Mechanical Engineering Commons^™

Sae Baja Drivetrain Capstone 2024-2025, Leslie Alvarez Cisneros

University Honors Theses

This thesis reviews the 2024-2025 Baja SAE Drivetrain capstone project. The Baja SAE competition mimics real world engineering problems where teams of students design and build off-road vehicles that can handle tough, rough terrain. The objective of this capstone was to design a functional and reliable drivetrain system for the vehicle, within the constraints of a limited budget and the SAE competition guidelines. As part of a 12-member capstone team divided into three subgroups: frame, suspension, and drivetrain. As part of a four person drivetrain team, we picked up where the 2023-2024 team left off by relying on their past …

Predicting Strut Geometry Of Pcl And Dmso2 Biocomposites From Nozzle To Deposition In Bio-Scaffold 3d Printing, Jae-Won Jang, Kyung-Eun Min, Jun-Hee Park, Cheolhee Kim, Sung Yi

Mechanical and Materials Engineering Faculty Publications and Presentations

The field of tissue engineering increasingly demands accurate predictive models to optimize the 3D printing process of bio-scaffolds. This study presents a unified numerical model that predicts extrusion velocity and strut diameter based on printing conditions and the material properties of polycaprolactone (PCL) and dimethyl sulfone (DMSO2) composites. The extrusion velocity was simulated using Navier–Stokes equations, while the strut diameter was calculated via a surface energy model. For PCL, the extrusion velocity showed a temperature coefficient of 23.3%/°C and a pressure coefficient of 19.1% per 100 kPa; the strut diameter exhibited a temperature coefficient of 21.6%/°C and a pressure coefficient …

Effects Of Wetting Events On Mass Timber Surface Microbial Communities And Voc Emissions: Implications For Building Operation And Occupant Well-Being, Gwynne Á. Mhuireach, Susan Collins, Leslie Dietz, Patrick Finn Horve, Aurélie Laguerre, Dale Northcutt, Jason Stenson, Kevin Van Den Wymelenberg, Elliott Gall, Mark Fretz

Mechanical and Materials Engineering Faculty Publications and Presentations

IntroductionHumans have used wood as a construction material throughout history. Currently, mass timber products, such as cross-laminated timber (CLT), are becoming more popular as a structural material, since they are renewable and have a lower carbon footprint than concrete or steel. Nonetheless, some building types, such as healthcare, veterinary, and food manufacturing, avoid using structural mass timber due to concerns about microbial growth in the event of wetting. One solution is to use protective coatings on mass timber products to increase moisture resistance, although the coatings themselves may generate concerns about volatile organic compound (VOC) emissions. Natural uncoated wood also …

Accelerating High-Throughput Phonon Calculations Via Machine Learning Universal Potentials, Huiju Lee, Vinay I. Hegde, Chris Wolverton, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

Phonons play a critical role in determining various material properties, but conventional methods for phonon calculations are computationally intensive, limiting their broad applicability. In this study, we present an approach to accelerate high-throughput harmonic phonon calculations using machine learning universal potentials (MLIPs) combined with an efficient training dataset generation strategy. Instead of computing phonon properties from a large number of supercells with small atomic displacements of a single atom, our approach uses a smaller subset of supercell structures where all atoms are randomly displaced by 0.01 to 0.05 UŮ, significantly reducing computational costs. We train a state-of-the-art MLIP based on …

Realizing Intrinsically Ultralow And Glass-Like Thermal Transport Via Chemical Bonding Engineering, Zhonghao Xia, Xingchen Shen, Jun Zhou, Yuling Huang, Yali Yang, Jiangang He, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

Crystals exhibiting glass-like and low lattice thermal conductivity ( ) are not only scientifically intriguing but also practically valuable in various applications, including thermal barrier coatings, thermoelectric energy conversion, and thermal management. However, such unusual are typically observed only in compounds containing heavy elements, with large unit cells, or at high temperatures. In this study, chemical bonding principles are utilized to weaken the Ag–Ag bonds and enhance lattice anharmonicity. The incorporation of a chalcogen anion as a bridge ligand is proposed to facilitate phonon rattling in Ag6-octahedron-based compounds. Guided by this design strategy, five Ag6 octahedron-based compounds, AAg3X2 (A = …

Advances In Theory And Computational Methods For Next-Generation Thermoelectric Materials, Junsoo Park, Alex M. Ganose, Yi Xia

Mechanical and Materials Engineering Faculty Publications and Presentations

This is a review of theoretical and methodological development over the past decade pertaining to computational characterization of thermoelectric materials from first principles. Primary focus is on electronic and thermal transport in solids. Particular attention is given to the relationships between the various methods in terms of the theoretical hierarchy as well as the tradeoff of physical accuracy and computational efficiency of each. Further covered are up-and-coming methods for modeling defect formation and dopability, keys to realizing a material's thermoelectric potential. We present and discuss all these methods in close connection with parallel developments in high-throughput infrastructure and code implementation …

Impact Of Roughness Spanwise Wavelength On Secondary Flow Rearrangement, Jianzhi Yang, Xiang I. A. Yang, Luoqin Liu, Jian Zhu, Xiaowei Zhu

