Engineering Commons^™

Data Reduction Procedure For An Experimental Method Of Measuring The Velocity-Coupled Response Function Of Solid Propellants, William H. Jarvis

Master's Theses - Daytona Beach

A computer program has been developed for calculation of the velocity-coupled response function of solid-propellants from experimentally measured pressure data. The proposed velocity-coupled response function measurement apparatus consists of an end-burner combustor where the propellant sample is oscillated in a direction normal to the flow in the presence of a standing acoustic wave within the combustion chamber. The pressure measurements are made at select points along the length of the chamber.

The data reduction program consists of a Runge-Kutta routine driven by a BFGS multivariable search routine. The Runge-Kutta routine determines the pressure distribution within the chamber of the proposed …

Expert Systems For Automated Maintenance Of A Mars Oxygen Production System, Ming-Tsang Ho

Mechanical & Aerospace Engineering Theses & Dissertations

A prototype expert system has been developed for maintaining autonomous operation of a Mars oxygen production system. Normal operation conditions and failure modes according to certain desired criteria are tested and identified. Several schemes for failure detection and isolation using forward chaining, backward chaining, knowledge-based and rule-based are devised to perform several housekeeping functions. These functions include self-health checkout, an emergency shut down program, fault detection and conventional control activities. An effort has been made to derive the dynamic model of the system using Bond-Graph technique in order to develop the model-based failure detection and isolation scheme by estimation method. …

Low Speed Flowfield Characterization By Infrared Measurements Of Surface Temperatures, Ehud Gartenberg

Mechanical & Aerospace Engineering Theses & Dissertations

An experimental program was aimed at identifying areas in low speed aerodynamic research where infrared imaging systems can make significant contributions. Implementing a new technique, a long electrically heated wire was placed across a laminar jet. By measuring the temperature distribution along the wire with the IR imaging camera, the flow behavior was identified. Furthermore, using Nusselt number correlations, the velocity distribution could be deduced. The same approach was used to survey wakes behind cylinders in a wind-tunnel. This method is suited to investigate flows with position dependent velocities, e.g., boundary layers, confined flows, jets, wakes and shear layers. It …

An Adaptive Remeshing Finite Element Method For High-Speed Compressible Flows Using Quadrilateral And Triangular Elements, Gururaja R. Vemaganti

Mechanical & Aerospace Engineering Theses & Dissertations

In this study a new adaptive remeshing method for high speed compressible flow analysis is presented. The method uses quadrilateral elements where possible, and triangles are introduced as needed. The primary goal of this study is to develop a remeshing method which uses both the concepts of unstructured and structured meshes for the finite element analysis to predict accurate aerodynamic heating in problems related to high speed viscous flows. The remeshing method uses a solution based on an old mesh to create a new mesh based on an advancing front technique. In the present implementation, a structured mesh of quadrilaterals …

Numerical Simulation Of F-18 Fuselage Forebody Flows At High Angles Of Attack, Lewis B. Schiff, Russell M. Cummings, Reese L. Sorenson, Yehia M. Rizk

Aerospace Engineering

As part of the NASA High Alpha Technology Program, fine-grid Navier-Stokes solutions have been obtained for flow over the fuselage forebody and wing leading edge extension of the F/A-18 High Alpha Research Vehicle at large incidence. The resulting flows are complex, and exhibit crossflow separation from the sides of the forebody and from the leading edge extension. A well-defined vortex pattern is observed in the leeward-side flow. Results obtained for laminar flow show good agreement with flow visualizations obtained in ground-based experiments. Further, turbulent flows computed at high-Reynolds-number flight-test conditions (M_∞ = 0.2, α = 30 °, and Re …

Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs

Physics Faculty Research & Creative Works

A systematic series of condensation coefficient measurements of water have been made using the University of Missouri-Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.

The Nusat I Project: Government, Industry And Academia Learning Together, Charles A. Bonsall

Robert "Bob" Twiggs STEM Education Collection

A report composed by Charles A. Bonsall on the history of the NUSat Project in March of 1989.

