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2002

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Articles 211 - 233 of 233

Full-Text Articles in Mechanical Engineering

A New Approach To Evaluate Fracture Strength Of Uv-Liga Fabricated Nickel Specimens, Catherine Oropeza Jan 2002

A New Approach To Evaluate Fracture Strength Of Uv-Liga Fabricated Nickel Specimens, Catherine Oropeza

LSU Master's Theses

One of the major difficulties faced by MEMS researchers today is the lack of data regarding properties of electroplated metals or alloys at micro-levels as those produced by the LIGA and LIGA related process. These mechanical properties are not well known and they cannot be extrapolated from macro-scale data without experimental verification. This lack of technical information about microscale physical properties has affected the consistency and reliability of batch-fabricated components and leads to very low rates of successful fabrication. Therefore, this material issue is of vital importance to the development of LIGA technology and to its industrial applications. This thesis ...


A Model Of Heat And Mass Transfer In An Idealized Micro Heat Pipe, Jin Zhang Jan 2002

A Model Of Heat And Mass Transfer In An Idealized Micro Heat Pipe, Jin Zhang

LSU Master's Theses

Micro heat pipes have been used to cool computer chips, but their heat transfer coefficients are low compared with that of conventional heat pipes. To understand this deficiency, an idealized micro heat pipe is proposed that has simplified interfacial geometry but retains the essential physics. It is a long and narrow cavity of rectangular cross section with the bottom made of a wetting material and the top a non-wetting material. A wetting liquid fills the bottom half of the cavity, and its vapor fills the rest. This configuration ensures that the liquid-vapor interface is pinned at the contact line. Since ...


Buckling Analysis Of Grid Stiffened Composite Structures, Samuel Kidane Jan 2002

Buckling Analysis Of Grid Stiffened Composite Structures, Samuel Kidane

LSU Master's Theses

Buckling of a stiffened composite cylinder is a very complex phenomenon that involves complex interactions between the skin and the stiffeners. Depending on different configurations of the skin and stiffener, different buckling failure modes and failure loads are observed in stiffened cylinders. In this work failure modes and buckling loads of stiffened composite cylinders under uniaxial loading condition is investigated by using analytical and experimental approaches. In the first Chapter an improved smeared method is developed to model the buckling problem of an isogird stiffened composite cylinder. In this model the stiffness contributions of the stiffeners is computed by analyzing ...


Tapered Liga Mold Insert, Ryan Anthony Turner Jan 2002

Tapered Liga Mold Insert, Ryan Anthony Turner

LSU Master's Theses

The applications of microstructures produced by the LIGA process are useful in a broad range of fields including: microfluidics, heat transfer, and mechanics. The Microsystems Engineering Team at Louisiana State University has used the LIGA process as a foundation for the team’s productivity in these areas. Many advances in the processes involved in producing these microstructures have been made in the past increasing the efficiency of the entire process. A modified exposure technique in the lithography stage of the LIGA process is being developed to produce microstructures with a draft angle as opposed to the standard straight walled structures ...


Development Of A Micro Power Relay With Static Electrical Actuator, Ren Yang Jan 2002

Development Of A Micro Power Relay With Static Electrical Actuator, Ren Yang

LSU Master's Theses

In this thesis, a research about design and fabrication of a micro power relay is presented. Compared with the traditional electromagnetic relay and solid-state relay, MEMS micro power relay is introduced. After introducing the advantage and other people's research about the MEMS relay, some design and simulation about a new prototype micro power relay are done. Based on the design, UV-LIGA is used as the fabrication method. The bottom part and top part of the micro power relay are fabricated separately. After assembly the top part on the bottom part, some simple tests about the micro power relay are ...


Effect Of Tip Geometry On Blade Tip Flow And Heat Transfer, David Michael Kontrovitz Jan 2002

Effect Of Tip Geometry On Blade Tip Flow And Heat Transfer, David Michael Kontrovitz

LSU Master's Theses

In an attempt to increase thrust to weight ratio and efficiency of modern gas turbines, engine designers are always interested in increasing turbine operating temperatures. The benefits are attributed to the fact that higher temperature gases yield a higher energy potential. However, the detrimental effects on the components along the hot gas path can offset the benefits of increasing the operating temperature. The High Pressure Turbine (HPT) first stage blade is one component that is extremely vulnerable to the hot gas. The present study explores the effects of gap height and tip geometry on heat transfer distribution. This investigation differs ...


