Engineering Commons^™

Nondestructive Evaluation And Structural Health Monitoring Of Manufacturing Flaws And Operational Damage In Composite Structures, Robin James

Theses and Dissertations

Advanced composite materials have begun to be used extensively in the manufacturing of aerospace structures. Composite aerospace structures can develop complex types of damages during the manufacturing stages and operational lifetime. This creates an indispensable demand for appropriate nondestructive evaluation (NDE) and structural health monitoring (SHM) methods that are tailored to specific types of damage. This dissertation addresses innovative methods for NDE and SHM of manufacturing flaws and operational damage in composite structures.

For the NDE of manufacturing flaws in carbon fiber reinforced polymer (CFRP) composites, an eddy current testing (ECT) NDE method has been developed by conducting multiphysics modeling …

An Acoustic Emission And Artificial Intelligence Approach To Structural Health Monitoring For Aerospace Application, Joseph Chandler Garrett

Theses and Dissertations

In the area of aerospace and other applications, structural health monitoring (SHM) has been a significant and growing area of research in recent years. Throughout the operational life of aerospace structures, various damage scenarios may manifest, and it is of great concern to the aerospace community to develop methodologies for detecting and assessing these damage scenarios. In this paper, fundamental research on the use of the acoustic emission (AE) approach to SHM for fatigue crack growth is presented. In general, the AE approach to SHM and non-destructive evaluation (NDE) involves the sensing of ultrasonic Lamb waves propagating through a structure. …

Experimental Investigation Of Single And Two-Phase Heat Transfer Performance In Microchannels With Surface Modifications And Multiple Inlet Restrictors, Saad Kadham Oudah

Theses and Dissertations

Due to shrinking component sizes and faster switching speeds, the volumetric heat generation rates and surface heat flux in many advanced power electronic devices have increased exponentially, creating an urgent need for efficient cooling technologies. It has become particularly challenging to maintain an optimal temperature at the device level. Among advanced cooling techniques, single-phase and two-phase microchannel heat sinks show considerable promise in removing a significant amount of heat from a small surface area. Considered one of the most efficient heat dissipaters, the two-phase microchannel heat sink can handle very high heat flux at a small footprint and requires relatively …

Multimodal Robotic Health In Future Factories Through Iiot, Data Analytics, And Virtual Commissioning, Clint Saidy

Theses and Dissertations

The manufacturing sector is continuously reinventing itself by embracing opportunities offered by the industrial internet of things and big data, among other advances. Modern manufacturing platforms are defined by the quest for ever increasing automation along all aspects of the production cycle. Furthermore, in the next decades, research and industry are expected to develop a large variety of autonomous robots for a large variety of tasks and environments enabling future factories. This continuing pressure towards automation dictates that emergent technologies are leveraged in a manner that suits this purpose. These challenges can be addressed through the advanced methods such as …

Separate Effects Tests For Studying Thermal Gradient Driven Cracking In Uo2 Pellets Undergoing Resistive Heating, Sobhan Patnaik

Theses and Dissertations

A variety of normal operation and accident scenarios can generate thermal stresses large enough to cause cracking in light-water reactor (LWR) fuel pellets. Cracking of fuel pellets can lead to reduced heat removal, larger centerline temperatures, and localized stress in cladding, all of which impact fuel performance. It is important to understand the temperature profile on the pellet before and after cracking to improve cracking models in fuel performance codes such as BISON. However, in reactor observation and measurement of cracking is very challenging owing to the harsh environment and design of fuel rods.

Recently, a state-of-the-art experimental pellet cracking …

Enhanced Flow Boiling And Bubble Dynamics With Hfe7100 & Di Water In Interconnected Microchannels, Jiaxuan Ma

Theses and Dissertations

Flow boiling in microchannels using dielectric fluids is one of the most desirable cooling solutions for high power electronics. Primary two-flow patterns, including bubbly flow, slug flow, and annular flow, have been well established in microchannels. However, it is challenging to promote flow boiling performance, particularly critical heat flux (CHF), due to their unfavorable thermophysical properties. Considering these situations, flow boiling in parallel and isolated microchannels have been extensively studied. In this dissertation, a novel concept that has five parallel microchannels (W=200 µm, H=250 µm, L=10 mm) are interconnected by micro-slots (20 µm wide and 250 µm deep) starting from …

