Engineering Commons^™

Numerical Simulation Of Laser Induced Elastic Waves In Response To Short And Ultrashort Laser Pulses., Alireza Zarei

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In an era of intensified market competition, the demand for cost-effective, high-quality, high-performance, and reliable products continues to rise. Meeting this demand necessitates the mass production of premium products through the integration of cutting-edge technologies and advanced materials while ensuring their integrity and safety. In this context, Nondestructive Testing (NDT) techniques emerge as indispensable tools for guaranteeing the integrity, reliability, and safety of products across diverse industries.

Various NDT techniques, including ultrasonic testing, computed tomography, thermography, and acoustic emissions, have long served as cornerstones for inspecting materials and structures. Among these, ultrasonic testing stands out as the most prevalent method, …

Cfrp Delamination Density Propagation Analysis By Magnetostriction Theory, Brandon Eugene Williams

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While Carbon Fiber Reinforced Polymers (CFRPs) have exceptional mechanical properties concerning their overall weight, their failure profile in demanding high-stress environments raises reliability concerns in structural applications. Two crucial limiting factors in CFRP reliability are low-strain material degradation and low fracture toughness. Due to CFRP’s low strain degradation characteristics, a wide variety of interlaminar damage can be sustained without any appreciable change to the physical structure itself. This damage suffered by the energy transfer from high- stress levels appears in the form of microporosity, crazes, microcracks, and delamination in the matrix material before any severe laminate damage is observed. This …

Multiscale Modeling And Gaussian Process Regression For Applications In Composite Materials, Joshua Arp

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An ongoing challenge in advanced materials design is the development of accurate multiscale models that consider uncertainty while establishing a link between knowledge or information about constituent materials to overall composite properties. Successful models can accurately predict composite properties, reducing the high financial and labor costs associated with experimental determination and accelerating material innovation. Whereas early pioneers in micromechanics developed simplistic theoretical models to map these relationships, modern advances in computer technology have enabled detailed simulators capable of accurately predicting complex and multiscale phenomena.

This work advances domain knowledge via two means: firstly, through the development of high-fidelity, physics-based finite …

Machine Learning-Based Data And Model Driven Bayesian Uncertanity Quantification Of Inverse Problems For Suspended Non-Structural System, Zhiyuan Qin

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Inverse problems involve extracting the internal structure of a physical system from noisy measurement data. In many fields, the Bayesian inference is used to address the ill-conditioned nature of the inverse problem by incorporating prior information through an initial distribution. In the nonparametric Bayesian framework, surrogate models such as Gaussian Processes or Deep Neural Networks are used as flexible and effective probabilistic modeling tools to overcome the high-dimensional curse and reduce computational costs. In practical systems and computer models, uncertainties can be addressed through parameter calibration, sensitivity analysis, and uncertainty quantification, leading to improved reliability and robustness of decision and …

The Effects Of Laser Shock Peening On The Fatigue Life Of Additive Manufactured Alsi10mg, Jacob L. Biddlecom

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Additive manufacturing (AM) is becoming a manufacturing process that is well established, even with all the resources and attention that has been brought to it, the field is still lacking some key understandings. Currently, there are certain aspects that are difficult to overcome. Some of the intrinsic obstacles include process-induced defects, such as porosity from lack of fusion and gaseous bubble entrapment, as well as complex thermal gradients. These defects can lead to altered material response especially when looking at the fatigue life. The fatigue behaviors of AM components can change from print to print as well as when compared …

Classification Of Electrical Current Used In Electroplastic Forming, Tyler Grimm

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Electrically assisted manufacturing (EAM) is the direct application of an electric current to a workpiece during manufacturing. This advanced manufacturing process has been shown to produce anomalous effects which extend beyond the current state of modeling of thermal influences. These purported non-thermal effects have collectively been termed electroplastic effects (EPEs).

While there is a distinct difference in results between steady-state (ideal DC) testing and pulsed current testing, the very definition of these two EAM methods has not been well established. A "long" pulse may be considered DC current; a "short" pulse may produce electroplastic effects; and even "steady-state" current shapes …

Mesoscale Modeling And Machine Learning Studies Of Grain Boundary Segregation In Metallic Alloys, Malek Alkayyali

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Nearly all structural and functional materials are polycrystalline alloys; they are composed of differently oriented crystalline grains that are joined at internal interfaces termed grain boundaries (GBs). It is well accepted that GB dynamics play a critical role in many phenomena during materials processing or under operating environments. Of particular interest are GB migration and grain growth processes, as they influence many crystal-size dependent properties, such as mechanical strength and electrical conductivity.

