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Articles 421 - 450 of 452

Full-Text Articles in Mechanical Engineering

Thermohydrodynamic Analysis Of Compressible Gas Flow In Compliant Foil Bearings, Zhengchun Peng Jan 2003

Thermohydrodynamic Analysis Of Compressible Gas Flow In Compliant Foil Bearings, Zhengchun Peng

LSU Master's Theses

This thesis deals with the development of mathematical models and numerical schemes for simulating the hydrodynamic pressure and temperature rise of compliant foil bearings lubricated by a thin gas film in between its compliant bearing surface and the rotating shaft. The model accounts for the compressibility of gas, the compliance of the bearing surface, and the interaction between the pressure field and temperature field of the gas film in the bearing system. Numerical solutions obtained over a fairly large range of operating speeds show excellent agreement with existing experimental data from both load performance test and bearing temperature measurement. A …

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Precipitate Growth Features In The Duplex Size Gamma Prime Distribution In The Superalloy In738lc, Indranil Roy Jan 2003

Precipitate Growth Features In The Duplex Size Gamma Prime Distribution In The Superalloy In738lc, Indranil Roy

LSU Master's Theses

IN738LC is a modern, nickel base superalloy utilized at high temperatures in aggressive environments. Durability of this superalloy is dependent on the retention of strengthening by Gamma Prime precipitates. The precipitate growth features in the duplex size (fine and coarse) precipitate distribution was studied by heating the alloy for various times in vacuum at selected temperatures in the range 800 °C to 1100 °C. Increasing the holding times from 1 hour to 100 hours shows joining of the fine particles to form bigger particles, leading to distinct raft patterns. Two different Gamma Prime precipitate growth processes had been observed: merging …

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Axis-Switching In Square Coaxial Jets, Victor Piffaut Jan 2003

Axis-Switching In Square Coaxial Jets, Victor Piffaut

LSU Master's Theses

Airflow from single and coaxial contoured nozzles with a square cross section is studied using constant temperature anemometry. The inner to outer jet velocity ratio is 1.5. The Reynolds number of the outer jet based on the hydraulic diameter of the outer nozzle exit is 15,300. Results are compared to previous data obtained with circular nozzles under the same conditions. Properties of the jets and their shear layers such as turbulence shear layer thicknesses and growth rates were derived from the velocity record. The mixing between the jets and with the external flow was found to be enhanced by passive …

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Effect Of Jet Hole Arrays Arrangement On Impingement Heat Transfer, Lujia Gao Jan 2003

Effect Of Jet Hole Arrays Arrangement On Impingement Heat Transfer, Lujia Gao

LSU Master's Theses

A comprehensive investigation on impingement heat transfer of different jet array arrangements is presented. Experiments on the inline jet arrays and the linearly stretched arrays are performed using transient liquid crystal technique. Three experimented basic inline jet arrays are configurations 4X4, 8X4 and 8X8. Two experimented cases for the linearly stretched arrays are the uniform diameter case and the varying diameter case. For the inline jet arrays, three jet heights Z/D=1, 3 and 5 and three Reynolds numbers Re=5000, 10000 and 15000 are investigated. For linearly stretched arrays, the same three jet heights and Re=2000, 6000 and 10000 are investigated. …

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Evaluation Of Mechanical Fitness For Service Of High Temperature Hydrogen Attacked Steels, Brent Matthew Saba Jan 2003

Evaluation Of Mechanical Fitness For Service Of High Temperature Hydrogen Attacked Steels, Brent Matthew Saba

LSU Master's Theses

A novel approach is introduced in evaluating one of industry’s most complex corrosion phenomena, high temperature hydrogen attack (HTHA). Limited efforts have been made by industry to address this degradation mechanism and even less data are available to properly utilize their evaluation techniques. The predominant fracture mechanics based analysis of HTHA relies on Charpy V-Notch (CVN) impact test data. In the face of limited CVN test data, accurate results are shaky at best. The HTHA evaluation set forth in this paper combines the analysis tools of plastic collapse and both static and dynamic fracture mechanics. The first condition addresses plastic …

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Effect Of Unsteady Wake, Free Stream Turbulence, Tip Geometry On Blade Tip Flow And Heat Transfer, Vikrant Saxena Jan 2003

Effect Of Unsteady Wake, Free Stream Turbulence, Tip Geometry On Blade Tip Flow And Heat Transfer, Vikrant Saxena

LSU Master's Theses

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer. The linear cascade is made of four blades scaled up HPT turbine in a low speed wind tunnel facility with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116 degree turn in the flow through the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83e5. The center blade …

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Predictions For Multi-Scale Shock Heating Of A Granular Energetic Material, Venugopal Jogi Jan 2003

