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Mechanical and Aerospace Engineering Faculty Research & Creative Works

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Articles 511 - 540 of 808

Full-Text Articles in Aerospace Engineering

Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu Oct 2008

Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication. Due to effects such as the air bubble release, agglomerate breakdown, change in paste properties during extrusion as a result of liquid phase migration, etc., the extrusion force is difficult to control. In this paper, an adaptive controller is proposed to regulate the extrusion force. Recursive Least Squares is used to estimate extrusion force model parameters during fabrication and a low-order control scheme capable of tracking general reference trajectories is designed …

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Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis Aug 2008

Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper traces the development of neural-network (NN)-based feedback controllers that are derived from the principle of adaptive/approximate dynamic programming (ADP) and discusses their closed-loop stability. Different versions of NN structures in the literature, which embed mathematical mappings related to solutions of the ADP-formulated problems called “adaptive critics” or “action-critic” networks, are discussed. Distinction between the two classes of ADP applications is pointed out. Furthermore, papers in “model-free” development and model-based neurocontrollers are reviewed in terms of their contributions to stability issues. Recent literature suggests that work in ADP-based feedback controllers with assured stability is growing in diverse forms.

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A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu Jul 2008

A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a novel method of contour reconstruction from dexel data solving the shape anomalies for the complex geometry in virtual sculpting. Grouping and traversing processes are developed to find connectivity between dexels along every two adjacent rays. After traveling through all the rays on one slice, sub-boundaries are connected into full boundaries which are desired contours. The complexity of the new method has been investigated and determined as O(n). We also demonstrate the ability of the described method for viewing a sculpted model from different directions.

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Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow Jun 2008

Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper we examine the robustness of norm optimal ILC with quadratic cost criterion for discrete-time, linear time-invariant, single-input single-output systems. A bounded multiplicative uncertainty model is used to describe the uncertain system and a sufficient condition for robust monotonic convergence is developed. We find that, for sufficiently large uncertainty, the performance weighting can not be selected arbitrarily large, and thus overall performance is limited. To maximize available performance, a time-frequency design methodology is presented to shape the weighting matrix based on the initial tracking error. The design is applied to a nanopositioning system and simulation results are presented.

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Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan Jun 2008

Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In literature leader - follower strategy has been used extensively for formation control of car-like mobile robots with the control law being derived from the kinematics. This paper takes it a step further and a nonlinear control law is derived using Lyapunov analysis for formation control of car-like mobile robots using robot dynamics. Controller is split into two parts. The first part is the development of a velocity controller for the follower from the error kinematics (linear and angular). The second part involves the use of the dynamics of the robot in the development of a torque controller for both …

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Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne Jun 2008

Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In many manufacturing applications contour tracking is more important than individual axis tracking. Many control techniques, including iterative learning control (ILC), target individual axis error. Because individual axis error only indirectly relates to contour error, these approaches may not be very effective for contouring applications. Cross-coupled ILC (CCILC) is a variation on traditional ILC that targets the contour tracking directly. In contour trajectories with rapid changes, high frequency control is necessary in order to meet tracking requirements. This paper presents an improved CCILC that uses a linear time-varying (LTV) filter to provide high frequency control for short durations. The improved …

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Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow Jun 2008

Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this work we examine the performance of iterative learning control (ILC) for systems with non-repeating disturbances and random noise. Single-input, single- output linear time-invariant systems and iteration-invariant learning filters are considered. We find that a tradeoff exists between the convergence rate and converged error spectrum. Optimal filter designs, which are dependant on the disturbance and noise spectra, are developed. We also present simple design guidelines for the case when explicit models of disturbance and noise spectra are not available. A numerical design example is presented.

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Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan Jun 2008

Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a systematic approach to solve for the optimal control of a variable-time impulsive system. First, optimality condition for a variable-time impulsive system is derived using the calculus of variations method. Next, a single network adaptive critic technique is proposed to numerically solve for the optimal control and the detailed algorithm is presented. Finally, two examples-one linear and one nonlinear-are solved applying the conditions derived and the algorithm proposed. Numerical results demonstrate the power of the neural network based adaptive critic method in solving this class of problems.

