Engineering Commons^™

Sensitivity Studies On The Shear Lag Parameter Β Using Analytical And Numerical Techniques, George Thomas Avery

Theses and Dissertations

The strength of fiber-reinforced composites is dependent on the strength of the fiber-matrix interface bond. Thermal, chemical, and other means have been used to modify the surface of fibers, resulting in increased fiber-matrix interface bond strength. However, researchers are still dependent on empirical methods to relate surface modifications to composite performance. Additional efforts are required to develop physics-based models for micro-mechanical effects on interfacial bond strength that will be needed for the improved design and processing of fiber reinforced composites. It is anticipated that experimental, numerical, and analytical efforts will be needed to contribute toward this endeavor.

A numerical approach …

Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed

Theses and Dissertations

The objective of this research is to generate design maps to identify functionally graded microstructures with enhanced fracture toughness. Several Functionally Graded Materials (FGMs) with an edge crack and membrane loading are considered and the resulting J-integral values are computed numerically using Finite Element Analysis. In order to capture the resulting stress fields accurately, Barsoum elements are used in the vicinity of the crack tip and the simulations are carried out for several crack lengths (a) and material contrasts (κ). The averages of the J-integral values are used to determine the normalized Stress Intensity Factors which are then benchmarked with …

Impact Location In An Isotropic Plate Without Training, Prasanna Rajbhandari

Theses and Dissertations

ABSTRACT

IMPACT LOCATION IN AN ISOTROPIC PLATE WITHOUT TRAINING

by

Prasanna Rajbhandari

The University of Wisconsin-Milwaukee, 2016

Under the Supervision of Professor Dr. Nathan Salowitz

Unexpected impacts are major concerns in the aerospace industry that can cause difficulty to detect damage. Techniques have been developed to determine the impact location using piezoelectric sensors. Most existing systems require training data to develop a database of known structural responses and properties that can be referenced for location of impacts. This data collection is time consuming and if an impact and corresponding sensor data is outside the range of training data, the system …

Advanced Self-Healing Polymer Composites For Wind Turbine Blades, Arun Kumar Koralagundi Matt

Theses and Dissertations

Wind energy is one of the prime sources of energy among the renewable sources of energy. Wind power has been one of the most promising sources of long-term, clean energy. Materials and design approach in commercial wind turbines have not seen a momentous change in the recent years. In this study, an intriguing bio-mimetic design approach is sought after, which is to heal damages as they arise in a composite material. Self-healing material systems in wind turbine blades have the potential to fulfill the requirement as an added safety mechanism to heal damages and prevent catastrophic failures. Effectively supplying healing …

Packing Sheet Materials Into Cylinders And Prisms Using Origami-Based Approaches, Jared Thomas Bruton

Theses and Dissertations

Packing sheet materials into cylinders and prisms using Origami-based approaches (Soft Origami or traditional Origami) is of interest in fields where sheet materials need folded into cylinders or prisms. Fully-dense packing has application in fields where a sheet material is to be folded with minimal gaps into a cylinder or prism. Partially-dense packing is applicable to fields where gaps are required between packed surfaces or where hollow volumes are to be filled, such as in fluid filter design. Soft Origami is explored as a method for folding soft-sheet materials into fully-dense cylinders. Two fold patterns, the "flasher'' and the "inverted-cone …

Position And Stiffness Control Of Inflatable Robotic Links Using Rotary Pneumatic Actuation, Charles Mansel Best

Theses and Dissertations

Inflatable robots with pneumatic actuation are naturally lightweight and compliant. Both of these characteristics make a robot of this type better suited for human environments where unintentional impacts will occur. The dynamics of an inflatable robot are complex and dynamic models that explicitly allow variable stiffness control have not been well developed. In this thesis, a dynamic model was developed for an antagonistic, pneumatically actuated joint with inflatable links.The antagonistic nature of the joint allows for the control of two states, primarily joint position and stiffness. First a model was developed to describe the position states. The model was used …

Comparing Efficacy Of Different Dynamic Models For Control Of Underdamped, Antagonistic, Pneumatically Actuated Soft Robots, Morgan Thomas Gillespie

