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Flightlines, Vol. 8, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Effect Of Interfacial Mobility On Flexural Strength And Fracture Toughness Of Glass/Epoxy Laminates, T. W. H. Wang, Frank D. Blum, Lokeswarappa R. Dharani

Chemistry Faculty Research & Creative Works

Mechanical testing and surface fractography were used to characterize the fracture of E-glass fiber reinforced epoxy composites as a function of the silane coupling agent used. gamma-Aminopropyltriethoxysilane (APS) and delta-aminobutyltriethoxysilane (ABS) were used because these have been shown to have different interfacial mobilities at multilayer coverage. The values of the properties studied generally increased from untreated c, as determined from a Mode I translaminar fracture toughness tests, for the untreated composites (10.5 ± 0.4 kJ/m2) was lower than that for the ABS-treated composites (14.3 ± 2.1 kJ/m2) which was lower than that for the APS-treated composites (17.1 ± 2.4 kJ/m2). …

A Five-Year Development Plan For The California Aviation Database, H.-S. Jacob Tsao

Faculty Publications

The California Aviation Database (CAvD) project was suggested by Caltrans Aeronautics Program to fulfill a need of the planners involved in aviation system planning and programming activities to locate and access aviation data and information in an efficient and comprehensive way. CAvD is being implemented in the form of an Internet website and is currently intended as a five-year project. However, the development can be accelerated, and the duration will depend on the available resources. CAvD is a joint project between the National Center of Excellence for Aviation Operations Research (NEXTOR) and the California Department of Transportation (Caltrans). Its primary …

Mixed Mode Stable Crack Extensions Through Stiffened Specimens, Abdel-Hamid I. Mourad, Eltahry Elghandour, Faysal A. Kolkailah

Aerospace Engineering

This study presents an experimental investigation of fracture mechanics for isotropic material, aluminum alloy D16AT. The problem of stable crack growth (SCG) has been addressed in this paper. Experimental results are presented for symmetrically stiffened and unstiffened three point bend specimens subjected to different modes, mode I and mixed mode. The stiffeners are doubly bonded to the fatigue pre-cracked specimens parallel to the length at a certain distance behind the crack tip using an adhesive Redux 410 NA. Results concerning load displacement variation, growth of plastic zones, instantaneous crack edge profiles, and tunneling are presented. There is evidence that the …

Sensors Location Effect On The Dynamic Behaviour Of The Composite Structure With Flaw Detection, Eltahry Elghandour, Faysal Kolkailah, Abdel- Hamid I. Mourad

Aerospace Engineering

In this paper presents an experimental and numerical investigation ofthe natural frequency of composite material cantilever plates. The stacking sequence of tbe composite plate is Quasi-isotropic laminated plate is [2(0j/±45°/2(90°)]" The plate was subjected to incremental cuts and tests to determine changes in new modal properties. The study included white noise and sinusoidal dynamic testing techniques and a virtual instrument dynamic analyzer. In this study also, determining the resonant frequencies of the undamaged and damaged plate, and evaluating the capabilities of piezoelectric ceramics (PZT's) for fault detection based on their sensitivity and accuracy changes in modal parameters. Numerical results are …

Variable Area Inlet For Vehicle Thermal Control, Thomas R. Layne, Milton E. Franke, Darrell B. Ridgedly

AFIT Patents

A variable area inlet structure for a vehicle utilizing ram air for coolant is described which comprises a variable area inlet device in the ram air inlet in the form of a butterfly valve, damper, shutter, or similar structure, a temperature sensor in thermal contact with a component within the vehicle to be cooled by ram air flow, a controller and actuator, responsive to the temperature sensor and operatively connected to the variable area device, for controlling the inlet area in response to the component temperature.

Flightlines, Vol. 7, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Portfolio Assessment In Aerodynamics, Nikos J. Mourtos

Faculty Publications

A new way of assessing student learning in an aerodynamics course through the use of portfolios is presented. The approach is portable to any engineering course, with a few modifications depending on content. The main idea is to allow students more responsibility for their own learning. Instead of having everyone in the class perform identical activities (homework, experiments, projects, tests, etc.), a cadre of assignments is made available to them. Students choose and perform (within reason) the ones that suit them better in terms of their own strengths and learning styles. The ultimate goal is for each student to demonstrate …

Electro-Hydrodynamic Pumped Hydraulic Actuation With Application To Active Vibration Control, Ahmad Reza Kashani, Sung Kang, Kevin P. Hallinan

Mechanical and Aerospace Engineering Faculty Publications

A new type of actuation device has been conceptualized that meets the needs of both large displacement, force and bandwidth within a package more compact than currently available magnetostrictive and stack-type piezoelectric actuators of similar rating. This concept relies on micro-scale electrohydrodynamic (EHD) pumping of a dielectric liquid within small channels. Configured as an actuator, the EHD pump(s) would be used to move fluid between two reservoirs—each having a compliant membrane that interfaces to the world to provide the means to achieve vibration cancellation or micro actuation.

Ordinarily limited to generating flow in macroscale applications, the EHD pump, when operating …

Book Review Of "Encyclopedia Of Women In Aviation And Space" By Rosanne Welch, Nancy Curtis

Library Staff Publications

No abstract provided.

