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Mechanical and Aerospace Engineering Faculty Research & Creative Works

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Full-Text Articles in Engineering

Hamiltonian Based Adaptive Critics For Aircraft Control, S. N. Balakrishnan, Jie Shen Jan 1995

Hamiltonian Based Adaptive Critics For Aircraft Control, S. N. Balakrishnan, Jie Shen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aircraft designs are becoming more complex in order to either operate more efficiently as in the commercial sector or to push the performance envelopes as in the military sector. An interesting outcome of this scenario is that `control'' has come to play an important role in helping realize these objectives. Increasingly, control is becoming an integral part of an aircraft design rather than an afterthought. More effective and efficient control of an aircraft is certain to lead to improved performance at a lower cost


On The Use Of Students For Developing Engineering Laboratories, Bopaya Bidanda, Richard E. Billo Jan 1995

On The Use Of Students For Developing Engineering Laboratories, Bopaya Bidanda, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes a unique and innovative approach that solved the dual problem of starting up a new engineering instructional laboratory in a timely manner, and for teaching engineering students advanced skills in Automatic Data Collection. Students enrolled in a special pilot course were used to develop and startup an Automatic Data Collection laboratory. These students were assigned individual Automatic Data Collection technologies of interest and given total responsibility for the successful startup of the laboratory. The organization and structure of the course modeled the typical team oriented project development efforts in industry. Feedback from students showed the course to …


Static And Dynamic Characteristics Of Spot Welded Sheet Metal Beams, K. Pal, Don L. Cronin Jan 1995

Static And Dynamic Characteristics Of Spot Welded Sheet Metal Beams, K. Pal, Don L. Cronin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Although widely employed as structural components in the auto industry, spot welded sheet metal beams manifest static and dynamic behavior that is not well characterized. For the present study, sample beams of three representative cross-sections—hat, box and box with partition—were fabricated of sheet steel. The spacing between the spot welds that hold these sections together was varied from 25.4 mm (1 in.) to 203.2 mm (8 in.) using a 25.4 mm (1 in.) increment. The beams were subjected to static bending and static torsion tests, and bending and torsional stiffnesses were determined as functions of spot weld spacing. The beams …


Improved Finite Element Modeling Of The Turbofan Engine Inlet Radiation Problem, I. Danda Roy, Walter Eversman Jan 1995

Improved Finite Element Modeling Of The Turbofan Engine Inlet Radiation Problem, I. Danda Roy, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Improvements have been made in the finite element model of the acoustic radiated field from a turbofan engine inlet in the presence of a mean flow. The problem of acoustic radiation from a turbofan engine inlet is difficult to model numerically because of the large domain and high frequencies involved. A numerical model with conventional finite elements in the near field and wave envelope elements in the far field has been constructed. By employing an irrotational mean flow assumption, both the mean flow and the acoustic perturbation problem have been posed in an axisymmetric formulation in terms of the velocity …


Vibration Of Point-Supported Rectangular Composite Plates, Serge Abrate Jan 1995

Vibration Of Point-Supported Rectangular Composite Plates, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A general approach is presented to study the free vibrations of rectangular symmetrically laminated composite plates with point supports by using the Rayleigh-Ritz method and the Lagrange multiplier technique for enforcing the zero displacement constraints at the support locations. Polynomial approximation functions are used, and the constitutive relationships are written in terms of four lamination parameters. With these lamination parameters, the number of design variables is reduced to a minimum, which is useful for design optimization purposes, while all symmetric lay-ups are considered. This paper illustrates how the lamination parameters can be used for optimal design of vibrating plates. Results …


A New Neural Architecture For Homing Missile Guidance, S. N. Balakrishnan, Victor Biega Jan 1995

A New Neural Architecture For Homing Missile Guidance, S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a new neural architecture which imbeds dynamic programming solutions to solve optimal target-intercept problems. They provide feedback guidance solutions, which are optimal with any initial conditions and time-to-go, for a 2D scenario. The method discussed in this study determines an optimal control law for a system by successively adapting two networks - an action and a critic network. This method determines the control law for an entire range of initial conditions; it simultaneously determines and adapts the neural networks to the optimal control policy for both linear and nonlinear systems. In addition, it is important to know that …


A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Jun 1994

A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recurrent neural networks have the potential to perform significantly better than the commonly used feedforward neural networks due to their dynamical nature. However, they have received less attention because training algorithms/architectures have not been well developed. In this study, a recursive least squares algorithm to train recurrent neural networks with an arbitrary number of hidden layers is developed. The training algorithm is developed as an extension of the standard recursive estimation problem. Simulated results obtained for identification of the dynamics of a nonlinear dynamical system show promising results.


Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Jun 1994

Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The problem of identifying the cutting force in end milling operations is considered in this study. Recurrent neural networks are used here and are trained using a recursive least squares training algorithm. Training results for data obtained from a SAJO 3-axis vertical milling machine for steady slot cuts are presented. The results show that a recurrent neural network can learn the functional relationship between the feed rate and steady-state average resultant cutting force very well. Furthermore, results for the Mackey-Glass time series prediction problem are presented to illustrate the faster learning capability of the neural network scheme presented here


Free Vibrations Of A Piezoelectric Body, J. S. Yang, R. C. Batra Mar 1994

Free Vibrations Of A Piezoelectric Body, J. S. Yang, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a systematic analysis of the eigenvalue problem associated with free vibrations of a finite piezoelectric body. The analysis is based on an abstract formulation of the three-dimensional theory of piezoelectricity. A series of fundamental properties of free vibrations of a piezoelectric body are proved concisely. The problem of free vibrations of a piezoelectric plate governed by the two-dimensional plate equations due to Mindlin is treated in a similar manner. © 1994 Kluwer Academic Publishers.


Experiences In The Integration Of Design Across The Mechanical Engineering Curriculum, Ashok Midha, J. M. Starkey, D. P. Dewitt, R. W. Fox Jan 1994

Experiences In The Integration Of Design Across The Mechanical Engineering Curriculum, Ashok Midha, J. M. Starkey, D. P. Dewitt, R. W. Fox

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Faculty of the School of Mechanical Engineering at Purdue University have effected a major change in the Purdue Mechanical Engineering program by integrating design throughout the curriculum. In doing so, a significant level of faculty interaction has been achieved as well. The goals of the curriculum revision are: (1) to improve student skills in how to solve open-ended design problems, (2) to reduce the core of the curriculum to allow flexibility in course selection, and allow time for solving design problems, (3) to improve student skills in team work and communications, and (4) to improve student skills in using …


Use Of Hopfield Neural Networks In Optimal Guidance, S. N. Balakrishnan, James Edward Steck Jan 1994

Use Of Hopfield Neural Networks In Optimal Guidance, S. N. Balakrishnan, James Edward Steck

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Hopfield neural network architecture is developed to solve the optimal control problem for homing missile guidance. A linear quadratic optimal control problem is formulated in the form of an efficient parallel computing device known as a Hopfield neural network. Convergence of the Hopfield network is analyzed from a theoretical perspective, showing that the network, as a dynamical system approaches a unique fixed point which is the solution to the optimal control problem at any instant during the missile pursuit. Several target-intercept scenarios are provided to demonstrate the use of the recurrent feedback neural net formulation.


Buckling Of A Coating Bonded To A Round Bar Subjected To Axial Extension. Mech. Mater. 15 (1993) 131-138, C. W. Bert, Victor Birman Jan 1994

Buckling Of A Coating Bonded To A Round Bar Subjected To Axial Extension. Mech. Mater. 15 (1993) 131-138, C. W. Bert, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.


Optimal Design Of Laminated Plates And Shells, Serge Abrate Jan 1994

Optimal Design Of Laminated Plates And Shells, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Designing structures made out of composite materials represents a challenging task, since not only the thickness of the element must be determined to satisfy the constraints of the problem, but, in addition, the number of plies in the laminate and their relative orientation must also be selected. Because of their strong anisotropy, a careful selection of lay-up is required to make the best use of the capabilities of the material. In this article the optimum design of laminated plates and shells subjected to constraints on strength, stiffness, buckling loads, and fundamental natural frequencies are examined. © 1994.


