Aerospace Engineering Commons^™

Fiber Bragg Grating (Fbg) Sensors For The Simultaneous Measurements Of Strain And Temperature, Abhay Kumar Singh

Mechanical and Aerospace Engineering Theses - Archive

This research presents a single fiber Bragg grating (FBG) sensor that is capable of measuring the axial load and temperature simultaneously. The FBG sensor is coated with a block of recrystallized Lophine, which introduces the bandwidth modulation of the FBG reflectance spectrum. Thermal-mechanical testing of the Lophine-coated FBG sensor under different load and temperature combinations was carried out. It was discovered that the FBG bandwidth is linearly proportional to the applied load and temperature. By fitting the measured FBG bandwidths and central Bragg wavelengths as linear functions of the axial load and temperature, we demonstrated that the axial load and …

Effect Of Viscoelastic Modeling Of Pcb On The Board Level Reliability Of Wafer Chip Scale Package (Wcsp) In Comparison To Orthotropic Linear Elastic Modeling, Avinash Anaskure

Mechanical and Aerospace Engineering Theses - Archive

The assessment of board level solder joint reliability during thermal cycling is very important for electronic packages. During thermal cycling, the mismatch in Coefficient of Thermal Expansion (CTE) between the materials used in the package induces stress on the solder interconnects and result in deformation stresses. Finite element tools are widely used for rapid design optimization and also for understanding board level reliability issues. Lumped board properties approach, explicit geometry approach, and ECAD approach are the three widely used approaches for creating models for PCBs. In the lumped board properties approach, orthotropic elastic material properties are assigned to PCBs. However, …

Effect Of Manufacturing-Induced Defects And Orientation On The Failure And Fracture Mechanism Of 3d Printed Structures, Amit Khatri

Mechanical and Aerospace Engineering Theses - Archive

Additive manufacturing is a rapidly growing cutting edge technology. Number of experimental studies have shown that strength of product manufactured by additive Fused Deposition Method (FDM) is influenced by different processing parameters involved during manufacturing. This thesis work presents experimental and theoretical investigation of mechanical behavior of ABS material fabricated with variation in some of process parameters such as Axis Orientations, Raster Orientation, Infill Percentage, Layer Height and Number of Shells. Different experiments were designed to understand the basics of 3D printing manufacturing and to characterize the mechanical behavior of 3D printed structures. This study helps to understand, how different …

Development Of An Analytical Model For Beams With Two Dimples In Opposing Directions, Mofareh H. Ghazwani

Masters Theses

Structures such as beams and steel plates can produce potentially high levels of unwanted vibrations and noises in the environment. A method of improving the vibration and acoustic characteristics of beams based on introducing dimples on its surfaces will be presented in this study. This method focuses on creating two dimples in the same and opposite direction on beam’s surface where the effect of dimples on the change in beam’s natural frequencies is the problems of interest.

A boundary value model (BVM) is developed for a beam with two dimples and subjected to various boundary conditions using Hamilton’s Variational Principle. …

Design Of Flow Control Device For Dynamic Cold Plate And Optimization Of Servers To Decrease Junction Temperature Of Heat Sinks, Kunal Atulkumar Shah

Mechanical and Aerospace Engineering Theses - Archive

Electronics cooling research is facing the challenges of high heat flux removal and increased pumping power. Not much attention has been focused related to server and module level cooling. The continued increase in heat fluxes at the chip level due to new and robust technology nodes following Moore’s law is starting to push the limits of air cooling and especially for high end servers. An alternative to air cooling is liquid (water and oil immersed) cooling. The optimized dynamic cold plates that use water as the cooling fluid have shown over 28 % and 52% of reduction in pumping power …

Accumulator Volume Sensor Final Project Report, Chris Naughton, Kinwei Yu, Michael George

Mechanical Engineering

Accumulator Volume Sensing Team has developed two sensor designs aimed at detecting the position of the piston within a 4024 accumulator. The two designs include the use of a Renishaw LMA10 magnetic encoder and a SpectraSymbol HotPot linear potentiometer. The magnetic encoder solution drastically increases the accuracy of sensing the piston position compared to the current solutions of both a string-pot and linear variable differential transformer while costing slightly less. The linear potentiometer seeks to provide a solution that drastically decreases the cost compared to the present sensing methods. Both designs call for a modification to one half of the …

Numerical Investigation Of Crossflow Instability On The Hifire-5, Matthew T. Lakebrink

