Control of Longitudinal Wave Propagation in Conical Periodic Structures

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.

Download Full-text

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

Applied Sciences ◽

10.3390/app11167257 ◽

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.

Download Full-text

Active Control of Periodic Structures

10.1115/imece2000-1734 ◽

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.

Download Full-text

Periodic Struts for Gearbox Support System

Journal of Vibration and Control ◽

10.1177/1077546305052784 ◽

2005 ◽

Vol 11 (6) ◽

pp. 709-721 ◽

Cited By ~ 16

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.

Download Full-text

Active Control of Periodic Structures

Journal of Vibration and Acoustics ◽

10.1115/1.1399052 ◽

2001 ◽

Vol 123 (4) ◽

pp. 472-479 ◽

Cited By ~ 83

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.

Download Full-text