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Articles 841 - 870 of 883
Full-Text Articles in Engineering
Bit Penetration Into Rock-A Finite Element Study, J. K. Wang, T. F. Lehnhoff
Bit Penetration Into Rock-A Finite Element Study, J. K. Wang, T. F. Lehnhoff
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The sequence of rock failure mechanisms and quantitative information on stress, displacement and material failure in the process of bit penetration have been obtained through computer simulation. A finite element approach has been developed to simulate bit penetration from bit-rock interaction to chip formation. A mathematical rock failure model, based on available rock failure experiments, has been proposed to represent post-failure rock behavior and applied in the penetration simulations. The finite element code was developed for two-dimensional plane strain problems to consider non-linear material properties, geometric non-linearity, and fracture propagation. An anistropic element as well as variable stiffness and stress …
Predicting Natural Frequencies Of A Hydrodynamically Lubricated Journal Bearing With Constant Oil Supply Pressure, D. C. Edwards, N. Khorzad, Charles L. Edwards
Predicting Natural Frequencies Of A Hydrodynamically Lubricated Journal Bearing With Constant Oil Supply Pressure, D. C. Edwards, N. Khorzad, Charles L. Edwards
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The analytical and experimental investigations reported here deal with the natural frequencies and system behavior of a full journal bearing subjected to a small sinusoidal load superimposed on a large unidirectional static load. The analysis, verified by experimentation, shows that the bearing can be regarded as two independent second-order systems acting perpendicular to each other. The variable coefficients of the equations of motion cause the bearing to behave as an underdamped system for low values of static eccentricity ratio to, and as an overdamped system for intermediate values of to. The bearing tends to be unstable above a particular to. …
Development Of Helicopter Flight Path Models, Alfred Fermelia, Donald A. Gyorog, V. J. Flanigan
Development Of Helicopter Flight Path Models, Alfred Fermelia, Donald A. Gyorog, V. J. Flanigan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The objective of this paper is to present general techniques for simulating helicopter flight trajectory response. During flight the pilot manipulates the controls either to trim the helicopter for steady flight by balancing the external forces and moments or to produce a desired maneuver by controlling the unbalance of these forces and moments. Discussions of the physical phenomena involved with the aerodynamics of the rotors and fuselage are given in [1] through [3]. The simulated control function will be composed forward-aft cyclic, lateral cyclic, pedal, and collective. This control will be represented by the vector
Measurement Of Growth Rate To Determine Condensation Coefficients For Water Drops Grown On Natural Cloud Nuclei., A. M. Sinnarwalla, Darryl J. Alofs, J. C. Carstens
Measurement Of Growth Rate To Determine Condensation Coefficients For Water Drops Grown On Natural Cloud Nuclei., A. M. Sinnarwalla, Darryl J. Alofs, J. C. Carstens
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Growth Rate Measurements Were Made for Water Drops Grown on Nuclei in Atmospheric Air Samples Taken in Rolla, Missouri. Rolla, Having a Population of 15,000 and Very Little Industry, is Relatively Free of Urban Pollutants. the Measurements Were Made in a Vertical Flow Thermal Diffusion Chamber at Supersaturations of 0. 5 and 1%. the Time to Grow from Near Dry Radius to the Final Radius (6 to 7. 5 Mu M) Was Measured. If One Assumes the Thermal Accomodation Coefficient is Unity, the Measurements Indicate an Average Value of 0. 026 for the Condensation Coefficient. the Temperature Ranged from 22. …
Insoluble Condensation Nuclei: The Effect Of Contact Angle, Surface Roughness And Adsorption., P. C. Mahata, Darryl J. Alofs
Insoluble Condensation Nuclei: The Effect Of Contact Angle, Surface Roughness And Adsorption., P. C. Mahata, Darryl J. Alofs
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Condensation of Water Vapor on Various Surfaces Was Studied Experimentally. for Surfaces with an Air-Water Contact Angle Theta Less Than 20 Degree, the Experimentally Determined Values of Critical Supersaturation S//c Agreed with Those Given by the Volmer Theory. at Higher Theta, the Experimental Values of S//c Were Below the Volmer Theory Values. When the Applied Supersaturation Was Less Than S//c, Condensation Was Avoided for Periods as Long as 20 H. It Was Determined Both by Experiment and Theoretical Analysis that the Effect of Surface Roughness is to Decrease S//c Only Slightly. These Results Suggest that Most Insoluble Airborne Particles Are …
Transport Phenomena In Thermally Stratified Boundary Layers, D. W. Pepper, S. C. Lee
Transport Phenomena In Thermally Stratified Boundary Layers, D. W. Pepper, S. C. Lee
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Studies of heat, mass, and momentum transfer are made to analyze the formation of marine fogs in thermally stratified boundary layers in the atmosphere. The governing partial differential equations of continuity, momentum, temperature, and concentration are used to describe the transport phenomena. An additional equation of turbulence energy is introduced to account for the development of the turbulent motions. Simultaneous solution of this system of equations allows the turbulent exchange coefficients to be treated in the same way as all other dependent parameters. Verification of the theoretical approach is made by comparing the numerical predictions with wind tunnel simulations of …
Thermal Stresses In A Sphere Due To Local Heating Followed By Complete Cooling, T. S. Chen, K. Thirumalai, J. B. Cheung
Thermal Stresses In A Sphere Due To Local Heating Followed By Complete Cooling, T. S. Chen, K. Thirumalai, J. B. Cheung
Mechanical and Aerospace Engineering Faculty Research & Creative Works
No abstract provided.