Experimental Investigation Of Spray Cooling Integrated With A Modified Vapor Compression Refrigeration System Using Several Refrigerants, Nabeel Mukhlif Abdulrazzaq

Theses and Dissertations

Spray cooling has gained increasing interest over the last three decades due to its high thermal performance as a direct cooling technique. Researchers are investigating spray cooling in thermal management systems for electronic applications, particularly focusing on the use of dielectric fluids including FC-72, FC-87, ammonia, and refrigerants such as R113 and R134a. Their studies indicate that the usage of dielectric fluids as a working fluid in spray cooling systems is promising and has significant thermal performance enhancement, which is suitable for a wide range of electronic applications. However, several deficiencies have been identified with the working fluids studied thus …

Nano-Engineered High-Performance Copper-Water Heat Pipes, Ahmed A. Abdulshaheed

Theses and Dissertations

Recently, heat pipes have gained an exceptional reputation as passive systems. They have become an attractive choice for many engineering applications due to their simple design, high rate of heat transfer, low weight, and low cost of maintenance [1]. A Heat pipe consists of a vacuumed shell filled partially with a compatible working fluid. Three main sections comprise a heat pipe: evaporator, adiabatic, and condenser section. The heat pipe utilizes the principle of evaporation and condensation for operations, i.e., the phase change of working fluid. Heat pipe allows high heat rates to transfer over considerable lengths with minimum temperature differences …

In Situ Tem Characterization Of Microstructure Evolution And Mechanical Behavior Of The 3d-Printed Inconel 718 Exposed To High Temperature, Supriya Koul, Le Zhou, Omar Ahmed, Yongho Sohn, Tengfei Jiang, Akihiro Kushima

Mechanical Engineering Faculty Research and Publications

This in situ transmission electron microscopy work presents a nanoscale characterization of the microstructural evolution in 3D-printed Inconel 718 (IN718) while exposed to elevated temperature and an associated change in the mechanical property under tensile loading. Here, we utilized a specially designed specimen shape that enables tensile testing of nano-sized thin films without off-plane deformations. Additionally, it allows a seamless transition from the in situ heating to tensile experiment using the same specimen, which enables a direct correlation of the microstructure and the mechanical property of the sample. The method was successfully used to observe the residual stress relaxation and …

Gradient-Based Tradeoff Design For Engineering Applications, Lena Alexis Royster

Mechanical & Aerospace Engineering Theses & Dissertations

This research presents a formal method for gradient based tradeoff design including methods that extend to cases with singularities and cases with more performance characteristics then design variables. The goal is to find revised design variables that can achieve the targeted performance characteristics and remove any violations to the constraint functions. The tradeoff design problem is formulation in the framework of the Sequential Quadratic Programming and is solved using the gradient based method. The optimal solution is the search direction, s, which represents the most effective way to reduce the current objective and correct the current violation. In this research …

A Model-Based Systems Engineering Approach To E-Vtol Aircraft And Airspace Infrastructure Design For Urban Air Mobility, Heidi Selina Glaudel

Mechanical & Aerospace Engineering Theses & Dissertations

This paper serves to contribute to Model-Based Systems Engineering (MBSE) by following the NASA Systems Engineering Handbook framework for a Systems Engineering (SE) design approach to an Electric Vertical Takeoff and Landing (e-VTOL) aircraft and the incorporating airspace infrastructure. The focus of this study is, by using the MBSE model created, to capture the technical requirements definition and design intent of the vehicle and airspace inclusive of community specific knowledge derived from the Federal Aviation Administration (FAA) NextGen Urban Air Mobility (UAM) Concept of Operations (ConOps) version 1.0. The stakeholder requirements derived from the FAA UAM NextGen ConOps will form …

Oxidation Polymerization Additive Manufacturing, Jonghyun Park, Tazdik Patwary Plateau, Hiep Pham

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Various processes for producing three dimensional electrically conductive polymer structures, such as three dimensional structures of poly(3,4-ethylenedioxythiophene), are described as well as materials produced by these processes.