Predictions For Multi-Scale Shock Heating Of A Granular Energetic Material, Venugopal Jogi

LSU Master's Theses

This thesis addresses the multi scale heating of a granular energetic solid due to shock loading. To this end, an existing mathematical model that has been used to predict low pressure bulk and localized heating of the granular high-explosive HMX ([CH2NNO2]4) is extended to account for compressibility and melting of the pure phase solid. Dense granular HMX has a heterogeneous structure composed of randomly packed small grains (average size ~ 100 µm) having a free-pour density that is approximately 65% of the pure phase solid density. The shock loading response of this material is …

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Film Cooling From Cylindrical Holes In Transverse Slots, Mohammed Altorairi Jan 2003

Film Cooling From Cylindrical Holes In Transverse Slots, Mohammed Altorairi

LSU Master's Theses

In this study, heat transfer coefficient and film effectiveness distributions are investigated for a film cooling hole configuration that has inclined holes discharging into a tangential slot before interactions with the mainstream. The cylindrical holes are inclined 35° along the mainstream direction. The effect of coolant-to-mainstream blowing ratio is examined for M=0.5 and M=1.0. Different slot width to hole ratios and also the effect of hole exit condition (square edge and triangular edge) is considered. The mainstream velocity and free-stream turbulence intensity in the low speed wind tunnel are 9 m/s and 7% respectively and the mainstream Reynolds number based …

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Numerical Solution Of Ocular Fluid Dynamics, Satish Kumar Jan 2003

Numerical Solution Of Ocular Fluid Dynamics, Satish Kumar

LSU Master's Theses

Numerical calculations of the aqueous humor dynamics in the anterior chamber of both the rabbit and the human eye are presented to delineate the basic flow and transport mechanisms. The calculations are based on a geometrical model of the eye, which represents the Trabecular mesh (TM) as a multi-layered porous zone of specified pore sizes and void fraction. Buoyancy is observed to be the dominant driving mechanism for the convective motion in both orientations (horizontal and vertical) of the eye. Reducing the TM pore size does not appear to have a significant influence on the intra-ocular pressure (IOP) until the …

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The Transcendental Eigenvalue Problem And Its Application In System Identification, Kumar Vikram Singh Jan 2003

The Transcendental Eigenvalue Problem And Its Application In System Identification, Kumar Vikram Singh

LSU Doctoral Dissertations

An accurate mathematical model is needed to solve direct and inverse problems related to engineering analysis and design. Inverse problems of identifying the physical parameters of a non-uniform continuous system based on the spectral data are still unsolved. Traditional methods, for the system identification purpose, describe the continuous structure by a certain discrete model. In dynamic analysis, finite element or finite difference approximation methods are frequently used and they lead to an algebraic eigenvalue problem. The characteristic equation associated with the algebraic eigenvalue problem is a polynomial. Whereas, the spectral characteristic of a continuous system is represented by certain transcendental …

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Manufacturing And Analysis Of A Liga Heat Exchanger For The Surface Of A Tube: A Cooling Simulation Of The Leading Edge Region Of A Turbine Blade, Christophe Marques Jan 2003

Manufacturing And Analysis Of A Liga Heat Exchanger For The Surface Of A Tube: A Cooling Simulation Of The Leading Edge Region Of A Turbine Blade, Christophe Marques

LSU Doctoral Dissertations

Fabricating nickel micro heat exchangers directly on planar or non-planar metal surfaces has been demonstrated using the LIGA micromachining process. These heat exchangers can effectively control the temperature of surfaces in high heat flux applications. Of particular interest is the temperature control of gas turbine engine components. The locations in the gas turbine engine where improved, efficient cooling is required includes gas turbine blades, stator vanes, the turbine disk, and the combustor liner. In this dissertation, the primary application of interest is the use of such heat exchangers to cool airfoils such as turbine blades. In the first part of …

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Large Eddy Simulations Of Complex Turbulent Flows, Mayank Tyagi Jan 2003

Large Eddy Simulations Of Complex Turbulent Flows, Mayank Tyagi

LSU Doctoral Dissertations

In this dissertation a solution methodology for complex turbulent flows of industrial interests is developed using a combination of Large Eddy Simulation (LES) and Immersed Boundary Method (IBM) concepts. LES is an intermediate approach to turbulence simulation in which the onus of modeling of “universal” small scales is appropriately transferred to the resolution of “problem-dependent” large scales or eddies. IBM combines the efficiency inherent in using a fixed Cartesian grid to compute the fluid motion, along with the ease of tracking the immersed boundary at a set of moving Lagrangian points. Numerical code developed for this dissertation solves unsteady, filtered …

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Micro Molding Of 3 D Ceramic Parts, Dinakar Palaparti Jan 2003