Open Access Dissertations

Stability analysis was performed with the Langley Stability and Transition Analysis Code (LASTRAC) on a 38.1% scale model of the HIFiRE-5 elliptic-cone forebody to study crossflow-induced transition in hypersonic boundary layers. A resolution study consisting of three grids (30e6, 45e6, and 91e6 points) indicated that the fine grid was sufficiently resolved. Results were largely insensitive to grid resolution over the acreage and near the attachment line. The percent variation in second-mode properties along the semi-minor axis was less than 1% between the medium and fine grids. The variation in crossflow-wave properties was less than 0.04% between the medium and fine …

Integration And Qualification Of The P-Pods On The Vega Maiden Flight, Ryan Nugent

Master's Theses

On February 13, 2012, California Polytechnic State University, San Luis Obispo flew three Poly-Picosatellite Orbital Deployers (P-PODs), carrying seven European University CubeSats sponsored by the European Space Agency (ESA), on the Vega Maiden Flight. This was the first time CubeSats shared a ride to space with other payloads on an ESA-owned launch opportunity. In order to meet launch requirements, it must be proven through proper documentation that the P-POD would operate properly and not interfere with the launch vehicle or other payloads on the mission. This thesis outlines the program flow, required documentation, and issues encountered during the launch campaign …

Assessing Fuel Burn Inefficiencies In Oceanic Airspace, Stephen Builta

Open Access Theses

Increasing the efficiency of aircraft operations offers a shorter term solution to decreasing aircraft fuel burn than fleet replacement. By estimating the current airspace inefficiency, we can get an idea of the upper limit of savings. Oceanic airspace presents a unique opportunity for savings due to increased separation differences vs. overland flight.

We assess fuel burn inefficiency by comparing estimated fuel burn for real world flights with the estimated optimal fuel burn. For computing fuel burn, we use the Base of Aircraft Data (BADA) with corrections based on research by Yoder (2005). Our fuel burn results show general agreement with …

Mechanism Of Shot Peening Enhancement For The Fatigue Performance Of Aa7050-T7451, Daniel James Chadwick

Open Access Theses

Shot peening is a dynamic cold working process involving the impingement of peening media onto a substrate surface. Shot peening is commonly employed as a surface treatment technique within the aerospace industry during manufacturing, in order to improve fatigue performance of structural components. The compressive residual stress induced during shot peening is understood to result in fatigue crack growth retardation, improving the performance of shot peened components. However, shot peening is a compromise between the benefit of inducing a compressive residual stress and causing detrimental surface damage. Due to the relatively soft nature of AA7050-T7451, shot peening can result in …

Flammability Limits Of Alternative Aviation Fuels, Ang Li

Open Access Theses

Alternative aviation fuels are being developed recently to partially replace the limited resources of traditional liquid fuels in the aviation industry. The fire-safety properties of these fuels, however, are unknown. Especially, the flammability limit of a fuel is a crucial parameter. The present work focuses on measurements of concentration and temperature flammability limits of four pure hydrocarbon fuels, as well as traditional and alternative aviation fuels, including Jet-A, HEFA, SIP, and FT-S8. The lower and upper concentration flammability limits of these selected fuels were determined under specific temperatures and pressures. An experiment including a customized power supply system to generate …

Characterization Of A Hypersonic Quiet Wind Tunnel Nozzle, Cameron J. Sweeney

Open Access Theses

The Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University has been able to achieve low-disturbance flows at high Reynolds numbers for approximately ten years. The flow in the nozzle was last characterized in 2010. However, researchers have noted that the performance of the nozzle has changed in the intervening years. Understand ing the tunnel characteristics is critical for the hypersonic boundary-layer transition research performed at the facility and any change in performance could have signif icant effects on research performed at the facility. Pitot probe measurements were made using Kulite and PCB pressure transducers to quantify the performance changes since characterization …

Helical Strakes On High Mast Lighting Towers And Their Effect On Vortex Shedding Lock-In, Ayah Zahour

Open Access Theses

An experimental study on the effect of helical strakes on vortex induced vibrations and the lock-in phenomenon in High Mast Lighting Towers (HMLTs) is investigated. Two multi-sided tapered scaled models are clamped in place in a subsonic wind tunnel that is equipped with a hot-wire sensor and a traverse mechanism. The shedding frequency data is collected for the models with and without helically patterned strakes with the use of two different ropes. The responses of the tower models, for a Reynolds number of 44, 000, are compared and discussed under different configurations including: two directions of the model with respect …

