filter of Grid-Connected Inverters

Vibration mitigation using finite graded metamaterials: a rod with attached local resonators

The paper concerns the analysis of vibration transmission and mitigation in a finite rod performing axial vibrations with attached multiple damped resonators. The resonators are not assumed to be periodically spaced or to have similar dynamic properties. The behaviour is analysed in terms of waves travelling between the discontinuities. Reflection and transmission coefficients of the rod with one local resonator attached are utilised in the analysis. Values of these coefficients for each of the attached resonators, along with the boundary conditions and field transfer function, are used to derive analytical expressions for the displacement of the finite rod at any point. Once the displacement is determined, the transmission loss is calculated. Moreover, the eigenfrequencies of the graded metamaterial finite rod are identified using the phase closure principle. The influence of the mass, the damping and the location of the resonators on the vibration attenuation are investigated. Numerical examples are presented. Good agreement is noted between the results of the analytical studies and finite element simulations in COMSOL. It is shown that the graded metamaterial rod can provide better vibration attenuation as compared to the conventional periodic metamaterial.

Novel method for measuring non-stationary pitch and roll angles with a pendulous accelerometer in the presence of vibrations

We developed a novel universal method to solve an important mechanics problem arising during wind tunnel tests of aircraft models: the measurement of non-stationary pitch and roll angles of aircraft models and strain-gauge balances using a pendulous accelerometer. The method is based on a physical model in which the accelerometer pendulum is replaced by a proof mass and its hinge is replaced by a spring with damping. This model makes it possible to measure non-stationary pitch and roll angles in a wide range of vibration frequencies, including the accelerometer’s eigenfrequency. We propose a method for determining the accelerometer’s natural frequency in the absence of damping (resonance frequency) as well as the ratio of the damping coefficient to the pendulum’s mass. We also conducted experimental studies in which an acceleration similar in form to the Heaviside function was applied to the accelerometer; the results verify the proposed method.

A novel buried periodic in-filled pipe barrier for Rayleigh wave attenuation: Numerical simulation, experiment and applications

Surface wave is a major concern in ambient vibration mitigation. To this end, a novel shallow buried periodic in-filled pipe barrier is proposed. Complex dispersion analysis is conduced to evaluate the decay of surface waves and the influence of material damping. Through a combination of numerical simulations and lab-scale experiments, the effectiveness and robustness of surface wave attenuation are verified. Result shows that the proposed periodic in-filled barrier exhibits excellent performance in low-frequency surface wave attenuation. Both the energy dissipation induced by material damping and local resonance of in-filled pipes contribute to surface wave attenuation. The influence of viscosity also enhances wave attenuation and it should be taken into full account in practice. In addition, these novel wave barriers are suitable for passive isolation as well as active isolation. To further widen the attenuation zones, the gradient layouts of in-filled pipes could be a good alternative considering the limited barrier width. Besides, the feasibility of periodic in-filled barriers to train-induced vibration mitigation is preliminary verified by analyzing the measured acceleration record in the time-domain. Thanks to the subwavelength size and shallow depth, these novel wave barriers are convenient for construction and cost-effective, thus showing great potential in ambient vibration mitigation.

Probing Linear to Nonlinear Damping in 2D Semiconductor Nanoelectromechanical Resonators toward a Unified Quality Factor Model.

In resonant nanoelectromechanical systems (NEMS), the quality (Q) factor is essential for sensing, communication, and computing applications. While a large vibrational amplitude is useful for increasing the signal-to-noise ratio, the damping in this regime is more complex because both linear and nonlinear damping are important, and an accurate model for Q has not been fully explored. Here, we demonstrate that by combining the time-domain ringdown and frequency-domain resonance measurements, we extract the accurate Q for two-dimensional (2D) MoS2 and MoTe2 NEMS resonators at different vibration amplitudes. In particular, in the transition region between linear and nonlinear damping, Q can be precisely extracted by fitting to the ringdown characteristics. By varying AC driving, we tune the Q by ΔQ/Q = 269% and extract the nonlinear damping coefficient. We develop the dissipation model that well captures the linear to nonlinear damping, providing important insights for accurately modeling and optimizing Q in 2D NEMS resonators.

