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Articles 1621 - 1650 of 2222

Full-Text Articles in Mechanical Engineering

A Finite Element Formulation For Aft Fan Duct Acoustic Radiation, Walter Eversman Jan 1997

A Finite Element Formulation For Aft Fan Duct Acoustic Radiation, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A finite element code has been developed for the prediction of the radiated acoustic field in and around the aft fan duct of a turbofan engine. The acoustic field is modeled based on the assumption that the steady flow in and around the nacelle is irrotational as is the acoustic perturbation. The geometry of the nacelle is axisymmetric, and the acoustic source is harmonic and decomposed into its angular harmonics. The steady flow is computed on the acoustic mesh and provides data for the acoustic calculations. The jet is included in the steady flow potential flow model by separating the …

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Numerical Simulations Of Full- Scale Corroded Pipe Tests With Combined Loading, Samit Roy, S. Grigory, M. Smith, M. F. Kanninen, M. Anderson Jan 1997

Numerical Simulations Of Full- Scale Corroded Pipe Tests With Combined Loading, Samit Roy, S. Grigory, M. Smith, M. F. Kanninen, M. Anderson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The ANSI/ASME B31G guideline has been useful to pipeline operators in assessing the integrity of corroded line pipe. Because large safety margins have had to be incorporated, the guidelines can be excessively conservative, which in turn can force costly repairs and replacements that may not actually be necessary. On the other hand, because the current guidelines consider only pressure loading and neglect bending and axial compression, they could give nonconservative failure predictions when combined loading exists. Therefore, a study was initiated to develop a theoretically sound methodology for assessing the integrity of corroded line pipe subjected to combined loading. A …

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Analysis Of Rockbolt Reinforcement Using Beam-Column Theory, Samit Roy, Anand B. Rajagopalan Jan 1997

Analysis Of Rockbolt Reinforcement Using Beam-Column Theory, Samit Roy, Anand B. Rajagopalan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A simple analytical procedure that applies classical beam-column theory for evaluating passive rock bolt roof reinforcement is presented in this paper. The analytical model is derived from first principles and is capable modelling any number of reinforcing bolts. Each rock bolt is modelled as a linear spring and the model allows for non-uniform bolt spacing. In this study the rock beam is assumed to be isotropic and linearly elastic for the sake of simplicity. However, the analytical model can be extended to include anisotropic rock mass as well as inelastic material behavior. The solution to the couped set of governing …

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Radiative Heating In Scramjet Combustors, Harlan F. Nelson Jan 1997

Radiative Heating In Scramjet Combustors, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Currently, there is considerable interest in scramjet engines for hypersonic aircraft and missiles. This paper presents preliminary calculations of the radiative heating of the walls of scramjet combustion chambers. The analysis assumes isothermal, constant property flow fields that are representative of actual combustor flow fields. The fuel is H2, and N2 is taken as inert. Temperature in the combustor is on the order of 2000-3000 K and the pressure is of the order of 5 atm. The combustion products consist mainly of H2O and OH. These gases are strong radiators in the infrared. Radiation heating can be significant because of …

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A System For Collecting Milligram Quantities Of Cloud Condensation Nuclei, Darryl J. Alofs, Donald E. Hagen, Steven D. Medley, Daniel R. White, John L. Schmitt, Allen L. Williams Jan 1997

A System For Collecting Milligram Quantities Of Cloud Condensation Nuclei, Darryl J. Alofs, Donald E. Hagen, Steven D. Medley, Daniel R. White, John L. Schmitt, Allen L. Williams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An Experimental System to Collect Cloud Condensation Nuclei (CCN) Onto Filters in Amounts Sufficient for Chemical Analysis is Described. This Experimental Apparatus is Designed to Process Ambient Air at a Rate of More Than 1 M3/min. Two Identical Systems Have Been Built. One is Installed in a Laboratory at Rolla, MO. the Other is Installed on an 11 M Long Trailer. the System Isolates Three Size Classes of CCN, Having Mass Median Diameters of 0.27, 0.12, and 0.075 Μm, Respectively, and Mass Collection Rates of 11.5, 1.28, and 0.13 Mg/day, Respectively. the above Sizes and Collection Rates Are Obtained from …

