Engineering Commons^™

Composite Structure Ultimate Strength Prediction From Acoustic Emission Amplitude Data, James Lewis Walker Ii

Master's Theses - Daytona Beach

The acoustic emission (AE) given off by a structure as it is stressed provides a passive means to characterize flaw growth activity in complex structures. This thesis demonstrates how the qualitative analysis of AE data can be refined to provide a quantitative tool for predicting the ultimate strength of composite tensile test specimens. From an original sample set of only six specimens, a multivariate statistical analysis was used to generate an ultimate strength prediction equation. The variables of the multivariate statistical analysis were obtained through the mathematical modeling of the specimen’s AE amplitude distributions produced during proof testing. Ultimate strengths …

Integrated Control Of Thermally Distorted Large Space Antennas, Robert H. Tolson

Mechanical & Aerospace Engineering Theses & Dissertations

Studies on controlling the thermal distortion of large space antennae have generally investigated a single orbital position and have optimized actuator locations based on minimizing the RMS surface deviation from the original parabolic shape. One study showed the benefits of directly using far zone electric field characteristics as the performance measure; but, this approach resulted in a nonlinear programming problem. The objective of the current study is to develop an approach to designing a control system that (1) recognizes the time dependence of the distortion and (2) controls variables that are directly related to far field performance in a quadratic …

The Development And Application Of A Trapezoidal Shear Panel For Use In Finite Element Codes, Glenn P. Greiner

Master's Theses - Daytona Beach

This thesis documents the efforts of the writer and his colleagues over the past several years to improve the theoretical foundation of the arbitrary quadrilateral shear panel used in structural analysis codes to model aircraft structures. An equilibrium stress-based element with pure shear resultants on its sides was developed using the principle of complementary virtual work. The internal stress field was derived from a complete polynomial Airy stress function. The element was numerically tested as a pure stress element and a hybrid element to assess the deflection properties for highly distorted planar panels. Linear-stress and quadratic-displacement rods were used, as …

Navier-Stokes Simulations Of Flows About Complex Configurations Using Domain Decomposition Techniques, Kamran Fouladi-Semnani

Mechanical & Aerospace Engineering Theses & Dissertations

An algorithm is developed to obtain numerical simulations of flows about complex configurations composed of multiple and nonsimilar components with arbitrary geometries. The algorithm uses a hybridization of the domain decomposition techniques for grid generation and to reduce the computer memory requirement. Three dimensional, Reynolds-averaged, unsteady, compressible, and complete Navier-Stokes equations are solved on each of the subdomains by a fully-vectorized, finite-volume, upwind-biased, approximately-factored, and multigrid method. The effect of Reynolds stresses is incorporated through an algebraic turbulence model with several modifications for interference flows. The present algorithm combines the advantages of an efficient, geometrically conservative, minimally and automatically dissipative …

Control And Mechanism Interaction For Ground-Based Testing Of Space Structures, Li-Farn Yang

Mechanical & Aerospace Engineering Theses & Dissertations

In the ground-based validation testing, the adverse effect of terrestrial conditions such as a gravitational force interferes with the dynamic behavior of space structures. A suspension system is developed to assess the structural characteristics in a simulated zero-gravity environment. Using a mechanisms approach, the synthesis of a noncircular disk with a torsional spring at its rotational axis is designed to counteract the gravitational force of test structures during the testing.

The multibody dynamics of a flexible steel beam carried on a rigid trolley has been investigated. The system is constructed in such a way that the rapid and large-angle slewing …

An Experimental Study Of An Axisymmetric Turbulent Boundary Layer Disturbed By A Periodic Freestream, Chithrabhanu Koodalattupuram

Mechanical & Aerospace Engineering Theses & Dissertations

Behavior of an axisymmetric equilibrium turbulent boundary layer disturbed by a propeller wake in the freestream was investigated experimentally. Tests were conducted in a low speed wind tunnel and measurements of turbulence quantities were made using an X wire probe and a constant temperature anemometer. The boundary layer flow on a cylindrical body was characterized by measuring its gross parameters and comparing them with classical values. Propeller speed was measured using an electronic circuit whose output signal was also used to trigger hot wire probe. Gross boundary later characteristics of the disturbed boundary layer did not deviate appreciably from the …

An Extension Of Essentially Non-Oscillatory Shock-Capturing Schemes To Multi-Dimensional Systems Of Conservation Laws, Jay Casper

Mathematics & Statistics Theses & Dissertations

In recent years, a class of numerical schemes for solving hyperbolic partial differential equations has been developed which generalizes the first-order method of Godunov to arbitrary order of accuracy. High-order accuracy is obtained, wherever the solution is smooth, by an essentially non-oscillatory (ENO) piecewise polynomial reconstruction procedure, which yields high-order pointwise information from the cell averages of the solution at a given point in time. When applied to piecewise smooth initial data, this reconstruction enables a flux computation that provides a time update of the solution which is of high-order accuracy, wherever the function is smooth, and avoids a Gibbs …