Theses and Dissertations

Research in soft robot hardware has led to the development of platforms that allow for safer performance when working in uncertain or dynamic environments. The potential of these platforms is limited by the lack of proper dynamic models to describe or controllers to operate them. A common difficulty associated with these soft robots is a representation for torque, the common electromechanical relation seen in motors does not apply. In this thesis, several different torque models are presented and used to construct linear state-space models. The control limitations on soft robots are induced by natural compliance inherent to the hardware. This …

Fundamental Principles Of Tremor Propagation In The Upper Limb, Andrew Doran Davidson

Theses and Dissertations

Although tremor is the most common movement disorder, there exist few effective tremor-suppressing devices, in part because the characteristics of tremor throughout the upper limb are unknown. To clarify, optimally suppressing tremor requires a knowledge of the mechanical origin, propagation, and distribution of tremor throughout the upper limb. Here we present the first systematic investigation of how tremor propagates between the shoulder, elbow, forearm, and wrist. We simulated tremor propagation using a linear, time-invariant, lumped-parameter musculoskeletal model relating joint torques and the resulting joint displacements. The model focused on the seven main degrees of freedom (DOF) from the shoulder to …

Modeling Atypical Building Use With Commercially Available Building Simulation Software, Sarah E. Schanck

Theses and Dissertations

National Guard armories are audited to provide recommendations for future energy reduction measures. The annual energy consumption of a New Jersey National Guard Armories cannot be modeled directly with commercially available building simulation software, due to discrepancies between the modeling capabilities of the software and the reality of the armory. A building simulation software, eQUEST, was chosen for use in this project. Discrepancies between eQUEST inputs and reality were identified and correction factors developed to minimize the effect of each discrepancy on predicted energy consumption, with the end goal of accuracy between predicted and actual energy consumption. In addition, an …

Numerical Modeling Of Soy Biodiesel To Maximize Engine Power And Efficiency While Minimizing Pollutant Emissions, Ehsan Tootoonchi

Theses and Dissertations

Biodiesel is a renewable fuel that can help to reduce dependence on foreign petroleum and to help control the negative environmental effects of combustion engines. This work develops a numerical model for soy biodiesel combustion in diesel engine applications. A comprehensive breakup model for diesel and biodiesel combustion calculations using the KIVA- 3V is presented. The primary breakup model calculates the outcome of the initial breakup stage using flow conditions, nozzle geometry, and liquid fuel characteristics, and assigns the Sauter Mean Radius (SMR) values to injecting droplets. The Kelvin-Helmholtz/Rayleigh-Taylor(KH-RT) model acts as the secondary model to break up injected particles. …

The Controlled Human Gyroscope, Randy Claude Arjunsingh

Theses and Dissertations

The objective of this thesis was to design an adaptive rotational motion simulator capable of replicating the attitudes of spacecrafts and aircrafts, while avoiding gimbal lock. Flight motion simulators are currently used for flight training and research, but there are many limitations to these existing systems. This thesis presents a low-cost design for a rotational motion platform titled, ‘The Controlled Human Gyroscope’. It uses a 4-axis system instead of the conventional 3-axis system to avoid gimbal lock and prevent the unnecessary motion of the user. The Human Gyroscope features unlimited rotation about the roll, pitch and yaw axes regardless of …

Study Of Friction Extrusion And Consolidation, Xiao Li

Theses and Dissertations

Friction extrusion and consolidation was invented by The Welding Institute (Cambridge, UK) in the early 1990’s. It is related to simple extrusion processes with the primary difference being that the extrusion die rotates about the extrusion axis and the die is required to impart substantial deformation to the initially, finely divided charge (like metal waste or chips) in order to consolidate it prior to extrusion. It can produce high quality wire and fully consolidated bulk material from low-cost precursors like metal chips or powders. The advantages lie in that it is a direct method to recycle metal chips or scraps …

Numerical Modeling Of Heat Transfer And Material Flow During Friction Extrusion Process, Hongsheng Zhang

Theses and Dissertations

Friction extrusion process is a novel manufacturing process that converts low-cost metal precursors (e.g. powders and machining chips) into high-value wires with potential applications in 3D printing of metallic products. However, there is little existing scientific literature involving friction extrusion process until recently. The present work is to study the heat transfer and material flow phenomena during the friction extrusion process on aluminum alloy 6061 through numerical models validated by experimental measurements.