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Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan Jun 2008

Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a systematic scheme to solve for the optimal controls of variable time impulsive systems. First, the optimality conditions for variable time impulse driven systems are derived using the calculus of variation. After wards, a neural network based adaptive critic method is proposed to numerically solve the two-point boundary value problems formulated based on the optimality conditions derived. Finally, two examples - one linear and one nonlinear - are presented to illustrate the conditions derived and to show the power of the neural network based adaptive critic method proposed.

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Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne Mar 2008

Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Iterative learning control (ILC) is a learning technique used to improve the performance of systems that execute the same task multiple times. Learning transient behavior has emerged as an important topic in the design and analysis of ILC systems. In practice, the learning control is often low-pass filtered with a ldquoQ-filterrdquo to prevent transient growth, at the cost of performance. In this note, we consider linear time-invariant, discrete-time, single-input single-output systems, and convert frequency-domain uncertainty models to a time-domain representation for analysis. We then develop robust monotonic convergence conditions, which depend directly on the choice of the Q-filter and are …

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Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch Jan 2008

Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The application of a Point-Collocation Non-Intrusive Polynomial Chaos method to the uncertainty quantification of a stochastic transonic aeroelastic wing problem has been demonstrated. The variation in the transient response of the first aeroelastic mode of a three-dimensional wing in transonic flow due to the uncertainty in free-stream Mach number and angle of attack was studied. A curve-fitting procedure was used to obtain time-independent parameterization of the transient aeroelastic responses. Among the uncertain parameters that characterize the time-dependent transients, the damping factor was chosen for uncertainty quantification, since this parameter can be thought as an indicator for flutter. Along with the …

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Nonlinear H(Infinity) Missile Longitudinal Autopilot Design With Theta-D Method, Ming Xin, S. N. Balakrishnan Jan 2008

Nonlinear H(Infinity) Missile Longitudinal Autopilot Design With Theta-D Method, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear H 1 control technique, called μ¡D H 1 method, is employed to design a missile longitudinal autopilot. The μ ¡D H 1 design has the same structure as that of linear H 1 , except that the two Riccati equations that are part of the solution process are state dependent. The μ ¡D technique yields suboptimal solutions to nonlinear optimal control problems in the sense that it provides an approximate solution to the Hamilton-Jacobi-Bellman (HJB) equation. It is also shown that this method can be used to provide an approximate closed-form solution to the …

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Discussion And Analysis Of Missile Igc Design, Michael W. Dancer, S. N. Balakrishnan, Ernest J. Ohlmeyer Jan 2008

Discussion And Analysis Of Missile Igc Design, Michael W. Dancer, S. N. Balakrishnan, Ernest J. Ohlmeyer

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Missile intercept systems used in the next generation missile defense system will require extremely accurate performance of all component systems. Such systems will need to guarantee successful intercept of highly maneuvering targets. as a result, such interceptor systems require much greater performance in its guidance, control, and estimation subsystems. in order to develop systems that meet the required accuracies, integrated guidance and control (IGC) systems are currently being studied. These IGC architectures infuse the guidance and control systems into a single framework thereby promoting natural synergy among the missile subsystems. Previous work in this area has relied on missile body-Based …

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Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt Jan 2008

Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Nanostructured membranes with precisely engineered nanopores were fabricated on a thin silicon nitride membrane, using a combination of bulk micromachining and focused-ion-beam drilling. These membranes are designed to preserve microscale blood channel dimensions, thereby permitting the red cell shape change that enhances gas exchange in the pulmonary capillary. The membranes were tested for their mechanical stability and the results were verified with finite element analysis. Initial studies have proven the membranes to be robust, and capable of withstanding pressures typically experienced in blood oxygenator channels. A novel MEMS-based blood oxygenation system employing the nanoporous membranes is also presented. The oxygenation …

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Analysis Of One-Dimensional And Two-Dimensional Thin Film "Pull-In" Phenomena Under The Influence Of An Electrostatic Potential, Gang Duan, Kai-Tak Wan Sep 2007

Analysis Of One-Dimensional And Two-Dimensional Thin Film "Pull-In" Phenomena Under The Influence Of An Electrostatic Potential, Gang Duan, Kai-Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A thin one-dimensional rectangular or two-dimensional axisymmetric film is clamped at the perimeter. an electrostatic potential (V*0) applied to a pad directly underneath the film leads to a "pull-in" phenomenon. the electromagnetic energy stored in the capacitive film-pad dielectric gap is decoupled from the mechanical deformation of the film using the Dugdale-Barenblatt-Maugis cohesive zone approximation. the ratio of film-pad gap (g) to film thickness (h), or γ=g/h, is found to play a crucial role in the electromechanical behavior of the film. Solution spanning a wide range of y is found such that V*0 ∝ γ3/2 for …