Effect Of Residual Thermal Stresses On Fracture Behavior And Mechanical Properties Of Al Sub 2 O Sub 3/Ni Cermets, Guo Jin Li, Da Ming Chen, Xiao Xian Huang, Jing Kun Guo Jan 2002

Effect Of Residual Thermal Stresses On Fracture Behavior And Mechanical Properties Of Al Sub 2 O Sub 3/Ni Cermets, Guo Jin Li, Da Ming Chen, Xiao Xian Huang, Jing Kun Guo

Faculty Publications

Effect of residual thermal stresses on fracture behavior and mechanical properties of Al2O3/Ni cermets was qualitatively explained by using theory on residual thermal stresses. When Ni particles are located within Al2O3 grains or Ni content is relatively low, tensile stresses are exerted at Al2O3-Al2O3 grain boundary. While fracturing, intergranular fracture is easily produced. When Ni particles are dispersed at Al2O3 grain boundary or Ni content is relatively high, compressive stresses are exerted at Al2O3-Al2O3grain boundary ...


Transient Thermomechanical Interactions Of Shaft-Bushing Pair In Bearings - A Finite Element Study, Rajesh Krithivasan Jan 2002

Transient Thermomechanical Interactions Of Shaft-Bushing Pair In Bearings - A Finite Element Study, Rajesh Krithivasan

LSU Master's Theses

This thesis presents a finite element parametric study of the transient thermomechanical interactions of shaft-bushing pairs in bearings to gain insight into the nature of two categories of failures encountered in practice. The first type of failure deals with occurrence of the so-called thermally induced seizure (TIS) during the start-up period followed by an investigation of TIS due to a transient flow-disturbance. The second part deals with the thermomechanical interactions of pin-bushing assembly under heavy oscillating loads where the failure is by TIS and/or thermal galling. An extensive set of parametric simulations covering a wide range of loads, speeds ...


Hard Surface Coating Experimental Evaluation And Thermomechanical Analysis Of A Seal With Micro Heat Exchanger, Yifan Qiu Jan 2002

Hard Surface Coating Experimental Evaluation And Thermomechanical Analysis Of A Seal With Micro Heat Exchanger, Yifan Qiu

LSU Master's Theses

Mechanical face seals are important components of many rotating machinery. Minimizing the friction between seal faces and efficiently removing the heat generated between seal surfaces are two crucial considerations in the design of mechanical seal. Thin film coating and MEMS technology hold great promise for improving the performance of mechanical seals from the viewpoint of reducing friction and heat at the interface in these two aspects. To reveal what effect the coating and MEMS technology can have on tribological properties of seals, friction and wear characteristics of Ti-C:H coatings on seal-like rings and heat transfer performances of a seal ...


Application Of Duhamel's Theorem To Problems Involving Oscillating Heat Source, Haribabu Krishnamurthy Jan 2002

Application Of Duhamel's Theorem To Problems Involving Oscillating Heat Source, Haribabu Krishnamurthy

LSU Master's Theses

This thesis deals with a systematic development of a method for predicting the temperature field in various domains subjected to oscillating heat sources on its boundaries using the Duhamel’s method. First a method is devised for single domain problems in both Cartesian and cylindrical coordinates for oscillating heat sources and also for unidirectional rotation of shafts in cylindrical coordinates. The analytically computed results for the problems in Cartesian coordinates compared favorably with the results from Finite Element Method, attesting to the validity of this novel approach. Later, the method is extended to predict the maximum temperature in oscillating Pin-Bushing ...


Liga Mold Insert Fabrication Using Su-8 Photoresist, Jian Zhang Jan 2002

Liga Mold Insert Fabrication Using Su-8 Photoresist, Jian Zhang

LSU Master's Theses

The LIGA process potentially enables economic mass-production of devices with high aspect ratio geometry. Central to the LIGA process is the fabrication of high quality LIGA molds. But in the traditional LIGA mold insert fabrication process, the x-ray photoresist poly-methyl-methacrylate (PMMA) is not highly sensitive to x-rays and a thick piece of PMMA sheet (>1mm) needs too much time to get exposed (bottom dose: 3500J/cm3), which results in excessive cost/ fabrication difficulty of the mold insert. Thus, in this thesis a negative photoresist SU-8 was tested as an x-ray photoresist in the LIGA fabrication process. SU-8 is much more ...