Numerical Representation Of Bodner Viscoplastic Constitutive Model, Faysal A. Kolkailah, Andrew J. Mcphate

Aerospace Engineering

Nonlinear analyses of structural components are normally carried out by finite element codes making Use of constitutive theories in which the material response is separated into the two important groups of phenomena known as rate‐dependent “creep” and rate‐independent “plasticity.” A number of viscoplastic constitutive theories in which creep and plasticity effects are combined into a unified plastic strain model have recently been proposed and are still undergoing active development. In this paper, the constitutive equations of the Bodner‐Partom model are used to present the time dependent, inelastic properties of Inconel 718 at 650 °C. This representation covers a wide range …

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The relation between dry diameter (X₀) and critical supersaturation (S_c) for atmospheric submicron aerosol particles is investigated using a long term air sampling program at Rolla, Missouri. The particles are passed through an electrostatic aerosol size classifier, and then through an isothermal haze chamber. Results are reported in terms of an apparent volume fraction of soluble material, ε_v defined such that for particles composed only of ammonium sulfate and water insoluble compounds, ε_v is the actual volume fraction of soluble material. The probability distribution of ε_v is found to be approximately Gaussian in …

Viscous Cross-Waves: An Analytical Treatment, Andrew J. Bernoff, L. P. Kwok, Seth Lichter

All HMC Faculty Publications and Research

Viscous effects on the excitation of cross‐waves in a semi‐infinite box of finite depth and width are considered. A formalism using matched asymptotic expansions and an improved method of computing the solvability condition is used to derive the relative contributions of the free‐surface, sidewall, bottom, and wavemaker viscous boundary layers. This analysis yields an expression for the damping coefficient previously incorporated on heuristic grounds. In addition, three new contributions are found: a viscous detuning of the resonant frequency, a slow spatial variation in the coupling to the progressive wave, and a viscous correction to the wavemaker boundary condition. The wavemaker …

Nonlinear Tracking Control Of Brushless Dc Motors For High-Performance Applications, N. Hemati, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The tracking control problem associated with brushless DC motors (BLDCMs) for high-performance applications is considered. To guarantee their high-dynamic-performance operation in motion control systems, the magnetic saturation and reluctance variation effects are accounted for in the BLDCM mathematical model. The trajectory tracking control problem is addressed in the context of the transformation theory of nonlinear systems. A nonlinear control law is implemented and shown to compensate for the nonlinearities of a BLDCM. A case study is presented in which a direct-drive inverted pendulum actuated by a BLDCM is used to investigate the effectiveness of the control law. The effectiveness of …

Generic Singularities Of Robot Manipulators, Ming-Chuan Leu, D. K. Pai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The singularities of the differential kinematic map, i.e. of the manipulator Jacobian, are considered. The authors first examine the notion of a generic kinematic map, whose singularities form smooth manifolds of prescribed dimension in the joint space of the manipulator. For three-joint robots, an equivalent condition for genericity using determinants is derived. The condition lends itself to symbolic computation and is sufficient for the study of decoupled manipulators, i.e. manipulators that an be separated into a three-joint translating part and a three-joint orienting part. The results are illustrated by analyzing the singularities of two classes of three-joint positioning robots.

Effects Of Nose Bluntness And Shock-Shock Interactions On Blunt Bodies In Viscous Hypersonic Flows, Dal J. Singh

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study has been conducted to investigate the effects of blunt leading edges on the viscous flow field around a hypersonic vehicle such as the proposed National Aero-Space Plane. Attention is focused on two specific regions of the flow field. Analysis of these flow regions is required to accurately predict the overall flow field as well as to get necessary information on localized zones of high pressure and intense heating.

The forebody is modeled by slender cones and ogives with spherically blunted nose. A combination of Navier-Stokes and parabolized Navier-Stokes equations is used to compute the flow field. The …

Optimal Design Rules Applied To The Design Of High-Speed Mechanisms Under Deflection And Stress Constraints, Frank W. Liou, Jenny Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Presented in this paper are two approaches for the design of flexible mechanisms under stress and deflection constraints. Based on the optimality conditions derived in this paper, two procedures are developed to design the minimum weight of mechanisms subject to stress and deflection limitations. The first procedure is the improvement of Thornton's design process r 17), and the second procedure is based on the interpolation technique. Several design examples are also presented to demonstrate these methods.

