Engineering Commons^™

The Characterization And Fatigue Life Impact From Surface Roughness On Structurally Relevant Features Produced Using Additive Manufacturing, Eric-Paul Daniel Tatman

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Additive manufacturing (AM) produces rough surfaces that are detrimental to the mechanical performance of the part. In this work, downward-facing surfaces were fabricated in alloy 718 using laser powder bed fusion and investigated with surface characterization and axial fatigue testing. Coupons with downward-facing surfaces at 45°, 60°, and 75° and flat axial fatigue bars with as-built and machined holes were built. Both specimens were fabricated with three levels of downskin laser power and the coupons with three levels of downskin laser speed. Surface characterization showed roughness increased as the downward-facing angle decreased. Fatigue testing with digital image correlation showed localized …

Structural Transformations In Porous Glasses Under Mechanical Loading. Ii. Compression, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

The role of porous structure and glass density in response to compressive deformation of amorphous materials is investigated via molecular dynamics simulations. The disordered, porous structures were prepared by quenching a high-temperature binary mixture below the glass transition into the phase coexistence region. With decreasing average glass density, the pore morphology in quiescent samples varies from a random distribution of compact voids to a porous network embedded in a continuous glass phase. We find that during compressive loading at constant volume, the porous structure is linearly transformed in the elastic regime and the elastic modulus follows a power-law increase as …

The Critical Pressure For Microfiltration Of Oil-In-Water Emulsions Using Slotted-Pore Membranes, Nikolai V. Priezjev, Tohid Darvishzadeh, Bishal Bhattarai

Mechanical and Materials Engineering Faculty Publications

The influence of geometrical parameters and fluid properties on the critical pressure of permeation of an oil micro-droplet into a slotted pore is studied numerically by solving the Navier-Stokes equations. We consider a long slotted pore, which is partially blocked by the oil droplet but allows a finite permeate flux. An analytical estimate of the critical permeation pressure is obtained from a force balance model that involves the drag force from the flow around the droplet and surface tension forces as well as the pressure variation inside the pore. It was found that numerical results for the critical pressure as …

Slow Relaxation Dynamics In Binary Glasses During Stress-Controlled, Tension-Compression Cyclic Loading, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

The effect of cyclic loading on relaxation dynamics and mechanical properties of metallic glasses is studied using molecular dynamics simulations. We consider the Kob-Andersen three-dimensional binary mixture rapidly cooled across the glass transition and subjected to thousands of tension-compression cycles in the elastic range. It was found that during cyclic loading at constant pressure, the system is relocated to progressively lower levels of the potential energy, thus promoting greater densification and higher strength. Furthermore, with increasing stress amplitude, the average glass density increases and the minimum of the potential energy becomes deeper, while the elastic modulus is reduced. The typical …

Feature-Based Discretization Of A Turbine Disk For Probabilistic Risk Assessment, Michael Thomas, Jace Carter, Lloyd Matson, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

There is an economic need to extend the useful life of jet engine rotors. Retirement-for-Cause (RFC) is a lifing method that allows for the continued operation of components passed traditional life limits. Under RFC, an extension of damage tolerance, components are deemed safe for a further service interval using non-destructive inspections (NDI) for crack like defe cts. As components are kept in-service beyond their designed service life it is essential that the probability of failure (POF), or risk, of continued service is known. Under current FAA rotor design certification practices the component POF is analyzed using a probabilistic framework focused …

Structural Transformations In Porous Glasses Under Mechanical Loading. I. Tension, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

The evolution of porous structure and mechanical properties of binary glasses under tensile loading were examined using molecular dynamics simulations. We consider vitreous systems obtained in the process of phase separation after a rapid isochoric quench of a glass-forming liquid to a temperature below the glass transition. The porous structure in undeformed samples varies from a connected porous network to a random distribution of isolated pores upon increasing average glass density. We find that at small strain, the elastic modulus follows a power-law dependence on the average glass density and the pore size distribution remains nearly the same as in …

The Yielding Transition In Periodically Sheared Binary Glasses At Finite Temperature, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