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Recent Developments In Extrusion Freeform Fabrication (Eff) Utilizing Non-Aqueous Gel Casting Formulations, Greg Hilmas, John L. Lombardi, Robert A. Hoffman, Kevin Stuffle Aug 1996

Recent Developments In Extrusion Freeform Fabrication (Eff) Utilizing Non-Aqueous Gel Casting Formulations, Greg Hilmas, John L. Lombardi, Robert A. Hoffman, Kevin Stuffle

Materials Science and Engineering Faculty Research & Creative Works

Extrusion Freeform Fabrication (EFF) was shown to be an extremely versatile method for fabricating Functionally Graded Materials (FGMs) The approach is inexpensive and potentially feasible for grading between any thermodynamically compatible ceramic-metal, ceramic-ceramic, or metal-metal material combination. Several material systems were investigated in this study including alumina-304 stainless steel, zirconia-304 stainless steel, alumina-Inconel 625, zirconiaInconel625, alumina-nickel aluminide, zirconia-nickel aluminide, titanium carbide-InconeI625, titanium diboride-nickel aluminide, and tungsten carbide-nickel aluminide. A controlled gradient was demonstrated between the end members for all of the above compositions. The FGMs were hot pressed to achieve near theoretical densities, providing flexural strengths as high as 1000 …

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A Finite Element Model Of Thermoacoustic Oscillations In Rayleigh Flow, Carlos A. Gutierrez, Walter Eversman Jan 1996

A Finite Element Model Of Thermoacoustic Oscillations In Rayleigh Flow, Carlos A. Gutierrez, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The work reported here describes a portion of the development of a finite element model of thermoacoustic oscillations in ducted flows, including three dimensional geometries and nonuniform mean flows with steady heat addition. The thermoacoustic problem is not modeled by a form of the convected wave equation but instead by the conservation equations in primitive form. In this paper the three-dimensional model is reduced to one dimension, applicable to a uniform geometry, but allowing an axially nonuniform flow with sharp gradients in temperature, density, and Mach number. The steady mean flow is computed as a Rayleigh flow. Calculations are shown …

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A Dual Neural Network Architecture For Linear And Nonlinear Control Of Inverted Pendulum On A Cart, S. N. Balakrishnan, Victor Biega Jan 1996

A Dual Neural Network Architecture For Linear And Nonlinear Control Of Inverted Pendulum On A Cart, S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The use of a self-contained dual neural network architecture for the solution of nonlinear optimal control problems is investigated in this study. The network structure solves the dynamic programming equations in stages and at the convergence, one network provides the optimal control and the second network provides a fault tolerance to the control system. We detail the steps in design and solve a linearized and a nonlinear, unstable, four-dimensional inverted pendulum on a cart problem. Numerical results are presented and compared with linearized optimal control. Unlike the previously published neural network solutions, this methodology does not need any external training, …

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A Class Of Modified Hopfield Networks For Aircraft Identification And Control, Jie Shen, S. N. Balakrishnan Jan 1996

A Class Of Modified Hopfield Networks For Aircraft Identification And Control, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a class of modified Hopfield neural networks and their use in solving aircraft optimal control and identification problems. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problems under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions are discussed. Energy minimization of the networks leads to identification of the system parameters. Numerical results are provided to identify the dynamics of an aircraft, and the corresponding optimal control is calculated online. Comparison of the …

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Heat Transfer In Two-Phase Solid-Rocket Plumes, Harlan F. Nelson, John C. Fields Jan 1996

