Vibrational Energy Flow Research Articles

Energy transfer and vibration suppression of laminated composite plates coupled with a line hinge

This study investigates the vibration energy flow transmission behavior of laminated composite plate structures coupled with a line hinge. The time-averaged vibration energy transfer is determined using the substructure-based power flow analysis (SPFA) method. The effects of the fiber orientation, boundary conditions and the position of the coupling hinge on the vibration transmission path and its level are examined. It is demonstrated that the fiber orientations can be used to modify substantially the power flow transmission path and locations of energy sinks. Enhancement of vibration suppression of the coupled structure can be achieved by tailor designing the fiber angles.

Influence of a Methyl Group on the Unidirectional Flow of Vibrational Energy in an Adenine-Thymine Base Pair.

The role of a methyl group in intramolecular vibrational energy redistribution (IVR) of the hydrogen-bonded adenine-thymine base pair has been studied using classical dynamics procedures. Energy transferred to the doorway bond thymine-NH from the vibrationally excited H2O(v) efficiently redistributes among various bonds of the base pair through vibration-to-vibration coupling, depositing a large fraction of the available energy in the terminal bond adenine-NH. On the other hand, the extent of energy flow in the reverse direction from the excited adenine-NH to thymine-NH is insignificant, indicating IVR in adenine-thymine resulting from the intermolecular interaction with a vibrationally excited H2O molecule, is direction-specific. The unidirectional flow is due to the coupling of stretch-torsion vibrations of a methyl group with conjugated bonds on the thymine ring, when the methyl rotor is present and is adjacent to the vibrationally excited thymine-NH. The insignificance of energy flow from the terminal-to-terminal bond in the reverse direction is attributed to the absence of a methyl group on the adenine moiety, even though the molecule has many CC and CN bonds coupled to their neighbors.

Time-resolved spectroscopic mapping of vibrational energy flow in proteins: Understanding thermal diffusion at the nanoscale.

Vibrational energy exchange between various degrees of freedom is critical to barrier-crossing processes in proteins. Hemeproteins are well suited for studying vibrational energy exchange in proteins because the heme group is an efficient photothermal converter. The released energy by heme following photoexcitation shows migration in a protein moiety on a picosecond timescale, which is observed using time-resolved ultraviolet resonance Raman spectroscopy. The anti-Stokes ultraviolet resonance Raman intensity of a tryptophan residue is an excellent probe for the vibrational energy in proteins, allowing the mapping of energy flow with the spatial resolution of a single amino acid residue. This Perspective provides an overview of studies on vibrational energy flow in proteins, including future perspectives for both methodologies and applications.

Vibration energy flow of main drive system of hot tandem mill

We analyzed the power flow of the vibration transmission of the F2 mill drive system coupled with complex beams using the substructure method. The system was divided into three cylindrical substructures, which were coupled to each other by three spring-dampers. The modal analysis of the substructures was conducted to describe their dynamic characteristics; subsequently, the substructure receiving function under free interface conditions was established. The dynamic characteristics of the transmission coupling system were calculated by synthesizing the force balance conditions and geometric coordination at the coupling interface. The input energy and transmission energy in the system were effectively evaluated. The effects of spring-damper stiffness change, excitation position, and loss factor on the transmission of vibration power flow were studied and verified by field experiments. This study provides an effective theoretical basis for vibration suppression measures for hot tandem rolling mills.

Generalized Resonance Energy Transfer Theory: Applications to Vibrational Energy Flow in Optical Cavities.

A general rate theory for resonance energy transfer (gRET) is formulated to incorporate any degrees of freedom (e.g., rotation, vibration, exciton, and polariton) as well as coherently coupled composite donor or acceptor states. The compact rate expression allows us to establish useful relationships: (i) detailed balance condition when the donor and acceptor are at the same temperature; (ii) proportionality to the product of dipole correlation tensors, which is not necessarily equivalent to spectral overlap; (iii) scaling with the effective coherent size, i.e., the number of coherently coupled molecules or modes; (iv) decomposition of collective rate in homogeneous systems into the monomer and coherence contributions such that the ratio of the two defines the quantum enhancement factor F; (v) spatial and orientational dependences as derived from the interaction potential. For the special case of exciton transfer, the general rate formalism reduces to FRET or its multichromophoric extension. When applied to cavity-assisted vibrational energy transfer between molecules or within a molecule, the general rate expression provides an intuitive explanation of intriguing phenomena such as cooperativity, resonance, and nonlinearity in the collective vibrational strong coupling (VSC) regime, as demonstrated in recent simulations. The relevance of gRET to cavity-catalyzed reactions and intramolecular vibrational redistribution is discussed and will lead to further theoretical developments.

