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Articles 1  23 of 23
FullText Articles in Mechanical Engineering
Ultrasonic Flaw Classification And Sizing , SungJin Song
Ultrasonic Flaw Classification And Sizing , SungJin Song
Retrospective Theses and Dissertations
Flaw classification (determination of the flaw type) and flaw sizing (prediction of the flaw shape, orientation and sizing parameters) are very important issues in ultrasonic nondestructive evaluation of materials. In this work, new techniques for both classification and sizing are described;In the area of flaw classification, a methodology is developed which can solve classification problems in weldments using probabilistic neural networks. In the area of flaw sizing, four new approaches are presented including (1) the determination of distancegainsize (DGS) curves and frequency response curves for flatbottom holes based on a theoretical ultrasonic scattering model, (2) a timeofflight equivalent (TOFE ...
Modification Of AxialFlow Compressor Stall Margin By Variation Of Stationary Blade Setting Angles , John Paul Rukavina
Modification Of AxialFlow Compressor Stall Margin By Variation Of Stationary Blade Setting Angles , John Paul Rukavina
Retrospective Theses and Dissertations
The useful operating range of the multistage, axialflow compressor component of a gas turbine engine limits the extent of operation of that engine. Generally, the compressor stalls or surges at low flow rates and chokes at high flow rates. Thus, any improvement in the range between these compressor aerodynamic limits is normally of benefit to the engine also. An idea for delaying the onset of rotating stall in a multistage, axialflow compressor which involved circumferentially varying the blade setting angles of stationary blades upstream of the compressor rotors was investigated. Tests involving two lowspeed, multistage, axialflow compressors and an intermediatespeed ...
Synthesis And Analysis Of Elastic HighSpeed CamOperated Mechanisms , HsinTing Jonathan Liu
Synthesis And Analysis Of Elastic HighSpeed CamOperated Mechanisms , HsinTing Jonathan Liu
Retrospective Theses and Dissertations
In the synthesis of highspeed cam profiles, we must compensate for the elastic deflections induced by large inertial effects generated during operation. Thus, differential equations with kinematic constraints need to be solved. The governing dynamic equations are in homogeneous, periodic, linear, ordinary differential equations which possess multiple unstable and high vibrational regions at various operating speed zones. These regions are found to be intrinsically determined by the changing geometry of the follower linkage during operation;This dissertation considers two types of cam driven linkages. Parts I and II consider a cam driving a lumped inertia through a massless elastic slidercrank ...
Ionic Structure Of Methane Flames , Timothy Wayne Pedersen
Ionic Structure Of Methane Flames , Timothy Wayne Pedersen
Retrospective Theses and Dissertations
The objective of this research was to predict the structure of ions generated in methane flames. These simulations might lead to a better understanding of the interactions between ions in hydrocarbon flames. It was thought that such an understanding could lead to technology for electrically controlling combustion processes, formation of soot, and heat transfer;The reaction mechanisms used in this study was for a methane or hydrogen/methane flame. It contains reactions for the oxidation of fuels, chemiionization, ionmolecule reactions, and dissociative recombination. A computer model was developed to evaluate the formation of ions based on the proposed reaction mechanism ...
A Numerical Model For A Bubble In Nucleate Pool Boiling , Rajendra K. Patil
A Numerical Model For A Bubble In Nucleate Pool Boiling , Rajendra K. Patil
Retrospective Theses and Dissertations
Growth of a hemispherical bubble in nucleate pool boiling is analyzed in two stages using a numerical technique. In the first stage, growth of a hemispherical bubble in viscous medium on an isothermally heated surface is investigated neglecting the microlayer contribution. The results are compared with an analytical solution for homogeneous growth in a superheated medium, to other numerical results for heterogeneous growth in an inviscid medium, and to previous experimental work. The flow field and temperature distribution around the bubble are found to exhibit similarity for large times when an appropriate nondimensionalization is used. The Jakob number (Ja), and ...
Reduction Of Bottleneck Operations In JustInTime Manufacturing, Shehzad Ahmed
Reduction Of Bottleneck Operations In JustInTime Manufacturing, Shehzad Ahmed
Retrospective Theses and Dissertations
No abstract provided.
Application Of The Boundary Element Method To Coupled FluidStructure Interaction Problems , Partha P. Goswami
Application Of The Boundary Element Method To Coupled FluidStructure Interaction Problems , Partha P. Goswami
Retrospective Theses and Dissertations
The direct boundary element method (BEM) is used to formulate and numerically simulate the interaction of acoustic waves with submerged elastic structures and subsequently specialized to model finite beam transmission through locally curved elastic surfaces. These are structuralacoustic or fluidsolid interaction problems coupling scalar (acoustic) and vector (elastic) media. The problem is formulated in the frequency domain and modelled in three dimensions, and the elastoacoustic phenomenon described by the acoustic and elastodynamic boundary integral equations (BIE) with pressure and displacement serving as the primarily variables;The general problem deals with a closed solid domain surrounded by an unbounded fluid medium ...
