Date of Award

2003

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Senthil S. Vel

Second Committee Member

Donald A. Grant

Third Committee Member

Vincent Caccese

Abstract

Active vibration damping using piezoelectric materials integrated with structural systems has found widespread use in engineering applications. Current vibration suppression systems usually consist of piezoelectric extension actuators bonded to the surface or embedded within the structure. The use of piezoelectric shear actuators/sensors has been proposed as an alternative, where the electric field is applied perpendicular to the direction of polarization to cause shear deformation of the material. We present an exact analysis and active vibration suppression of laminated composite plates and cylindrical shells with embedded piezoelectric shear actuators and sensors. Suitable displacement and electric potential fknctions are utilized to identically satisfy the boundary conditions at the simply supported edges. A solution to the resulting set of coupled ordinary differential equations is obtained by using either a power series or Frobenius series. The natural frequencies, mode shapes and through-thickness profiles of displacements, potential and stresses are presented for several lamination schemes. Active vibration suppression is implemented with positive position feedback (PPF) and velocity feedback. Frequency response curves with various controller frequencies, controller damping ratios and scalar gains demonstrate that an embedded shear actuator can be utilized to actively damp the fundamental mode of vibration. In addition, it is shown that suppression of the thickness modes is feasible using a piezoelectric shear actuator. An experimental and finite element investigation of the active vibration suppression of a sandwich cantilever beam using piezoelectric shear actuators is also performed. The beam is constructed with aluminum facings, foam core and two piezoelectric shear actuators. The finite element analyses are performed using the commercial finite element package ABAQUSIStandard 6.3- 1. It is shown experimentally for the first time that piezoelectric shear actuators can be utilized for active vibration suppression. There are significant reductions in beam tip acceleration amplitudes and settling time as a result of the positive position feedback and strain-rate feedback. The finite element shows good comparison with the experimental results.

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