Engineering Commons^™

The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman

Theses and Dissertations

As part of a joint AFRL/DAGSI turbine blade research effort, a computer program has been developed that uses a von Karman large-deflection two-dimensional finite element approximation to determine stress levels and patterns in isotropic thin plates. The dynamic loading of various plates has been carried out in order to model a high cycle fatigue situation. The research considered the various effects of mode shapes, resident frequency, non-linear cyclic effect, endurance limits, and stress variations within a high cycle fatigue environment. Two main initiatives were taken. First, a transient analysis tool was developed that calculates stress and displacement patterns over a …

The Use Of Systems Engineering Processes And Tools To Develop A System Dynamic Simulation Model Of Engineering Support During The Development Phase Of An Acquisition Program, Jason E. Bartolomei

Theses and Dissertations

Due to the increase of system complexity and the existing draw down of manpower allocations, today's acquisitions environment desperately needs a systems approach to decision making. Many studies have been performed to model the entire government acquisition environment. Due to the high degree of aggregation, front line decision-makers have had no use for the information these models provide. This research focuses on the Air Force's largest functional support element in aircraft systems development, engineering. I will only consider one phase of the government acquisition cycle the Engineering, Manufacturing, and Development (EMD). This is the development cycle, which begins with initial …

Environmental Disturbance Modeling For Large Inflatable Space Structures, Donald J. Davis

Theses and Dissertations

Tightening space budgets and stagnating spacelift capabilities are driving the Air Force and other space agencies to focus on inflatable technology as a reliable, inexpensive means of deploying large structures in orbit. Recent improvements in rigidization techniques make the use these inflatable structures feasible for a growing number of missions. For many of these missions, the primary design requirement is dimensional accuracy of the structure. Finite element analysis offers a means of predicting structural behavior in orbit. The analysis requires knowledge of external loads. This thesis examines the environmental disturbances which act upon large, orbiting structures. Calculations are made on …

Vibration Suppression Of A Rotationally Periodic Structure Using An Adaptive/Ppf Control Law, Mark J. Keller

Theses and Dissertations

For a compressor disk, effective vibration suppression requires broadband control, and the elimination of inter-blade coupling forces. Previous researchers achieved this using an active/passive piezoelectric shunt network. Unfortunately, optimal tuning of the shunt requires prior knowledge of the coupling strength, which is not well defined. This thesis uses an adaptive parameter estimator to eliminate the inter-blade coupling forces. In addition, the passive shunt is replaced with an analogous positive position feedback method. The resulting control law was used on a simulated four and eight bladed system. While substantial reductions in system response were achieved for the Adaptive/PPF control technique, the …

Proactive Rideshare Opportunity Brokering Services (Probs), Robert J. Twiggs, Brian Horais, Charles Byvik

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professors Bob Twiggs, Brian Horais, and Charles Byvik titled "Proactive Rideshare Opportunity Brokering Services (PROBS) presented at the 2001 IEEE Aerospace Conference on February 26, 2001.

Spacecraft Program, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Spacecraft Program" from January 8, 2001.

Antarctic 2000: An Expedition To Prepare For Mars Missions, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Antarctic 2000: An Expedition to Prepare for Mars Missions" from January 7, 2001.

Low-Latitude Auroras: The Magnetic Storm Of 14–15 May 1921, S. M. Silverman, E. W. Cliver

United States Air Force: Publications

We review solar/geophysical data relating to the great magnetic storm of 14–15 May 1921, with emphasis on observations of the low-latitude visual aurora. From the reports we have gathered for this event, the lowest geomagnetic latitude of de6nite overhead aurora (coronal form) was 40° and the lowest geomagnetic latitude from which auroras were observed on the poleward horizon in the northern hemisphere was 30°. For comparison, corresponding overhead/low-latitude values of 48°/32° and 41°/20° were reported for the great auroras on 28–29 August and 1–2 September 1859, respectively. However, for the 1921 event, there is a report of aurora from Apia, …

Cd-Rom Nutrient Analysis Database Assists Self-Monitering Behavior Of Active Duty Air Force Personnel Receiving Nutrient Counseling For Weight Loss, Jane E. Heetderks-Cox, Betty B. Alford, Carolyn M. Bednar, Cynthia J. Heiss, Lisa A. Tauai, Kimberly K. Edgren

United States Air Force: Publications

This study observed the effect of using a computerized vs. a manual method of self-monitoring among Air Force personnel receiving nutrition counseling for weight loss.