The first part is a study of a simplified process in which flow of a transparent Newtonian fluid in a cylindrical chamber caused by frictional contact with a …

Investigation Of Thermal Scaling Effects For A Turbine Blade Leading Edge And Pressure Side Model, Ryan A. Lynch

Theses and Dissertations

Recent experiments have attempted to quantify the overall cooling effectiveness at elevated temperature conditions. The Film Cooling Rig (FCR) at the Air Force Institute of Technology has been modified to better match the configuration of a similar large scale, low temperature rig at the Air Force Research Laboratory. This has enabled comparison and trend identification of how various properties scale from the low to high temperature condition. Various internal cooling and hole geometry configurations were investigated over a range of temperatures while utilizing the thermal scaling capability of Inconel 718. Film cooling trends and measures of overall effectiveness were matched, …

Implementations Of Fourier Methods In Cfd To Analyze Distortion Transfer And Generation Through A Transonic Fan, Marshall Warren Peterson

Theses and Dissertations

Inlet flow distortion is a non-uniform total pressure, total temperature, or swirl (flow angularity) condition at an aircraft engine inlet. Inlet distortion is a critical consideration in modern fan and compressor design. This is especially true as the industry continues to increase the efficiency and operating range of air breathing gas turbine engines. The focus of this paper is to evaluate the Computational Fluid Dynamics (CFD) Harmonic Balance (HB) solver in STAR-CCM+ as a reduced order method for capturing inlet distortion as well as the associated distortion transfer and generation. New methods for quantitatively describing and analyzing distortion transfer and …

Heteromorphic To Homeomorphic Shape Match Conversion Toward Fully Automated Mesh Morphing To Match Manufactured Geometry, Robert Ivan Yorgason

Theses and Dissertations

The modern engineering design process includes computer software packages that require approximations to be made when representing geometries. These approximations lead to inherent discrepancies between the design geometry of a part or assembly and the corresponding manufactured geometry. Further approximations are made during the analysis portion of the design process. Manufacturing defects can also occur, which increase the discrepancies between the design and manufactured geometry. These approximations combined with manufacturing defects lead to discrepancies which, for high precision parts, such as jet engine compressor blades, can affect the modal analysis results. In order to account for the manufacturing defects during …

Design And Analysis Of Two Compliant Mechanism Designs For Use In Minimally Invasive Surgical Instruments, Jason Lon Dearden

Theses and Dissertations

Minimally invasive surgery (MIS) has several advantages over traditional methods. Scaling MIS instruments to smaller sizes and increasing their performance will enable surgeons to offer new procedures to a wider range of patients. In this work, two compliant mechanism-based minimally invasive surgical instrument wrist or gripper mechanisms are designed and analyzed.The cylindrical cross-axis flexural pivot (CCAFP) is a single-degree-of-freedom wrist mechanism that could be combined with existing gripper mechanisms to create a multi-degree-of freedom instrument. The simplicity of the CCAFP mechanism facilitates analysis and implementation. The flexures of the CCAFP are integral with the instrument shaft, enabling accessories to be …

Non-Schmid Effects And Criteria For Dislocation Nucleation On Different Slip Systems At Grain Boundaries, Richard Durtschi Wyman

Theses and Dissertations

Criteria for grain boundary dislocation nucleation are developed. A bicrystal containing two grain boundaries is placed under varying triaxial stress states using molecular dynamics. The local resolved shear, normal, and co-slip stresses needed for grain boundary dislocation nucleation are found. A framework is developed to detect the slip system grain boundary dislocation nucleation occurs on. A survey of the different ways grain boundary dislocation nucleation occurs in the sample shows a single grain boundary can nucleate dislocations in a rich variety of ways. Using the nucleation system and resolved stress values, criteria for grain boundary dislocation nucleation on different slip …