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Response To "Comment On 'Adhesion-Delamination Mechanics Of A Presented Rectangular Film Adhered Onto A Rigid Substrate' [J. Appl. Phys. 101, 024903 (2007)]", Kai-Tak Wan, Gang Duan Aug 2007

Response To "Comment On 'Adhesion-Delamination Mechanics Of A Presented Rectangular Film Adhered Onto A Rigid Substrate' [J. Appl. Phys. 101, 024903 (2007)]", Kai-Tak Wan, Gang Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

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Cooperative Uav Formation Flying With Obstacle/Collision Avoidance, Xiaohua Wang, Vivek Yadav, S. N. Balakrishnan Jul 2007

Cooperative Uav Formation Flying With Obstacle/Collision Avoidance, Xiaohua Wang, Vivek Yadav, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Navigation problems of unmanned air vehicles (UAVs) flying in a formation in a free and an obstacle-laden environment are investigated in this brief. when static obstacles popup during the flight, the UAVs are required to steer around them and also avoid collisions between each other. In order to achieve these goals, a new dual-mode control strategy is proposed: a “safe mode” is defined as an operation in an obstacle-free environment and a “danger mode” is activated when there is a chance of collision or when there are obstacles in the path. Safe mode achieves global optimization because the dynamics of …

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A Novel Cylindrical Punch Method To Characterize Interfacial Adhesion And Residual Stress Of A Thin Polymer Film, Bing Feng Ju, Kuo Kang Liu, Ming Fung Wong, Kai Tak Wan May 2007

A Novel Cylindrical Punch Method To Characterize Interfacial Adhesion And Residual Stress Of A Thin Polymer Film, Bing Feng Ju, Kuo Kang Liu, Ming Fung Wong, Kai Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adhesion of a pre-stressed silicone rubber film to a planar graphite surface was investigated by a new cylindrical punch method. a homemade apparatus was constructed to meet force and displacement resolutions of 0.1 μN and 10 nm. When the punch approached the intersurface force range across the punch-film gap, the film jumped into contact at "pull-in". Upon unloading, once the tensile load reached a threshold, a spontaneous delamination occurred at "pull-off" with a non-zero contact circle. a theoretical model was constructed based a simple energy balance. the new method can be used to characterize an adhesion interface between a pre-stressed …

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Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong Apr 2007

Coupled-Mode Theory For Stimulated Raman Scattering In High-Q/Vm Silicon Photonic Band Gap Defect Cavity Lasers, Xiaodong Yang, C. W. Wong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We examine the dynamics of stimulated Raman scattering in designed high-Q/Vm silicon photonic band gap nanocavities through the coupled-mode theory framework towards optically-pumped silicon lasing. The interplay of other X(3) effects such as two-photon absorption and optical Kerr, related free-carrier dynamics, thermal effects, as well as linear losses such as cavity radiation and linear material absorption are included and investigated numerically. Our results clarify the relative contributions and evolution of the mechanisms, and demonstrate the lasing and shutdown thresholds. Our studies illustrate the conditions for continuous-wave and pulsed highly-efficient Raman frequency conversion for practical realization in monolithic silicon …

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Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch Apr 2007

Efficient Sampling For Non-Intrusive Polynomial Chaos Applications With Multiple Uncertain Input Variables, Serhat Hosder, Robert W. Walters, Michael Balch

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The accuracy and the computational efficiency of a Point-Collocation Non-Intrusive Polynomial Chaos (NIPC) method applied to stochastic problems with multiple uncertain input variables has been investigated. Two stochastic model problems with multiple uniform random variables were studied to determine the effect of different sampling methods (Random, Latin Hypercube, and Hammersley) for the selection of the collocation points. The effect of the number of collocation points on the accuracy of polynomial chaos expansions were also investigated. The results of the stochastic model problems show that all three sampling methods exhibit a similar performance in terms of the the accuracy and the …

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Adhesion-Delamination Mechanics Of A Prestressed Rectangular Film Adhered Onto A Rigid Substrate, Ming Fung Wong, Gang Duan, Kai-Tak Wan Mar 2007