Axisymmetric Vibrations Of Reinforced Orthotropic Shallow Spherical Caps, Victor Birman, George J. Simitses

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Axisymmetric vibrations of reinforced shallow, spherical caps manufactured from orthotropic materials are considered. The closed form solution is obtained for the natural frequency of the cap with a clamped and immovable circular edge by assuming that the motion component parallel to the cap boundary plane (in plane) is negligible. Parametric studies are performed to assess the effect of various geometric and structural parameters on the natural frequency of the cap and, most importantly, to identify the most influencing parameters of the problem. From the generated data, it is concluded that the national frequency increases with increasing extensional stiffness and eccentricity …

Adiabatic Shear Banding In Plane Strain Problems, R. C. Batra, De Shin Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Plane strain thermomechanical deformations of a viscoplastic body are studied with the objective of analyzing the localization of deformation into narrow bands of intense straining. Two different loadings, namely, the top and bottom surfaces subjected to a prescribed tangential velocity, and these two surfaces subjected to a preassigned normal velocity, are considered. In each case a material defect, flaw, or inhomogeneity is modeled by introducing a temperature bump at the center of the specimen. The solution of the initial boundary value problem by the Galerkin-Adams method reveals that the deformation eventually localizes into a narrow band aligned along the direction …

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Relation between Dry Diameter (Xo) and Critical Supersaturation (Sc) for Atmospheric Submicron Aerosol Particles is Investigated. the Particles Are Passed through an Electrostatic Aerosol Size Classifier, and Then through an Isothermal Haze Chamber. Results Are Reported in Terms of an Apparent Volume Fraction of Soluble Material, Εv, Defined Such that for Particles Composed Only of Ammonium Sulfate and Water Insoluble Compounds, Εv is the Actual Volume Fraction of Soluble Material. the Probability Distribution of Εv is Found to Be Approximately Gaussian in the Εv Range 0.2 to 1.3. the Mean Εv is 0.5, for Electrostatic Aerosol Classifier Settings of …

System For Boundary Layer Control Through Pulsed Heating Of A Strip Heater, Milton E. Franke, Lawrence Kudelka

AFIT Patents

A system is described for controlling the transition of laminar/turbulent flow at a surface which comprises a thin narrow strip heater disposed adjacent the surface and extending substantially transversely of the flow of the air stream thereacross, the heater being resiliently held in tension on or in closely spaced relationship to the surface, and a power source operatively connected to the heater for applying pulsed voltage of preselected amplitude and frequency to the heater.

Calculations Of Three-Dimensional Transonic Flows Using The Implicit Formulation Of The Isenthalpic Euler Equations With Flux Vector Splitting, Frank E. Cannizzaro

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical method for solving three-dimensional transonic flows using the isenthalpic formulation of the Euler equations is developed. The method uses van Leer's flux vector splitting to solve the implicit formulation of the governing equations, which are applied to a cell centered finite-volume scheme. A three factor spatial approximate factorization is implemented in solving the implicit part of the governing equations. Time marching to a steady state solution requires short computational times due to the relative efficiency of the basic method. Computational times are further reduced by the implementation of the multigrid acceleration technique, which provided converged solutions in approximately …

Numerical Simulation Of Turbulent Flows Past Three-Dimensional Cavities, Shivakumar Srinivasan

Mechanical & Aerospace Engineering Theses & Dissertations

Computations have been performed to simulate turbulent supersonic, transonic, and subsonic flows past three-dimensional deep, transitional, and shallow cavities. Simulation of these self sustained oscillatory flows has been generated through time accurate solutions of Reynolds averaged full Navier-Stokes equations using the explicit MacCormack scheme. The Reynolds stresses have been modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses have been performed for the instantaneous pressure values on the cavity floor. Comparison with experimental data is made in terms of the mean …

A Finite Element Formulation For The Large Deflection Random Response Of Thermally Buckled Structures, James Eugene Locke

Mechanical & Aerospace Engineering Theses & Dissertations

The effects of temperature and acoustic loading are included in a theoretical finite element large deflection formulation for thin, isotropic plate and beam type structures. Thermal loads are applied as steady-state temperature distributions, and acoustic loads are taken to be stationary and Gaussian with zero mean and uniform magnitude and phase over the surface of the structure. Material properties are considered to be independent of temperature. Also, inplane and rotary inertia terms are assumed to be neglegible, and all inplane edge conditions are taken to be immovable. For the random vibration analysis, cross correlation terms are included.

The nature of …

Full-Potential Integral Solutions For Steady And Unsteady Transonic Airfoils With And Without Embedded Euler Domains, Hong Hu

Mechanical & Aerospace Engineering Theses & Dissertations

The integral equation solution of the full-potential equation is presented for steady and unsteady transonic airfoil flow problems. The method is also coupled with an embedded Euler domain solution to treat flows with strong shocks for steady flows.

