Periodic Struts for Gearbox Support System

2005 ◽  
Vol 11 (6) ◽  
pp. 709-721 ◽  
Author(s):  
S. Asiri ◽  
A. Baz ◽  
D. Pines
Keyword(s):  
Wave Propagation ◽  
Critical Frequency ◽  
Periodic Structures ◽  
Design Parameters ◽  
Force Transmission ◽  
Frequency Bands ◽  
New Class ◽  
Spatial Domains ◽  
Specific Frequency ◽  
Vibration And Sound Radiation

Passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called “pass bands” and wave propagation is completely blocked within other frequency bands called “stop bands”. In this paper, the emphasis is placed on developing a new class of these periodic structures called passive periodic struts, which can be used to support gearbox systems on the airframes of helicopters. When designed properly, the passive periodic strut can stop the propagation of vibration from the gearbox to the airframe within critical frequency bands, consequently minimizing the effects of transmission of undesirable vibration and sound radiation to the helicopter cabin. The theory governing the operation of this class of passive periodic struts is introduced and their filtering characteristics are demonstrated experimentally as a function of their design parameters. The presented concept of the passive periodic strut can be easily used in many applications to control the wave propagation and the force transmission in both the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.

scholarly journals Broadband Vibration Attenuation Using Hybrid Periodic Rods

2008 ◽  
Vol 5 (1) ◽  
pp. 7 ◽  
Author(s):  
S. Asiri
Keyword(s):  
Wave Propagation ◽  
Spectral Width ◽  
Design Parameters ◽  
Vibration Source ◽  
Vibration Isolator ◽  
Force Transmission ◽  
Frequency Bands ◽  
Spatial Domains ◽  
Specific Frequency ◽  
Vibration And Sound Radiation

This paper presents both theoretically and experimentally a new kind of a broadband vibration isolator. It is a table-like system formed by four parallel hybrid periodic rods connected between two plates. The rods consist of an assembly of periodic cells, each cell being composed of a short rod and piezoelectric inserts. By actively controlling the piezoelectric elements, it is shown that the periodic rods can efficiently attenuate the propagation of vibration from the upper plate to the lower one within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation. In such a system, longitudinal waves can propagate from the vibration source in the upper plate to the lower one along the rods only within specific frequency bands called the "Pass Bands" and wave propagation is efficiently attenuated within other frequency bands called the "Stop Bands". The spectral width of these bands can be tuned according to the nature of the external excitation. The theory governing the operation of this class of vibration isolator is presented and their tunable filtering characteristics are demonstrated experimentally as functions of their design parameters. This concept can be employed in many applications to control the wave propagation and the force transmission of longitudinal vibrations both in the spectral and spatial domains in an attempt to stop/attenuate the propagation of undesirable disturbances. 

scholarly journals Tunable Mechanical Filter for Longitudinal Vibrations

2007 ◽  
Vol 14 (5) ◽  
pp. 377-391 ◽  
Author(s):  
S. Asiri
Keyword(s):  
Wave Propagation ◽  
Spectral Width ◽  
Design Parameters ◽  
Vibration Source ◽  
Vibration Isolator ◽  
Force Transmission ◽  
Longitudinal Vibrations ◽  
Frequency Bands ◽  
Mechanical Filter ◽  
Vibration And Sound Radiation

This paper presents both theoretically and experimentally a new kind of vibration isolator called tunable mechanical filter which consists of four parallel hybrid periodic rods connected between two plates. The rods consist of an assembly of periodic cells, each cell being composed of a short rod and piezoelectric inserts. By actively controlling the piezoelectric elements, it is shown that the periodic rods can efficiently attenuate the propagation of vibration from the upper plate to the lower one within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation. In such a filter, longitudinal waves can propagate from the vibration source in the upper plate to the lower one along the rods only within specific frequency bands called the “Pass Bands” and wave propagation is efficiently attenuated within other frequency bands called the “Stop Bands”. The spectral width of these bands can be tuned according to the nature of the external excitation. The theory governing the operation of this class of vibration isolator is presented and their tunable filtering characteristics are demonstrated experimentally as functions of their design parameters. The concept of this mechanical filter as presented can be employed in many applications to control the wave propagation and the force transmission of longitudinal vibrations both in the spectral and spatial domains in an attempt to stop/attenuate the propagation of undesirable disturbances.