On The Propagation Of A Shear Band In A Steel Tube, R. C. Batra, Xiangtong Zhang Jan 1994

On The Propagation Of A Shear Band In A Steel Tube, R. C. Batra, Xiangtong Zhang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Marchand and Duffy tested thin-walled steel tubes in a split Hopkinson torsion bar at a nominal strain-rate of approximately 1600/s and could not determine conclusively whether a shear band initiating at a point in the tube propagated around the circumference in one direction or in both directions. They estimated the speed of propagation to be 520 m/s in the former case and 260 m/s in the latter. Here we simulate their test numerically and find that the shear band propagates in both directions around the circumference of the tube. When the tube is twisted at a nominal strain-rate of 5000/s, …


Approximate Analytical Guidance Schemes For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery Jan 1994

Approximate Analytical Guidance Schemes For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Closed form solutions for the guidance laws are developed using modern control techniques. The resulting two-point boundary value problem is solved through the use of the state transition matrix of the intercept dynamics. Results are presented in terms of a design parameter.


Impact On Laminated Composites: Recent Advances, Serge Abrate Jan 1994

Impact On Laminated Composites: Recent Advances, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Impact damage in structures made out of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be drastically reduced as a result. In a previous review of the literature on impact on composite materials, this author considered 285 published before 1989. In this article over 300 articles most of which appeared after 1989 are reviewed. These figures indicate that this is a very active area of research, and the present paper seeks to present a comprehensive view of the latest developments. Taken together, these two reviews …


On The Interface Stability Of A Neck Propagating In A Sheet Reinforced With Shape-Memory Fibers, C. Q. Ru, R. C. Batra Jan 1994

On The Interface Stability Of A Neck Propagating In A Sheet Reinforced With Shape-Memory Fibers, C. Q. Ru, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We propose a simple model of necking in a sheet reinforced with straight fibers made of a shape-memory alloy and examine conditions under which the interface between the necked and the unnecked region is morphologically stable. We use the Mullins and Sekerka (1963, J. Appl. Phys. 34, 323-330; 1964, J. Appl. Phys. 35, 444-450) method, established for studying the stability of a moving interface in a solidification problem, to investigate the interface stability of a propagating neck. It is found that the moving straight interface is morphologically stable for several typical cases even in the absence of surface-tension effects, and …


A Kinematically Intelligent Blackboard For Computer Aided Instruction, J. Keith Nisbett, D. Watkins, Clark R. Barker Nov 1993

A Kinematically Intelligent Blackboard For Computer Aided Instruction, J. Keith Nisbett, D. Watkins, Clark R. Barker

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A CAI (computer-aided instruction) package is being developed to be used as a classroom tool for the instruction of undergraduate mechanical engineering students in an introductory kinematics of mechanisms course. This graphical environment allows the instructor to emulate on the projected graphics screen everything that is currently done on the blackboard for planar mechansims. Unlike the blackboard, the software will have the intelligence to interpret the drawings in a kinematic sense so that the drawing of the linkage will behave as a linkage. The software environment involves three principal components: (1) a sketching method for defining the linkage, (2) the …


Analytical Guidance Laws And Integrated Guidance/Autopilot For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery, J. H. Evers, J. R. Cloutier Jan 1993

Analytical Guidance Laws And Integrated Guidance/Autopilot For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery, J. H. Evers, J. R. Cloutier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approach to integrated guidance/autopilot design is considered in this study. It consists of two parts: 1) recognizing the importance of polar coordinates to describe the end game in terms of problem description and measurement acquisition, the terminal guidance problem is formulated in terms of polar coordinates; 2a) through the use of the state transition matrix of the intercept dynamics, a closed form solution for the transverse command acceleration is obtained; and 2b) through a commonly used approximation on time-to-go and a coordinate transformation, a family of proportional navigation optimal guidance laws is obtained in a closed form. A typical …


On Minimizing Thermal Deflections Of Laminated Plates, Serge Abrate Jan 1993

On Minimizing Thermal Deflections Of Laminated Plates, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Thermal deflections of symmetrically laminated plates that are continuous over many line supports are determined using the Rayleigh-Ritz method. The constitutive equations and the thermal loads are expressed in terms of four non-dimensional lamination parameters. Layups that minimize thermal deflections are determined for several types of composite plates subjected to temperature increases that vary linearly through the thickness.