Vibration suppression and energy flow tailoring of coupled metal and composite plates with curvilinear fibers

This study investigates the vibration transmission in coupled metal and composite plates with curvilinear fibers from the power flow viewpoint. The time-averaged power flow variables are obtained using a substructure method to assess the levels of vibration transmission of coupled structures with various configurations and fiber angles. It is demonstrated that by adopting tailored curvilinear fiber designs, the vibration transmission through the coupling edge of the plates can be effectively suppressed. Variable fiber angle designs are shown to exert significant effects on the dominant-excited mode and can be exploited to achieve desirable energy transmission paths for low-vibration transmission and effective suppression.

Identifying dominant components of vibrational energy flow in U-rib plates of bridge based on structural intensity

Stiffened U-rib plates are the elementary components of steel box girders in bridges that directly bear the input external energy before transferring it to other components. Research on the dynamic characteristics of stiffened U-rib plates is the basis for examining vibration and noise in steel box girders. Most relevant studies have focused on the vibrational modes and single-frequency responses in this context, and few researchers have sought to optimize the design of stiffened U-rib plates to reduce responses due to vibrations and noise. This study identifies the global and local laws of vibrational transmission in stiffened U-rib plates subjected to harmonic loads through structural intensity (SI) analysis that is carried out by jointly using standard finite element software and a post-processing code created by the authors. The contributions of each component of vibrational waves are represented to reflect the dominant roles of the bending wave in the baseplate and the in-plane wave in the U-ribs, respectively. The effects of parameters of the U-rib plates on SI are also quantitatively investigated. SI analysis can be used as a new criterion for designing and optimizing bridges as well as formulating measures for vibration reduction.

Vibration transmission and energy flow analysis of variable stiffness laminated composite plates

This study investigates the vibration transmission and energy flow tailoring of variable stiffness laminated composite (VSLC) plates with curvilinear fibres subjected to harmonic excitation. The free vibration characteristics of VSLC plates are firstly studied. The steady-state dynamic responses are then obtained based on the first-order shear deformation theory. The effects of variable angle fibres on the time-averaged input power and kinetic energy of the plate are examined using the power flow analysis approach. The time-averaged power flow density vector is used to determine the primary energy transmission paths, which are shown to depend on the dominant mode excited by the applied force. Curvilinear fibre designs are found to have a significant influence on the main energy flow transmission paths and vibration level. For enhanced vibration suppression, the fibre angles can be tailored to modify the vibration transmission paths according to a specific excitation.

Monitoring abnormal vibration and structural health conditions of an in-service structure from its SHM data

Vortex-induced vibration occurred recently in several important engineering structures in China. Very large mono-frequency periodic vibration was noted. This study reports on the analysis of recorded data from the structural health monitoring (SHM) system of a suspension bridge with the aim to develop some indicators that may be useful to evaluate if there is any abnormal vibration or change of health conditions of a structure in future. The power spectrum of measured acceleration responses is plotted in three-dimensions of time, frequency and power. Acceleration responses from 16 sensors on the target bridge deck in 233 days are analyzed. The evolution of different dynamic parameters in the period encompassing the occurrences of large vortex-induced vibration are reported. The changes in these parameters are identified to be closely associated with some temporary installations on the deck and temporary measures for vibration suppression. The changes in vibration power at different natural frequencies of the structure can be used to demonstrate the evolution of the unexpected event. The trend and abrupt changes of natural frequencies and modal components show the flow of vibration energy between different vibration modes. In addition to the intuitive three-dimension power spectral plot, two state vectors are also developed from the power spectrum. The identification of abnormal vibration and structural state can then be carried out automatically with the novelty detection method and a threshold. The analysis of the SHM acceleration responses of the bridge deck demonstrates the implementation procedure and the effectiveness of the proposed method.