Non-equilibrium molecular dynamics simulations are performed to investigate the dynamic behavior of three-dimensional binary glasses prepared via an instantaneous quench across the glass transition. We found that with increasing strain amplitude up to a critical value, the potential energy approaches lower minima in steady state, whereas the amplitude of shear stress oscillations becomes larger. Below the yielding transition, the storage modulus dominates the mechanical response, and the gradual decay of the potential energy over consecutive cycles is accompanied by reduction in size of transient clusters of atoms with large nonaffine displacements. In contrast, above the yield strain, the loss modulus …

Aligned Carbon Nanotube Arrays Bonded To Solid Graphite Substrates: Thermal Analysis For Future Device Cooling Applications, Betty T. Quinton, Levi Elston, James D. Scofield, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

Carbon nanotubes (CNTs) are known for high thermal conductivity and have potential use as nano-radiators or heat exchangers. This paper focuses on the thermal performance of carpet-like arrays of vertically aligned CNTs on solid graphite substrates with the idea of investigating their behavior as a function of carpet dimensions and predicting their performance as thermal interface material (TIM) for electronic device cooling. Vertically aligned CNTs were grown on highly oriented pyrolytic graphite (HOPG) substrate, which creates a robust and durable all-carbon hierarchical structure. The multi-layer thermal analysis approach using Netzsch laser flash analysis system was used to evaluate their performance …

In Situ Defect Detection Using Three Color Spectroscopy In Laser Powder Bed Additive Manufacturing, Andrew Drieling

The University Honors Program

Additive Manufacturing (AM) provides a way to create parts that would be extremely difficult or impossible with conventional manufacturing processes. However, AM also introduces defects, which are detrimental to the mechanical performance. These defects are potentially unknown until post-processing inspection and testing, wasting time and resources on an unusable part or initiating unexpected failure. Historically, spectroscopy has successfully been used for in situ monitoring of laser welding, using changing parameters in the generated plume to predict defects. In situ monitoring using a visible spectrometer for fabrication of Alloy 718 on a test bed laser powder bed fusion system is performed. …

Modeling And Visualization Of Uncertainty-Aware Geometries Using Multi-Variate Normal Distributions, Christina Gillman, Thomas Wischgoll, Bernd Hamann, James Ahrens

Computer Science and Engineering Faculty Publications

Many applications are dealing with geometric data that are affected by uncertainty. It is important to analyze, visualize, and understand the properties of uncertain geometry. We present a methodology to model uncertain geometry based on multi-variate normal distributions. In addition, we propose a visualization technique to represent a hull for uncertain geometry capturing a user-defined percentage of the underlying uncertain geometry. To show the effectiveness of our approach, we have modeled and visualized uncertain datasets from different applications.

Failure Analysis Of Philos Plate Construct Used For Pantalar Arthrodesis Paper Ii-Screws And Fem Simulations, Farah Hamandi, Richard T. Laughlin, Tarun Goswami

Biomedical, Industrial & Human Factors Engineering Faculty Publications

A fractured stainless steel 3.5 mm proximal humerus internal locking system (PHILOS) plate and screws were investigated in this paper. This plate was used for ankle arthrodesis of a 68-year-old female with a right ankle deformity. Both the plate and screws were considered in this investigation. Optical and scanning electron microscopes (SEM) were used to document fracture surface characteristics, such as extensive scratching, plastic deformation, rubbed surfaces, discoloration, and pitting, along with cleavage, secondary cracking, deposits of debris, striations, and dimples. Indications of these features show that the plate failed by corrosion fatigue, however, overloading separated the screw(s) in two …

Wright State University's Symposium Of Student Research, Scholarship & Creative Activities From Friday April 13, 2018, Wright State University

Celebration of Undergraduate & Graduate Research, Scholarship, and Creative Activities Materials

The student abstract booklet is a compilation of abstracts from students' oral and poster presentations at Wright State University's Symposium of Student Research, Scholarship & Creative Activities on April 13, 2018.

