9402802 Kawiecki The objective of this project is to develop an approach to control torsional and torsional-bending vibrations in structural elements. This problem will be solved using two methods. One of the methods is based on a concept of generating torsional, bending and axial control loads using the extension/compression action of piezoceramic elements distributed over the structural element. The other method is based on a concept of improving the damping characteristics of a structure by using a piezofilm to modify the distribution of shear strain in a viscoelastic layer bonded to a structure. The project involves experimental and numerical investigations. The experimental research will be performed with three different specimentss: (1) a composite beam with an embedded set of piezoelements designed to generate torsional and bending control loads, (2) a thin walled aluminum beam with a set of piezoelements laminated to the walls, and (3) a thin-walled aluminum beam with a set of ACLD elements laminated to its walls. In the analytical work, a finite element code capable of modeling the dynamics of the beams will be developed. The research plan is formulated to allow the correlation of the results obtained at each step to code development with the results obtained at each corresponding step of the experimental investigation. In the control experiments, the piezoelements bonded to the beams will be driven by a simple analog control system based on proportional and derivative control gains. The attenuation effectiveness of torsional bending vibrations will be tested. Eventually, the same system will be used to control finite element models. The degree of correlation with real system behavior will allow the evaluation of the accuracy of the numerical model. ***