Energy Flow Analysis of High-Frequency Flexural Vibration of Wedge Beam Structures

Wedge members with variable thickness are widely used in ship structures, aerospace structures, and building structures. Considering their application scenarios, their high-frequency vibration characteristics have important research value. Energy finite element analysis (EFEA) is a powerful tool to predict high-frequency vibration response. EFEA is essentially applying finite element analysis to solve the energy density governing equation. However, the equation for wedge beam is missing. Energy flow analysis aims to obtain energy density governing equation. The energy flow model of wedge beam with variable thickness is established in this paper. Firstly, according to the geometric acoustic approximation method, the general displacement solution of the bending deformation equation for a wedge beam is deduced. Furthermore, the wave dispersion relation of bending deformation of wedge beam is derived. Then, the relationship between the time-averaged vibration energy density and energy flow of the wedge beam is also derived. Also, the governing equation taking energy density as a variable of the wedge beam structure is derived through the energy balance relationship in the microelement body. The governing equation is numerically solved, and the energy density distribution on the wedge beam structure is calculated. Finally, the energy density distribution of uniform beam and wedge beam under the same excitation is analyzed and summarized; the influence of different excitation frequencies and power exponent of thickness change on the performance of wedge beam structure is also summarized. Geometrically, the wedge beam satisfies the one-dimensional acoustic black hole structure. The calculation results show that the energy density on the beam structure increases with the decrease of thickness and reaches its maximum near the tip. The wedge acoustic black hole beam structure has a good energy absorption effect with a frequency between 250 Hz and 2000 Hz. With the further increase of excitation frequency, the energy absorption effect of the wedge beam structure has dropped significantly.

High suitability of tryptophan residues as a spectroscopic thermometer for local temperature in proteins under nonequilibrium conditions.

Vibrational energy flow in the many degrees of freedom in proteins governs energy-barrier-crossing processes, such as conformational exchanges and thermal reactions. The intensity of anti-Stokes Raman bands arises from vibrationally excited populations and can thus function as a selective probe for the excess energy. Time-resolved observations of the anti-Stokes ultraviolet resonance Raman (UVRR) intensity of amino acid residues provide information about the flow of excess energy in proteins, with the spatial resolution of an amino acid residue. The answer to the question of whether the extent of vibrational excitation in any given vibrational modes reflects the extent of excitation in the whole molecule under nonequilibrium conditions is not straightforward. Here, we calculated the occupation probabilities of vibrational states for model compounds of amino acids under equilibrium and nonequilibrium conditions. At a given temperature, the occupation probability of the model compound of tryptophan under nonequilibrium conditions was nearly identical to that under equilibrium conditions at high temperature. Thus, the anti-Stokes band intensities of Trp residues in the nonequilibrium condition indicate the temperature of the molecules with equivalent energy in the equilibrium condition. In addition, we showed that the temperatures calculated on the basis of two UVRR bands of tryptophan in a time-resolved spectrum agreed with each other within the experimental uncertainty. The present results demonstrate that anti-Stokes UVRR bands of Trp residues serve as an excellent spectroscopic thermometer for determining the local temperature in proteins under nonequilibrium conditions.

Basic Study on Technique for Design Requirement of Vehicle Body frame Characteristics Based on Vibration Energy Flow Analysis

Basic Study on Technique for Design Requirement of Vehicle Body frame Characteristics Based on Vibration Energy Flow Analysis

Vibration energy flow transmission in systems with Coulomb friction

This study focusses on the vibration transmission and energy flow characteristics of low dimensional models of dynamical systems with Coulomb friction. The Karnopp friction model and smooth Coulomb friction models are employed to estimate the dry friction force. The steady-state responses of the system are determined by the harmonic balance (HB) approximations with numerical continuations and a time-marching method. The level of vibration transmission and energy dissipation within the system are assessed by the force transmissibility and power flow variables. For a single degree-of-freedom oscillator system, in the low- and high-frequency ranges away from the resonance, it is found that the dry frictional contact can suppress the vibration response and effectively dissipate vibrational energy. For the coupled system, the existence of frictional contact at the interface can lead to a significant growth in the force transmissibility and energy transfer from the force-excited subsystem to the secondary system, especially at the high excitation frequencies. The interfacial frictional contact can also result in a large amount of energy dissipation at the interface. The studies show that vibration transmission and energy dissipation in a dynamic system with contacting subsystems can be tailored by adjusting the properties of the frictional contact. Design strategies can be developed using frictional contacts for vibration suppression by minimizing vibration energy transmission or maximizing energy dissipation.