Computer Simulation Of Three-Dimensional Mechanical Assemblies: Part I - General Formulation, Yong Fang, Frank W. Liou Jan 1993

Computer Simulation Of Three-Dimensional Mechanical Assemblies: Part I - General Formulation, Yong Fang, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In Part I of this paper, a dynamic modeling system for the simulation of three-dimensional mechanical assemblies is presented. With this simulation tool, a designer can interactively create an assembly of mechanical components ready for dynamic analysis. The modeling system presented in this paper include» the derivation of the equations of motion of spatial multi-body systems, and the formulation of the equations to model the associated collision detection and collision responses. Part II of this paper is to introduce the geometry modeling and computer simulation of 3D systems.


Computer Simulation Of Three-Dimensional Mechanical Assemblies: Part Ii - Computer Simulation, T. C. Chou, Frank W. Liou Jan 1993

Computer Simulation Of Three-Dimensional Mechanical Assemblies: Part Ii - Computer Simulation, T. C. Chou, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Computer simulation of the kinematic and dynamic behaviors of mechanical assemblies has become a very important tool in design and manufacturing, because the designer can foresee how a product is going to perform before the product is actually fabricated. However, up to now, the most current simulation modules are based on analysis from another kinematic or dynamic module by specifying the mating conditions between components, and then displaying the motion on the screen. This computer simulation actually performs similarly to a movie and can only provide visual checking. The drawback of this simulation approach is that designers are forced to …


On The Use Of Levy's Method For Symmetrically Laminated Composite Plates, Serge Abrate Jan 1993

On The Use Of Levy's Method For Symmetrically Laminated Composite Plates, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

For rectangular plates with two opposite edges simply supported and no bending twisting coupling, Levy's method can yield exact solutions for static deflections, free vibrations and buckling loads. However, three distinct solutions are obtained, depending on the relative magnitude of the plate rigidities, which in turn are functions of material properties, laminate thickness and lay-up. In this communication a stiffness invariant formulation is used to identify those laminates which fall under the three cases defined. © 1993.


Procase: A Prototype Of Intelligent Case-Based Process Planning System With Simulation Environment, Hao Yang, Wen F. Lu Jan 1993

Procase: A Prototype Of Intelligent Case-Based Process Planning System With Simulation Environment, Hao Yang, Wen F. Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An intelligent case-based process planning system with interactive graphic simulation environment, PROCASE, is developed lo demonstrate an integrated methodology of case-based process planning system. In PROCASE, both the mechanical part features and the machining operations are represented with a frame-based scheme. PROCASE contains a retriever, a modifier, a simulator and a repairer. It distinguishes itself from traditional rule-based process planning systems by representing the process planning knowledge through previous process planning cases instead of production rules. It therefore can overcome some problems in the traditional rule-based expert systems. PROCASE currently resides in IRIS Indigo workstation. With a user-friendly graphic environment, …


Second Law Analysis Of Active Magnetic Regenerative Hydrogen Liquefiers, L. Zhang, S. A. Sherif, T. N. Veziroglu, John W. Sheffield Jan 1993

Second Law Analysis Of Active Magnetic Regenerative Hydrogen Liquefiers, L. Zhang, S. A. Sherif, T. N. Veziroglu, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recent published work in the area of magnetic refrigeration reports on its potential for greater efficiency and high reliability. This paper presents an exergy analysis of a three-stage active magnetic regenerative (AMR) hydrogen liquefier which cools a hydrogen gas stream at 77 K and 1 atm to hydrogen liquid at 20 K. Ortho - para conversion of hydrogen is accomplished in a heat exchanger employing a 10 atm helium fluid that cycles in the refrigerator. The performance of the system is described in terms of the cooling capacity and exergy losses as functions of the magnetic material type, magnetic bed …


Observations On Higher-Order Beam Theory, A. Bhimaraddi, K. Chandrashekhara Jan 1993