Active Control of Periodic Structures

2000 ◽  
Author(s):  
A. Baz
Keyword(s):  
Wave Propagation ◽  
Active Control ◽  
Periodic Structures ◽  
Spectral Width ◽  
Structural Vibration ◽  
Frequency Bands ◽  
Spatial Domains ◽  
Specific Frequency ◽  
The Individual ◽  
Unique Potential

Abstract Conventional passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the “Pass Bands” and wave propagation is completely blocked within other frequency bands called the “Stop Bands”. In this paper, the emphasis is placed on providing the passive structures with active control capabilities in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration. Apart from their unique filtering characteristics, the ability of periodic structures to transmit waves, from one location to another, within the pass bands can be greatly reduced when the ideal periodicity is disrupted resulting in the well-known phenomenon of “Localization”. In the case of passive structures, the aperiodicity (or the disorder) can result from unintentional material, geometric and manufacturing variability. However, in the case of active periodic structures the aperiodicity is intentionally introduced by proper tuning of the controllers of the individual substructure or cell. The theory governing the operation of this class of Active Periodic structures is introduced and numerical examples are presented to illustrate their tunable filtering and localization characteristics. The examples considered include periodic/aperiodic spring-mass systems controlled by piezoelectric actuators. The presented results emphasize the unique potential of the active periodic structures in controlling the wave propagation both in the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.

Active Control of Periodic Structures

2001 ◽  
Vol 123 (4) ◽  
pp. 472-479 ◽  
Author(s):  
A. Baz
Keyword(s):  
Wave Propagation ◽  
Active Control ◽  
Periodic Structures ◽  
Spectral Width ◽  
Structural Vibration ◽  
Frequency Bands ◽  
Spatial Domains ◽  
Specific Frequency ◽  
The Individual ◽  
Unique Potential

Conventional passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the “Pass Bands” and wave propagation is completely blocked within other frequency bands called the “Stop Bands.” In this paper, the emphasis is placed on providing the passive structures with active control capabilities in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration. Apart from their unique filtering characteristics, the ability of periodic structures to transmit waves, from one location to another, within the pass bands can be greatly reduced when the ideal periodicity is disrupted resulting in the well-known phenomenon of “Localization.” In the case of passive structures, the aperiodicity (or the disorder) can result from unintentional material, geometric and manufacturing variability. However, in the case of active periodic structures the aperiodicity is intentionally introduced by proper tuning of the controllers of the individual substructure or cell. The theory governing the operation of this class of Active Periodic structures is introduced and numerical examples are presented to illustrate their tunable filtering and localization characteristics. The examples considered include periodic/aperiodic spring-mass systems controlled by piezoelectric actuators. The presented results emphasize the unique potential of the active periodic structures in controlling the wave propagation both in the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.

Localization and Control of Wave Propagation in Active Periodic Fluid-Loaded Shells

2001 ◽  
Author(s):  
M. Ruzzene ◽  
A. Baz
Keyword(s):  
Wave Propagation ◽  
Periodic Structures ◽  
Effective Means ◽  
Sound Radiation ◽  
Excitation Source ◽  
Proportional Control ◽  
Frequency Bands ◽  
Control Gain ◽  
Vibration And Sound Radiation ◽  
Attenuation Characteristics