The Effect Of Projectile Nose Shape On The Formation Of The Water Entry Cavity, Jeremy Conrad Ellis

Theses and Dissertations

This research focuses on the effect of several convex and concave nose shapes on cavity formation for both hydrophilic and hydrophobic projectiles. It specifically investigates the effect of convex shape on the threshold velocity for cavity formation as well as the effect of concave shapes on cavity formation in terms of impact velocity, geometry of the concave shape and wettability of the projectile. For the convex cases, the streamlined axisymmetric shape significantly increases the threshold velocity when cavities form and is most pronounced for the ogive and cone. The study demonstrates that measuring the wetting angle and impact velocity is …

Numerical And Experimental Studies Of Atomic Layer Deposition For Sustainability Improvement, Dongqing Pan

Theses and Dissertations

Atomic layer deposition (ALD) is an approved nano-scale thin films fabrication technique with remarkable uniformity and conformity in surface geometry. This dissertation presents numerical and experimental studies to investigate the transient physical and chemical ALD process in order to improve its sustainability performance in terms of throughput, wastes and emissions.

To be specific, in this dissertation, the transient process of ALD is studied extensively through both numerical and experimental approaches to find the influential factors on the two main critical sustainability issues: low throughput and negative environmental impacts. Different numerical schemes are developed and studied for ALD process simulations. In …

Application Of Reynolds Stress Model Using Direct Modeling And Actuator Disk Approaches For A Small-Scale Wind Turbine, Randall Scott Jackson

Theses and Dissertations

The Reynolds Stress Model (RSM) has been avoided for turbulence closure in CFD simulations of wind turbines, largely due to the computational expense and the high potential for numerical instability. The advantage of using RSM is having access to shear stresses that are not available from two-equation RANS-based closure models like k-e and k-w. Access to the shear stresses will aide in the understanding of how the blade design will affect the wake, particularly in the near-wake region. In this research, the RSM turbulence model has been successfully applied in simulating a three-bladed small-scale wind turbine through a direct-model approach …

Covert Contrast: The Acquisition Of Mandarin Tone 2 And Tone 3 In L2 Production And Perception, Liya Mar

Theses and Dissertations

This dissertation investigates the occurrence of an intermediate stage, termed a covert contrast, in the acquisition of Mandarin Tone 2 (T2) and Tone 3 (T3) by adult speakers of American English. A covert contrast is a statistically reliable distinction produced by language learners that is not perceived by native speakers of the target language (TL). In second language (L2) acquisition, whether a learner is judged as having acquired a TL phonemic contrast has largely depended on whether the contrast was perceived and transcribed by native speakers of the TL. However, categorical perception has shown that native listeners cannot perceive a …

Design Of Three-Dimensional Near-Zero Refractive Index Metamaterials, David Flores Iii

Theses and Dissertations

Near-zero refractive index metamaterials exhibit remarkable electromagnetic properties which can and will be applied in the near future. From the known methods of achieving near-zero refractive index, this work primarily focuses on the design of 3D metamaterials whose permittivity and permeability are both close to zero while maintaining relatively low loss factor. The design of the metamaterials is based on the chiral shape “omega” and designed to weave periodically as a fishnet. Theoretical analysis, computer modeling and simulation are steps taken in the design of metamaterials. A computational tool based on the robust method for effective parameter extraction is successfully …

Experimental And Numerical Characterization Of Scalable Cellulose Nano-Fiber Composite, Bamdad Barari Barari

Theses and Dissertations

Fiber-reinforced polymer composites have been used in recent years as an alternative to the conventional materials because of their low weight, high mechanical properties and low processing temperatures. Most polymer composites are traditionally made using reinforcing fibers such as carbon or glass fibers. However, there has been recent interest in making these reinforcing fibers from natural resources. The plant-derived cellulose nano-fibers (CNF) are a material with remarkable mechanical properties at the nano-scale that are much superior to the mechanical properties of the traditional natural fibers (such as jute, hemp, kenaf, etc) used in the natural-fiber based polymer composites. Because CNF …