Tribological And Arc Erosion Behaviors Of CopperRefractory Metal In Situ Composites , Ping Liu
Tribological And Arc Erosion Behaviors Of CopperRefractory Metal In Situ Composites , Ping Liu
Retrospective Theses and Dissertations
Tribological and arc erosion behaviors of CuNb and CuCr in situ composites were investigated in this dissertation. Dry sliding tests were performed in a pinondisk wear tester with the composites rubbing against a rotating tool steel disk under ambient conditions with a pressure of 0.68 MPa, sliding speeds up to 2.5 m/s, and electrical current densities up to 2.89 MA/m[superscript]2. Electrical arc erosion tests were performed in a makeandbreak test setup and a highenergy stationary arc gap test facility;Sliding friction and wear behaviors of CuNb composites with and without electrical loads were ...
An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , WanShik Jang
An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , WanShik Jang
Retrospective Theses and Dissertations
This study is to develop a practical control scheme called threestep input method whereby a flexible robot arm is moved from one position to another in the least amount of time with a minimum of residual vibration when the arm reaches its defined end point. The basic premise is to use open loop selfadjusting input signals that take system dynamic characteristics into account;In particular, the class of problem addressed in this thesis is restricted to the elimination of residual vibration when the fastest response is done in time steps of one half of the robot's fundamental natural period ...
Methods Of Measuring The Solubility And Viscosity Of Lubricating Oil/Refrigerant Mixtures At High Discharge Pressures And Temperatures , Nolan A. Van Gaalen
Methods Of Measuring The Solubility And Viscosity Of Lubricating Oil/Refrigerant Mixtures At High Discharge Pressures And Temperatures , Nolan A. Van Gaalen
Retrospective Theses and Dissertations
The design and construction of a test facility and methodology for measuring the solubility and viscosity of lubricating oil/refrigerant mixtures at high pressures and temperatures are described. An auxiliary charging system, developed to provide precisely measured quantities of oil and refrigerant to the test facility, is also presented. The test facility was developed under the sponsorship and supervision of ASHRAE which funded this research project (RP580);The solubility, viscosity and density of mixtures of R22 and of R502 with commonly used 150 SUS lubricants have been measured by using this facility. Specifically, results for liquid mixtures of 10% to ...
Automatic Programming Of Arc Welding Robots , Srikanth Padmanabhan
Automatic Programming Of Arc Welding Robots , Srikanth Padmanabhan
Retrospective Theses and Dissertations
Automatic programming of arc welding robots requires the geometric description of a part from a solid modeling system, expert weld process knowledge and the kinematic arrangement of the robot and positioner automatically. Current commercial solid modelers are incapable of storing explicitly product and process definitions of weld features. This work presents a paradigm to develop a computeraided engineering environment that supports complete weld feature information in a solid model and create an automatic programming system for robotic arc welding;In the first part, welding features are treated as properties or attributes of an object, features which are portions of the ...
Adaptive Torque Control Of A Diesel Engine For Transient Test Cycles , Taner Tuken
Adaptive Torque Control Of A Diesel Engine For Transient Test Cycles , Taner Tuken
Retrospective Theses and Dissertations
Adaptive control techniques have been applied to the problem of diesel engine torque control. Adaptive control has the potential of greater versatility than classical control techniques. Three adaptive control strategies are tested and compared to each other: selftuning control with oneshot parameter identification and controller design, selftuning gainscheduling control, and selftuning control with continuous adaptation of system and controller parameters. A continuoustime parameter identification approach, namely the Poisson Moment Functional (PMF) method, is employed due to its superior noise rejection capability. To ensure the applicability of time delay systems, a Smith predictor is employed. The controller design is implemented using ...
Elevated Temperature Erosion Studies On Some Materials For High Temperature Applications , Jianren Zhou
Elevated Temperature Erosion Studies On Some Materials For High Temperature Applications , Jianren Zhou
Retrospective Theses and Dissertations
The surface degradation of materials due to high temperature erosion or combined erosioncorrosion is a serious problem in many industrial and aeronautical applications. As such, it has become an important design consideration in many situations. The materials investigated in the present studies are stainless steels, Ti6Al4V, alumina ceramics, with and without silicate glassy phase, and zirconia. These are some of the potential materials for use in the high temperature erosivecorrosive environments;The erosion or erosioncorrosion experiments were performed in a high temperature sandblast type of test rig. The variables studied included the temperature, material composition, heat treatment condition, impingement velocity ...
Numerical Solution Of Inverse Problems In Mechanics Using The Boundary Element Method , Shuvra Das
Numerical Solution Of Inverse Problems In Mechanics Using The Boundary Element Method , Shuvra Das
Retrospective Theses and Dissertations
Due to the illposed nature of inverse problems, it is difficult to obtain solutions using well known analytical and numerical techniques. The use of boundary element method as a numerical technique to solve inverse problems is quite new. In this work, the algorithms for the solution of two kinds of inverse problems are examined in detail. For the first kind, the shape and location of a part of the boundary is unknown; and for the second kind, the boundary condition is not specified on a part of the boundary;Boundary value problems with partially unknown boundary are illposed. To solve ...
Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch
Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch
Retrospective Theses and Dissertations
The boundary element method (BEM) is used to numerically simulate the interaction of ultrasonic waves with material defects such as voids, inclusions, and open cracks. The time harmonic formulation is in 3D and therefore allows flaws of arbitrary shape to be modeled. The BEM makes such problems feasible because the underlying boundary integral equation only requires a surface (2D) integration and difficulties associated with the seemingly infinite extent of the host domain are not encountered. The computer code utilized in this work is built upon recent advances in elastodynamic boundary element theory such as a scheme for self adjusting integration ...
A Study Of High Speed Flows In An Aircraft Transition Duct , Bruce A. Reichert
A Study Of High Speed Flows In An Aircraft Transition Duct , Bruce A. Reichert
Retrospective Theses and Dissertations
Circulartorectangular transition ducts are used on aircraft with rectangular exhaust nozzles to connect the engine and nozzle. Often, the incoming flow of these transition ducts includes a swirling velocity component remaining from the gas turbine engine. Previous transition duct studies have either not included inlet swirl or when inlet swirl was considered, only overall performance parameters were evaluated. This dissertation reports the study of circulartorectangular transition duct flows with and without inlet swirl. This study was completed in order to understand the effect of inlet swirl on the transition duct flow field and to provide detailed duct flow data for ...
Drag On Object Moving Through Foam , Chinwha Chung
Drag On Object Moving Through Foam , Chinwha Chung
Retrospective Theses and Dissertations
Foams consist of small gas bubbles separated by thin liquid films. Although many complex models have been developed to describe the rheological properties of foam, very little information is available concerning the flow charateristics of foam flowing past an object. The purpose of this research was to investigate foam flow properties by performing simple experiments to determine the drag charateristics of simpleshaped bodies moving through foam;A rotating tank apparatus was built and used as the equivalent of a wind tunnel in aerodynamic testing. Foam with consistent properties was produced and models of various shapes were suspended in the moving ...
Control Of A Very Flexible Robot In Gravity , Jay E. Shannan
Control Of A Very Flexible Robot In Gravity , Jay E. Shannan
Retrospective Theses and Dissertations
This thesis presents several algorithms used to control a very flexible robot in gravity. The flexible arm is modelled using an assumed modes method to characterize the elastic behavior. Gravity is included in the model. Control algorithms are developed and simulated numerically. The control schemes include proportionalderivative (PD), linear quadratic regulator (LQR), and linear quadratic regulator with a prescribed degree of stability algorithms. The PD algorithms use only hub position and velocity for feedback. Simulations show fast response times with large overshoot and long settling times. The LQR algorithms have the benefit of modal feedback. These responses settle quicker than ...
Prediction Of Diesel Engine Particulate Emission During Transient Cycles, Qiqing Jiang
Prediction Of Diesel Engine Particulate Emission During Transient Cycles, Qiqing Jiang
Retrospective Theses and Dissertations
A computer model has been developed to predict diesel engine particulate emission during transients in speed and torque. The computer model consists of a quasisteadystate engine combustion model, a dynamic engine model, and a dynamic turbocharger model. The model predictions were compared to experimentally measured particulate emissions. Particulate matter was measured under steadystate conditions, over an EPA transcient cycle, and for discrete segments of various transient cycles;The computer model accurately predicts engine air flow rate, turbocharger speed, and instantaneous engine equivalence ratio. The fuel consumption given by the model is within 3% of the experimental measurement over the transient ...
A Genetic Algorithm Approach To Optimization Of Asynchronous Automatic Assembly Systems, Mark A. Wellman
A Genetic Algorithm Approach To Optimization Of Asynchronous Automatic Assembly Systems, Mark A. Wellman
Retrospective Theses and Dissertations
No abstract provided.
A Study Of The Relative Importance Of Jit Implementation Techniques Using The Analytic Hierarchy Process Model, Sutthira Thanyavanich
A Study Of The Relative Importance Of Jit Implementation Techniques Using The Analytic Hierarchy Process Model, Sutthira Thanyavanich
Retrospective Theses and Dissertations
No abstract provided.
Characterization And Analysis Of The BulkAcousticWave Thin Film Resonator In SubNanogram Mass Detection, Ronald Patrick O'Toole
Characterization And Analysis Of The BulkAcousticWave Thin Film Resonator In SubNanogram Mass Detection, Ronald Patrick O'Toole
Retrospective Theses and Dissertations
No abstract provided.
Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc22 And Hfc134a, Steven Charles Zoz
Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc22 And Hfc134a, Steven Charles Zoz
Retrospective Theses and Dissertations
No abstract provided.