For steady transonic flows, three integral equation schemes are well developed. The first two schemes are based on the integral equation solution of the full-potential equation in terms of the velocity field. The Integral Equation with Shock-Capturing (IE-SC) and the Integral Equation with Shock-Capturing Shock-Fitting (IE-SCSF) schemes have been developed. The IE-SCSF scheme is an extension of the IE-SC scheme, which consists …

A Comment On ‘Failure Modes Of Hybrid Composites …’, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper comments on an earlier paper on the failure modes of hybrid composites by Pitkethly and Bader, which appeared in the Carbon Fiber Conference issue. © 1988 IOP Publishing Ltd.

Stability Of Steady Cross-Waves: Theory And Experiment, Seth Lichter, Andrew J. Bernoff

All HMC Faculty Publications and Research

A bifurcation analysis is performed in the neighborhood of neutral stability for cross waves as a function of forcing, detuning, and viscous damping. A transition is seen from a subcritical to a supercritical bifurcation at a critical value of the detuning. The predicted hysteretic behavior is observed experimentally. A similarity scaling in the inviscid limit is also predicted. The experimentally observed bifurcation curves agree with this scaling.

Predicting Burst Pressures In Filament Wound Composite Pressure Vessels Using Acoustic Emission Data, Frederick R. Kalloo

Master's Theses - Daytona Beach

This work presents a statistical method for predicting the burst pressures in filament wound composite pressure vessels by analyzing acoustic emission data obtained during hydroproof testing. First the acoustic emission data is plotted in the form of amplitude distributions. Then, by using statistical models with characteristics similar to Rayleigh and Gaussian distributions, failure mechanism percentages are found, at which point multiple regression analysis is used to predict burst pressures. Next, the predicted burst pressures are compared to the actual burst pressures and the significance of the data is analyzed using standard statistical theories. The research shows that the predicted burst …

A Kinematical Investigation Of Some External Wind Tunnel Force Measurement Systems, Gary A. Peterson

Master's Theses - Daytona Beach

A discussion on the fundamental concepts associated with wind tunnel forces measurement systems (balances) is presented. Detailed static analyses are performed on the six component pyramidal, six component floating beam, and three component strain gaged strut balances. These static analyses lead to a dimensional uncertainty investigation of the pyramidal and strain gaged strut balances. The critical dimensions for the pyramidal balance are found to be the lengths of the pyramidal links, like platform half-width, and the model attachment strut. No single dimension on the strain gaged strut is more critical than the others.

A new method for the classification of …

Characteristics And Optimal Design Of Variable Airgap Linear Force Motors, Ming-Chuan Leu, E. V. Scorza, D. L. Bartel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An analytical model for predicting the characteristics of variable airgap linear force motors is developed. the model takes into account magnetic losses including the leakage and fringing effects and the reluctance existing at the contacts between permanent magnets and pole pieces. the model is validated by comparing its predicted characteristics with the results obtained from experiments and a finite element program. with the use of the modelled characteristics, computer programs based on the method of constrained steepest descent with state equations are developed for automating and optimising the design of linear force motors. Numerical studies are made for both minimisation …

Condensation Method For Humidity Measurement In The Umr Cloud Simulation Chamber., Donald E. Hagen, Daniel R. White, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Cloud Simulation Facility Has Been Developed for the Study of Various Atmospheric Cloud Processes. the Initial Relative Humidity of the Air Sample Put into the Cloud Chamber is a Key Parameter in Virtually Any Experiment and Needs to Be Known Accurately. This Report Describes How the Cloud Simulation Chamber itself Has Been Used as a Condensation Type Hygrometer to Calibrate the System's Humidifier. Two Distinct and Physically Different Methods for Inferring Mixing Ratio Are Used, One Exploiting the Sensitivity of Aerosol Activation to Humidity, and the Other Exploiting the Sensitivity of the Rate of Growth of Cloud Droplets to …

Effect Of Nominal Strain-Rates On The Initiation And Growth Of Adiabatic Shear Bands In Steels, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

University Of Missouri-Rolla Cloud Simulation Facility: Proto Ii Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Graduate Center for Cloud Physics Research at UMR Has Developed a Cloud Simulation Facility to Study Phenomena Occurring in Terrestrial Clouds and Fogs. the Facility Consists of a Pair of Precision Cooled-Wall Expansion Chambers Along with Extensive Supporting Equipment. the Smaller of These Chambers, Described in This Article, is Fully Operational, and is Capable of Simulating a Broad Range of In-Cloud Thermodynamic Conditions. It is Currently Being Used to Study Water Drop Growth and Evaporation for Drops Nucleated (Activated) on Well-Characterized Aerosol Particles. Measurements Have Been Made Not Only for Continuous Expansions (Simulated Updraft) But Also for Cyclic Conditions, …