Metrics Of Critical Pair Identification, Zixu Zhang

Open Access Theses

Critical Pair Identification works as a potential assistive tool for human air traffic controllers by identifying potentially dangerous situations that are not detected by proposed automated separation assurance systems. This concept specifically considers conflicts that might arise if aircraft unexpectedly deviate from their planned flight path in the near future. Five metrics of the critical pair concept, Critical Pair Count, Time to Risk Exposure, Lead Time, Risk Exposure Duration and Blunder Sensitivity Index, have been developed and mathematically defined to characterize the safety level of an aircraft pair or a volume of air space. Algorithm that computes proposed metrics is …

Analysis Of Composite Plates By Using Mechanics Of Structure Genome And Comparison With Ansys, Banghua Zhao

Open Access Theses

Motivated by a recently discovered concept, Structure Genome (SG) which is defined as the smallest mathematical building block of a structure, a new approach named Mechanics of Structure Genome (MSG) to model and analyze composite plates is introduced. MSG is implemented in a general-purpose code named SwiftComp™, which provides the constitutive models needed in structural analysis by homogenization and pointwise local fields by dehomogenization. To improve the user friendliness of SwiftComp™, a simple graphic user interface (GUI) based on ANSYS Mechanical APDL platform, called ANSYS-SwiftComp GUI is developed, which provides a convenient way to create some common SG models or …

Free Edge Stress Analysis Of Laminated Structures With Arbitrary Cross Sections Using Mechanics Of Structure Genome, Lingxuan Zhou

Open Access Theses

Composite laminates have been increasingly used in advanced structural applications, due to their excellent strength-to-weight properties and considerable flexibility on designing with respect to the laminate layup. However, the heterogeneity and anisotropy of composite laminates have brought many challenges for analysis and numerous researches have been devoted in this field. A well known problem which has been studied intensively is the so-called free-edge problem. It states that due to the mismatch in elastic properties of adjacent layers, full-scale three-dimensional (3D) and highly concentrated stress fields will occur in the vicinity of the free edges. The interlaminar stresses grow very rapidly …

Modeling Methods For Merging Computational And Experimental Aerodynamic Pressure Data, Jacob Courtney Haderlie

Open Access Dissertations

This research describes a process to model surface pressure data sets as a function of wing geometry from computational and wind tunnel sources and then merge them into a single predicted value. The described merging process will enable engineers to integrate these data sets with the goal of utilizing the advantages of each data source while overcoming the limitations of both; this provides a single, combined data set to support analysis and design. The main challenge with this process is accurately representing each data source everywhere on the wing. Additionally, this effort demonstrates methods to model wind tunnel pressure data …

Gravity-Assist Trajectories To Venus, Mars, And The Ice Giants: Mission Design With Human And Robotic Applications, Kyle M. Hughes

Open Access Dissertations

Gravity-assist trajectories to Uranus and Neptune are found (with the allowance of impulsive maneuvers using chemical propulsion) for launch dates ranging from 2024 to 2038 for Uranus and 2020 to 2070 for Neptune. Solutions are found using a patched conic model with analytical ephemeris via the Satellite Tour Design Program (STOUR), originally developed at the Jet Propulsion Laboratory (JPL). Delivered payload mass is computed for all solutions for select launch vehicles, and attractive solutions are identified as those that deliver a specified amount of payload mass into orbit at the target body in minimum time. The best cases for each …

Development Of Inverse Methods For Reconstruction Of Flight Environments On Ablators, A. Brandon Oliver

Open Access Dissertations

Obtaining measurements of flight environments on ablative heatshields is both critical for spacecraft development and extremely challenging due to the harsh heating environment and surface recession. Thermocouples installed several millimeters below the surface are commonly used to measure the heatshield temperature response, but an ill-posed inverse heat conduction problem must be solved to reconstruct the surface heating environment from the embedded thermocouple measurements. The material properties of typical ablators make the reconstruction process more challenging when the measurements are deep, but measurements often must be located deep to allow for surface recession. Compounding the complexity of the surface reconstruction problem, …

A New Approach To Modeling Aviation Accidents, Arjun Harsha Rao

Open Access Dissertations

General Aviation (GA) is a catchall term for all aircraft operations in the US that are not categorized as commercial operations or military flights. GA aircraft account for almost 97% of the US civil aviation fleet. Unfortunately, GA flights have a much higher fatal accident rate than commercial operations. Recent estimates by the Federal Aviation Administration (FAA) showed that the GA fatal accident rate has remained relatively unchanged between 2010 and 2015, with 1566 fatal accidents accounting for 2650 fatalities. Several research efforts have been directed towards betters understanding the causes of GA accidents. Many of these efforts use National …