Heat Transfer In Two-Phase Solid-Rocket Plumes, Harlan F. Nelson, John C. Fields

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Results of a direct simulation Monte Carlo (DSMC) and free molecule (FM) analysis of convective heat transfer to Al2O3 particles in solid-rocket plume environments are presented. The particle diameters are assumed to be 4μm, and the plume gases are CO2, H2O, CO, and N2. The plume gas temperature is 2000 K. Particle temperatures of 1500, 2000, and 2500 K are investigated for Knudsen numbers from 1/2 to 1000 (from slip flow to FM flow). The Nusselt number is presented in terms of Knudsen number and Reynolds number (or relative velocity). Both the Kavanau and the Kashmarov and Svirshevskii correlations generally …

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Compliant Pliers, Ashok Midha, S. C. Visser Jan 1996

Compliant Pliers, Ashok Midha, S. C. Visser

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The pliers include an endless loop, a top jaw appended to the endless loop, and a bottom jaw appended to the endless loop. The endless loop includes in series a top grip handle, a spring segment, a bottom grip handle and a compliant strip interconnecting the top and bottom grip handles. A rolling surface on the top grip handle rolls on a contact portion of the bottom grip handle. The rolling action causes the compliant strip to flex which causes the top and bottom jaws to move toward one another. The endless loop provides a built-in automatic spring and enhances …

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Plastic Fiber Rolling For Concrete Reinforcement, Jeffery S. Thomas Jan 1996

Plastic Fiber Rolling For Concrete Reinforcement, Jeffery S. Thomas

Masters Theses

"Fiber reinforced concrete is gaining in acceptance and usage as its strength and toughness benefits are realized. Polypropylene fibers are currently the most commonly used fibers. However, the cost of virgin plastics limits the percent content that can be economically added to concrete. One would first believe that recycled plastics could offer a viable alternative to virgin-plastic fibers, but at present time extra selection and cleaning steps required to reprocess the recycled plastic into fibers makes it more expensive than virgin-plastic fibers. A fiber rolling process conceived and developed at the University of Missouri-Rolla has the potential of making recycled …

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Effect Of Inflow Pressure And Wall Heat Transfer On Shock-Induced Combustion/Detonation, B. S. Green, Harlan F. Nelson Jan 1996

Effect Of Inflow Pressure And Wall Heat Transfer On Shock-Induced Combustion/Detonation, B. S. Green, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Oblique detonation waves are possible ignition mechanisms for scramjet engines. Results from a numerical study of the effects of changing the inflow pressure on oblique detonation wave structure for supersonic flow of a stoichiometric hydrogen-air mixture over a flat plate followed by a ramp are presented. Viscous effects and finite-rate chemistry are considered. Inflow pressure is varied from 0.1 to 1 atmosphere for Mach 4 inflow over a 30-degree ramp. Also, the effect of wall heat transfer rate is examined by comparing adiabatic wall, and constant temperature wall solutions. A separation bubble forms at the intersection of the flat plate …

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Hamiltonian Based Adaptive Critics For Missile Guidance, S. N. Balakrishnan, Jie Shen Jan 1996

Hamiltonian Based Adaptive Critics For Missile Guidance, S. N. Balakrishnan, Jie Shen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Hamiltonian based adaptive critic structure is proposed for solving missile guidance problems. This structure consists of a supervisor neural network called 'critic' and a controller network called 'action'. Together they are used to solve model-based guidance problems. The advantage of this approach is that: i) the training data for each network is created by the other network, ii) the converged solutions yield near optimal guidance over the entire span of the training range, and iii) they can be used as feedback controllers though trained off-line. A main contribution is that we establish a direct link between traditional optimal control …

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Target Profile Estimation Using Haar Functions, William R. Bockman, S. N. Balakrishnan, Christopher D'Souza, James Cloutier Jan 1996

Target Profile Estimation Using Haar Functions, William R. Bockman, S. N. Balakrishnan, Christopher D'Souza, James Cloutier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approach to estimating the target acceleration in a maneuvering target model using Haar function partial summations to model the target acceleration is developed. A kinematic constraint is applied to the maneuvering target model and the effects of the use of this constraint are reviewed.

