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Characterizing Anisotropy In Fibrous Soft Materials By Mr Elastography Of Slow And Fast Shear Waves, John Larson Schmidt

McKelvey School of Engineering Theses & Dissertations

The general objective of this work was to develop experimental methods based on magnetic resonance elastography (MRE) to characterize fibrous soft materials. Mathematical models of tissue biomechanics capable of predicting injury, such as traumatic brain injury (TBI), are of great interest and potential. However, the accuracy of predictions from such models depends on accuracy of the underlying material parameters. This dissertation describes work toward three aims. First, experimental methods were designed to characterize fibrous materials based on a transversely isotropic material model. Second, these methods are applied to characterize the anisotropic properties of white matter brain tissue ex vivo. Third, …

Investigation Of Ductile Crack Growth And Normalization Method For Se(T) Specimen Using Finite Element Analyses, Cheng Qian

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve (e.g. J-R curve) is widely used in integrity assessment and strain-based design of oil and gas pipelines with respect to planar defects (i.e. cracks). This thesis includes two-dimensional (2D) and three-dimensional (3D) finite element analyses (FEA) of ductile crack growth of X80-grade pipeline steel based on the Gurson-Tvergaard-Needleman (GTN) constitutive model, and investigation of the normalization (NM) method to generate the J-R curve for the single-edge tension (SE(T)) specimen.

First, the GTN model implemented in the computational cell is adopted in the commercial software ABAQUS to calibrate the micromechanical parameters for the pipeline steel. Subsequently, …

Testing The Arousal Hypothesis: The Effect Of Music On Arousal As Measured By Electrodermal Activity During Verbal Processing, Meghan E. Feeman

Masters Theses

The purpose of this thesis project is to assess the arousal hypothesis by implementing an auditory stimulus (music) at various times during a task (Verbal Processing section of the GRE) to analyze changes in arousal, as measured by electrodermal activity (EDA). Testing is administered for one hour with music implemented before testing and twice during testing. EDA levels are used to measure physiological response and are collected over the one hour testing period. For analysis, testing material is broken into different time blocks to assess arousal levels through mean slope, mean skin conductance level (SCL), mean skin conductance response (xSCR), …

Computational Prediction Of Conductivities Of Disk-Shaped Particulate Composites, Jian Qiu

Electronic Theses and Dissertations

The effective conductivities are determined for randomly oriented disk-shaped particles using an efficient computational algorithm based on the finite element method. The pairwise intersection criteria of disks are developed using a set of vector operations. An element partition scheme has been implemented to connect the elements on different disks across the lines of intersection. The computed conductivity is expressed as a function of the density and the size of the circular disks or elliptical plates. It is further expressed in a power-law form with the key parameters determined from curve fittings. The particle number and the trial number of simulations …

Study On Agricultural Tractor Operator Safety In Rollover Accidents, Farzaneh Khorsandi Kouhanestani

Doctoral Dissertations

Agriculture is one of the most dangerous industries in the US. Tractor accidents are the major cause of death in agriculture, producing about one half of the fatal accidents. Tractor overturn is the most common cause of death in tractor accidents. Three projects related to tractor operator safety in rollover accident were defined.

The aim of first project is to develop a Finite Element (FE) model to predict the Roll-Over Protective Structure (ROPS) performance under the standard SAE J2194 (SAE, 2009) static test. The developed model was validated by comparing the model results with experimental test results. The developed model …

Water-Tree Modelling And Detection For Underground Cables, Qi Chen

All Dissertations

In recent years, aging infrastructure has become a major concern for the power industry. Since its inception in early 20th century, the electrical system has been the cornerstone of an industrial society. Stable and uninterrupted delivery of electrical power is now a base necessity for the modern world. As the times march-on, however, the electrical infrastructure ages and there is the inevitable need to renew and replace the existing system. Unfortunately, due to time and financial constraints, many electrical systems today are forced to operate beyond their original design and power utilities must find ways to prolong the lifespan of …

Large Payload Hiad Systems: Development Of Computationally Efficient Modeling Strategies And Structural Investigations, Andrew C. Young