Micro Molding Of 3 D Ceramic Parts, Dinakar Palaparti

LSU Master's Theses

The objective of this research was to manufacture and evaluate three-dimensional (3D) ceramic parts with microstructures, characterize the ceramic injection molding process used for it along with fabrication and evaluation of various mold insert formats, electroplated patterns and X-ray masks used in the process. The patterns were electroplated in nickel on two formats of mold insert substrates. The first format was a modified 1” diameter stainless/tool steel plug suitable for test structures and for complete penetration by melt during injection. The molding was done by CoorsTekâ (Golden CO) as they possessed the required wherewithal and the mold base. The second …

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Minimization Of Power Losses In Active Magnetic Bearing Control, Nader Motee Jan 2003

Minimization Of Power Losses In Active Magnetic Bearing Control, Nader Motee

LSU Master's Theses

A solution to the problem of AMB control with reduced electrical power losses will be presented in this thesis. The proposed control solution will be founded on the integrator backstepping technique, which decouples the rotor stabilization problem from the bias flux design problem. It further allows for the easy redesign of the control law to compensate for uncertainties in the AMB system. A class of nonlinear controllers will be developed that reduces the AMB power losses in comparison to standard fixed-bias controllers, while containing no control singularity. Control laws will be presented for the standard AMB operating mode where both …

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The Rapid Template Fabrication Process For Producing A Liga Heat Exchanger Bonded To A Mechanical Seal, Jason Patrick Tuma Jan 2003

The Rapid Template Fabrication Process For Producing A Liga Heat Exchanger Bonded To A Mechanical Seal, Jason Patrick Tuma

LSU Master's Theses

Mechanical seals are widely used in the chemical processing, aerospace, and automotive, industries. When a mechanical seal fails, considerable cost is typically involved in replacing the seal. Most seal failures are a result of high temperatures generated by frictional heating. Effectively removing the heat generated would significantly increase the mechanical seal’s work life and lead to significant monetary savings. One method of removing the heat generated is bonding an effective LIGA micro heat exchanger to the mechanical seal and forcing coolant through the heat exchanger. Previous work on this subject revealed promising results, especially for micro heat exchangers with microstructures …

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Advanced Turbulence Modeling For Industrial Flows, Raymond Michael Jones Jan 2003

Advanced Turbulence Modeling For Industrial Flows, Raymond Michael Jones

LSU Doctoral Dissertations

This dissertation deals with the development of an improved two-equation turbulence model and its application to various flows. Six different conventional turbulence models were initially tested for predicting the flow inside of an unbaffled stirred tank reactor (STR), and the results are compared with experimental LDV data. Each of the models use low Reynolds number corrections. Results indicate that the radial velocity component in the impeller discharge region is overpredicted by each of the models. The tangential velocity component in the impeller discharge region is predicted well by the models, but is underpredicted near the shaft. The low Reynolds number …

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Design, Development, And Analysis Of A Twin-Fluid Fire Suppression Atomizer And Characterization Of Electrostatically Charged Droplet Sprays, Chad Everett Moore Jan 2003

Design, Development, And Analysis Of A Twin-Fluid Fire Suppression Atomizer And Characterization Of Electrostatically Charged Droplet Sprays, Chad Everett Moore

LSU Master's Theses

A twin-fluid water mist fire suppression atomizer is designed, developed, and analyzed. Of primary interest is the development of a twin-fluid atomizer that produces a large droplet diameter and velocity distribution and also produces a mist with sufficient cone angle to be effective in fire suppression applications. Spray characterization experiments are conducted utilizing Phase Doppler Particle Analysis (PDPA). The effect of atomizer nozzle geometry on internal two-phase flow and resulting spray pattern is investigated. National Fire Protection Association (NFPA) Standard 750 characterization experiments are conducted to verify that the sprays produced by the developed atomizer are classified as a water …

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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, operating …

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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 prototype …

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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 …

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Parametric And Sensitivity Analysis Of A Vibratory Automobile Model, Kanika Nicole Vessel Jan 2002

Parametric And Sensitivity Analysis Of A Vibratory Automobile Model, Kanika Nicole Vessel

LSU Master's Theses

Vibration response is an important aspect of any engineering problem. This thesis deals with developing a method to obtain the vibration, parametric and sensitivity of an automobile analyzed as a 2-DOF rigid body system with damping. The focus of the vibration analysis is to obtain the poles, eigenvectors, and natural frequencies of the system. The parametric analysis gave information on how the natural frequency is affected when one of the parameters is perturbed. Information about how much the system is affected by the change in one parameter is what is obtained from the sensitivity analysis. The theoretical solution contained in …

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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 …

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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 …

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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 mechanism, …

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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 …

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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 …

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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 done. …

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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 …

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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 on Ni-200 for the purpose of …

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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 …

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