In metallic alloys, GBs offer a plethora of preferential atomic sites for alloying elements to occupy. Indeed, recent experimental studies employing in-situ microscopy revealed strong GB solute segregation …

Multi-Robot Symbolic Task And Motion Planning Leveraging Human Trust Models: Theory And Applications, Huanfei Zheng

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Multi-robot systems (MRS) can accomplish more complex tasks with two or more robots and have produced a broad set of applications. The presence of a human operator in an MRS can guarantee the safety of the task performing, but the human operators can be subject to heavier stress and cognitive workload in collaboration with the MRS than the single robot. It is significant for the MRS to have the provable correct task and motion planning solution for a complex task. That can reduce the human workload during supervising the task and improve the reliability of human-MRS collaboration. This dissertation relies …

Crack Control And Bond Performance Of Alternative Coated Reinforcements In Concrete, Sachin Sreedhara

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Concrete cracking in structures is a ubiquitous problem which can lead to the deterioration of the structure. Other than affecting the strength aspect of a structure, cracking impacts the serviceability criteria as well. Although cracking phenomenon in any structure is highly inevitable, it has to be minimized in order to maintain a structure’s life effectively. Cracking in reinforced concrete structures is related to the bond strength developed between the bar and the concrete. It also depends on an ability of the bar to resist the stresses due to shrinkage to minimize the crack. Another important aspect is the resistance offered …

Effects Of Transportation Hazards On Package Performance And Food Product Shelf Life, Kyle Dunno

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This research studied the effect of transportation hazards on food product shelf life and package performance. Studies were conducted to determine the effect of package headspace volume, product viscosity and storage temperature on package integrity. Finally, accelerated shelf life testing (ASLT) was utilized to determine how simulated transportation hazards affected the shelf life of a specific food product. Institutional retort pouches containing either water or 5% starch solution were filled with varying amounts of headspace volume to determine if package headspace volume could aid in package performance during simulated engineering tests for packaged products. Fixed displacement vibration testing and compression …

Cushop: A Simulated Shopping Environment Fostering Consumer-Centric Packaging Design & Testing, Charles Tonkin

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Consumer product packaging provides product damage protection, extends product shelf life, and communicates product usage instructions to the consumer. Its collective contribution to the waste stream is notorious, but its role in product salability is much less understood. Consumers now make the majority of product purchase decisions while present at the shelf, and since they do it very quickly (within 5-8 seconds), and do not appear to adhere to strong brand loyalty as was once more common, packaging (and more specifically, its aesthetics and contrast with its competitors) plays a dominant role in the decision-making process. It is difficult, however, …

Modeling Of Cell Transfer And Process-Induced Cell Damage In Laser-Assisted Cell Direct Writing, Wei Wang

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Laser-assisted cell direct-write technique has been obtaining more and more attention in different biomaterial direct writing applications. A typical laser-assisted cell direct-write process can be divided into two main stages: the cell droplet ejection and cell droplet landing. The objective of this study is to model the cell mechanical profile during the cell droplet ejection and cell landing and further model the cell damage.
The possible cell damage during the droplet ejection process in laser-assisted cell direct writing may come from two different sources: the phase explosion-induced bubble expansion and the thermoelastic stress wave. The bubble expansion-induced stress wave is …

Friction Measurement In Precision Glass Molding, Peiman Mosaddegh

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Extensive growth of state-of-the-art technologies has created a demand for high quality lenses and has driven the industry toward an inexpensive process for manufacturing of aspheric glass lenses called Precision Glass Molding (PGM). Finite Element Analysis (FEA) has been used to predict the right mold geometry. Having a realistic simulation to predict mold geometry depends on the correct model of material behavior and friction coefficient at elevated temperature.
Finding the static and dynamic coefficient of friction experimentally between two flat surfaces at elevated temperature is the subject of this research. The equipment used in this study was originally designed for …

Development Of A Finite Element Model To Predict The Behavior Of A Prototype Wheel On Lunar Soil, Marisa Orr

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The All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) is a mobile lunar lander under development by the National Aeronautics and Space Administration's Lunar Architecture Team. While previous lunar missions have lasted only a few days, the ATHLETE is designed to last for 10 years, which will enable a sustained U.S. presence on the moon and exploration of the more treacherous regions which are not suitable for landing. Because the ATHLETE will carry entire astronaut habitats, its six wheels must be carefully designed to support a large load on soft lunar soil efficiently.
The purpose of this thesis is to develop a finite …

Investigation Of Subgrid-Scale Mixing And Turbulence-Chemistry Interaction In Turbulent Partially Premixed Flames Using Experimental Data, Jian Cai

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The filtered mass density function (FMDF) of mixture fraction, temperature and species used in large eddy simulation (LES) of turbulent combustion is studied experimentally using line images obtained in turbulent partially premixed methane flames (Sandia flames D and E). Cross-stream filtering is employed to obtain the FMDF and other filtered variables. The mean of the FMDF conditional on the subgrid-scale (SGS) scalar variance at a given location are found to vary from unimodal to bimodal, corresponding to quasi-equilibrium distributed reaction zones and laminar flamelets (including extinguished flamelets), respectively. The conditionally filtered mixture fraction dissipation for small SGS variances has a …