Adhesion-Delamination Mechanics Of A Prestressed Rectangular Film Adhered Onto A Rigid Substrate, Ming Fung Wong, Gang Duan, Kai-Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A prestressed rectangular film clamped at both ends delaminates from a rigid punch. based on a thermodynamic energy balance, the delamination mechanics is derived to relate the simultaneous external tensile force applied to the punch, punch displacement, and contact area. Effects of the coupled tensile residual membrane stress and adhesion energy at the punch-film interface are investigated. a "pinch off" (stable shrinking of the contact area to a line) is predicted, contrasting the nonzero "pull-off" radius in a clamped circular film. the model is useful in understanding the behavior of various adhesion-delamination phenomena, especially in one dimensional capacitive microelectromechanical systems …

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Multifrequency Eddy Current Inspection Of Corrosion In Clad Aluminum Riveted Lap Joints And Its Effect On Fatigue Life, Shridhar Natarajan, Anthony Chukwujekwu Okafor Mar 2007

Multifrequency Eddy Current Inspection Of Corrosion In Clad Aluminum Riveted Lap Joints And Its Effect On Fatigue Life, Shridhar Natarajan, Anthony Chukwujekwu Okafor

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.

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Exploring Effective Methods For Simulating Damaged Structures With Geometric Variation: Toward Intelligent Failure Detection, Daniel A. Mcadams, David Comella, Irem Y. Tumer Mar 2007

Exploring Effective Methods For Simulating Damaged Structures With Geometric Variation: Toward Intelligent Failure Detection, Daniel A. Mcadams, David Comella, Irem Y. Tumer

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Inaccuracies in the modeling assumptions about the distributional characteristics of the monitored signatures have been shown to cause frequent false positives in vehicle monitoring systems for high-risk aerospace applications. to enable the development of robust fault detection methods, this work explores the deterministic as well as variational characteristics of failure signatures. Specifically, we explore the combined impact of crack damage and manufacturing variation on the vibrational characteristics of beams. the transverse vibration and associated eigenfrequencies of the beams are considered. Two different approaches are used to model beam vibrations with and without crack damage. the first approach uses a finite …

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Product Family Design Knowledge Representation, Aggregation, Reuse, And Analysis, Jyotirmaya Nanda, Henri Thevenot, Timothy W. Simpson, Robert B. Stone, Matt R. Bohm, Steven B. Shooter Jan 2007

Product Family Design Knowledge Representation, Aggregation, Reuse, And Analysis, Jyotirmaya Nanda, Henri Thevenot, Timothy W. Simpson, Robert B. Stone, Matt R. Bohm, Steven B. Shooter

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A flexible information model for systematic development and deployment of product families during all phases of the product realization process is crucial for product-oriented organizations. In current practice, information captured while designing products in a family is often incomplete, unstructured, and is mostly proprietary in nature, making it difficult to index, search, refine, reuse, distribute, browse, aggregate, and analyze knowledge across heterogeneous organizational information systems. To this end, we propose a flexible knowledge management framework to capture, reorganize, and convert both linguistic and parametric product family design information into a unified network, which is called a networked bill of material …

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Determination Of Laser Absorption Coefficients Of Gas Mixtures Using An Ab Initio Md Model, Zhi Liang, Hai-Lung Tsai, Lan Jiang Jan 2007

Determination Of Laser Absorption Coefficients Of Gas Mixtures Using An Ab Initio Md Model, Zhi Liang, Hai-Lung Tsai, Lan Jiang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In an Effort to Study the Laser Induced Dissociation of Gas Mixtures for an Ongoing Research Project on Diamond Thin Film Coating using Multiple Lasers, It is Necessary to Determine the Absorption Coefficient of Laser Energy by CO2 Gas. an Ab Initio Molecular Dynamics (AIMD) Model is Used to Determine the Laser Absorption Coefficient of CO2 Gas as a Function of Laser Wavelength and Gas Temperature. the Translational, Rotational, and Vibration Motions of Molecules Are All Taken into Account in Our Model. the Intra-Molecular Potential Energy is Obtained by Solving the Kohn-Sham Equation. the Projector-Augmented Wave (PAW) Exchange-Correlation Potential Function …

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Optimal Neuro-Controller Synthesis For Impulse-Driven System, Xiaohua Wang, S. N. Balakrishnan Jan 2007