High-Order Wave-Damage Interaction Coefficients (Wdic) Extracted Through Modal Decomposition, Hanfei Mei, Victor Giurgiutiu

Faculty Publications

This paper presents a new technique for the extraction of high-order wave-damage interaction coefficients (WDIC) through modal decomposition. The frequency and direction dependent complex-valued WDIC are used to model the scattering and mode conversion phenomena of guided wave interaction with damage. These coefficients are extracted from the harmonic analysis of local finite element model (FEM) mesh with non-reflective boundaries (NRB) and they are capable of describing the amplitude and phase of the scattered waves as a function of frequency and direction. To extract the WDIC of each wave mode, all the possible propagating wave modes are considered to be scattered …

Numerical Study Of A Buckling Restrained Brace (Brb) In Steel Structures And Comparison With A Convergent Ordinary Brace (Ocb) Under Static And Dynamic Loading, Fatemeh Habibpour

Makara Journal of Technology

Bulk metallic glass (BMG) has good mechanical strength, high hardness, wear resistance, and corrosion resistance with promising application in various industries. However, for the industrial production of BMG, the main issue is how to overcome limitations of joining with other materials. The present study focuses on solder processing at low operating temperature to avoid exceeding the recrystallization temperature. A feasible joining process for BMG was developed using lead-free solders. The BMG surface is pre-plated with copper, nickel, or titanium as a wetting layer. The reaction temperature is set between the glass transition temperature of BMG and the melting point of …

Composition-Dependent Solidification Cracking Of Aluminum-Silicon Alloys During Laser Powder Bed Fusion, Holden Hyer, Le Zhou, Abhishek Mehta, Sharon Park, Thinh Huynh, Shutao Song, Yuanli Bai, Kyu Cho, Brandon Mcwilliams, Yongho Sohn

Mechanical Engineering Faculty Research and Publications

Consistent manufacturing of volumetrically dense engineering components, free of solidification cracks by laser powder bed fusion (LPBF), has been demonstrated for Al-Si alloys such as AlSi10Mg and Al12Si. The success in LPBF of these alloys is attributed to the near eutectic composition with a small freezing range. To illuminate this observation, cracking susceptibility was examined from Scheil-Gulliver solidification modeling by calculating the hot cracking susceptibility, |dT/df_S^1/2|. To validate the findings from hot cracking susceptibility calculations, six binary Al-Si alloys, whose compositions were strategically chosen at hypo-, near-, and hyper-eutectic compositions, were gas atomized into alloy powders, and …

Anisotropic Scaffolds For Peripheral Nerve And Spinal Cord Regeneration, Wen Xue, Wen Shi, Yunfan Kong, Mitchell Kuss, Bin Duan

Department of Mechanical and Materials Engineering: Faculty Publications

The treatment of long-gap (>10 mm) peripheral nerve injury (PNI) and spinal cord injury (SCI) remains a continuous challenge due to limited native tissue regeneration capabilities. The current clinical strategy of using autografts for PNI suffers from a source shortage, while the pharmacological treatment for SCI presents dissatisfactory results. Tissue engineering, as an alternative, is a promising approach for regenerating peripheral nerves and spinal cords. Through providing a beneficial environment, a scaffold is the primary element in tissue engineering. In particular, scaffolds with anisotropic structures resembling the native extracellular matrix (ECM) can effectively guide neural outgrowth and reconnection. In …

Drive Leg And Stride Leg Ground Reaction Forces Relationship To Medial Elbow Stress And Velocity In Collegiate Baseball Pitchers, Brett Smith

Biomedical Engineering Theses & Dissertations

This study examines several different kinetic variables in relation to pitch velocity and elbow varus torque in collegiate baseball pitchers using force plates, an inertial measurement unit, and a radar unit. The purpose of this study is to investigate the kinetic variables being measured and their relationship to pitch velocity and loads being placed on the medial elbow. Twelve collegiate baseball pitchers participated in this study, which was approved by the IRB. Impulse of the drive leg in the anterior-posterior direction, stride leg peak force in the anterior-posterior (AP) direction, elbow varus torque, and pitch velocity were all measured. Two …

Improved Strain Gage Instrumentation Strategies For Rotorcraft Blade Measurements, Timothy S. Davis