Design And Microfabrication Of A Molded Polycarbonate Continuous Flow Polymerase Chain Reaction Device, Michael Mitchell Jan 2002

Design And Microfabrication Of A Molded Polycarbonate Continuous Flow Polymerase Chain Reaction Device, Michael Mitchell

LSU Master's Theses

The polymerase chain reaction (PCR) is an amplification technique that is used with deoxyribonucleic acid (DNA) and can produce millions of copies of the starting material, even from single molecules. Since its discovery by Kary Mullis in the mid-1980s, PCR has been one of the most important techniques in the arsenal of tools used for genetic analyses. For this research a continuous flow polymerase chain reaction (CFPCR) system was designed, microfabricated from molded polycarbonate, and tested. Finite element modeling was used to model thermal and microfluidic response of the system. X-ray LIGA was used to fabricate mold inserts for the ...


Prediction Of Heat Transfer & Flow In Rotating Two-Pass Channels Connected By Holes., Achintya Kumar Pramanick Jan 2002

Prediction Of Heat Transfer & Flow In Rotating Two-Pass Channels Connected By Holes., Achintya Kumar Pramanick

LSU Master's Theses

A computational study of the effect of rotation on the velocity and thermal field for a two-pass channel connected by rows of holes on the divider wall has been conducted. Detailed velocity and Nusselt number distributions are presented inside the rotating two-pass coolant channel. The enhanced cooling in this passage design is achieved by a combination of impingement and crossflow-induced swirl. The cross flow is generated from one coolant passage to the adjoining coolant passage through a series holes placed along the dividing wall. The holes deliver the flow from one passage to another typically achieved in a conventional design ...


Comparison Of Numerical And Experimental Results Of Four Liquid Spray Combustors, Dong Hu Jan 2002

Comparison Of Numerical And Experimental Results Of Four Liquid Spray Combustors, Dong Hu

LSU Master's Theses

Validation of CFD predictions for liquid spray combustion application is a challenging task due to difficulties in both modeling and experimental measurements. Validation is considered to be a key step for successful CFD predictions of combustion systems. The goals of this thesis are threefold: (1) validation of models used for spray combustion predictions, (2) using the validated predictions to explain steady flow and combustion physics, and (3) using the validated procedure to simulate conditions where unstable combustion behavior is observed experimentally, and to explore if such unstable behavior can be predicted correctly. The model validation is done with respect to ...


Tribological Behavior Of Nanostructured Nickel, Dean Joseph Guidry Jan 2002

Tribological Behavior Of Nanostructured Nickel, Dean Joseph Guidry

LSU Master's Theses

The present study reports the effects of electroplating parameters on the microstructure, and thus the mechanical and tribological properties, of nanostructured nickel. Electroplating was conducted in a Watt's type bath with a pH of 3.0 carried out using direct current in galvanostatic mode at current densities of 30 mA/cm2 and 15 mA/cm2 in electroplating bath temperatures of 30°C and 50°C. Grain size and distributions were determined from TEM (Transmission Electron Microscope) and SEM (Scanning Electron Microscope) micrographs. Tribological tests were carried out on a pin-on-disc type tribometer. The same tests were conducted ...


Chemical Partitioning During Crystallization And Its Effect On The Microstructure And Magnetic Behavior Of Modified Nd–Fe–B Permanent Magnets, Jeffrey E. Shield, B. B. Kappes, D. J. Branagan, J. Bentley Jan 2002

Chemical Partitioning During Crystallization And Its Effect On The Microstructure And Magnetic Behavior Of Modified Nd–Fe–B Permanent Magnets, Jeffrey E. Shield, B. B. Kappes, D. J. Branagan, J. Bentley

Mechanical & Materials Engineering Faculty Publications

In this paper, the effect of alloy composition on the microstructural development of devitrified Nd–Fe–B-based alloys is investigated. While crystallization of simple ternary Nd2Fe14B resulted in a highly variable microstructure and relatively poor demagnetization behavior, alloying additions, notably Ti and C, were found to significantly refine and homogenize the crystallized microstructure. High spatial resolution energy dispersive X-ray spectroscopy revealed that partitioning to the grain boundaries led to the grain refinement by slowing interface kinetics. The more homogeneous grain structure resulted in improved demagnetization behavior, but segregating elements isolated grains and limited intergranular exchange coupling.