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Non-Axisymmetric Matrix Cracking And Interface Debonding With Friction In Ceramic Composites, F. S. Ji, Lokeswarappa R. Dharani Jan 1996

Non-Axisymmetric Matrix Cracking And Interface Debonding With Friction In Ceramic Composites, F. S. Ji, Lokeswarappa R. Dharani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An three-dimensional analytical model based on the principle of minimum potential energy is developed and applied to determine the stress state in a discrete fiber/matrix composite cylinder subjected to axial tensile loading in the fiber direction and containing a non-symmetric transverse matrix crack and an interface debond. The friction over the debonded interface is incorporated into the analysis. The strain energy release rates associated with the matrix crack and the interface debonding under the combination of the applied load and the interface frictional force are computed. The strain energy release rate criterion has been employed to evaluate the critical applied …

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Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett Jan 1996

Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A model based on similarity transformation, for the nitrogen-diluted, H2-air opposed-jet laminar counterflow diffusion flame (CFDF), was developed independently of earlier models, and numerically solved to study flame location and flame structure and extinction limits. Numerical stiffness is handled by a special treatment of the species production term. Flame location with respect to the stagnation plane is identified as an important parameter that governs H2-air diffusion flames, and physical explanations are given to show how flame location is affected by fuel dilution, strain rate, and Lewis number. Results show very good agreement with experimental extinction conditions. The effect of thermal …

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Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier Jan 1996

Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An infrared extinction technique was used to characterize spatially and temporally the vapor phase of a transient fuel spray. Optical extinction data were taken at two laser wavelengths and compared to obtain fuel vapor partial pressure values averaged over the line-of-sight through the spray. A transient fuel injector spray was characterized at several axial positions with a spatial resolution of 0.125 cm and a temporal resolution of 0.2 ms. With the knowledge of an axisymmetric spray pulse, the line-of-sight averaged results were deconvoluted to obtain spatially resolved vapor pressure data. The same spray was also characterized using phase/doppler interferometry to …

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Radiative Heating In Scramjet Combustors, Harlan F. Nelson Jan 1996

Radiative Heating In Scramjet Combustors, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Currently, there is considerable interest in scramjet engines for hypersonic aircraft and missiles. This paper presents preliminary calculations of the radiative heating of the walls of scramjet combustion chambers. The analysis assumes isothermal, constant property flow fields which are representative of actual combustor flow fields. The fuel is H2 and N2 is taken as inert. Temperature in the combustor is on the order of 2000 to 3000 K and pressure is of the order of 5 atm. The combustion products consist mainly of H2O and OH. These gases are strong radiators in the infrared. Radiation heating can be significant because …

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Fuzzy Logic In Restructurable Flight Control Systems, S. N. Balakrishnan, H. S. Ho Jan 1995

Fuzzy Logic In Restructurable Flight Control Systems, S. N. Balakrishnan, H. S. Ho

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a fuzzy logic controller (FLC) is proposed for restructurable flight control systems. The role of the FLC is to stabilize the aircraft upon a fault occurrence. The FLC derives pitch/roll/yaw controls from a generic knowledge base characterized by 49 if-then rules. A linearized model representative of a modern jet fighter provides the basis for the numerical simulation. Simulated faults include various degrees of surface loss at the right stabilator, combined with reduced ailerons and rudder control power. The FLC accomplishes the stabilization task under test conditions without any knowledge of the system parameters. The numerical results demonstrate …

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Intercomparison Between Commercial Condensation Nucleus Counters And An Alternating Temperature Gradient Cloud Chamber, Darryl J. Alofs, C. K. Lutrus, Donald E. Hagen Jan 1995