Vehicle Steering Systems - Hardware-In-The-Loop Simulator, Driving Preferences, And Vehicle Intervention, Jesse Black

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The steering system is a critical component of all ground vehicles regardless of their propulsion source. Chassis directional control is provided by the steering system, which in turn relays valuable feedback about the road and vehicle behavior. As the primary feedback channel to the driver, the steering system also delivers the initial perception of a vehicle's handling and responsiveness to the consumer. Consequently, the steering system is an important aspect of the vehicle's evaluation and purchasing process, even if drivers are unaware of its direct influence in their decision making. With automobile purchases potentially hinging on the steering system, a …

Evaluation Of Fluid Diodes As Pulmonary Heart Valve Replacements, Tiffany Camp

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Children born with congenital heart disease often times suffer from severe chronic pulmonary insufficiency. Palliative treatments for this condition may come early on in the life of the patient; however, if it becomes severe enough, a pulmonary valve replacement may be required. There currently is not a permanent option for a replacements valve. Therefore, a need exists to develop a permanent solution. Knowing that the right heart circulation is more tolerant of moderate levels of regurgitation (0 - 35%) and pressure gradient (0 - 30 mmHg), this study investigates the hypothesis that a fluid diode, a motionless valve that offers …

Dynamics Of Ultrasonic Consolidation, James Gibert

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Ultrasonic consolidation (UC) is a solid state rapid manufacturing process derived from ultrasonic welding of thin metal foils coupled with contour milling to achieve functional accurate components. The bonding of metal is accomplished by the local application of high frequency vibration energy under pressure producing a metallurgical bond without melting the base material. Its unique nature allows the design and fabrication of structural panels for satellites, production of injection molding tools, functionally graded structures, metal-matrix composites, embedded sensors, armor, and fiber embedded adaptive structures. It is commonly theorized that interfacial motion and friction at the bonding interface play a prominent …

Development And Integration Of Geometric And Optimization Algorithms For Packing And Layout Design, Santosh Tiwari

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The research work presented in this dissertation focuses on the development and application of optimization and geometric algorithms to packing and layout optimization problems. As part of this research work, a compact packing algorithm, a physically-based shape morphing algorithm, and a general purpose constrained multi-objective optimization algorithm are proposed. The compact packing algorithm is designed to pack three-dimensional free-form objects with full rotational freedom inside an arbitrary enclosure such that the packing efficiency is maximized. The proposed compact packing algorithm can handle objects with holes or cavities and its performance does not degrade significantly with the increase in the complexity …

Microcantilever-Based Force Sensing, Control And Imaging, Reza Saeidpourazar

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This dissertation presents a distributed-parameters base modeling framework for microcantilever (MC)-based force sensing and control with applications to nanomanipulation and imaging. Due to the widespread applications of MCs in nanoscale force sensing or atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the involved MCs is essential. Along this line, a distributed-parameters modeling framework is proposed which is followed by a modified robust controller with perturbation estimation to target the problem of delay in nanoscale imaging and manipulation. It is shown that the proposed nonlinear model-based controller can stabilize such nanomanipulation process in a very short …

Foundations Of Design Method Development, Sudhakar Teegavarapu

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A systematic procedure for developing design methods, tools, and/or processes, referred to as meta-method, is proposed. It is hypothesized that design methods developed without following a systematic procedure are not effective and thus are not widely accepted by industry and academia likewise. The systematic framework provided by the meta-method will ensure 1) faster development of design methods, 2) enable tracking of requirements throughout the development process, 3) facilitate efficient exploration and selection of alternatives, 4) document the development process for future reuse, 5) help in testing and validation of design methods, and 6) bridge gap between multiple disciplines by forming …

Development, Parameterization And Validation Of Dynamic Material Models For Soil And Transparent Armor Glass, Bhaskar Pandurangan

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Despite the signing of several mine ban treaties in the 1990's, it is widely recognized that there is a landmine crisis. The following are some of the main aspects of this crisis: (a) Millions of unexploded landmines remain deployed all over the world; (b) Thousands of civilians are killed or maimed every year by unintended detonations of the mines; (c) The cost of medical treatment of landmine injuries runs into the millions; (d) the ability of the international community to provide the humanitarian relief in terms of medical services, safe drinking water and food, etc., is greatly hampered by landmine …