Mechanical & Aerospace Engineering Theses & Dissertations

In this work, a new strategy is presented to wire, calibrate, and measure strain gages for rotor blade testing that will provide more information and is robust to individual gage loss. The additional information can be used in several ways. including reducing redundancy, offering rapid identification of damage locations, and in some cases reducing risk allowing tests to continue to collect calibrated data after one or more sensors have failed. This strategy replaces the classical four-gage full Wheatstone bridge with four separately wired quarter bridges that are combined into a full bridge in the data acquisition system using a calculated …

Thermal Evaluation Of Advanced Leading Edge For Rotating Gas Turbine Blade: Numerical And Experimental Investigations, Amin Safi

Dissertations

Gas turbine engines play a vital role in our life. Our power demand is significantly and continuously growing. One approach to improve thermal efficiency in gas turbine engines requires a higher turbine inlet gas temperature. Advanced gas turbine engines operate at high temperatures, around 2000 K. Since operating at high temperatures may compromise the blade structure integrity, different cooling systems are used in a turbine blades. One of the most efficient cooling techniques is impingement cooling, mostly used in the leading edge. The leading edge experiences the highest temperature in the blade exposed to the hottest gas.

Researchers studied different …

Bending-Torsion Flutter Analysis Of A Viscoelastic Tapered Wing Carrying An Engine And Subjected To A Follower Thrust Force, Youssef Shaaban Abdelfattah Matter

Theses

Flutter, a dynamic divergent instability, is one of the significant phenomena of Aeroelasticity. This dangerous aeroelastic phenomenon can occur to any flexible structure subjected to aerodynamic forces such as aircraft wings, bridges, buildings, etc. It is important to analyze the flutter in order to predict the speed and frequency at which it occurs so that structural damages and failures can be avoided. This thesis is concerned with non-dimensional parametric modeling of the flutter of a viscoelastic tapered wing with an attached engine. The main objectives of this thesis are to determine regions of stability and boundaries of flutter speed and …

Development Of Piezoelectric Energy Harvesting System For Low-Frequency Vibrations, Mai Rabie Mahmoud Ismail

Theses

Harvesting energy from vibration sources has attracted the interest of researchers for the past three decades. Researchers have been working on the potential of achieving self-powered MEMS scale devices. Piezoelectric cantilever harvesters have caught the attention in this field because of the excellent combination of high-power density and compact structure. The main objective of this thesis is to develop a novel and optimum piezoelectric harvester system using lumped parameter model (LPM) for given vibration sources. The finite element model (FEM) is used in this work as an original approach to be utilized for optimal design optimization. Three types of validations …

Thermo Hydraulic Performance Of Polymer Double-Pipe Heat Exchanger For Single-Phase Heating/Cooling Application, Ahmed Mohamed Gafar

Theses

This thesis details the model-based study carried out for understanding the thermal and hydraulic performance of double pipe heat exchangers with and without pin-fins; both counter and parallel flow configurations are considered in the study. The pin-fins are located on the outer wall of the inner pipe thereby extending into the annulus and in this study, the hot fluid is assumed to pass through the annulus. The model consists of multiple governing equations such as continuity equations, Navier-Stokes equations, and energy equations. A fluent module of Ansys Workbench is used for conducting the model-based study. Double pipe heat exchangers constructed …

Modelling And Control Of A Two-Link Rigid-Flexible Manipulator, Rahma Saeed Rasheed Alnajjar

Theses

The literature lacks data on the reliability of 3D models created by Autodesk Inventor software and imported to MATLAB Simulink software in comparison to mathematically generated models. In this contribution, a two-link rigid-flexible manipulator modelled in two different methods was demonstrated, one of which is using Lagrange equations and Finite Element Method to generate a mathematical model of the manipulator, and the other is creating a 3D model with the aid of Autodesk Inventor then import to MATLAB Simulink, both models were subsequently controlled by three types of controllers, conventional PID controller, LQR controller, and LQG controller. The research demonstrated …

Numerical Investigation Of Mesh-Based Enhancement Of Vapor Bubble Condensation, Omar Darwish Ali Alqadi Alhammadi

