Accepted Manuscripts

Toshihiko Asami
J. Vib. Acoust   doi: 10.1115/1.4038108
This paper considers the optimal design of double-mass dynamic vibration absorbers (DVAs) attached to an undamped single-degree-of-freedom system. Three different optimization criteria, the Hinf optimization, H2 optimization, and stability maximization criteria, were considered for the design of the DVAs, and a performance index was defined for each of these criteria. First, the analytical models of vibratory systems with double-mass DVAs were considered, and seven dimensionless parameters were defined. Five of these parameters must be optimized to minimize or maximize the performance indices. Assuming that all dimensionless parameters are nonnegative, the optimal value of one parameter for a double-mass DVA arranged in series (series-type DVA) was proven to be zero. The optimal adjustment conditions of the other four parameters were derived as simple algebraic formulae for the H2 and stability criteria and numerically determined for the Hinf criterion. For a double-mass DVA arranged in parallel (parallel-type DVA), all five parameters were found to have nonzero optimal values, and these values were obtained numerically by solving simultaneous algebraic equations. Second, the performance of these DVAs was compared with a single-mass DVA. The result revealed that for all optimization criteria, the performance of the series-type DVA is the best among the three DVAs and that of the single-mass DVA is the worst. Finally, a procedure for deriving the algebraic or numerical solutions for H2 optimization is described. The derivation procedure of other optimal solutions will be introduced in the future paper.
TOPICS: Acoustics, Design, Vibration, Vibration absorbers, Optimization, Algebra, Stability
Christopher G. Cooley and Tan Chai
J. Vib. Acoust   doi: 10.1115/1.4038106
This study investigates the vibration of and power harvested by typical electromagnetic and piezoelectric vibration energy harvesters when applied to vibrating host systems that rotate at constant speed. The governing equations for these electromechanically coupled devices are derived using Newtonian mechanics and Kirchhoff's voltage law. The natural frequency for these devices is speed-dependent due to the centripetal acceleration from their constant rotation. Resonance diagrams are used to identify excitation frequencies and speeds where these energy harvesters have large amplitude vibration and power harvested. Closed-form solutions are derived for the steady state response and power harvested. These devices have multifrequency dynamic response due to the combined vibration and rotation of the host system. Multiple resonances are possible. The average power harvested over one oscillation cycle is calculated for a wide range of operating conditions. Electromagnetic devices have a local maximum in average harvested power that occurs near a specific excitation frequency and rotation speed. Piezoelectric devices, depending on their mechanical damping, can have two local maxima of average power harvested. Although these maxima are sensitive to small changes in the excitation frequency, they are much less sensitive to small changes in rotation speed.
TOPICS: Vibration, Energy harvesting, Rotation, Excitation, Resonance, Kirchhoff's circuit laws, Damping, Classical mechanics, Oscillations, Steady state, Cycles, Dynamic response
Jihad E. ALQASIMI and Hassen M. OUAKAD
J. Vib. Acoust   doi: 10.1115/1.4038107
This paper focus on the influence of sudden drop tests on the nonlinear structural behavior of electrically actuated bi-table shallow Micro-Electro-Mechanical-Systems (MEMS) arches. The assumed structure consist of an initially bell-shaped doubly clamped microbeam with a rectangular cross-section. The Euler-Bernoulli beam theory is assumed to model the nonlinear structural behavior of the bi-stable system under the combined effect of both the DC actuating load and the shaking waves. Moreover, the structural model takes into account both geometric mid-plane stretching and electric actuation nonlinear terms. A multi-modes Galerkin based decomposition is used to discretize the beam equations to extract a reduced-order model (ROM). The convergence of the ROM simulations are first verified and furthermore compared to published experimental data. A thorough ROM parametric study showed that the effect of increasing the shallow arch initial rise alter drastically the system behavior from undergoing a uninterrupted snap-through motion to a sudden snap-through instability. Moreover, the arch rise relationship with its shock spectrum response is investigated and it was concluded that as increasing the rise value can cause the system to collapse under the combined DC and shock wave loadings if the shock wave duration is lower or near the system fundamental natural period. All the presented graphs in this investigation represent some robust numerical approaches and design tools to help MEMS designers in improving both the reliability and efficiency of these bi-stable based micro-devices under shaking dynamic environments.
TOPICS: Stress, Shock (Mechanics), Microbeams, Microelectromechanical systems, Arches, Shock waves, Euler-Bernoulli beam theory, Reliability, Simulation, Waves, Design, Engineering simulation, Collapse
Wander Gustavo Rocha Vieira, Fred Nitzsche and Carlos De Marqui, Jr.