The Application Of Impact Dampers To Continuous Systems, Ranjit K. Roy, Richard D. Rocke, J. Earl Foster
The Application Of Impact Dampers To Continuous Systems, Ranjit K. Roy, Richard D. Rocke, J. Earl Foster
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A study has been made of the application of impact dampers to two types of continuous systems, a simply supported and a clamped beam. Experimental models were tested in the laboratory and computer programs were developed to calculate response by two separate approaches. Results from calculations agreed favorably with experimental tests. Curves presented show the response to be expected for values of significant system parameters and enable the user to apply impact dampers to these types of continuous systems. © 1975 by ASME.
Transient Thermal Stresses In A Sphere By Local Heating, J. B. Cheung, T. S. Chen, K. Thirumalai
Transient Thermal Stresses In A Sphere By Local Heating, J. B. Cheung, T. S. Chen, K. Thirumalai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The problem of transient thermal stresses in a solid, elastic, homogeneous, and isotropic sphere is solved for uniform and nonuniform, local surface heating. The temperature solutions are obtained by using separation of variables and integral transformation. The corresponding thermal stresses are derived by superposing a particular displacement potential function on Boussinesq solutions. Numerical solutions for two particular cases of localized heating of a typical brittle spherical solid have been obtained and presented. The results indicate a tensile stress concentration in the interior of the solid below the heated zone. © 1974 by ASME.
Vibration Characteristics Of Free Thin Cylindrical Shells, Floyd M. Cunningham, D. E. Leanhardt
Vibration Characteristics Of Free Thin Cylindrical Shells, Floyd M. Cunningham, D. E. Leanhardt
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper considers the flexural vibrations of free thin circular cylinders. A frequency equation is derived using free-free characteristic beam functions to represent the variation of mid-surface shell displacement components, u, v and w, with respect to the axial direction. Timoshenko strain-displacement relations for thin cylinders are used to determine elastic vibratory strain energy. Energy methods are applied to obtain the frequency equation and associated amplitude ratios for each of its roots. This energy solution is checked experimentally using a vibration exciter and numerically using the SABOR IV finite element program. With minor modification, the frequency equation conforms to the …
Engineering And Scientific Manpower- A Scarce Resource For The 1970'S, Merl Baker
Engineering And Scientific Manpower- A Scarce Resource For The 1970'S, Merl Baker
Mechanical and Aerospace Engineering Faculty Research & Creative Works
No abstract provided.