U.S. Air Force Long-Range Strike Aircraft White Paper, United States Air Force

United States Air Force: Publications

As a result of DoD transformation plans and recent operational experience (Air War Over Serbia and Operation ENDURING FREEDOM) portions of the 1999 U.S. Air Force White Paper on Long Range Bombers have become outmoded. In October 2001, the Secretary of the Air Force directed an updated Long-range Strike Aircraft White Paper incorporating our new defense planning guidance. This document provides an update to the 1999 White Paper and reflects current decisions concerning bomber force structure and basing. While modification plans remain largely intact, the focus has been refined to support the Global Strike Task Force concept.

Lab Fattening And Non-Invasive Estimates Of Body Composition In Deer Mice, Edward T. Unangst, Michael J. Blair, Matthew W. Granger, David W. Hale

United States Air Force: Publications

Total body electrical conductivity measurements and lipid composition were determined for the deer mouse (Peromyscus maniculatus) to derive species specific calibration equations for use with EM-SCAN estimates of lean and fat tissue. For each individual, total body electrical conductivity was measured by EM-SCAN, and actual lipid content was determined by chemical extraction. Then, using estimated and actual lipid values, separate calibration equations were generated for freshly captured (lean) and laboratory maintained (fat) individuals, and a combined equation was derived for all individuals. These equations were variable in the accuracy of lipid estimates; the lowest relative error estimate (percent …

Market Assessment Of Forward-Looking Turbulence Sensing Systems, Paul Kauffmann, Andres Sousa-Poza

Engineering Management & Systems Engineering Faculty Publications

[Executive Summary] This study examined the feasibility of the next generation of forward sensing turbulence systems for the Part 121 market segment: Enhanced X band radar, LIDAR, and a product that combines these first two technologies. Highlights of the findings include:

• On an annual basis, Part 121 carriers experience at least 567.8 turbulence related injury events that result in 687 minor flight attendant injuries, 38.4 serious flight attendant injuries, 119.5 minor passenger injuries, and 17.1 serious passenger injuries.
• The expected cost of turbulence injuries to airlines is $164,286 for a serious flight attendant injury, $25,000 for a minor flight attendant …

Multi -Mission Attitude Determination System For Balloon Flight, Liping Mo

Doctoral Dissertations

MADS (Multi-mission Attitude Determination System) is a new software package used to determine the attitude of instruments on a high-altitude balloon employed for scientific experiments. There is no existing system for the automated determination of the attitude of instruments in balloon experiments, so we have developed MADS to do the data analysis for balloon experiments to find the location of astrophysical sources such as gamma-ray or x-ray sources.

The two areas that required most work were modeling star trackers and modeling the motion of the balloon. Star trackers are used on satellites, but are far too expensive and sophisticated to …

Robust State Dependent Riccati Equation Based Guidance Laws, S. N. Balakrishnan, Ming Xin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A robust state dependent Riccati equation based guidance/control is investigated in this study. In order to have a better design tool in terms of required interceptor accelerations, the target intercept geometry is formulated in a set of polar coordinates. With this formulation, we formulate a cost function with state dependent weights. In this study, we investigate the effects of such cost functions on the levels of interceptor accelerations. We also synthesize a neural network based extra controller to achieve the robustness in the presence of the target acceleration. In this manner, we will not need target acceleration estimation explicitly in …

An Optimal Control Based Treatment Strategy For Parturient Paresis Using Neural Networks, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An optimal online feedback treatment strategy is developed for the parturient paresis of cows, based on nonlinear optimal control theory. A limitation in the development of an existing mathematical model for calcium homeostasis is addressed and the model is extended to incorporate control inputs. An optimal feedback controller is synthesized for the nonlinear system using neural networks. Though the main aim of this paper is to solve the biomedical control problem, the methodology presented in this paper is a general computational tool, which can be applied to solve a fairly general class nonlinear optimal control problems.

Robust State Dependent Riccati Equation Based Robot Manipulator Control, Ming Xin, S. N. Balakrishnan, Zhongwu Huang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a new optimal control approach to robust control of robot manipulators in the framework of state dependent Riccati equation (SDRE) technique. To treat this highly nonlinear control system, we formulate it as a nonlinear optimal regulator problem. SDRE technique was used to synthesize an optimal controller to this class of robot control problem. We also synthesize a neural network based extra controller to achieve the robustness in the presence of the parameter uncertainties. A typical two-link robot position control problem was studied to show the effectiveness of SDRE approach and robust extra control design to robotic application.