Enhancing Vibration Isolation Performance by Exploiting Novel Spring-Bar Mechanism

This study investigates the use of a spring-bar mechanism (SBM) in a vibration suppression system to improve its performance. The SBM, comprising bars and springs, is configured with a conventional linear spring-damper isolator unit. The dynamic response, force transmissibility, and vibration energy flow behaviour are studied to evaluate the vibration suppression performance of the integrated system. It is found that the SBM can introduce hardening, softening stiffness, or double-well potential characteristics to the system. By tuning the SBM parameters, constant negative stiffness is achieved so that the natural frequency of the overall system is reduced for enhanced low-frequency vibration isolation. It is also found that the proposed design yields a wider effective isolation range compared to the conventional spring-damper isolator and a previously proposed isolator with a negative stiffness mechanism. The frequency response relation of the force-excited system is derived using the averaging method and elliptical functions. It is also found that the system can exhibit chaotic motions, for which the associated time-averaged power is found to tend to an asymptotic value as the averaging time increases. It is shown that the time-averaged power flow variables can be used as uniform performance indices of nonlinear vibration isolators exhibiting periodic or chaotic motions. It is shown that the SBM can assist in reducing force transmission and input power, thereby expanding the frequency range of vibration attenuations.

Vibration transmission and energy flow analysis of L-shaped laminated composite structure based on a substructure method

This study investigates the vibration power flow characteristics of a harmonically excited L-shaped laminated composite structure with flat sub-plates connected at a right angle. A substructure-based power flow analysis (SPFA) method is developed based on analytical, numerical, and hybrid approaches of determining the receptance functions of sub-plates and by using the force balance and geometrical compatibility conditions at the coupling edge. The SPFA methods are then used to evaluate the vibration energy input into the structure and energy transmission through the coupling edge. The power flow density vector is defined, and its time-averaged value is used to clearly illustrate the energy sources and sinks as well as the energy transmission paths within the sub-plates. The influence of different combinations of fibre orientations for the sub-plates and the excited dominant global modes of the joined structure on the major vibration energy transfer paths are investigated. It is found that the fibre orientation can have significant effects on transmission paths and potential positions of sinks. From the vibration energy flow perspective, the fibre angles of the integrated laminated composite structure can be tailored for desirable energy transmission paths.

Design and analysis of motion and energy regulating vibration harvester

In this paper a novel design of energy harvester has been proposed, which converts harmonic or random vibrations energy into useful electric power. The energy harvester comprises of mechanical motion rectifier, motion regulator, strain energy storage element and a rotary electric generator. The mechanical motion rectifier comprises of a spatial mechanism with unidirectional bearings and spherical joint that converts the linear oscillating force into unidirectional torque pulses. Further, motion regulating mechanism directs the energy flow to the strain energy storage element and drives the electric generator. The arrangement ensures that flow of vibration energy is regulated such that it is stored in the spring up to a threshold limit and thereafter dissipated to the electric generator. Rigid body simulations in Adams and Matlab have been used in design and analysis of the energy harvester with investigations for the effect of significant design parameters. Experimentation on a prototype has been performed to validate the numerical model which delivered 4.13 W of peak power and average power of 0.12–0.52 W within frequency range of 1–15 Hz. Simulation results on a real size device with higher torsion spring stiffness indicates that the harvester can operate with 69.8% efficiency and deliver 0.32–2.45 W of average power for frequency of 0.5–4 Hz.

