Resonant Vibration Research Articles

Structural Optimization of Lightweight Composite Floors with Integrated Constrained Layer Damping for Vibration Control

Due to current architectural trends, contemporary public buildings are becoming open-plan spaces with much less weight and damping. Consequently, Vibration Serviceability Limit State (VSLS) due to human-induced vibrations has become an increasing concern for structural engineers, especially when designing offices, hospitals, or gymnasiums. When dealing with resonant vibrations, a slight increase in the floor-damping enables decreasing considerably the vibration level. The damping strategy studied in this work is usually known in the literature as Constrained Layer Damping (CLD) and consists of a viscoelastic layer constrained between the concrete slab and the steel beam of a lightweight composite floor. In this paper, a complete structural checking methodology has been developed for analyzing all the limit states that determine the final sizing of a steel–concrete composite floor treated with CLD, including a detailed analysis of the VSLS. The methodology has been used for setting a structural optimization problem for floors with and without CLD treatments. Thus, it has been demonstrated that the integration of CLD treatments at the design stage of the building allows the development of lighter floor structures with a smaller embodied carbon (EC) footprint, especially for long-span schemes with restrictive vibration limitations.

Modeling of the shear thickening fluid damper and vibration control for stay-cable

Based on the arctangent function, this work proposes a parametric model to predict the mechanical behavior of a shear thickening fluid damper. The parameters of this model are a function of the maximum operating velocity of the damper. The validity and accuracy of the model's damping force and displacement relationship under different sinusoidal loads and various seismic wave excitations are verified based on experimental data. On this basis, compared to a viscous damper, the finite element models of a stay-cable and shear thickening fluid damper system are established to evaluate the vibration reduction performance and mechanical advantages of the shear thickening fluid damper. The research shows that a shear thickening fluid damper can significantly reduce the amplitude of the stay-cable's primary resonance and main parametric vibration, with displacement reduction rates of 72.5 and 81.9%, respectively. Importantly, compared to viscous dampers, under the premise that both have the same damping force, the vibration reduction effect of shear thickening fluid dampers is more significant, 1.3 times and 1.15 times that of viscous dampers, and the stroke is only 55.2 and 59.7% of that of viscous dampers. These data indicate that shear thickening fluid dampers can provide a more significant damping force for stay-cable in limited space.

Effect of Prestresses on the Resonant Vibrations and Heating of a Cylindrical Viscoelastic Shell*

Effect of Prestresses on the Resonant Vibrations and Heating of a Cylindrical Viscoelastic Shell*

Application of ultrasonic vibration to shape-casting based on resonance vibration analysis

Application of ultrasonic vibration to shape-casting based on resonance vibration analysis

Genetic Algorithm-Wavelet Transform Feature Extraction for Data-Driven Acoustic Resonance Spectroscopy

Acoustic Resonance Spectroscopy enables highly accurate measurement of the properties (geometry/material) of a structure based on the structure's natural vibrational resonances. In general, measuring a specific property in multibody structures presents a significant challenge due to the complex overlapping peaks within the resonance spectrum. We present a technique for extracting useful features from a complex spectrum by isolating resonance peaks that are sensitive to the measured property and insensitive to other properties (noise peaks). We isolate specific peaks by selecting frequency regions of interest and performing wavelet transformation, where the frequency regions and wavelet scales are tuned via a Genetic Algorithm. This contrasts greatly from traditional wavelet transformation/decomposition techniques, which use a large number of wavelets at different scales to represent the signal, including the noise peaks, and results in a large feature size, thus decreasing Machine Learning generalizability. We provide a detailed description of the technique and demonstrate the feature extraction technique for example regression and classification problems. We observe reductions of 95% and 40% in regression and classification errors, respectively, when using the Genetic algorithm/Wavelet Transform feature extraction, compared to using no feature extraction, or using Wavelet Decomposition, which is common in optical spectroscopy. The feature extraction has potential to significantly increase the accuracy of spectroscopy measurements based on a wide range of Machine Learning techniques. This would have significant implications for ARS, as well as other data-driven methods for other types of spectroscopy, e.g. optical.