Re-Examination Of The Crypto-Steady Pressure-Exchanger (Virtual Turbomachine), T. Scott, David W. Riggins

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A crypto-steady pressure-exchanger (rotating center body ejecting fluid in a supersonic flow field) is investigated based on fundamental fluid dynamic principles. The results are then compared to computational fluid dynamic (CFD) simulations of a simplified device. On the basis of this comparison the device studied is correctly classified as an unsteady ejector instead of a type of turbomachinery. Entropy gains (total pressure losses) associated with the complex fluid-fluid and fluid-center body interactions are shown to be greater than total pressure gains due to work addition. Compared to a steady ejector, the virtual turbomachine shows increased entrainment (mixing) of the main …

A Numerical Study Of Automotive Gas Tank Filler Pipe Two Phase Flow, R. Banerjee, Kakkattukuzhy M. Isaac, L. Oliver, W. Breig

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Automotive refueling is gaining greater importance because fuel vapors released during refueling are believed to increase ozone levels in urban areas. As a step towards On-Board Refueling Vapor Recovery (ORVR) designs, vapor generation and transport during refueling needs to be understood to develop recovery techniques. The objective of the present study is to understand the fluid flow inside the automotive gas tank filler pipe using commercially available Computational Fluid Dynamics (CFD) software. This effort is expected to yield detailed flow field information, including air entrainment. The phenomena of well-back, the process of fuel flooding the filler pipe and flowing backwards …

Finite Element Analysis And Active Control For Nonlinear Flutter Of Composite Panels Under Yawed Supersonic Flow, Khaled Abdel-Motagaly

Mechanical & Aerospace Engineering Theses & Dissertations

A coupled structural-electrical modal finite element formulation for composite panels with integrated piezoelectric sensors and actuators is presented for nonlinear panel flutter suppression under yawed supersonic flow. The first-order shear deformation theory for laminated composite plates, the von Karman nonlinear strain-displacement relations for large deflection response, the linear piezoelectricity constitutive relations, and the first-order piston theory of aerodynamics are employed. Nonlinear equations of motion are derived using the three-node triangular MIN3 plate element. Additional electrical degrees of freedom are introduced to model piezoelectric sensors and actuators. The system equations of motion are transformed and reduced to a set of nonlinear …

An Integrated Risk Analysis Methodology In A Multidisciplinary Design Environment, Katrina R. Hampton

Engineering Management & Systems Engineering Theses & Dissertations

Design of complex, one-of-a-kind systems, such as space transportation systems, is characterized by high uncertainty and, consequently, high risk. It is necessary to account for these uncertainties in the design process to produce systems that are more reliable. Systems designed by including uncertainties and managing them, as well, are more robust and less prone to poor operations as a result of parameter variability.

The quantification, analysis and mitigation of uncertainties are challenging tasks as many systems lack historical data. In such an environment, risk or uncertainty quantification becomes subjective because input data is based on professional judgment. Additionally, there are …

Nonlinear Response And Fatigue Estimation Of Surface Panels To White And Non-White Gaussian Random Excitations, Jean-Michel Dhainaut

Mechanical & Aerospace Engineering Theses & Dissertations

In stochastic structural dynamics, the majority of analyses have dealt with linear structures under stationary, Gaussian, and band-limited white noise excitations. Although these simplifying assumptions may be justified, in many processes experimental data have shown quite frequently the non-stationary and non-Gaussian characteristics of the loads. An efficient finite element modal formulation has recently been developed to extend the analysis to nonlinear structural responses. Laminated plate theory and von Karman large displacement relations are used to derive the nonlinear equations of motion for an arbitrarily laminated composite panel subjected to combined acoustic and thermal loads. The nonlinear equations of motion in …

Collegiate Aviation Research And Education Solutions To Critical Safety Issues, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 2001-5

This document contains four papers concerning collegiate aviation research and education solutions to critical safety issues. “Panel Proposal Titled Collegiate Aviation Research and Education Solutions to Critical Safety Issues for the Tim Forte Collegiate Aviation Safety Symposium” (Brent Bowen) presents proposals for panels on the following topics: geographic north versus magnetic north to provide enhanced national airspace system safety; weather safety training for general aviation pilots through computer flight simulation; identification of human behavior and aircraft maintenance safety issues; disaster preparedness, emergency response, and curriculum development; the collegiate aviation emergency response checklist; and systemic initiatives in aviation …