A Study Of The Hydrostatic And Hydrodynamic Properties Of Aeoliscus Straigatus, Jeremy J. Keifenheim

Theses and Dissertations

Aeoliscus strigatus is a highly maneuverable fish found in the Indo-Pacific region. It boasts a unique head down posture and employs median paired fin propulsion to perform precise movements. The need for highly maneuverable underwater AUVs for exploration and testing drove the examination of the hydrostatics and hydrodynamics influencing Aeoliscus. To determine the stability of Aeoliscus the center of gravity and buoyancy were found. Center of gravity was experimentally located using the three plumb line method while center of buoyancy was located using two separate methods. The first method utilized the measured buoyant force, a rigidly mounted fish and a …

Effects Of Surface Topography And Vibrations On Wetting: Superhydrophobicity, Icephobicity And Corrosion Resistance, Rahul Ramachandran

Theses and Dissertations

Concrete and metallic materials are widely used in construction and water industry. The interaction of both these materials with water and ice (or snow) produces undesirable results and is therefore of interest. Water that gets absorbed into the pores of dry concrete expands on freezing and can lead to crack formation. Also, the ice accretion on concrete surfaces such as roadways can have disastrous consequence. Metallic components used in the water industry undergo corrosion due to contact with aqueous corrosive solutions. Therefore, it is desirable to make concrete water/ice-repellent, and to make metallic surfaces corrosion-resistant.

Recent advances in micro/nanotechnology have …

Coding Strategies For Cochlear Implants Under Adverse Environments, Qudsia Tahmina

Theses and Dissertations

Cochlear implants are electronic prosthetic devices that restores partial hearing in patients with severe to profound hearing loss. Although most coding strategies have significantly improved the perception of speech in quite listening conditions, there remains limitations on speech perception under adverse environments such as in background noise, reverberation and band-limited channels, and we propose strategies that improve the intelligibility of speech transmitted over the telephone networks, reverberated speech and speech in the presence of background noise. For telephone processed speech, we propose to examine the effects of adding low-frequency and high- frequency information to the band-limited telephone speech. Four listening …

Graphene-Based Nanomaterials For Hydrogen Generation And Storage, Lin Wei

Theses and Dissertations

Hydrogen energy is promising candidate to replace fossil fuel. However, the usage of hydrogen energy was greatly limited due to its generation and storage. In this thesis report, the author synthesized novel metal/carbon nanomaterials used for the hydrogen storage and hydrogen evolution reaction. These materials were characterization by XRD, Raman, XPS, SEM, EDX, etc. And the surface area and the hydrogen storage properties were tested by ASAP 2020, using the BET measurement and hydrogen isotherm curves to discuss the gas adsorption properties. As for hydrogen evolution reaction, the materials were made into electrodes and tested with LSV, CV to shows …

Numerical And Experimental Study Of Liquid Breakup Process In Solid Rocket Motor Nozzle, Yi-Hsin Yen

Theses and Dissertations

Rocket propulsion is an important travel method for space exploration and national defense, rockets needs to be able to withstand wide range of operation environment and also stable and precise enough to carry sophisticated payload into orbit, those engineering requirement makes rocket becomes one of the state of the art industry. The rocket family have been classified into two major group of liquid and solid rocket based on the fuel phase of liquid or solid state. The solid rocket has the advantages of simple working mechanism, less maintenance and preparing procedure and higher storage safety, those characters of solid rocket …

Nonlinear Dynamics Of Electrostatically Actuated Nanotweezers, Bin Liu

Theses and Dissertations

Bin Liu, Nonlinear Dynamics of Electrostatically Actuated Nanotweezers. Master of Science (MS), May 2016, 77 pp, 6 tables, 59 figures, references, 25 titles. The amplitude-frequency response of electrostatic nanotube nanotweezer device system is investigated; soft alter current was setting at near half natural frequency impulse on nanotubes which are referred to as two arms, parametric and primary resonances will be shown in the results, respectively. Firstly we are using the Method of Multiple Scales (MMS) analytical model; results will be compared with Reduced Order Model (ROM). By variation and comparison of multiple parameters including van der wall molecular forces, electrostatic …