Mid-infrared photoacoustic spectroscopy based on ultrasound detection for blood component analysis.

For the non-invasive measurement of biological tissue, a piezoelectric photoacoustic spectroscopy (PZT-PAS) system that detects a single frequency of ultrasound induced by the irradiation of pulse-modulated mid-infrared laser light was developed. PA spectra of the optical phantom and biological samples were obtained, and the relationship between the PA signal intensity and optical absorbance in the fingerprint region (930-1,200 cm-1) was analyzed to estimate the optical absorbance. The resonance vibration of the induced ultrasound was utilized to further increase the signal strength for biological tissue measurement. Consequently, PA spectrum reflecting the absorption of components in biological tissues was obtained.

Anti-icing characteristics of hierarchical micro-dimple textured surface generated by 3D resonant vibration assisted machining

Anti-icing techniques are essential for safe functioning in applications such as aircraft and power transmission lines. In the present study, a long lasting and minimal maintenance required hierarchical micro-dimple surface textures were produced on a cylindrical specimen using a dual frequency surface texturing method. The water contact angle and time delay in freezing on five diverse type of micro-dimples with three different surface texture densities and non-textured surfaces were examined and compared experimentally. The textured surfaces showed an approximately 28 % increase in delayed time compared to non-textured surfaces. A size effect on the performance of micro-dimples was observed. Smaller size micro-dimples have better delayed time for higher texture density surfaces. The delayed time increases with the increase in micro-dimple size for optimum and low texture density surfaces. Introducing of hierarchical structures increased the delayed time by 8 % compared to single scale micro-dimple surface textures. The idea of introducing hierarchical micro-dimples as an anti-icing technique will directly result in improving the delayed time, which in turn reduces the load on the secondary system for ice removing and improves its working efficiency.

RESEARCH OF PARAMETERS AND MODES OF THE VIBRATION CRUSHER

One of the main directions of research on machines for the production of building ma-terials is the reduction of energy consumption. Solving the problem related to the determination of energy consumption is a rather difficult task, since energy consumption depends on a number of factors that change during the operation of the machine and are difficult to accurately describe. One of the areas of development of machines for the production of construction materials is the creation of resonant vibration machines. Based on the analysis of the latest researches, the prospects of vibrating jaw crushers have been established. The correct selection of parameters that will ensure the operation of the crusher in a stable resonance mode will make it possible to reduce energy costs for crushing. For this purpose, the study of the dynamic parameters of the vibrating jaw crusher is presented in the paper. The efficiency of the double-acting vibratory crusher under study is ensured in the resonance mode with the synchronous adjustment of the movement of the first and third masses and the counterphase movement of the second mass. For this, the stiffness of the elastic connections c1 and c2 is calculated from the condition of resonance of the reduced masses m23 and m12, respectively, and the stiffness of the support springs from the condition of vibration isolation. The physical model of the crusher is presented and the equations of motion of oscillating masses with and without material in the crushing chamber are given. Graphs of the effect on the amplitude of the stiffness adjustment coeffi-cient by frequency were obtained. Based on the equations of motion, the amplitude-frequency characteristics for the corresponding natural angular frequencies (resonance frequencies) are constructed. The mass of the oscillating parts of the crusher has a great influence on the amplitude of oscillations. Rationally selected ratios of oscillating masses provide the required operating mode (in-phase, anti-phase) and provide the re-quired amplitudes of oscillations of these masses. For the given input conditions, the rational limits of the ratios of the oscillating masses are determined to ensure the corresponding frequency regimes. Based on the analysis of the amplitude-frequency characteristics, graphs of the amplitudes of the movement of the oscillating masses of the crusher were constructed. Recommendations for choosing effective frequency modes are given.

Role of Polarization Interactions in the Formation of Dipole-Bound States.