Abstract Periodically placed actuators are used to control the wave propagation and to localize the vibration and sound radiation of fluid-loaded shells. The filtering capabilities of the resulting periodic structure can be actively tuned by modifying the feedback control gain of the actuators thus allowing for controlling the spectral width and location of the stop and pass bands as well as introducing controlled aperiodicity in the structure. A finite element model is developed to study the fundamental phenomena governing the coupling between the shell, actuators and the fluid domain surrounding the shell. The geometry of the shell and the fluid domain allows for the formulation of a harmonic-based model with uncoupled circumferential modes. The model is used to predict the pass and stop frequency bands for different proportional control gains and to evaluate the shell harmonic response and the sound radiation into the surrounding fluid. The obtained results indicate that the location and width of the stop bands as well as the attenuation characteristics of the shell can be modified by proper choice of the proportional control gain. Numerical simulations also demonstrate that the location of the stop bands can be identified from the frequency response function of the shell and from the sound intensity. The tunable characteristics of the proposed active shells allow for the introduction of controlled aperiodicty through proper adjustments of the actuators’ feedback gains. Disorder in periodic structures typically extends the stopbands into adjacent propagation zones and, more importantly, localizes the vibration energy near the excitation source. Both structural response and sound radiation are evaluated for increasing levels of aperiodicity. The results presented demonstrate the effectiveness of the proposed concept as an effective means for controlling the attenuation characteristics of fluid-loaded shells and for confining both vibration and sound radiation near the excitation source. Also, the presented analysis provides an invaluable means for designing fluid-loaded shells, which are quiet over desired frequency bands and where the energy can be spatially confined in well-defined restricted areas.

Control of Longitudinal Wave Propagation in Conical Periodic Structures

2004 ◽  
Vol 10 (12) ◽  
pp. 1795-1811 ◽  
Author(s):  
T. N. Tongele ◽  
T. Chen
Keyword(s):  
Wave Propagation ◽  
Longitudinal Wave ◽  
Periodic Structure ◽  
Periodic Structures ◽  
Single Cells ◽  
Frequency Bands ◽  
Active Devices ◽  
Theoretical Predictions ◽  
Longitudinal Wave Propagation ◽  
Specific Frequency

Conical periodic structure with single cells and multiple subcells is used to control longitudinal wave motion. It is well known that periodic structures by nature act as mechanical filters, allowing waves to propagate within specific frequency bands called pass bands, and blocking wave propagation within other frequency bands called stop bands. However, the conical geometry of cells and the use of conical subcells provide a conical periodic structure with the possibility of adjusting its impedance mismatch without the use of conventional active devices such as electromechanical, electrohydraulic, or piezoelectric actuators. The behavior of such a conical periodic structure is evaluated using single cells and cells with two, three, and four subcells. Theoretical predictions obtained by means of finite element modeling are compared with experimental results. Both experimental and theoretical results have converged in pointing to the effectiveness and the potential of using conical cells, and the concept of cells with subcells as tools for controlling longitudinal wave propagation in a periodic structure.

Passive Periodic Engine Mount

2008 ◽  
Author(s):  
Ling Zheng ◽  
Woojin Jung ◽  
Zheng Gu ◽  
A. Baz
Keyword(s):  
Spectral Width ◽  
Shear Mode ◽  
Effective Width ◽  
Frequency Bands ◽  
Automotive Engine ◽  
New Class ◽  
Mechanical Filter ◽  
Transfer Matrix Approach ◽  
Specific Frequency ◽  
Engine Mount

The transmission of automotive engine vibrations to the chassis is isolated using a new class of mounts which rely in their operation on optimally designed and periodically distributed viscoelastic inserts. The proposed mount acts as mechanical filter for impeding the propagation of vibration within specific frequency bands called the ‘Stop Bands’. The spectral width of these bands is enhanced by making the viscoelastic inserts operate in a shear mode rather than compression mode. The theory governing the operation of this class of periodic mounts is presented using the theory of finite elements combined with the transfer matrix approach. The predictions of the performance of the mount are validated against the predictions of the commercial finite element code ANSYS and against experimental results obtained from prototypes of plain and periodic mounts. The obtained results demonstrate the feasibility of the shear mode periodic mount as an effectiveness means for blocking the transmission of vibration over a broad frequency band. Extending the effective width of the operating frequency bands of this class of mount through active control means is the ultimate goal of this study.