Optimal Neuro-Controller Synthesis For Impulse-Driven System, Xiaohua Wang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a new controller design technique for systems driven with impulse inputs. Necessary conditions for optimal impulse control are derived. A neural network structure to solve the resulting equations is presented. The solution concepts are illustrated with a few example problems that exhibit increasing levels of difficulty. Two linear problems-one scalar and one vector-and a benchmark nonlinear problem-Van Der Pol oscillator-are used as case studies. Numerical results show the efficacy of the new solution process for impulse driven systems. Since the theoretical development and the design technique are free from restrictive assumptions, this technique is applicable to many …

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Robust/Optimal Temperature Profile Control Of A High-Speed Aerospace Vehicle Using Neural Networks, Vivek Yadav, Radhakant Padhi, S. N. Balakrishnan Jan 2007

Robust/Optimal Temperature Profile Control Of A High-Speed Aerospace Vehicle Using Neural Networks, Vivek Yadav, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approximate dynamic programming (ADP)-based suboptimal neurocontroller to obtain desired temperature for a high-speed aerospace vehicle is synthesized in this paper. a 1-D distributed parameter model of a fin is developed from basic thermal physics principles. ldquoSnapshotrdquo solutions of the dynamics are generated with a simple dynamic inversion-based feedback controller. Empirical basis functions are designed using the ldquoproper orthogonal decompositionrdquo (POD) technique and the snapshot solutions. a low-order nonlinear lumped parameter system to characterize the infinite dimensional system is obtained by carrying out a Galerkin projection. an ADP-based neurocontroller with a dual heuristic programming (DHP) formulation is obtained with a …

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Acoustic Emission Detection And Prediction Of Fatigue Crack Propagation In Composite Patch Repairs Using Neural Networks, Navdeep Singh, Navrag Singh, Anthony Chukwujekwu Okafor Jan 2007

Acoustic Emission Detection And Prediction Of Fatigue Crack Propagation In Composite Patch Repairs Using Neural Networks, Navdeep Singh, Navrag Singh, Anthony Chukwujekwu Okafor

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An aircraft is subjected to severe structural and aerodynamic loads during its service life. These loads can cause damage or weakening of the structure especially for aging military and civilian aircraft, thereby affecting its load carrying capabilities. Hence composite patch repairs are increasingly used to repair damaged aircraft metallic structures to restore its structural efficiency. This paper presents the results of Acoustic Emission (AE) monitoring of crack propagation in 2024-T3 Clad aluminum panels repaired with adhesively bonded octagonal, single sided boron/epoxy composite patch under tension-tension fatigue loading. Crack propagation gages were used to monitor crack initiation. The identified AE sensor …

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Simple Penning Ion Source For Laboratory Research And Development Applications, Joshua L. Rovey, Brandon P. Ruzic, Thomas J. Houlahan Jan 2007

Simple Penning Ion Source For Laboratory Research And Development Applications, Joshua L. Rovey, Brandon P. Ruzic, Thomas J. Houlahan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A simple Penning ion generator (PIG) that can be easily fabricated with simple machining skills and standard laboratory accessories is described. The PIG source uses an iron cathode body, samarium cobalt permanent magnet, stainless steel anode, and iron cathode faceplate to generate a plasma discharge that yields a continuous 1 mA beam of positively charged hydrogen ions at 1 mTorr of pressure. This operating condition requires 5.4 kV and 32.4 W of power. Operation with helium is similar to hydrogen. The ion source is being designed and investigated for use in a sealed-tube neutron generator; however, this ion source is …

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Investigation Of Soft Failure Of Small Form Factor Hdd Under Forced Vibration, K. T. Chua, A. Yudhanto, E. H. Ong, J. Q. Mou Dec 2006

Investigation Of Soft Failure Of Small Form Factor Hdd Under Forced Vibration, K. T. Chua, A. Yudhanto, E. H. Ong, J. Q. Mou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

As small form factor hard disk drives (HDD) are increasingly used in portable consumer devices, the performance of the HDD in daily activity is highly concerned. In this paper, the soft failure of the hard disk drive under forced vibration is investigated. To investigate the cause of the soft failure, experimental frequency analysis was conducted. Modal analysis of HDD was completed by experiment and verified by FEM simulations and the result was compared to the frequency response result. Studies show that the vibration modes of head suspension assembly (HSA) and disk platter at higher resonant frequencies do not directly relate …

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