J. Vib. Acoust   doi: 10.1115/1.4038034
In recent decades, semi-active control strategies have been investigated for vibration reduction. In general, these techniques provide enhanced control performance when compared to traditional passive techniques and lower energy consumption if compared to active control techniques. In semi-active concepts, vibration attenuation is achieved by modulating inertial, stiffness or damping properties of a dynamic system. The Smart Spring is a mechanical device originally employed for the effective modulation of its stiffness through the use of semi-active control strategies. This device has been successfully tested to damp aeroelastic oscillations of fixed and rotary wings. In this paper, the modeling of the Smart Spring mechanism is presented and two semi-active control algorithms are employed to promote vibration reduction through enhanced damping effects. The first control technique is the Smart-Spring Resetting, which resembles resetting control techniques developed for vibration reduction of civil structures as well as the piezoelectric synchronized switch damping on short technique. The second control algorithm is referred as the Smart-Spring Inversion, which presents some similarities with the synchronized switch damping on inductor technique previously presented in the literature is electromechanically coupled systems. The effects of the Smart-Spring Resetting and Smart-Spring Inversion control algorithm on the free and forced responses of the Smart-Spring are investigated in time and frequency domains. An energy flow analysis is also presented in order to explain the enhanced damping behavior of the Smart Spring when the Smart-Spring Inversion control algorithm is employed.
TOPICS: Damping, Springs, Control algorithms, Vibration, Stiffness, Switches, Wings, Dynamic systems, Modeling, Oscillations, Flow (Dynamics), Inductors, Energy consumption
Qunlin Zhang, Yijun Mao and Datong Qi
J. Vib. Acoust   doi: 10.1115/1.4038035
An analytical model is developed to investigate the vibro-acoustic response of a double-walled cylindrical shell with the inner wall perforated when excited by the external turbulent boundary layer pressure fluctuations. The shell motion is governed by the Donnell's thin shell theory, and the mean particle velocity model is employed to describe the boundary condition between the micro-perforated shell and fluid media. Numerical results indicate that the transmission loss for the configuration of micro-perforating the inner wall could be larger than that for the conventional solid double-walled cylindrical shell with and without the core of porous material over a wide frequency range. Comparison between transmission loss results with excitations from the turbulent boundary layer and the acoustic diffuse field shows that with the thought of micro-perforating the inner shell, to reduce the acoustical excitation will be of more importance than the flow excitation over the ring frequency for a quiet interior space. Parametric studies illustrate that the perforation ratio is the main factor affecting the sound insulation performance through the total reactance.
TOPICS: Pressure, Fluctuations (Physics), Modeling, Pipes, Boundary layer turbulence, Acoustics, Shells, Excitation, Thin shells, Impedance (Electricity), Acoustical materials, Boundary-value problems, Flow (Dynamics), Fluids, Porous materials, Particulate matter
Xining Zhang, Xu Liu and Huan Zhao
J. Vib. Acoust   doi: 10.1115/1.4037955
Grinding is a vital method in machining techniques and an effective way to process materials such as hardened steels and silicon wafers. However, as the running time increases, the unbalance of grinding wheels produce a severe vibration and noise of grinding machines because of the uneven shedding of abrasive particles and the uneven adsorption of coolant, which has a severe and direct impact on the accuracy and quality of parts. Online balancing is an important and necessary technique to reduce the unbalance causing by these factors and adjust the time-varying balance condition of the grinding wheel. A new active online balancing method using liquid injection and free dripping is proposed in this paper. The proposed online balancing method possesses a continuous balancing ability and the problem of losing balancing ability for the active online balancing method using liquid injection is solved effectively because some chambers are full of liquid. The residual liquid contained in the balancing chambers is utilized as a compensation mass for reducing rotor unbalance, where the rotor phase is proposed herein as a target for determining the machine unbalance. A new balancing device with a controllable injection and free dripping structure is successfully designed. The relationship between the mass of liquid in the balancing chamber and the centrifugal force produced by liquid is identified. The performance of the proposed method is verified by the balancing experiments and the results of these experiments show that the vibration of unbalance response is reduced by 87.3% at 2700 r/min.
TOPICS: Grinding wheels, Rotors, Vibration, Martensitic steel, Noise (Sound), Machinery, Machining, Particulate matter, Centrifugal force, Grinding equipment, Semiconductor wafers, Grinding, Coolants
David Griese, Joshua D. Summers and Lonny Thompson
J. Vib. Acoust   doi: 10.1115/1.4029043
This work defines a finite element model to study the sound transmission properties of aluminium honeycomb sandwich panels. Honeycomb cellular metamaterial structures offer many distinct advantages over homogenous materials because their effective material properties depend on both their constituent material properties and their geometric cell configuration. From this, a wide range of targeted effective material properties can be achieved thus supporting forward design by tailoring the honeycomb cellular materials for specific applications. One area that has not been fully explored is the set of acoustic properties of honeycomb materials and how these can offer increased acoustic design flexibility. Understanding these relations, the designer can effectively tune designs to perform better in specific acoustic applications. One such example is the insulation of target sound frequencies to prevent sound transmission through a panel. This work explores how certain geometric and effective structural properties of in-plane honeycomb cores in sandwich panels affect the sound pressure transmission loss properties of the panel. The two acoustic responses of interest in this work are the general level of sound transmission loss of the panel and the location of the resonance frequencies that exhibit high levels of sound transmission, or low sound pressure transmission loss. Constant mass honeycomb core models are studied with internal cell angles ranging from -45° to +45°. It is shown in this work that models with lower core internal cell angles, under constant mass constraints, have more resonances in the 1-1000 Hz range, but exhibit a higher sound pressure transmission loss between resonant frequencies.
TOPICS: Sound, Honeycomb structures, Geometry, Acoustics, Materials properties, Sound pressure, Resonance, Design, Finite element model, Insulation, Metamaterials, Aluminum, Mechanical properties, Acoustical properties

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