Prediction Of Soakout Time Using Analytical Models, B. Chakravarthy, H. P. Cherukuri, R. G. Wilhelm Jan 2002

Prediction Of Soakout Time Using Analytical Models, B. Chakravarthy, H. P. Cherukuri, R. G. Wilhelm

Mechanical & Materials Engineering Faculty Publications

In precision manufacturing enterprises, machine parts at nonstandard temperatures are often soaked to standard temperature prior to making any dimensional measurements. The soakout times are usually determined using lumped heat-transfer models where the part temperatures are assumed to be uniform. This article discusses conditions under which lumped model assumptions are valid by comparing lumped analyses for various shapes and materials with the more general finite element results. In addition, the effect of ambient temperature cycling on part response is also studied.


Acoustic Competition In The Gulf Toadfish Opsanus Beta: Acoustic Tagging, Robert F. Thorson, Michael L. Fine Jan 2002

Acoustic Competition In The Gulf Toadfish Opsanus Beta: Acoustic Tagging, Robert F. Thorson, Michael L. Fine

Biology Publications

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male–male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound-pressure levels and frequency spectra that correspond with ...


Supersonic Combustion And Mixing Characteristics Of Hydrocarbon Fuels In Screamjet Engines, Ahmed A. Taha Jan 2002

Supersonic Combustion And Mixing Characteristics Of Hydrocarbon Fuels In Screamjet Engines, Ahmed A. Taha

Mechanical & Aerospace Engineering Theses & Dissertations

The combustion characteristics of gaseous propane in supersonic airflow using the rearward-facing step that is swept inward from both end sides is studied. The effect of sweeping the step on the flow field features of propane combustion is investigated.

The study of the supersonic combustion of ethylene is carried out using different combustor configurations, different main fuel equivalence ratios, and different pilot fuel equivalence ratios.

The swept step shows the ability to hold the propane flame in the supersonic air stream without extinction. It was found that the side sweeping of the combustor exhibits the high temperature and combustion products ...


A Comparison Of The Level Of Maturity Of Manufacturers In The Lake Land College School District In Lean Manufacturing Techniques As Compared To Goodson's Survey Data, Mark W. Henderson Jan 2002

A Comparison Of The Level Of Maturity Of Manufacturers In The Lake Land College School District In Lean Manufacturing Techniques As Compared To Goodson's Survey Data, Mark W. Henderson

Masters Theses

The purpose of this study was to determine if manufacturers in the Lake Land College School District have implemented Lean Manufacturing techniques and score as high as the manufacturers in Goodson's Michigan study. Lean Manufacturing techniques have revolutionized the auto industry, with the Toyota Production system the benchmark in Lean Manufacturing techniques. A survey using Goodson's Rapid Plant Assessment compares the level of maturity in the utilization of the Lean Manufacturing techniques with the manufacturers in the Lake Land College School District and Goodson's survey of manufacturers in Michigan. The mean score of 57.67 for the ...


Ole Miss Engineer 2002 Jan 2002

Ole Miss Engineer 2002

The Ole Miss Engineer

No abstract provided.


Flow Patterns In A Two-Roll Mill, Christopher Hills Jan 2002

Flow Patterns In A Two-Roll Mill, Christopher Hills

Articles

The two-dimensional flow of a Newtonian fluid in a rectangular box that contains two disjoint, independently-rotating, circular boundaries is studied. The flow field for this two-roll mill is determined numerically using a finite-difference scheme over a Cartesian grid with variable horizontal and vertical spacing to accommodate satisfactorily the circular boundaries. To make the streamfunction numerically determinate we insist that the pressure field is everywhere single-valued. The physical character, streamline topology and transitions of the flow are discussed for a range of geometries, rotation rates and Reynolds numbers in the underlying seven-parameter space. An account of a preliminary experimental study of ...


Brachial Burning And Gasification Split Of A Two-Droplet System, Wei-Hsin Chen Dec 2001

Brachial Burning And Gasification Split Of A Two-Droplet System, Wei-Hsin Chen

Wei-Hsin Chen

No abstract provided.