Capacitorless Synchronous Reluctance Motor Drives for Pump Applications With Resonance Damping and Line Current Harmonics Reduction

Capacitorless Synchronous Reluctance Motor Drives for Pump Applications With Resonance Damping and Line Current Harmonics Reduction

Monitoring beam charge during FLASH irradiations

In recent years, FLASH irradiation has attracted significant interest in radiation research. Studies have shown that irradiation at ultra-high dose rates (FLASH) reduces the severity of toxicities in normal tissues compared to irradiation at conventional dose rates (CONV), as currently used in clinical practice. Most pre-clinical work is currently carried out using charged particle beams and the beam charge monitor described here is relevant to such beams. Any biological effect comparisons between FLASH and CONV irradiations rely on measurement of tissue dose. While well-established approaches can be used to monitor, in real time, the dose delivered during CONV irradiations, monitoring FLASH doses is not so straightforward. Recently the use of non-intercepting beam current transformers (BCTs) has been proposed for FLASH work. Such BCTs have been used for decades in numerous accelerator installations to monitor temporal and intensity beam profiles. In order to serve as monitoring dosimeters, the BCT output current must be integrated, using electronic circuitry or using software integration following signal digitisation. While sensitive enough for FLASH irradiation, where few intense pulses deliver the requisite dose, the inherent insensitivity of BCTs and the need for a wide detection bandwidth makes them less suitable for use during CONV “reference” irradiations. The purpose of this article is to remind the FLASH community of a different mode of BCT operation: direct monitoring of charge, rather than current, achieved by loading the BCT capacitively rather than resistively. The resulting resonant operation achieves very high sensitivities, enabling straightforward monitoring of output during both CONV and FLASH regimes. Historically, such inductive charge monitors have been used for single pulse work; however, a straightforward circuit modification allows selective resonance damping when repetitive pulsing is used, as during FLASH and CONV irradiations. Practical means of achieving this are presented, as are construction and signal processing details. Finally, results are presented showing the beneficial behaviour of the BCT versus an (Advanced Markus) ionisation chamber for measurements over a dose rate range, from <0.1 Gys−1 to >3 kGys−1.

Nonlinear/linear resonance ultrasound spectroscopy (N/RUS) of additively manufactured 316L stainless steel samples using in-contact and non-contact excitation

Due to their sensitivities to defects and microstructural changes, the linear and nonlinear parameters measured with nonlinear resonance ultrasound spectroscopy (NRUS) have the potential to evaluate the quality of additively manufactured parts. Here, NRUS with in-contact and non-contact excitation configurations is used to test a set of 316L stainless steel samples manufactured by laser powder bed fusion. Subgroups of the samples are heat treated to three temperatures to alter the samples' microstructure and mechanical performance. Results show that the hysteretic nonlinearity parameter measured with in-contact NRUS demonstrates sensitivity to heat-treatment-induced microstructural changes. However, due to the unwanted nonlinearity introduced by the bonding, variations in the repeated in-contact measurements of a single sample are almost as large as the differences between the heat treatment subgroups. The non-contact configuration allows measurement of two linear parameters (resonance frequency and damping) with exceptional repeatability, and results show clear distinction between samples in different heat treatment groups. The non-contact NRUS configuration could not produce a sufficient dynamic strain amplitude to allow a reliable measurement of the samples’ nonlinear response. In-contact and non-contact NRUS results are analyzed in relation to independently measured mechanical properties and microstructural information to investigate the feasibility of NRUS for the nondestructive evaluation of additively manufactured metals.

Elucidating Surface Plasmon Damping and Fano Resonance Induced by Epitaxial Growth of Palladium on Single Gold Nanorods.

Plasmon damping and Fano resonance induced in the growth of palladium (Pd) on gold nanorods (AuNRs) have been poorly understood. Herein, we investigated the optical properties and morphologies of single AuNRs@Pd (core@shell) synthesized using epitaxial Pd growth at different Pd concentrations. The localized surface plasmon resonance (LSPR) spectra of single AuNRs@Pd showed characteristic subradiant and superradiant peaks as well as Fano resonance as a spectral dip, which was highly influenced by the Pd shell thickness. The occurrence of the Fano resonance during the Pd growth was further verified by in situ real-time observation experiments. We then elucidated time-dependent, real-time variations in LSPR peak wavelength, metal-induced surface damping, and Fano resonance mode of single AuNRs@Pd during Pd shell formation in three successive phases: Pd reduction, nucleation, and growth. Therefore, this study provides new insights into metal interface damping, the Fano resonance, and optical tunability by engineering the Fano resonance energy and Pd shell thickness.