Modeling And Control Of Piezoactive Micro And Nano Systems, Saeid Bashash

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Piezoelectrically-driven (piezoactive) systems such as nanopositioning platforms, scanning probe microscopes, and nanomechanical cantilever probes are advantageous devices enabling molecular-level imaging, manipulation, and characterization in disciplines ranging from materials science to physics and biology. Such emerging applications require precise modeling, control and manipulation of objects, components and subsystems ranging in sizes from few nanometers to micrometers. This dissertation presents a comprehensive modeling and control framework for piezoactive micro and nano systems utilized in various applications.
The development of a precise memory-based hysteresis model for feedforward tracking as well as a Lyapunov-based robust-adaptive controller for feedback tracking control of nanopositioning stages are …

Computional Modeling Of Precision Molding Of Aspheric Glass Optics, Balajee Ananthasayanam

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In this dissertation, research in two parallel directions is presented; the first involves the prediction of the final size and shape of a glass lens during a precision glass lens molding process and the second introduces a method to compute and quantify the importance of higher order terms in fracture mechanics for different modes of fracture.
The process of precision lens molding has received attention in recent years due to its potential to mass produce aspherical lenses. Aspherical lenses have significantly better optical properties and conventional lens making techniques are limited to manufacturing of spherical lenses only. The conventional technique …

A Comprehensive Multiphysics, Multiscale Modeling Framework For Carbon Nanotube Fabrication Process By Chemical Vapor Deposition, Mahmoud Reza Hosseini

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Carbon nanotubes (CNTs) are among the most promising nanosize materials as evidenced by the attention they have received since their discovery in 1991 and a wide range of scientific and industrial applications. Each of these applications requires unique CNTs with specific length, diameter and chirality. However, control of these parameters is considered as one of the main challenges for large scale production of CNTs. Furthermore, these processes are not well designed so as to limit the number of CNT defect sites or the production of unwanted byproducts such as amorphous carbon. Therefore, it is crucial to develop a controlled CNTs …

Similarity Metrics Applied To Graph Based Design Model Authoring, Srinivasan Anandan

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Model reuse is typically facilitated by search and retrieval tools, matching the sought model with models in a database. This research aims at providing similar assistance to users authoring design exemplars, a data structure to represent parametric and geometric design problems. The design exemplar represents design problems in the form of a bi-partite graph consisting of entities and relations. Authoring design exemplars for relatively complex design problems can be time consuming and error prone. This forms the motivation of developing a search and retrieval tool, capable of retrieving exemplars that are similar to the exemplar that a user is trying …

Modeling Of The Effect Of Tool Wear On Cutting Forces In Turning, Yu Long

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Machining is the most widely used and efficient material removal process, and tool wear in machining is usually of great interest in order to improve machining efficiency and effectiveness. Cutting tool wear patterns such as the flank and crater wear and the dead metal zone (DMZ) may induce the cutting tool geometry variation in machining. As a result, cutting forces may increase or decrease due to the change of tool effective cutting geometry during machining operations. A quantitative understanding of and the ability to predict cutting forces in relation to tool wear are important to the tool life estimation, chatter …

Physics-Based Shape Morphing And Packing For Layout Design, Hong Dong

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The packing problem, also named layout design, has found wide applications in the mechanical engineering field. In most cases, the shapes of the objects do not change during the packing process. However, in some applications such as vehicle layout design, shape morphing may be required for some specific components (such as water and fuel reservoirs). The challenge is to fit a component of sufficient size in the available space in a crowded environment (such as the vehicle under-hood) while optimizing the overall performance objectives of the vehicle and improving design efficiency. This work is focused on incorporating component shape design …

Vibration Analysis Of Piezoelectric Microcantilever Sensors, Amin Salehi-Khojin

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The main objective of this dissertation is to comprehensively analyze vibration characteristics of microcantilever-based sensors with application to ultra small mass detection and low dimensional materials characterization. The first part of this work focuses on theoretical developments and experimental verification of piezoelectric microcantilevers, commercially named Active Probes, which are extensively used in most today's advanced Atomic Force Microscopy (AFM) systems. Due to special geometry and configuration of Active Probes, especially multiple jump discontinuities in their cross-section, a general and comprehensive framework is introduced for forced vibration and modal analysis of discontinuous flexible beams. More specifically, a general formulation is obtained …

A Comparative Fault Diagnosis Methodology Based On Time Series Analysis Of System's Signals, Hany Bassily

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The detection of system anomalies represents an important task in safety critical systems. Over the past two decades, advances in data manipulation techniques and sensor technology have contributed to the widespread application of signal processing concepts for fault diagnosis. However, the majority of these signal processing, or data driven, diagnostics do not possess the redundancy level exhibited in conventional model-based methods. Among signal processing methods, time series analysis is advantageous since it offers insight into the underlying dynamics and forecasts system behavior. Furthermore, the data driven method allows the depiction of system dynamics with an increased level of redundancy. This …