Location Effects Of Passive Damping Material In Cross-Ply Laminates On Natural Frequency And Mode Shape, E. I. Elghandour, F. A. Kolkailah

Aerospace Engineering

This study presents an experimental investigation of the free vibration of cantilevered composite laminated plates with embedded passive damping material at different stages. A total of five composite laminated plates are considered. The lay-up sequences for the five composite laminated plates with and without two embedded layers of passive damping material are [90°/0°/90°/0°]_s, [90°/0°/90°/0°/d]_s, [90°/0°/90°/d/0°]_s, [90°/0°/d/90°/0°]_s, and [90°/d/0°/90°/0°]_s. The passive damping material employed is a 3M material, SJ-2015 ISD 112, with peak damping properties in the ambient temperature range of 32°F to 140°F. The composite material used is a carbon …

Frequency Domain Robustness Analysis Of Hopfield And Modified Hopfield Neural Networks, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A variant of Hopfield neural network, called the modified Hopfield network, is formulated in this study. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problem under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions of this network are discussed. The robustness of this network and the classical Hopfield network are carried out in the frequency domain using describing functions

Vortex Generated Rotor Wake Model For Real-Time Simulation, Kenneth S. Graham

Link Foundation Modeling, Simulation and Training Fellowship Reports

The University of Alabama Flight Dynamics Laboratory (UA FDL) has been simulating helicopters since 1981. The real-time, man-in-the-loop, simulator was developed locally and is continuously being upgraded. The hardware, software, architecture and math models are all developed in-house by a team of faculty and graduate students. Since 1994, the UA rotor model has been Bladehelo [2] - a true blade model that numerically integrates the flapping motion of individual blades and the shaft rotation. The approach is physically based. Discrepancies are studied until they are understood. Bladehelo played a key role in the discovery of residual bending [3], [4]. Bladehe!o …

Fundamentals Of Linear State Space Systems, John Bay

Electrical and Computer Engineering Faculty Scholarship

This book addresses two primary deficiencies in the linear systems textbook market: a lack of development of state space methods from the basic principles and a lack of pedagogical focus. The book uses the geometric intuition provided by vector space analysis to develop in a very sequential manner all the essential topics in linear state system theory that a senior or beginning graduate student should know. It does this in an ordered, readable manner, with examples drawn from several areas of engineering. Because it derives state space methods from linear algebra and vector spaces and ties all the topics together …

Online Identification And Control Of Aerospace Vehicles Using Recurrent Networks, Zhenning Hu, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Methods for estimating the aerospace system parameters and controlling them through two neural networks are presented in this study. We equate the energy function of Hopfield neural network to integral square of errors in the system dynamics and extract the parameters of a system. Parameter convergence is proved. For control, we equate the equilibrium status of a "modified" Hopfield neural network to the steady state Riccati solution with the system parameters as inputs. Through these two networks, we present the online identification and control of an aircraft using its nonlinear dynamics.

Control Of The Air: The Enduring Requirement, Richard P. Hallion

U.S. Air Force Research

Throughout the military history of the twentieth century, the role of aerospace forces has become more predominant. Today, wars typically start, are prosecuted, and reach their decisive culminating point--whether surrender of a foe, agreement to a ceasefire, or the ceasing of combat operations--thanks to air action. Given these circumstances, to lose control of the air is to lose a war, particularly in an era (as we now are in since the end of the Cold War) when deployable overseas forces are small, and, thus, particularly vulnerable to the tremendous leverage an opponent gains by sudden and swift air attack. If …

Adaptive Critic Based Neural Networks For Control-Constrained Agile Missile Control, Dongchen Han, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We investigate the use of an `adaptive critic' based controller to steer an agile missile with a constraint on the angle of attack from various initial Mach numbers to a given final Mach number in minimum time while completely reversing its flightpath angle. We use neural networks with a two-network structure called `adaptive critic' to carry out the optimization process. This structure obtains an optimal controller through solving Hamiltonian equations. This approach needs no external training; each network along with the optimality equations generates the output for the other network. When the outputs are mutually consistent, the controller output is …

Design, Optimization, And The Prototyping Of A Small Tuning-Fork Ultrasonic Piezoelectric Linear Motor, Daniel S. Stutts, James R. Friend

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The design, optimization, and properties of a prototype small traveling-wave ultrasonic piezoelectric linear motor design are described. A method for optimizing the geometry of the motor to maximize its mechanical output for a given electrical input is described, as is the inherent properties of the design to maximize the motors durability and utilization of the piezoelectric material. Results from testing the motor demonstrate the design and indicate a maximum speed of 2.5 cm/s with a preload of 16 g due to an applied voltage of 80 V/RMS/ at an applied current of 15 mA.

Environmental Performance Analysis Of Solid Freedom Fabrication Processes, Yanchun Luo, Zhiming Ji, Ming-Chuan Leu, R. J. Caudill

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a method for analyzing the environmental performance of solid freeform fabrication (SFF) processes. In this method, each process is divided into life phases. Environmental effects of every process phase are then analyzed and evaluated based on the environmental and resource management data. These effects are combined to obtain the environmental performance of the process. The analysis of the environmental performance of SFF processes considers the characteristics of SFF technology, includes material, energy consumption, processes wastes, and disposal. Case studies for three typical SFF processes: stereolithography (SL); selective laser sintering (SLS); and fused deposition modeling (FDM) are presented …

Stability Analysis Of Nonlinear Machining Force Controllers, Robert G. Landers, Yen-Wen Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Model parameters vary significantly during a normal operation, thus, adaptive techniques have predominately been used. However, model-based techniques that carefully account for changes in the force process have again been examined due to the reduced complexity afforded by such techniques. In this paper, the effect of model parameter variations on the closed-loop stability for two model-based force controllers is examined. It was found that the stability boundary in the process parameter space can be exactly determined for force control systems designed for static force processes. For force control systems designed for first-order force processes, it was found that the stability …