Even though there is a critical dipole moment required to support a dipole-bound state (DBS), how molecular polarizability may influence the formation of DBSs is not well understood. Pyrrolide, indolide, and carbazolide provide an ideal set of anions to systematically examine the role of polarization interactions in the formation of DBSs. Here, we report an investigation of carbazolide using cryogenic photodetachment spectroscopy and high-resolution photoelectron spectroscopy (PES). A polarization-assisted DBS is observed at 20 cm-1 below the detachment threshold for carbazolide, even though the carbazolyl neutral core has a dipole moment (2.2 D) smaller than the empirical critical value (2.5 D) to support a dipole-bound state. Photodetachment spectroscopy reveals nine vibrational Feshbach resonances of the DBS, as well as three intense and broad shape resonances. The electron affinity of carbazolyl is measured accurately to be 2.5653 ± 0.0004 eV (20,691 ± 3 cm-1). The combination of photodetachment spectroscopy and resonant PES allows fundamental frequencies for 14 vibrational modes of carbazolyl to be measured. The three shape resonances are due to above-threshold excitation to the three low-lying electronic states (S1-S3) of carbazolide. Resonant PES of the shape resonances is dominated by autodetachment processes. Ultrafast relaxation from the S2 and S3 states to S1 is observed, resulting in constant kinetic energy features in the resonant PES. The current study provides decisive information about the role that polarization plays in the formation of DBSs, as well as rich spectroscopic information about the carbazolide anion and the carbazolyl radical.

Quantitative nanopatterning of fg-scale liquids with dip-pen nanolithography

The ability to precisely pattern nanoscale amounts of liquids is essential for biotechnology and high-throughput chemistry, but controlling fluid flow on these scales is very challenging. Scanning probe lithography methods such as dip-pen nanolithography (DPN) provide a mechanism to write fluids at the nanoscale, but this is an open loop process as methods to provide feedback while patterning sub-pg features have yet to be reported. Here, we demonstrate a novel method for programmably nanopatterning liquid features at the fg-scale through a combination of ultrafast atomic force microscopy probes, the use of spherical tips, and inertial mass sensing. We begin by investigating the required probe properties that would provide sufficient mass responsivity to detect fg-scale mass changes and find ultrafast probes to be capable of this resolution. Further, we attach a spherical bead to the tip of an ultrafast probe as we hypothesize that the spherical tip could hold a drop at its apex which both facilitates interpretation of inertial sensing and maintains a consistent fluid environment for reliable patterning. We experimentally find that sphere-tipped ultrafast probes are capable of reliably patterning hundreds of features in a single experiment. Analyzing the changes in the vibrational resonance frequency during the patterning process, we find that drift in the resonance frequency complicates analysis, but that it can be removed through a systematic correction. Subsequently, we quantitatively study patterning using sphere-tipped ultrafast probes as a function of retraction speed and dwell time to find that the mass of fluid transferred can be modulated by greater than an order of magnitude and that liquid features as small as 6 fg can be patterned and resolved. Taken together, this work addresses a persistent concern in DPN by enabling quantitative feedback for nanopatterning of aL-scale features and lays the foundation for programmably nanopatterning fluids.

Surface-acoustic-wave-driven graphene plasmonic sensor for fingerprinting ultrathin biolayers down to the monolayer limit

Surface plasmon polaritons in graphene can enhance the performance of mid-infrared spectroscopy, which is key for the study of both the composition and the conformation of organic molecules via their vibrational resonances. In this paper, a plasmonic biosensor using a graphene-based van der Waals heterostructure on a piezoelectric substrate is theoretically demonstrated, where far-field light is coupled to surface plasmon-phonon polaritons (SPPPs) through a surface acoustic wave (SAW). The SAW creates an electrically-controlled virtual diffraction grating, suppressing the need for patterning the 2D materials, that limits the polariton lifetime, and enabling differential measurement schemes, which increase the signal-to-noise ratio and allow a quick commutation between reference and sample signals. A transfer matrix method has been used for simulating the SPPPs propagating in the system, which are electrically tuned to interact with the vibrational resonances of the analytes. Furthermore, the analysis of the sensor response with a coupled oscillators model has proven its capability of fingerprinting ultrathin biolayers, even when the interaction is too weak to induce a Fano interference pattern, with a sensitivity down to the monolayer limit, as tested with a protein bilayer or a peptide monolayer. The proposed device paves the way for the development of advanced SAW-assisted lab-on-chip systems combining the existing SAW-mediated physical sensing and microfluidic functionalities with the chemical fingerprinting capability of this novel SAW-driven plasmonic approach.