Fatigue Assessment Of Traffic Signal Mast Arms Based On Field Test Data Under Natural Wind Gusts, Genda Chen, Jingning Wu, Jiaqing Yu, Lokeswarappa R. Dharani, Michael G. Barker

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In recent years, several states including Missouri, Wyoming, California, and Texas experienced fracture failures of traffic signal mast arms. Almost all the failures are associated with the propagation of defects or cracks. It is therefore imperative to evaluate existing mast arms using a simple yet accurate procedure. A statistical methodology is proposed to predict the fatigue life of signal mast arm structures on the basis of field-measured strain data. The annual occurrence of various stress levels is determined using the historical wind speed data in the vicinity of a mast arm structure and the strain readings of the structure under …

Robust Adaptive Critic Based Neurocontrollers For Missiles With Model Uncertainties, Zhongwu Huang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Lyapunov theory-based controller is proposed in this paper for robustness against model uncertainties in the control of a missile. The controller design consists of two parts; in the first phase, an optimal nonlinear controller is designed with neural networks for tracking. This is based on the adaptive critic method that consists of one neural network called the supervisor or critic and a second network called an action network or a controller. Each network is trained through the output of the other network and equations related to optimal control. When their outputs are mutually consistent, the controller network output is …

Amplitude Modulated Droplet Formation In High Precision Solder Droplet Printing, Qingbin Liu, M. Orme, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There are many methods used at present to apply solder to wafers, ceramics, laminate and flex circuit boards, and other substrates. Among these, high-precision solder droplet printing technology, which is noncontact, data driven, flexible and environmentally friendly, is a key enabling technology. This technology selectively deposits solder droplets only where required, and therefore needs no mask or secondary resist removal, uses materials more efficiently and creates less waste than other methods. Currently, continuous droplet formation from capillary streams is mainly achieved by application of the well-known Rayleigh instability in which a sinusoidal disturbance is applied to the stream, resulting in …

Adaptive Critic Based Neuro-Observer, Xin Liu, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A new Neural Network (NN) based observer design method for nonlinear systems represented by nonlinear dynamics and linear/nonlinear measurement is proposed in this paper. In this new approach, as the first step, the observer design problem is changed into a "controller" design problem by establishing the error dynamics, and then the Adaptive Critic (AC) based approach is applied on this error dynamics to design a 'controller', such that the errors are driven to zero. The resulting observer has inherent robustness from the AC based design approach. Some simulations are presented to illustrate the effectiveness of this approach.

Cubesat: The Development And Launch Support Infrastructure For Eighteen Different Satellite Customers On One Launch, Robert J. Twiggs, Jordi Puig-Suari, Clark Turner

Robert "Bob" Twiggs STEM Education Collection

An article written by Professors Bob Twiggs, Jordi Puig-Suari, and Clark Turner titled "CubeSat:  The Development and Launch Support Infrastructure for Eighteen Different Satellite Customers on One Launch" and published in 2001.

Bioexplorer Bus‐Low Cost Approach, Robert J. Twiggs, Seiji Kuroki

Robert "Bob" Twiggs STEM Education Collection

An article titled "BioExplorer Bus‐Low Cost Approach" by Professor Bob Twiggs and Seiji Kuroki from 200.

Proactive Rideshare Opportunity Brokering Services (Probs) For Secondary Payloads, Robert J. Twiggs, Brian Horais, Chuck Byvik

Robert "Bob" Twiggs STEM Education Collection

An article written by Bob Twiggs, Brian Horias, and Byvik titled "Proactive Rideshare Opportunity Brokering Services (PROBS) for Secondary Payloads" and published in 2001.

Detection And Classification Of Impact-Induced Damage In Composite Plates Using Neural Networks, Rohit Dua, Steve Eugene Watkins, Donald C. Wunsch, K. Chandrashekhara, Farhad Akhavan

Electrical and Computer Engineering Faculty Research & Creative Works

Artificial neutral networks (ANN) can be used as an online health monitoring systems (involving damage assessment, fatigue monitoring and delamination detection) for composite structures owing to their inherent fast computing speeds, parallel processing and ability to learn and adapt to the experimental data. The amount of impact-induced strain on a composite structure can be found using strain sensors attached to composite structures. Prior work has shown that strain-based ANN can characterize impact energy on composite plates and that strain signatures can be associated with damage types and severity. This paper reports the extension of this approach for damage classification using …