Nonequilibrium Structure Of Argon Shock Waves, Harlan F. Nelson
Nonequilibrium Structure Of Argon Shock Waves, Harlan F. Nelson
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This theoretical study investigates the influence of (1) the nonequilibrium excited state population in the relaxation region and (2) line radiation in the precursor on shock wave structure by considering strong shock waves propagating at Mach 18 and 24 into a theoretical argon-like gas at a pressure of 1 cm Hg and a temperature of 300°K. The argon atom is modeled as having two bound states plus a continuum, and the calculations include finite atom-atom and electron-atom collisional ionization and excitation rates as well as continuum and line radiation. The electron gas is allowed to be at a different temperature …
Breakdown Of The Laminar Flow Regime In Permeable-Walled Ducts, E. M. Sparrow, G. S. Beavers, T. S. Chen, J. R. Lloyd
Breakdown Of The Laminar Flow Regime In Permeable-Walled Ducts, E. M. Sparrow, G. S. Beavers, T. S. Chen, J. R. Lloyd
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The stability of laminar flow in a parallel-plate channel having one permeable bounding wall is investigated by means of linear theory. The analysis lakes account of the coupling of the disturbance, fields in the channel and in the permeable material and of velocity slip at the surface of the permeable wall. Complementary experiments are performed in which the breakdown of the laminar regime in flat rectangular ducts is identified from pressure-drop measurements and from flow visualization studies. The experiments cover the range of slip velocities from 15-30 percent of the mean velocity and, in addition, the case of zero slip …
Decision-Directed Detector For Overlapping Pcm/Nrz Signals, Cheng Wang, Thomas L. Noack
Decision-Directed Detector For Overlapping Pcm/Nrz Signals, Cheng Wang, Thomas L. Noack
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A decision-directed (DD) technique for the detection of overlapping PCM/NRZ signals in the presence of white Gaussian noise is investigated. The performance of the DD detector is represented by probability of error PE versus input signal-to-noise ratio (SNR). To examine how much improvement in performance can be achieved with this technique, PE's with and without DD feedback are evaluated in parallel. Further, analytical results are compared with those found by Monte Carlo simulations. The results are shown in good agreement. © 1973, IEEE. All rights reserved.
An Experimental And Numerical Study Of Elastic Strain Waves On The Center Line Of A 6061-T6 Aluminum Bar, J. L. Habberstad, K. G. Hoge, J. Earl Foster
An Experimental And Numerical Study Of Elastic Strain Waves On The Center Line Of A 6061-T6 Aluminum Bar, J. L. Habberstad, K. G. Hoge, J. Earl Foster
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The elastic strain waves resulting from the impact of two 3/4-in-dia 6061-T6 aluminum bars are studied experimentally and analytically. Experimental data are obtained from strain gages on the center line and outer surface of the bar, located at various distances from the impact end of the bar. Experimental data are compared to numerical results obtained from integrating the exact equations of two-dimensional motion. In general, agreement between the numerical and experimental results is very good. © 1972 by ASME.
Effects Of Cold Working Under Pressure On Subsequent Yield, J. G. Hoeg, Robert L. Davis
Effects Of Cold Working Under Pressure On Subsequent Yield, J. G. Hoeg, Robert L. Davis
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A method utilizing high pressure fluid environments is described whereby a three-dimensional subsequent yield surface was determined for 304 stainless steel cylindrical parent specimens of this material were prestrained in axial compression under fluid pressure and then small sub specimens were sectioned from these parent specimens. Finite element techniques were used to optimize the parent specimen size so that a zone of uniform axial stress woidd result during the prestraining. Longitudinal strains in this zone were monitored during the prestraining and the subspecimens were cut from this region in a manner that did not allow the machining to appreciably affect …
An Application Of Bubble Shape Theory To The Determination Of Air Transfer Through Adsorbed Surface Films, Robert A. Medrow
An Application Of Bubble Shape Theory To The Determination Of Air Transfer Through Adsorbed Surface Films, Robert A. Medrow
Mechanical and Aerospace Engineering Faculty Research & Creative Works
No abstract provided.