Observations On Higher-Order Beam Theory, A. Bhimaraddi, K. Chandrashekhara

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A parabolic shear-deformation beam theory assuming a higher-order variation for axial displacement has been recently presented. In this theory, the axial displacement variation can be selected so that it results in a suitable admissible transverse shear-strain variation across the depth of the beam. This paper examines several transverse shear-strain variations that can go with the aforementioned higher-order theory. Apart from the usual simple parabolic variation, six other shear-strain variations are considered: the sinusoidal variation, cubic, quartic, quintic, and sixth-order polynomials. All these variations for transverse shear-strain satisfy the requirement that the shear strain be zero at the extreme fibers (z …


Neural Modeling And Control Of A Distillation Column, James Edward Steck, K. Krishnamurthy, Bruce M. Mcmillin, Gary G. Leininger Jul 1992

Neural Modeling And Control Of A Distillation Column, James Edward Steck, K. Krishnamurthy, Bruce M. Mcmillin, Gary G. Leininger

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control of a nine-stage three-component distillation column is considered. The control objective is achieved using a neural estimator and a neural controller. The neural estimator is trained to represent the chemical process accurately, and the neural controller is trained to give an input to the chemical process which will yield the desired output. Training of both the neural networks is accomplished using a recursive least squares training algorithm implemented on an Intel iPSC/2 multicomputer (hypercube). Simulated results are presented for a numerical example.


Determining The Chemical Composition Of Cloud Condensation Nuclei, Allen L. Williams, Jane E. Rothert, Kent E. Mcclure, Darryl J. Alofs, Donald E. Hagen, Daniel R. White, A. R. Hopkins, Max B. Trueblood Feb 1992

Determining The Chemical Composition Of Cloud Condensation Nuclei, Allen L. Williams, Jane E. Rothert, Kent E. Mcclure, Darryl J. Alofs, Donald E. Hagen, Daniel R. White, A. R. Hopkins, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This second progress report describes the status of the project one and one-half years after the start. The goal of the project is to develop the instrumentation to collect cloud condensation nuclei (CCN) in sufficient amounts to determine their chemical composition, and to survey the CCN composition in different climates through a series of field measurements. Our approach to CCN collection is to first form droplets on the nuclei under simulated cloud humidity conditions, which is the only known method of identifying CCN from the background aerosol. Under cloud chamber conditions, the droplets formed become larger than the surrounding aerosol, …


Moving Object Recognition And Guidance Of Robots Using Neural Networks, Abhijit Neogy, S. N. Balakrishnan, Cihan H. Dagli Jan 1992

Moving Object Recognition And Guidance Of Robots Using Neural Networks, Abhijit Neogy, S. N. Balakrishnan, Cihan H. Dagli

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The design of a robust guidance system for a robot is discussed. The two major tasks for this guidance system are the online recognition of a moving object invariant to rotation and translation, and tracking the moving object using a neural-network-driven vision system. This system included computer software ported to the IBM PC and interfaced with an IBM 7535 robot. The operation of this guidance system involved recognition of a moving object and the ability to track it till the robot and effector was in close proximity of the object. It was found that the robot was able to track …


Hydration Behavior Of Laser Dye Aerosols Of Mixed Composition Having High Critical Supersaturations, Max B. Trueblood, Donald E. Hagen, Darryl J. Alofs Jan 1992

Hydration Behavior Of Laser Dye Aerosols Of Mixed Composition Having High Critical Supersaturations, Max B. Trueblood, Donald E. Hagen, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This Study Concerns Aerosol Particles of Mixed Composition. the Particles Contain a Water Insoluble Core (Polystyrene Latex), Surrounded by a Water Soluble Shell (Various Fluorescent Dyes). a Collison Nebulizer and an Electrostatic Aerosol Classifier Are Used to Prepare the Aerosol; its Critical Supersaturation Spectrum is Measured with a Diffusion Cloud Chamber. Experiments Were Done using Four Different Dyes (Disodium Fluorescein, Sulforhodamine 640, Sulforhodamine B and Rhodamine 560 Chloride) with Five Different Polystyrene Latex Sphere Sizes. the Results Indicate that a Kohler-Type Behavior is Obeyed. This Technique of Putting a Soluble Coating Onto an Insoluble Core is Found to Be a …