Vibrational energy flow cancelling by loading a reverse excitation: Visualization and analysis

Vibration control is a permanent and significant issue in all forms of structural dynamic analysis with the consistent objective being to minimize vibration levels. Considering that the propagation of vibration waves is essentially the transmission of vibrational energy flow (VEF), the fundamental requirement, therefore, is to minimize the VEF transmitted from sources to sinks and then to control and block the flow of vibration energy. Structural intensity (SI) method, combining forces with velocities to assess the magnitude and directions of VEF, is alternative to classical dynamic assessment methods offering insight into the transmission of VEF and studying additional phenomena which cannot be obtained by conventional dynamic analysis. In the field of noise, active noise control has been widely used in vehicles and headphones, which has achieved remarkable results by introducing a cancelling ‘anti-noise’ wave through an appropriate array of secondary sources. Analogically, it is considered whether the vibration of the structure can be attenuated by introducing a secondary reverse excitation (SRE) to offset the VEF transmitted in the structure. Therefore, this article combines the SI method and SRE to carry out related research on this issue. The rectangular plate with the circular hole subjected to the transient sinusoidal force, being widely used and found in various engineering branches, is taken as the research object. The developed simulation system consisting of the finite element tool and the in-house program is used to assess and visualize the instantaneous SI fields. The effects of the SRE acting on this structure on the transmission behaviours of VEF and the vibration suppression have been investigated in detail. Moreover, the transmission, conversion and balance relationships of the VEF have been derived from the general equation of motion and analysed as well. This study sheds new light on the vibration attenuation by introducing the secondary source from the perspective of VEF.

Corrected Statistical Energy Analysis Model in a Non-Reverberant Acoustic Space

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. This study investigates the application of the corrected SEA model in a non-reverberant acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the classical SEA model assumption is based on. A corrected SEA model is proposed where the direct field component in the energy is removed and the power injected in the subsystem considers only the remaining power after the loss at first reflection. Measurement was conducted in a box divided into two rooms separated by a partition with an opening where the condition of reverberant and non-reverberant can conveniently be controlled. In the case of a non-reverberant space where acoustic material was installed inside the wall of the experimental box, the signals are corrected by eliminating the direct field component in the measured impulse response. Using the corrected SEA model, comparison of the coupling loss factor (CLF) and damping loss factor (DLF) with the theory shows good agreement.

Influences of the temperature rise on the vibration energy flow in a dissipative elastic metamaterial plate based on the structural intensity approach

The effects of the temperature rise on the vibration energy flow in a dissipative elastic metamaterial plate with a nonlinear membrane strain are investigated based on the structural intensity approach using the finite element method. The thermal field is assumed to be uniform throughout the entire metamaterial plate with local resonances and constituent viscoelastic materials. The dissipative plate elements are considered because analysis of the vibration energy flow is shown to depend on the loss factor. The stiffness matrix of the plate element can be regarded as a function of the temperature rise. In the numerical calculation, the band gaps of the finite metamaterial plate agree well with the band structures, which verifies the effectiveness of the method. The Influences of the temperature rise and mechanical load on the vibration energy flow path are analyzed. For a given mechanical load, the magnitude of the vibration energy flow increases with the increase in the temperature rise. The vibration energy flow magnitude increases with increasing mechanical load for a given temperature rise. Additionally, the divergence of the vibration energy flow is calculated to localize the energy sources and sinks, which validates the effectiveness of the streamline representation technique. It is also observed that the vibration energy flow direction can be controlled by the temperature rise provided that the temperature rise is sufficiently large, and the direction can be controlled by the mechanical load provided that the mechanical load is sufficiently large. Therefore, a temperature rise region (TRR) can be found in which the temperature rise plays a more important role in controlling the direction of the vibration energy flow than the mechanical load.

RETRACTED: Reliability Evaluation of Engineering Anti-Vibration Force Based on Wireless Sensor

Rotating machinery usually has the function of shockproof. This shockproof function is mainly achieved by reducing the power signal of the vibration source to the receiver. But in some simulation experiments, it is not easy to determine the energy properties by direct measurement. In general, vibration energy and dynamic flow should be combined to evaluate the shock resistance of rotating machinery. This method is to reduce the energy generated by resisting the vibration of the electric sensor. Then the first frequency and the second harmonic frequency method are used to calculate the vibration energy per unit time, and then the vibration power is calculated. In addition, an experimental simulation device is set up to simulate the shock-proof function of the rotating machine. Under multiple motions, the first frequency method is used to calculate the generated energy flow, and the vibration rate is calculated.