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Articles 1 - 23 of 23

Full-Text Articles in Mechanical Engineering

Ultrasonic Flaw Classification And Sizing , Sung-Jin Song Jan 1991

Ultrasonic Flaw Classification And Sizing , Sung-Jin 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 distance-gain-size (DGS) curves and frequency response curves for flat-bottom holes based on a theoretical ultrasonic scattering model, (2) a time-of-flight equivalent (TOFE ...


Modification Of Axial-Flow Compressor Stall Margin By Variation Of Stationary Blade Setting Angles , John Paul Rukavina Jan 1991

Modification Of Axial-Flow Compressor Stall Margin By Variation Of Stationary Blade Setting Angles , John Paul Rukavina

Retrospective Theses and Dissertations

The useful operating range of the multistage, axial-flow 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, axial-flow compressor which involved circumferentially varying the blade setting angles of stationary blades upstream of the compressor rotors was investigated. Tests involving two low-speed, multistage, axial-flow compressors and an intermediate-speed ...


Synthesis And Analysis Of Elastic High-Speed Cam-Operated Mechanisms , Hsin-Ting Jonathan Liu Jan 1991

Synthesis And Analysis Of Elastic High-Speed Cam-Operated Mechanisms , Hsin-Ting Jonathan Liu

Retrospective Theses and Dissertations

In the synthesis of high-speed 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 slider-crank ...


Ionic Structure Of Methane Flames , Timothy Wayne Pedersen Jan 1991

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, ion-molecule 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 Jan 1991

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 non-dimensionalization is used. The Jakob number (Ja), and ...


Reduction Of Bottleneck Operations In Just-In-Time Manufacturing, Shehzad Ahmed Jan 1991

Reduction Of Bottleneck Operations In Just-In-Time Manufacturing, Shehzad Ahmed

Retrospective Theses and Dissertations

No abstract provided.


Application Of The Boundary Element Method To Coupled Fluid-Structure Interaction Problems , Partha P. Goswami Jan 1991

Application Of The Boundary Element Method To Coupled Fluid-Structure 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 structural-acoustic or fluid-solid interaction problems coupling scalar (acoustic) and vector (elastic) media. The problem is formulated in the frequency domain and modelled in three dimensions, and the elasto-acoustic 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 Copper-Refractory Metal In Situ Composites , Ping Liu Jan 1991

Tribological And Arc Erosion Behaviors Of Copper-Refractory Metal In Situ Composites , Ping Liu

Retrospective Theses and Dissertations

Tribological and arc erosion behaviors of Cu-Nb and Cu-Cr in situ composites were investigated in this dissertation. Dry sliding tests were performed in a pin-on-disk 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 make-and-break test set-up and a high-energy stationary arc gap test facility;Sliding friction and wear behaviors of Cu-Nb composites with and without electrical loads were ...


An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , Wan-Shik Jang Jan 1991

An Open Loop Control Scheme To Minimize Flexible Robot Response Time While Minimizing Residual Vibrations , Wan-Shik Jang

Retrospective Theses and Dissertations

This study is to develop a practical control scheme called three-step 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 self-adjusting 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 Jan 1991

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 (RP-580);The solubility, viscosity and density of mixtures of R-22 and of R-502 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 Jan 1991

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 computer-aided 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 Jan 1991

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: self-tuning control with one-shot parameter identification and controller design, self-tuning gain-scheduling control, and self-tuning control with continuous adaptation of system and controller parameters. A continuous-time 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 Jan 1991

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 erosion-corrosion 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, Ti-6Al-4V, alumina ceramics, with and without silicate glassy phase, and zirconia. These are some of the potential materials for use in the high temperature erosive-corrosive environments;The erosion or erosion-corrosion experiments were performed in a high temperature sand-blast 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 Jan 1991

Numerical Solution Of Inverse Problems In Mechanics Using The Boundary Element Method , Shuvra Das

Retrospective Theses and Dissertations

Due to the ill-posed 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 ill-posed. To solve ...


Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch Jan 1991

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 Jan 1991

A Study Of High Speed Flows In An Aircraft Transition Duct , Bruce A. Reichert

Retrospective Theses and Dissertations

Circular-to-rectangular 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 circular-to-rectangular 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 Jan 1991

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 simple-shaped 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 Jan 1991

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 proportional-derivative (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 Jan 1991

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 quasi-steady-state 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 steady-state 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 Jan 1991

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 Jan 1991

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 Bulk-Acoustic-Wave Thin Film Resonator In Sub-Nanogram Mass Detection, Ronald Patrick O'Toole Jan 1991

Characterization And Analysis Of The Bulk-Acoustic-Wave Thin Film Resonator In Sub-Nanogram Mass Detection, Ronald Patrick O'Toole

Retrospective Theses and Dissertations

No abstract provided.


Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc-22 And Hfc-134a, Steven Charles Zoz Jan 1991

Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc-22 And Hfc-134a, Steven Charles Zoz

Retrospective Theses and Dissertations

No abstract provided.