Usability Assessment For Caregiver Behavior Analysis Using Gaming Technology, Alexandrea C. Oliver, Tanvi Banerjee, Jennifer Hughes, Noah L. Schroeder

Computer Science and Engineering Faculty Publications

The proposed research focuses on developing a mobile application for Android systems that will detect changes in behavior and activity patterns of those who are primary caregivers for dementia patients. This application will be used to detect fluctuation in the behavior and the task performance of the caregivers as a measure of caregiver stress. By detecting these changes in behavior, the goal is to analyze the effects of caregiving to evaluate caregiver burnout. A usability study was conducted for this application to find the optimal design factors and features that benefit the target user: the caregiver.

The purpose of this …

Distributions Of Pore Sizes And Atomic Densities In Binary Glasses Revealed By Molecular Dynamics Simulations, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

We report on the results of a molecular dynamics simulation study of porous glassy media, formed in the process of isochoric rapid quenching from a high-temperature liquid state. The transition to a porous solid occurs due to the concurrent processes of phase separation and material solidification. The study is focused on topographies of the model porous structures and their dependence on temperature and average density. To quantify the pore-size distributions, we put forth a scaling relation that provides a satisfactory data collapse in systems with high porosity. We also find that the local density of the solid domains in the …

Wetting Properties Of Structured Interfaces Composed Of Surface-Attached Spherical Nanoparticles, Nikolai V. Priezjev, Bishal Bhattarai

Mechanical and Materials Engineering Faculty Publications

The influence of the external pressure and surface energy on the wetting transition at nanotextured interfaces is studied using molecular dynamics and continuum simulations. The surface roughness of the composite interface is introduced via an array of spherical nanoparticles with controlled wettability. We find that in the absence of an external pressure, the liquid interface is flat and its location relative to the solid substrate is determined by the particle size and the local contact angle. With increasing pressure on the liquid film, the interface becomes more curved and the three-phase contact line is displaced along the spherical surface but …

An Uncertainty-Aware Workflow For Keyhole Surgery Planning Using Hierarchical Image Semantics, Christina Gillmann, Robin G.C. Maack, Tobias Post, Thomas Wischgoll, Hans Hagen

Computer Science and Engineering Faculty Publications

Keyhole surgeries become increasingly important in clinical daily routine as they help minimizing the damage of a patient's healthy tissue. The planning of keyhole surgeries is based on medical imaging and an important factor that influences the surgeries' success. Due to the image reconstruction process, medical image data contains uncertainty that exacerbates the planning of a keyhole surgery. In this paper we present a visual workfiow that helps clinicians to examine and compare different surgery paths as well as visualizing the patients' affected tissue. The analysis is based on the concept of hierarchical image semantics, that segment the underlying image …

Trust In Visualization (And What It Has To Do With Theory), Thomas Wischgoll

Computer Science and Engineering Faculty Publications

There are different issues with trust involved when working with domain experts to visualize their data. There may be limitations with the data that require special precautions, such as sensitivity or security limitations. It may have taken a lot of effort to collect or create the data so that a certain level of trust is required for the domain expert to share the data. At the same time, the domain expert needs to be able to trust in the final visualization results. This presentation discusses these issues with trust and what requirements for a theoretical foundation this results in. Furthermore, …

Developing A High-Dimensional Dataset Of The Changes In Ion Channels Expression Level At The Cholinergic Boutons In Amyotrophic Lateral Sclerosis, Joshua Harris

The University Honors Program

ALS, or Amyotrophic Lateral Sclerosis, is a neurodegenerative disease that causes motor neuron degeneration. Affecting nerve cells in the brain and spinal cord, this disease eventually leads to respiratory muscle failure and death. Although ALS is fairly uncommon, our lack of information on how ALS develops drives the need for further study. In the Neuro Engineering, Rehabilitation, and Degeneration laboratory at Wright State University, immunohistochemical data has been collected on a mouse model (SOD1-G93A) throughout their lifespan to better examine the neurological effects of ALS. To better organize and interpret the data, a high-dimensional dataset was created in this project …