Vibrational control and resonance of a nonlinear tilted cantilever beam under multi-harmonic low and high-frequency excitations

This paper investigates the vibrational resonance and control of the response of a nonlinear tilted cantilever beam under combined multi-harmonic low and non-resonant, high-frequency excitations. The basic system considers the first mode of vibration of a nonlinear tilted beam under parametric and direct base excitation with the frequency components locked in 2:1 ratio. Such a system is susceptible to parametric amplification of resonance, which may be detrimental for structural health in many mechanical systems. The primary objective of the research is to investigate the non-trivial effects of non-resonant high-frequency excitation on parametric amplification, vibrational resonance and chaos in the system, which, to the best of the authors’ knowledge, is not reported previously in the literature. The slow dynamic equations of the system are obtained using the method of direct partition of motion (MDPM), which is then analysed using the harmonic balance method (HBM). It has been shown that the high-frequency base excitation considerably influences the effective damping and stiffness of the system under consideration. The results of the research demonstrate that high-frequency excitation can effectively control the parametric amplification by shifting the resonance curve in the frequency axis and eliminating undesirable bifurcations by increasing the effective damping. The phenomenon of vibrational resonance has been found for specific parameter values in the presence of high-frequency base excitation. Detail parametric studies are performed to reveal the system’s rich nonlinear dynamics and bifurcations, like multiple jumps in response, dual peaks, isolated resonance response (isola), loop formation in frequency response plot, etc. The numerical results reveal that high-frequency excitation transforms chaotic responses into regular periodic responses. Direct numerical simulations are performed in MATLAB SIMULINK to validate the analytical results.

Use of a Resonant Vibrator Positioned Perpendicularly to the Optical Axis of a Combustion Chamber for Amplification of the Electromagnetic Field in it

Use of a Resonant Vibrator Positioned Perpendicularly to the Optical Axis of a Combustion Chamber for Amplification of the Electromagnetic Field in it

Ultracompact single-nanowire-morphed grippers driven by vectorial Lorentz forces for dexterous robotic manipulations

Ultracompact and soft pairwise grippers, capable of swift large-amplitude multi-dimensional maneuvering, are widely needed for high-precision manipulation, assembly and treatment of microscale objects. In this work, we demonstrate the simplest construction of such robotic structures, shaped via a single-nanowire-morphing and powered by geometry-tailored Lorentz vectorial forces. This has been accomplished via a designable folding growth of ultralong and ultrathin silicon NWs into single and nested omega-ring structures, which can then be suspended upon electrode frames and coated with silver metal layer to carry a passing current along geometry-tailored pathway. Within a magnetic field, the grippers can be driven by the Lorentz forces to demonstrate swift large-amplitude maneuvers of grasping, flapping and twisting of microscale objects, as well as high-frequency or even resonant vibrations to overcome sticky van de Waals forces in microscale for a reliable releasing of carried payloads. More sophisticated and functional teamwork of mutual alignment, precise passing and selective light-emitting-diode unit testing and installation were also successfully accomplished via pairwise gripper collaborations. This single-nanowire-morphing strategy provides an ideal platform to rapidly design, construct and prototype a wide range of advanced ultracompact nanorobotic, mechanical sensing and biological manipulation functionalities.

Radial–axial feeding process design for large-scale flat ring by quantitative estimation of ring roundness error

Due to the large size and thin wall characteristics, the large-scale ring is prone to plastic instability, resulting in loss of ring roundness. An analytical calculation model of roundness error is proposed to design the feeding process. This model is established by analytically deriving the relationships between feeding process, ring geometry, contact arc length, rolling force, ring vibration angle, ring bending angle, contact arc length increment and ring roundness error at different rolling stages. Compared with numerical calculation and production trial, the analytical model can predict the roundness error with reasonable accuracy and high efficiency and guide feeding process design.

