Dunn, Stanley E.

An energy method is presented for predicting the natural frequencies,
radiation loss factor and system loss factor of simply supported
rectangular plates under fluid loading. Both bare plates and plates
with complete damping treatments are considered. Results obtained
using the method developed are compared with two other theories.
The agreement is generally good. The study points out the need for
detailed analyses of plate vibration patterns and their associated
radiation output under various plate boundary conditions. There also
exists a need for carefully conducted experimental work to verify
the applicability of the current theory.

Steel reinforced concrete specimens of loaded and unloaded
configuration were placed in contact with seawater in a state of
accelerated corrosion. They were simultaneously monitored for acoustic
emission and the results were analyzed in an evaluation of the use of
acoustic emission as a nondestructive monitor of corrosion induced
cracking. It was shown that, in a laboratory environment, counts and
amplitude information are sensitive indicators of the levels of
cracking within the concrete specimen; and thereby the degree of
corrosion damage may be inferred. Analytical models applicable to the
representation of acoustic emission amplitude distribution are
discussed also.

Limited development of buoyancy powered underwater vehicles has occurred with little analysis of the efficiency of this form of propulsion. A nondimensional method of analysis of the propulsion efficiency of these vehicles has been developed. A dimensional analysis was conducted by applying the nondimensional propulsion efficiency to the analysis of vehicles with various hull and wing sizes. Propulsion efficiencies of 70% to 75% were found to be obtainable with existing wing designs. A prototype was designed and built using the relationships between actual hull and wing size obtained from the dimensional analysis. This prototype was tested at sea to determine the accuracy of the prediction of performance of an underwater glider. These tests showed that the method of buoyancy propulsion is both predictable and reliable when applied to an underwater glider.

The parameters underlying the design of an Inertial Navigation System (INS) for an Autonomous Underwater Vehicle (AUV) are studied. The strapdown approach for this design is discussed. The performance of a mathematical model of an INS is investigated using a simulation program developed for this purpose. An algorithm is outlined for investigating the accuracy of the computed position of an AUV as compared to the actual or expected position. The results of the simulation program developed using the above mentioned algorithm are presented in a graphical form. The Ring Laser Gyro (RLG), a recent development in the field of inertial sensor technology, is studied with reference to possible use in an INS for an AUV.

This project addresses the simulation, control and optimization of underwater vehicle performance. An analytical model of underwater vehicle motion has been developed. This model is based on a set of six degree of freedom nonlinear differential equations of motion. These equations incorporate inertial, hydrodynamic, hydrostatic, gravity and thruster forces to define the vehicle's motion. The forces are calculated and the equations of motion solved using a finite difference method of integration. An automatic closed loop control strategy has been developed and integrated into the motion model. The controller determines control plane deflection and thruster output based on sensor provided input, maneuver request and control gain constants. The motion model simulates the effects of these controller requests on the vehicle motion. The controller effects are analyzed and an optimal set of control gains is determined. These optimal gains are determined based on a quantitative comparison of a pre-defined Performance Index (PI) function. The PI is a function of critical performance values, i.e., energy consumption, and user defined weighted constants. By employing an iteration technique the PI is minimized to provide an optimal set of control gains.

The energy flow and the acoustic radiation of fluid-loaded
panels are investigated using the Energy Accountancy
Concept. The various energy components of the systems are
defined and studied. Each component is a function of the
excitation, the structure, the medium and their coupling.
An energy balance equation is written for the system. This
method is applied to study the acoustic radiation from a
point-excited clamped plate placed on the free surface of a
water tank. The radiation efficiency of the plate is
measured and compared to previous works. The energy
balance equation gives very good results at frequencies
between 50 Hz and 12 kHz. An undefined source of energy
dissipation is observed in one experiment. The results of
this study have shown that the Energy Accountancy Concept
can be used to describe the energy flow in a vibrating
structure under water-loading.

The Energy Accountancy method is used to describe the
response of a system by accounting for the various energy
components in a system, that is components describing the
input energy, the energy dissipated, and the energy
transfered by the system. These components are functions of
quantities that can be determined either through measurement
or finite element analysis of the system. This concept is
used in this study to determine the response of a small
diameter pipe containing two different fluids, air and
water. The results of this study have shown that the Snergy
Accountancy method can be used to describe the response of a
thin walled shell structure with good results. It has also
been shown in this study that in small diameter pipes the
fluid contained by the system can be considered to act as a
reactive medium in the response of the structure.

The acoustic emission (AE) testing reported herein was
conducted on a large size prestressed concrete slab placed
in contact with sea water in a state of electrically induced
accelerated corrosion. AE signals were monitored and
successfully analyzed in an attempt to evaluate the severity
of the deformation process in the concrete as a result of
the corrosion induced cracking. Several features of the AE
data which were sensitive to the process were plotted to
show the different levels of the cracking due to the
corrosion. These were amplitude, counts and energy
distributions, and event distribution with time. A location
test was employed to find the source of the activities. The
results of the amplitude distributions were found to have
similar characteristics to those obtained from the
reinforced concrete AE experiments performed at Florida
Atlantic University (1,2). These tests can be easily
applied to a field location for an early detection of the
deformation process in the concrete structures.

Measured values of attenuation with distance, amplitude distribution,
and propagation velocity of acoustic emissions associated with
embedded metcil corrosion induced cracking in a concrete slab are
presented. An extensive review of acoustic emission signal processing
techniques and theoretical background material is also included.
The study points out how attenuation and propagation velocity of the
acoustic emission signal affects various signal processing techniques
and verifies an amplitude distribution spreading rrodel. The need
for further defirlition of attentuation values caused by fluid loading
of the concrete surface is also discussed.

A method of analysis addressing the problem of predicting the performance
of beams with viscoelastic damping layer coating of varying degrees of
coverage undergoing free vibrations is presented. Results based on this
analysis and using mechanical properties of selected materials are generated
for five different boundary conditions. The analytical results
are verified experimentally for the case of a clamped-free beam. Also
the main hypotheses employed in the theoretical approach are verified.
Finally, an analysis of the results leads to a discussion of the dynamic
properties of coated beams.