Nonlocal dual-phase-lag thermoelastic damping in small-sized circular cross-sectional ring resonators

The purpose of current research is to establish a theoretical size-dependent framework for estimating the amount of thermoelastic damping (TED) in miniaturized rings with circular cross section via the nonlocal dual-phase-lag (NDPL) generalized thermoelasticity theory, as one of the most exhaustive non-Fourier heat conduction models. The method used to achieve this goal is based on the definition of TED in the energy dissipation (ED) approach. To do so, after deriving heat equation in the context of NDPL model, the distribution of temperature all over the volume of the ring is specified. Then, the relations of dissipated thermal energy and strain energy in the ring are obtained. Lastly, by employing ED approach, a formula comprising the nonclassical parameters of NDPL model is rendered to determine TED value in small-scaled toroidal rings. By presenting various numerical examples, the dependence of TED on influential parameters including nonclassical thermal constants in NDPL model, ring geometry, vibrational mode number and ring material is surveyed. The Findings enlighten that the inclusion of nonlocal parameter into the model can have conspicuous impacts on TED value, especially in smaller rings or higher vibrational mode numbers. The results also reveal that among the investigated materials (i.e. silicon, copper, silver, and lead), rings made of lead and silicon exhibit the maximum and minimum TED values, respectively.

Decoupled Mitigation Control of Series Resonance and Harmonic Load Current for HAPFs With a Modified Two-Step Virtual Impedance Shaping

Hybrid active power filter (HAPF) with large series capacitor can reduce the rating of power converter, but it is associated with the risk of low frequency <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonance. The overlapping of series <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonance frequencies and the dominated load harmonic current frequencies makes the conventional active damping approaches less effective. To overcome this challenge, a two-step harmonic virtual impedance control approach is developed to compensate the load harmonic current and reshape the closed-loop equivalent circuit of the HAPF for resonance damping. First, the shunt capacitor harmonic voltage is regulated according to a term that is associated with both the harmonic load current and the HAPF harmonic line current. Further investigation on the equivalent circuit transformations indicates that HAPF is equivalent to a controlled current source to compensate for load harmonic current and a virtual harmonic damping resistor between the series capacitor and grid impedance. Accordingly, the resonance damping and the nonlinear load low order harmonic current compensation can be well decoupled with minimal interference.

Modified active disturbance rejection control scheme for systems with time delay

AbstractActive disturbance rejection control (ADRC) has been gaining attention in recent years and has shown its performance in multiple applications including non‐linear ones, without the need of accurate models. Despite the good results of this technique, time delay can deteriorate the performance of ADRC, limiting its application. Here, the effect of time delay on the stability of a linear ADRC is analysed, using an alternative mathematical description, and a new effective design technique, based on a modified ADRC scheme, is proposed to overcome the delay effect while maintaining the disturbance rejection properties of the ADRC. An experimental example is discussed considering a system with low damped mechanical resonances, showing good results using the proposed technique.

Model reference adaptive controllers with improved performance for applications in LCL-filtered grid-connected converters

This work presents a control strategy combining a direct Model Reference Adaptive Control (MRAC) with a robust state feedback for current control of grid-connected converters with LCL filters operating under grid impedance variations. The MRAC is based on a gradient law, providing properly current reference tracking and voltage disturbance rejection. The inclusion of a state feedback inner loop provides robust active damping of the filter resonance for an entire range of grid impedances. A systematic control design procedure is proposed, and the combination of both control actions in a multi-loop approach does not add significant computational complexity. The proposal allows to increase the MRAC gains adaptation dynamics, providing suitable responses under grid current reference variations and under typical grid voltage disturbances, including grid faults. Performance indexes as the grid-currents total harmonic distortion and the mean squared error are also improved. In addition, robust stability analysis based on Lyapunov functions are carried out for the inner control loop and for the outer control loop, considering the grid impedance uncertain and with unmodeled dynamics. The strategy is implemented in a commercial digital signal processor, and the compliance of the grid currents with the IEEE 1547 Std. is verified with controller hardware-in-the-loop and experimental results in a 5.4 kW prototype.