A Strain Energy Comparison Of Discrete Modeling For Vibrating Continuous Systems, S. K. Tolani, Richard Dale Rocke
A Strain Energy Comparison Of Discrete Modeling For Vibrating Continuous Systems, S. K. Tolani, Richard Dale Rocke
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Lumped parameter models commonly used to describe continuous one-dimensional and Bernoulli-Elder beam vibration problems have been compared on the basis of maximum system, strain energy. The consistent mass matrix approach has been included in the comparison. Standard matrix techniques have been employed to mathematically obtain desired solutions. Closed form solutions and solutions via the models to Ike system strain energy were obtained for all systems in three dynamic states: Free vibrations, constant base acceleration, and half sine base acceleration. Behavior of the strain energy errors, in general, were found to be similar to those of the frequency root errors. © …
Magnetohydrodynamic Stability Of The Developing Laminar Flow In A Parallel-Plate Channel, T. S. Chen, T. E. Eaton
Magnetohydrodynamic Stability Of The Developing Laminar Flow In A Parallel-Plate Channel, T. S. Chen, T. E. Eaton
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Linear stability of the developing laminar flow of an electrically conducting, incompressible fluid in a parallel-plate channel under a transverse magnetic field is investigated. The case of small magnetic Reynolds numbers is treated. The developing flows whose stability characteristics are studied correspond to those induced by a uniform and a parabolic velocity distribution at the channel inlet. The stability of the fully developed Hartmann flow is also reexamined. Neutral stability curves and axial variations of the critical Reynolds number are presented for a range of Hartmann numbers between 0 and 4. It is found that for Hartmann numbers larger than …
Reply To The Comments Of H. M. Princen [2], Robert A. Medrow, B. T. Chao
Reply To The Comments Of H. M. Princen [2], Robert A. Medrow, B. T. Chao
Mechanical and Aerospace Engineering Faculty Research & Creative Works
No abstract provided.
Forming Of 7075-T6 Aluminum In High Pressure Environments, Richard L. Pendleton, Robert L. Davis
Forming Of 7075-T6 Aluminum In High Pressure Environments, Richard L. Pendleton, Robert L. Davis
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Plates of 7075-T6 Aluminum have been folded along a major axis in pressure environments of atmospheric, 20,000 psi, and 40,000 psi. A finite element computer program is used to determine the stress state in the plates at various loads. Tension and compression tests conducted in pressure environments up to 70,000 psi were used to construct models using effective stress, effective strain, and pressure as parameters to predict the behavior of the material under various stress conditions. A prediction of the occurrence of fracture in the folded plate was possible using the computer results and the pressure dependent model. As better …
Finite-Element Analysis Of Pressure Vessels, Robert L. Davis, H. Dean Keith
Finite-Element Analysis Of Pressure Vessels, Robert L. Davis, H. Dean Keith
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The finite-element technique has been applied in the analysis of a variety of pressure vessel problems. The example problems described in this paper suggest that the finite element method is perhaps the most suitable means currently available for obtaining quick and accurate solutions for real-life pressure vessel problems. Finite-element programs can be used by the practicing engineer. Companion programs are available that can be used to check the input data and graphically display both the input and output data. © 1972 by ASME.
An Approximate Model For The Static Operation Of A Fluidic Amplifier Employing Axisymmetric Jets, Richard T. Johnson
An Approximate Model For The Static Operation Of A Fluidic Amplifier Employing Axisymmetric Jets, Richard T. Johnson
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An approximate mathematical model for the static, no-load (blocked receiver) operation of a fluidic amplifier employing axisymmetric jets is developed. The amplifier is similar in concept to the three-terminal modulator developed by the Johnson Service Co. The approach used in developing the model assumes that the complex flow phenomena can be represented by the combination of several elementary flow problems. The model employs the concept of an equivalent power nozzle in describing downstream flow with a control signal present. Experimental results are presented to justify assumptions and evaluate parameters. © 1971 by ASME.
Heat Transfer From An Oscillating Horizontal Wire, Bassem F. Armaly, D. H. Madsen
Heat Transfer From An Oscillating Horizontal Wire, Bassem F. Armaly, D. H. Madsen
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The effect of vibration on heat transfer by natural convection has been investigated experimentally using a thin wire, 0.010 in. in diameter, and air as a convection medium. Horizontal reciprocating motion of varying amplitudes, peak-to-peak values of 0-2.655 in., and frequencies, 0-20 cps, was applied to an electrically heated horizontal wire. The average wire velocity (frequency times total path length traveled per cycle by the wire) was used to correlate and predict the experimental results. © 1971 by ASME.