Adaptive linear quadratic regulator for optimal structural control based on wavelet transform and genetic algorithm

PurposeIn real life, excitations are highly non-stationary in frequency and amplitude, which easily induces resonant vibration to structural responses. Conventional control algorithms in this case cannot guarantee cost-effective control effort and efficient structural response alleviation. To this end, this paper proposes a novel adaptive linear quadratic regulator (LQR) by integrating wavelet transform and genetic algorithm (GA).Design/methodology/approachIn each time interval, multiresolution analysis of real-time structural responses returns filtered time signals dominated by different frequency bands. Minimization of cost function in each frequency band obtains control law and gain matrix that depend on temporal-frequency band, so suppressing resonance-induced filtered response signal can be directly achieved by regulating gain matrix in the temporal-frequency band, leading to emphasizing cost-function weights on control and state. To efficiently subdivide gain matrices in resonant and normal frequency bands, the cost-function weights are optimized by a developed procedure associated to genetic algorithm. Single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) structures subjected to near- and far-fault ground motions are studied.FindingsResonant band requires a larger control force than non-resonant band to decay resonance-induced peak responses. The time-varying cost-function weights generate control force more cost-effective than time-invariant ones. The scheme outperforms existing control algorithms and attains the trade-off between response suppression and control force under non-stationary excitations.Originality/valueProposed control law allocates control force amounts depending upon resonant or non-resonant band in each time interval. Cost-function weights and wavelet decomposition level are formulated in an elegant manner. Genetic algorithm-based optimization cost-efficiently results in minimizing structural responses.

Vibration Resonance Spectrometry (VRS) for the Advanced Streaming Detection of Rotor Unbalance

Determination of the diagnosis thresholds is crucial for the fault diagnosis of industry assets. Rotor machines under different working conditions are especially challenging because of the dynamic torque and speed. In this paper, an advanced machine learning based signal-processing innovation termed the multivariate state estimation technique is proposed to improve the accuracy of the diagnosis thresholds. A novel preprocessing technique called vibration resonance spectrometry is also applied to achieve a low computation cost capability for real-time condition monitoring. The monitoring system that utilizes the above methods is then applied for prognostics of a fan model as an example. Different levels of radial unbalance were added on the fan and tested, and then compared with the health state. The results show that the proposed methodology can detect the unbalance with a good accuracy and low computation cost. The proposed methodology can be applied for complex engineering assets for better predictive monitoring that could be processed with on-premise edge devices, or eventually a cloud platform due to its capacity for loss-less dimension reduction.

STUDY OF VACUUM HIGH-GRADIENT BREAKDOWNS FROM THE ION-MODIFIED SURFACE OF COPPER ELECTRODES

The influence on the resistance to high-voltage breakdown of samples irradiated with double-charged copper ions Cu2+ with an energy of 300 keV and different irradiation doses was studied. It is experimentally shown that when irradiating a copper electrode with Cu2+ ions, the values of breakdown characteristics improve by 17…28% with increasing irradiation dose. A theoretical study of the effect of material defects such as pores on the emission current was carried out. It is shown that the field emission current from the metal surface near nano-objects has a vibrational resonance feature. The resonance condition is determined by the depth of the nanoscale void from the metal surface. If the resonance conditions are not met or if the size of the defects increases, the emission current decreases rapidly.

Vibrational resonance in a damped and two-frequency driven system of particle on a rotating parabola

Vibrational resonance in a damped and two-frequency driven system of particle on a rotating parabola

On the flexural in-plane vibrations of a thin circular ring made from an elastic solid with cubic crystalline symmetry

We present a rigorous analysis of the in-plane flexural vibrations of a thin circular ring, made from anisotropic material with cubic symmetry (e.g. single-crystalline silicon). We do not make any assumptions on the mode shapes of vibration, but rather derive them as part of the solution. Rings in which the cross-section has a finite radius of gyration (i.e. with a finite radial thickness) are considered. In our analysis we present an analytic proof of the degeneracy of odd-ordered modes. The results are compared with previous studies and numerical simulations.