Comparing And Enhancing The Analytical Model For Exposure Of A Retail Facility Layout With Human Performance, Bradley R. Guthrie, Pratik Parikh, Tyler Whitlock, Madison Glines, Thomas Wischgoll, John Flach, Scott Watamaniuk

Computer Science and Engineering Faculty Publications

Recent research in retail facility layout has focused on developing analytical models to estimate visibility measures of novel rack layouts based on assumptions about a shopper’s field of view. However, because of the human element involved in the shopping experience, it is vital to compare these models relative to actual human performance. In this study, we evaluate the predictions of our previously developed analytical model (that estimates exposure of every location on a given rack layout assuming expected head movement) in a 3D Virtual Environment (VE). We conducted trials with 18 participants who were asked to find targets strategically placed …

Implementation Of Unmanned Aerial Vehicles Reporting Plume Cloud Concentration Values In A 3d Simulation Environment, Emily Catherine Novak

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Unmanned aerial vehicles, or UAVs, have the potential to vastly improve plume cloud tracking at low cost. Plume clouds can be produced from blast mining, chemical warfare, unintended man-made disasters, and natural causes. This thesis provides implementation of the capability to simulate a 3D environment in which UAVs are individually controlled and each report a plume's concentration value at a specific location. It leverages existing industry standard technologies, including the PX4 autopilot system, the Gazebo simulation environment, the Robot Operating System (ROS), and QGroundControl. The provided system integrates the existing tools with a plume model plug-in that provides simulated plume …

Design Of A Novel Tissue Culture System To Subject Aortic Tissue To Multidirectional Bicuspid Aortic Valve Wall Shear Stress, Janet Liu

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Blood vessels experience complex hemodynamics marked by three-dimensionality and pulsatility. Arterial endothelial cells interact with the characteristics of the fluid wall shear stress (WSS) to maintain homeostasis or promote disease states. In particular, the bicuspid aortic valve (BAV), a congenital heart valve anatomy consisting of two leaflets instead of three, is associated with aortic complications presumably promoted by hemodynamic abnormalities. While devices have been used to test this hypothesis, their capabilities are limited to the generation of time-varying WSS magnitude in one direction. However, the increased flow helicity generated by BAVs in the aorta is expected to result in increased …

Simulation Of A Mos Or Mis Structured Spatial Light Modulator For Terahertz (Thz) Imaging, Md Shahanur Alam

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A large area, square-gate Metal-Oxide/Insulator-Semiconductor (MOS or MIS) structured `Spatial Light Modulator' has been proposed for the Terahertz (THz) imaging at room temperature. This theoretical study has been done entirely by using the MATLAB platform. The 1D Poisson's equation has been solved iteratively by Euler's method with the exact Fermi-Dirac integral for n-doped Si-MOS and GaAs- MIS capacitors in deep accumulation mode. Free carrier density and the potential profile have been found for the degenerate case. The results have been compared with the analytical method, which is approximated by Boltzmann statistics, and clearly, show the difference between the degenerate case …

Threats And Mitigation Of Ddos Cyberattacks Against The U.S. Power Grid Via Ev Charging, Glenn Sean Morrison

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Cars are an ever changing and integral part of modern society. Two of the biggest changes in vehicles today are their heavy integration with wireless communication and the push toward battery powered Electric Vehicles (EV). EV and EV charging stations have become a part of the Internet of Things (IoT). While this connectedness increases the convenience and functionality of the vehicles and charging stations, it also opens them up to a wide range of cyber threats. This thesis examines the potential threats against the EV charging ecosystem through a historical analysis of past cyberattacks and identified vulnerabilities. As EV charging …

Evaluation Of Consumer Drone Control Interface, Thomas William Merrell

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The development and use of consumer grade drones is becoming a larger part of our society for many different applications. There has been a great amount of discussion and constant review of proper operation of consumer drones including proper methods of control. In turn, regulation of such devices has been inconsistent. This study aims to better understand the effects of the three primary control interface methods (line of sight, video aided, and first-person view) on flight performance, situational awareness, and perceived mental workload of the operator. Secondarily, this study aims to provide design recommendations for future interfaces. This study shows …