Cylindrical Couette Flow Experiments In The Transition Regime, Darryl J. Alofs, George S. Springer
Cylindrical Couette Flow Experiments In The Transition Regime, Darryl J. Alofs, George S. Springer
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Density Distributions Were Measured in Rarefied Argon Contained between Two Concentric Cylinders, the Inner One Rotating, the Outer One Stationary. the Experiments Were Performed with a Mach Number Near Unity, based on the Surface Speed and Surface Temperature of the Rotating Cylinder. Particular Attention Was Focused on Obtaining Data in the Slip and Transition Regimes Where the Knudsen Number, Defined as the Ratio of the Mean Free Path to the Gap Size between the Cylinders, Varied from 0.04 to 1.07. the Density Distributions Were Measured by Observing the Gas Luminescence Induced by the Passage of a Narrow Beam of High …
Density Distribution Measurements In Rarefied Gases Contained Between Parallel Plates At High Temperature Differences, Darryl J. Alofs, Richard C. Flagan, George S. Springer
Density Distribution Measurements In Rarefied Gases Contained Between Parallel Plates At High Temperature Differences, Darryl J. Alofs, Richard C. Flagan, George S. Springer
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Density Distributions Were Experimentally Determined in Rarefied Gases at Rest Contained between Two Parallel Plates Maintained at Widely Different Temperatures. the Temperatures of the Hot and Cold Plates Were ∼79°K and ∼294°K, Respectively, Resulting in a Temperature Ratio of About 4:1. Both Helium and Nitrogen Were Used as Test Gases. Particular Attention Was Focused on Obtaining Data in the Temperature Jump and Transition Regimes. the Gas Densities Were Measured by Observing the Luminescence Produced by a High-Energy Electron Beam Traversed between the Plates. in Addition to the Density Measurements, Heat Transfer Measurements Were Also Made in Order to Estimate the …
Charges On Jet Drops Produced By Bursting Bubbles, Robert A. Medrow, B. T. Chao
Charges On Jet Drops Produced By Bursting Bubbles, Robert A. Medrow, B. T. Chao
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The sizes and charges of jet drops produced by bursting air bubbles are examined experimentally. The variation in charge for bubble lifetimes of up to 200 sec in NaCl and KCl solutions is reported. Jet drops refer to drops produced by a jet rising from a cavity left in a liquid surface by a bursting bubble; bubble lifetime is the interval during which a bubble is in motion between generation and rupture. With other variables held constant, drop charge shows a characteristic variation of a rise to a maximum followed by a decrease to an asymptotic value, as bubble lifetime …
Floating Bubble Configurations, Robert A. Medrow, B. T. Chao
Floating Bubble Configurations, Robert A. Medrow, B. T. Chao
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The configurations of bubbles floating at a vapor-liquid interface are investigated both analytically and experimentally. The differential equations governing the shape of a single bubble at rest in a liquid of infinite extent are deduced under the assumption of zero dome thickness, uniform surface tension, and equal gas densities within the bubble and above the interface. These equations show that nondimensional bubble shapes depend upon the value of a single parameter. An analytical solution, valid for small bubbles, is developed and shown to be in good agreement with the general numerical solution. Good agreement with theory is demonstrated for floating …
The Axial Contact Of Finite Elastic Cylinders With Application To Thermal Contact Resistance, Ross Orlo Mcnary
The Axial Contact Of Finite Elastic Cylinders With Application To Thermal Contact Resistance, Ross Orlo Mcnary
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Predictions of the macroscopic thermal contact resistance have been severely restricted because the macroscopic contact area between finite members could not be determined. A new method of solution to this contact problem in elasticity is developed which is applicable to a wide variety of geometries and boundary conditions. A physical lumped-parameter model is employed from which the finite difference equations in terms of displacement are derived. Calculations using this method indicate that large errors in the prediction of the thermal contact resistance can result if solutions for bodies of infinite extent are employed for finite regions of interest. Especially large …
Rotating Cylinder Apparatus For Rarefied Gas Flow Studies, Darryl J. Alofs, George S. Springer
Rotating Cylinder Apparatus For Rarefied Gas Flow Studies, Darryl J. Alofs, George S. Springer
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A Rotating Cylinder Type Apparatus is Described, Suitable for Determining Drag in Cylindrical Couette Flow of Rarefied Gases, and for Evaluating Tangential Momentum Accommodation Coefficients at Gas-Solid Boundaries. the Apparatus is Equipped with a Damping Device using Diffusion Pump Oil for Eliminating Undesirable Oscillations in the System. Tangential Momentum Accommodation Coefficients of Argon on Aluminum Were Determined with an Accuracy of ±2.5%. the Results Obtained Indicate that the Apparatus May Be Used over a Wide Pressure Range, Corresponding to Free Molecule and Continuum Flow Conditions. © 1970 the American Institute of Physics.