Origami Metastructures for Tunable Wave Propagation

2016 ◽  
Author(s):  
M. Thota ◽  
S. Li ◽  
K. W. Wang
Keyword(s):  
Wave Propagation ◽  
Periodic Structures ◽  
Bravais Lattice ◽  
The Novel ◽  
Acoustic Wave Propagation ◽  
New Class ◽  
Wave Characteristics ◽  
Propagation Behavior ◽  
Numerical Studies ◽  
Wave Tailoring

Wave propagation inside a host media with periodically distributed inclusions can exhibit bandgaps. While controlling acoustic wave propagation has large impact on many engineering applications, studies on broadband acoustic bandgap (ABG) adaptation is still outstanding. One of the important properties of periodic structure in ABG design is the lattice-type. It is possible that by reconfiguring the periodic architectures between different lattice-types with fundamentally distinct dispersion relations, we may achieve broadband wave propagation tuning. In this spirit, this research pioneers a new class of reconfigurable periodic structures called origami metastructures (OM) that can achieve ABG adaption via topology reconfiguration by rigid-folding. It is found that origami folding, which can enable significant and precise topology reconfigurations between distinct Bravais lattice-types in underlying periodic architecture, can bring about drastic changes in wave propagation behavior. Such versatile wave transmission control is demonstrated via numerical studies that couple wave propagation theory with origami folding kinematics. Further, we also exploit the novel ABG adaptation feature of OM to design structures that can exhibit unique tunable non-reciprocal behavior. Overall the broadband adaptable wave characteristics of the OM coupled with scale independent rigid-folding mechanism can bring on-demand wave tailoring to a new level.

scholarly journals A Study of Longitudinal Waveguide with Band Gap Using Cylindrical and Conical Shape Periodic Structure

2021 ◽  
Vol 11 (16) ◽  
pp. 7257
Author(s):  
Dong Hyeon Oh ◽  
Gil Ho Yoon
Keyword(s):  
Wave Propagation ◽  
Longitudinal Wave ◽  
Wave Motion ◽  
Periodic Structures ◽  
Experimental Studies ◽  
Frequency Wave ◽  
Active Devices ◽  
Mechanical Filter ◽  
Specific Frequency ◽  
Mass Spring

This research presents the theoretical and experimental studies for cylindrical and conical periodic structures to control longitudinal wave motion. Many relevant researches exist to stop and pass a certain frequency wave without active devices with periodic structures called metamaterials. To modify or control longitudinal wave propagation, i.e., passing or blocking mechanical wave within specific frequency ranges, repeated mass-spring systems or metamaterials can be applied. By integrating a few identical structural components to form a whole structure, it is possible to make a mechanical filter for wave propagation. Most studies rely on straight bar with cylindrical structure. Thus, with a unit cell that have a cylindrical and conical structure, this research presents the extensions toward the studies of the wave motions for straight and curved bars with finite element simulations and experiment studies. The results show that the hybrid cylindrical and conical periodic structures can be effective in terms of wave motion control and stiffness.

Invariant Representation of Wave Propagation Properties for a Mono-Coupled Electro-Mechanical Periodic Structure

2016 ◽  
Author(s):  
Edoardo Belloni ◽  
Francesco Braghin ◽  
Gabriele Cazzulani ◽  
Mattia Cenedese
Keyword(s):  
Wave Propagation ◽  
Periodic Structure ◽  
Seismic Isolation ◽  
Periodic Structures ◽  
Design Parameters ◽  
Invariant Representation ◽  
Electric Circuits ◽  
Peculiar Characteristic ◽  
Potential Applications ◽  
Propagation Properties

During the last decades, a growing interest has been devoted to periodic structures and metamaterials. One of the most interesting characteristics of this class of materials is that they present a transmission gap for given frequency ranges. This peculiar characteristic has many potential applications: from optics to seismic isolation, from filtering to wave guiding. In literature, different approaches were developed to study such kind of structures. In this paper, using an approach based on transfer matrices of a single unit cell and its invariants, a way to represent in compact form the behavior of a mono-coupled periodic structure is presented. As a result, the wave propagation properties are shown as being dependent both on the frequency range and on some chosen design parameters. Furthermore, the adding of multiphysics materials (in the case of this paper piezoelectric inserts with dedicated electric circuits) inside the structure allows, through the tuning of both the mechanical and the electrical parameters, to actively control the bandgap position. This approach also allows checking the robustness of parameter choices with respect to desired bandgap frequency ranges. Finally, some applications of this method for active control of wave propagation are presented.

Sign in / Sign up

Export Citation Format

Share Document