Theses

The aim of this work is to study the vapor bubble condensation process and the enhancement technique via affecting bubbles dynamic using a mesh-based structure. The bubble dynamics and thermal behavior are studied by considering the heat and mass transfer through the bubble’s interface area between the vapor and liquid regions and the resulting condensation effects. The thermal characteristics of bubbles are observed considering the initial and final liquid temperatures. Additionally, the bubble dynamics are studied in terms of several parameters including the relative velocity of the bubble, bubble deformation, interfacial area, and the bubble diameters. The relation between the …

Survey Of Unvented Attics In Climate Zone 2a, Florida Solar Energy Center, Eric Martin

FSEC Energy Research Center®

Moisture risk must be managed in unvented attics to ensure durability of components and longevity of the system. The FSEC Energy Research Center (FSEC), at the University of Central Florida tested and collected data in six homes in the northern Florida portion of IECC Climate Zone 2A built after 2015 with unvented (semi-conditioned) attics to add to the body of knowledge on the accumulation of moisture in the attic and its effects on roof moisture that can impact durability.

Dynamics Of Running Processes In The Area Of Underless Water Intake, D.R. Bazarov, M.P. Tashkhanova, A. Gayur, M. Sapaeva

Irrigation and Melioration

The paper analyzes the dynamics of channel processes based on the results of field studies of the Amudarya River at the site of the damless water intake to the Karshi Magistralny Canal (KMK) and developed recommendations for improving the water intake conditions. Based on the results of field studies of the head section of the inlet channel, an assessment of the state of the Amudarya river bed in the water intake zone was made. The results of studies of the hydraulic and alluvial regimes of the Amu Darya River in the area of the damless water intake are generalized The …

Determination Of The Optimal Hydromodule Of Irrigation Network For Drip Irrigation, R.Zh. Karshiev, A. Urazkeldiev, A.H. Radjabov, A.I. Ernazarov

Irrigation and Melioration

Most of the irrigation canals operating in the country were built in the 60s and 80s of the XX century, their hydraulic parameters were designed and adapted to the irrigation regimes of agricultural crops, mainly for surface irrigation, and the average hydromodule values were 0,8-1,0 l / s. , the hydraulic parameters of the channel are designed to carry large volumes of water in a short period of time. Over the next 3-4 years, the introduction of water-saving technologies in the irrigation of agricultural crops by farms and "Clusters" requires the improvement of hydraulic methods of irrigation management, the use …

Assessment Of The Impact Of Climate Change On Hydrological Processes In The Chirchik River Basin, Kh.Sh. Gafforov, Sh.D. Sh.D.Tursunboev

Irrigation and Melioration

The importance of assessing past and future climate differences plays an important role in future planning in relation to climate change. This situation requires urgent and concerted action in several areas: technology, infrastructure, politics, economics, and the environment. The article evaluates the impact of changes in precipitation intensity on the water level in the global circulation model (GCM) RCP 4.5 and 8.5 scenarios in the 2030s, 2050s, and 2070s. This study is a useful reference for improving water resource management and ensuring the sustainability of agricultural products in the future, as well as for improving operational water management and agricultural …

Assessment Of The Impact Of Climate Change On Hydrological Processes In The Chirchik River Basin, В.K. Saliev

Irrigation and Melioration

The article examines the assessment of the state and problems of irrigation water use in the republic in the past and in the near future. A comparative analysis of the state of water resources use for the period of the last 30 years from 1989 to 2019 was carried out.According to the estimates, own water withdrawal for 5 years (2014/15-2018/19) shows that an average of 53.2 m3, including 50.5 billion m3 from rivers At present (2018-2019), an average of 57.06 billion m3 of water is taken for irrigation of 4.289 million hectares of land, against 63.02 billion m3 approved in …

Environmental Damage Caused By Transport Equipment Waste, M. Radkevich, K. Shipilova, M. Abdukodirova, O. Pochugevski

Irrigation and Melioration

The article suggests a new approach to the monetary assessment of the damage caused to the environment by the processed waste of the transport sector. The proposed assessment method is based on the waste collection factor, all types of irretrievable losses and the volume of necessary compensatory release of materials. Based on a survey among vehicle owners, it was found that the solid waste collection rate is about 50 %, while the waste collection rate for operating fluids does not exceed 32 %. In this regard, the bulk of the damage to the environment is caused by liquid waste. Calculations …