Intercomparison Between Commercial Condensation Nucleus Counters And An Alternating Temperature Gradient Cloud Chamber, Darryl J. Alofs, C. K. Lutrus, Donald E. Hagen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Three Commercial CNC Counters (TSI Models 3010, 3022A, and 3025A) Are Compared with an Alternating Temperature Gradient Cloud Chamber (ALGR). Electrically Size Classified Aerosols of Sodium Chloride and Silver Are Used. Diffusional Losses within the ALGR Are Much Larger Than for the TSI Instruments: Therefore the ALGR Concentrations Are Corrected for Internal Diffusional Losses, But the TSI Instruments Are Not. the Particle Size Range Tested is 4–90 Nm. for Sodium Chloride, the TSI Concentrations Agreed Fairly Well with the Corrected ALGR at Larger Sizes, and Were Below the Corrected ALGR at Smaller Sizes. the Electrical Aerosol Classifier (EAC) Setting at …

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On A Method For Obtaining Approximate Solutions To Sturm-Liouville Problems, Serge Abrate Jan 1995

On A Method For Obtaining Approximate Solutions To Sturm-Liouville Problems, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A method presented recently to find approximate solutions to a Sturm-Liouville problem is shown to be a special case of a classical weighted residual method. The choice of approximation functions and convergence of the method are also examined. © 1995 American Mathematical Society.

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Thermal Contact Conductance Of Ceramic Substrate Junctions, K. C. Chung, H. K. Benson, John W. Sheffield Jan 1995

Thermal Contact Conductance Of Ceramic Substrate Junctions, K. C. Chung, H. K. Benson, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

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Adaptive Critic Based Neural Networks For Control (Low Order System Applications), S. N. Balakrishnan, Victor Biega Jan 1995

Adaptive Critic Based Neural Networks For Control (Low Order System Applications), S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Dynamic programming is an exact method of determining optimal control for a discretized system. Unfortunately, for nonlinear systems the computations necessary with this method become prohibitive. This study investigates the use of adaptive neural networks that utilize dynamic programming methodology to develop near optimal control laws. First, a one dimensional infinite horizon problem is examined. Problems involving cost functions with final state constraints are considered for one dimensional linear and nonlinear systems. A two dimensional linear problem is also investigated. In addition to these examples, an example of the corrective capabilities of critics is shown. Synthesis of the networks in …

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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

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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 …

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System Modeling And Control Of Smart Structures, Frank J. Kern, Leslie Robert Koval, K. Chandrashekhara, Vittal S. Rao Jan 1995

System Modeling And Control Of Smart Structures, Frank J. Kern, Leslie Robert Koval, K. Chandrashekhara, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents multidisciplinary research and curriculum efforts at the University of Missouri-Rolla in the smart structures area. The primary objective of our project is to integrate research results with curriculum development for the benefit of students in electrical, and mechanical and aerospace engineering and engineering mechanics. The approach to the accomplishment of curriculum objectives is the development of a two-course sequence in the smart structures area with an integrated laboratory. The research portion of the project addresses structural identification and robust control methods for smart structures. A brief summary of the research results and a description of curriculum development …

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A Neural Network Thrust Force Controller To Minimize Delamination During Drilling In Graphite Epoxy Laminates, Robert B. Stone Jan 1995

A Neural Network Thrust Force Controller To Minimize Delamination During Drilling In Graphite Epoxy Laminates, Robert B. Stone

Masters Theses

"Delamination is a well-recognized problem associated with drilling in fiber-reinforced composite materials (FRCM). The most noted problems occur as the drill enters and exits the FRCM. Since drilling is often a final operation during assembly, any defects introduced in parts by drilling represent an expensive loss. Studies based on linear elastic fracture mechanics theory have proposed critical thrust forces in the various drilling regions that will prevent crack growth or delamination. Using these critical thrust force curves as a guide, a thrust force controller was developed to minimize the delamination while drilling in graphite epoxy laminates. A neural network control …

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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 …

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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 …

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