Malware Analysis Skills Taught In University Courses, Swetha Gorugantu

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Career opportunities for malware analysts are growing at a fast pace due to the evolving nature of cyber threats as well as the necessity to counter them. However, employers are often unable to hire analysts fast though due to a lack of the required skillset. Hence, the primary purpose of the thesis is to conduct a gap analysis between the binary analysis skills taught in universities with those that the recruiters are looking for. Malware can be analyzed using three main types of tools and techniques: high-level profiling, static analysis, and dynamic analysis. These methods provide detailed information about the …

Hardware Security And Vlsi Design Optimization, Hao Xue

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Microelectronic circuit is ubiquitous component of modern electrical devices. The increasing complexity and professionality of phases in microelectronic supply chain bring more global cooperation to integrated circuit (IC) production. Therefore, providing a secure environment for microelectronic circuit design does not ensure the integrity of the hardware since any participator of IC fabrication has the opportunity to implant a malicious alteration in original IC design. Especially overseas chip-fabrication is a vital potential threat for national defense products. In theory, anyone who has access to fabrication process can tamper with the original design, with the potential to change function, modify parametric properties …

Multi-Scale And Multi-Modal Streaming Data Aggregation And Processing For Decision Support During Natural Disasters, Shruti Kar

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With the surge in digital information systems, there is a data deluge from various sources that can be analyzed and integrated to produce relevant, reliable and actionable information, for better decision making. We employ multi-modal data (i.e., unstructured text, gazetteers, and imagery) for an aggregate level analysis and location-centric demand/request matching in the context of disaster relief. After classifying the Need expressed in a tweet (the WHAT), we leverage OpenStreetMap to geolocate that Need on a computationally accessible map of the local terrain (the WHERE) populated with location features such as hospitals and housing. Further, our novel use of flood …

Real-Time Path Planning And Obstacle Avoidance For Mobile Robots With Actuator Faults, Ravindra Vibha Bellur

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In this research, a fault-tolerant path planning and obstacle avoidance algorithm is implemented for mobile ground robots. The fault-tolerant system architecture consists of the following three components: (1) an online fault diagnosis module for detecting and estimating actuator faults in the mobile robot; (2) a localization and mapping module for dynamic terrain mapping and obstacle detection; (3) a path planning and obstacle avoidance module for generating way points from a given point to the desired destination, avoiding the detected obstacles and moving along these way points. The online fault diagnostic information is used to compensate for the effect of faults, …

Development Of An Ios App For Learning Intonation Of Wind Instruments, Swathi Pamidi

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Learning music instrument is a challenging task for a beginner without constant guidance from an instructor. The primary objective of this thesis research is to design and develop an iOS mobile / iPad learning app that helps users to learn and practice intonation for a suite of wind instruments by themselves with comfort and ease through app-provided tuning and charting guidance and app-assisted self-assessment. Particularly, our successfully-implemented app provides the following features to enhance the user's learning experience: 1 ) Provides learners easy-to-access information for the fingering and tuning techniques of wind instruments by converting Dr. Shelley Jagow's book - …

Visual Analytics Of Cascaded Bottlenecksin Planar Flow Networks, Tobias Post, Thomas Wischgoll, Bernd Hamann, Hans Hagen

Computer Science and Engineering Faculty Publications

Finding bottlenecks and eliminating them to in-crease the overall flow of a network often appears in real world applications, such as production planning, factory layout, flowrelated physical approaches, and even cyber security. In many cases, several edges can form a bottleneck (cascaded bottlenecks). This work presents a visual analytics methodology to analyze these cascaded bottlenecks. The methodology consists of multiple steps: identification of bottlenecks, identification of potential improvements, communication of bottlenecks, interactive adaption of bottlenecks, and a feedback loop that allows users to adapt flow networks and their resulting bottlenecks until they are satisfied with the flow network configuration. To …