Electronic Theses and Dissertations

The hypersonic inflatable aerodynamic decelerator (HIAD) system under development by the National Aeronautics and Space Administration (NASA) has the potential to deliver the size of payloads to the Martian surface that will be necessary for future human-scale missions. An important step in realizing the promise of the HIAD system is to understand the structural behavior of this inflatable, textile, relatively compliant system. This is accomplished through structural testing and the development of structural modeling and analysis methodologies and tools. The structural modeling tools that have been developed to date utilize a continuum, shell-based finite element (FE) analysis approach. This methodology …

Localized Therapeutic Hypothermia To Preserve Residual Hearing Against Cochlear Implantation: Analytical And Experimental Studies, Ilmar Tamames

Open Access Dissertations

Objective: Cochlear implants are the most successful neuroprostheses. Unfortunately, the trauma caused during cochlear implant insertion can lead to a loss of residual hair cells in the cochlea. Localized therapeutic hypothermia has the potential to be the standard of clinical care for neuroprotective intervention. This study demonstrates the design, operation and protocols, in an animal and a cadaver temporal bone model, for efficacious delivery of mild therapeutic hypothermia to the cochlea that can be translated to clinical practice in patients undergoing surgical cochlear implantation to preserve residual hearing. Main Results: The study found that localized hypothermia protects cochlear hair cells …

Design And Behavior Of Steel Delta Girders, Omar El Masri

Dissertations - ALL

In steel structures, I-sections are commonly used for beams and columns. These cross-sections usually lack lateral rigidity and torsional stiffness. An effective method to improve their lateral rigidity and overall flexural resistance is to weld two inclined rectangular plates to the compression flange and the compression portion of the web of hot-rolled or welded I-section to form what is known as a Delta girder. This mixed cross-section, i.e., cross-section composed of an open profile attached to a closed profile, can provide enhanced torsional stiffness and hence noticeably higher lateral-torsional buckling (LTB) capacity for the beam. While Delta girders can be …

Computational Modeling Of Percolation Conduction And Diffusion Of Heterogeneous Materials, Jian Qiu

Electronic Theses and Dissertations

Heterogeneous materials provide a unique combination of desirable mechanical, thermal or electrical properties. This dissertation presents several micro-structure modeling approaches to predict the effective properties of heterogeneous materials and demonstrates its certain application toward two highly heterogeneous, unconventional structural composite materials (carbon fiber reinforced composite materials and graphene nanoplatelets composite). By using the efficient computational algorithm based on the FEA, a randomly oriented disk-shaped particles system are generated. A new element partition scheme based on the vector operations and geometry of inclusion has been implemented to mesh the intersected disks. The computed equivalent conductivity is expressed as a power-law function …

The Effect Of Separations On The Assessment Of Charpy Impact Tests, Bradley Jacob Davis

University of Wollongong Thesis Collection 2017+

In the pipeline industry, the Charpy impact test is the most common method for determining the fracture arrestability (or toughness) of a line pipe steel. Since the 1960s, line pipe steel has increased in both its stress capacity and toughness through advanced steel making and rolling processes. However, due to the lower finishing temperature, pronounced levels of microstructural anisotropy is generated. One consequence of anisotropy is the formation of weakly bonded planes along the rolling plane of the material. This can result in a phenomenon known as separations. Separations are fissures that form along the rolling plane of the material …

Design Of Experiment Analysis Of An Electronics Package Lid Using Finite Element Analysis, Nupur Bajad

Graduate Dissertations and Theses

A design of experiment analysis is reported on data from warpage simulations using finite element analysis of a lidded electronics package. Warpage in a lid of an optical electronics package can detrimentally affect the reliability of the package as well as its optical performance. The present study focuses on the variety of materials and designs of lids relevant to recent technologies in electronics packaging. The finite element analysis (FEA) formulation in this study accurately predicts deformation and warpage in the elastic region with optimal computational time achieved through a choice of boundary conditions and mesh sensitivity studies.

The results from …