Mechanical and Materials Engineering Faculty Publications and Presentations

Spanwise heterogeneity in surface roughness generates secondary mean flows in a rough-wall turbulent boundary layer. This study investigates the influence of roughness spanwise wavelength on the arrangement of these secondary flows using direct numerical simulation (DNS). We systematically vary the spanwise wavelength, δS/δ⁠, from ππ/16 to π2π⁠, while maintaining constant roughness height and surface coverage density. Here, S represents the roughness spanwise wavelength, and δδ denotes the outer length scale, which in this case is the half-channel height. Secondary flows are observed in all DNS cases, but their configurations depend on the spanwise wavelength. Specifically, small wavelengths result in low-momentum …

Introduction To The Special Issue On Verification And Validation Of Source And Propagation Models For Underwater Sounda), Kathleen J. Vigness-Raposa, Klaus Lucke, Michael A. Ainslie, Michele B. Halvorsen, Christ A. F. De Jong, Stanley J. Labak, Martin Siderius

Electrical and Computer Engineering Faculty Publications and Presentations

This joint Special Issue of JASA and JASA Express Letters focuses on underwater sound source and propagation modelling, both of ambient sound as well as sources of relevance to possible effects of sound on aquatic life, and corresponding acoustical metrics. Combining information on the sound field with information on a dose-effect relationship enables estimation of the potential effects. The Special Issue presents a collection of eighteen articles on the following topics: (1) verification of source and propagation models, (2) validation of source and propagation models, and (3) bioacoustical metrics for assessment of the risk of environmental effects. This special issue …

Direct Graphene Growth On Low-Alloy And Mild Steel Surfaces Controlled By Carbon Solubility And Surface Microstructural Transformations During Chemical Vapor Deposition, Kaleb Hood, Nam Nguyen, Sebastian Lara, Adan Velasquez, Samuel Olson, Yi Xia, Jun Jiao

Mechanical and Materials Engineering Faculty Publications and Presentations

This study demonstrates for the first time, graphene grown directly on the iron-rich surfaces of bulk 8620 low-alloy and 1018 mild steel by chemical vapor deposition, a key step toward developing thin graphene coatings with strong graphene-steel bonding. Low growth temperatures of 660 °C–680 °C, were used to manipulate the steel's carbon solubility, confining carbon diffusion and microstructural transformations to the surface regions, with the bulk relatively unchanged. For 1018, a growth temperature of 680 °C resulted in a multilayer graphene coating with 80 % coverage. The alloying elements in 8620 improved graphene formation by influencing the surface microstructure transformations …

Identifying The Effect Of Architecture Morphology On Wind Fields And Pm2.5 Dispersion At The Urban Block Scale Via A Combined Scheme, Bin Guo, Lu Li, Xiaowei Zhu, Zheng Wang, Miaoyi Chen, Lin Pei, Tengyue Guo

Mechanical and Materials Engineering Faculty Publications and Presentations

This study explores the potential of architecture morphology to mitigate PM2.5 pollution through enhanced urban ventilation. Despite the recognized influence of building designs on wind and air pollution distribution at the urban block scale, specific mechanisms remain poorly understood. To address this gap, we have developed an integrative approach combining in-situ observations, Geographic Information System (GIS), Remote Sensing (RS), Computational Fluid Dynamics (CFD), and statistical modeling. Here, CFD simulates the flow field and PM2.5 dispersion, using in-situ observations for turbulence model selection. GIS quantify architecture morphology parameters to establish accurate CFD boundary conditions, ensuring simulations reflect real-world conditions and precise …

Effects Of The Upwind Spanwise Heterogeneous Terrain On The Wind Resource Distribution, Haosen H.A. Xu, Tianxiang Yu, Raúl Bayoán Cal, Xiaowei Zhu

Mechanical and Materials Engineering Faculty Publications and Presentations

Wind energy has become increasingly crucial among renewable energy resources, and as the prerequisite for effective wind energy utilization, accurate wind resource assessments are hence prominent. Topography significantly affects near-surface wind fields and is thus an essential factor to be considered for wind resource assessment. However, few studies have addressed the wind resource distribution downwind of spanwise-heterogeneous terrains, which are frequently encountered in both natural and urban environments. To fill this gap, large eddy simulations were performed to investigate wind distributions over a uniform terrain downwind of terrains featuring spanwise-alternating strips of low and high surface roughness, and the high …

Momentum Transport In Heterogeneous Forest Canopies, Hawwa Kadum, Ryan Scott, Sarah E. Smith, Marc Calaf, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

This study investigates the impact of spatial heterogeneity on momentum transport within forest canopies through wind tunnel experiments using 1:200 scale forest models. The models, crafted from 10 Pores Per Inch reticulated foam, emulate a leaf area index of 5.3 and include alternating patches and gaps of various sizes. Statistical results of the mean velocity profiles and velocity standard deviations show that the canopies develop a mixing layer. By employing lacunarity analysis to quantify spatial heterogeneity, we establish that the heterogeneity scale effectively represents variations in canopy height. The success of the lacunarity analysis as a metric is particularly noteworthy, …

Review: Dielectric Barrier Discharge Plasma Actuators For In-Flight Applications, Sabeel Saleem Mohammed

Anthós

Dielectric barrier discharge (DBD) is a phenomenon observed when high voltage is passed through a dielectric barrier at high frequencies. Current DBD plasma actuators (PAs) excel at laminar fluid boundary layer control but suffer from limited momentum flux and fluid mechanic inefficiencies. In this article, Mohammed analyzes previous discourse on DBD PAs and offers directions for future research and potential DBD PA applications. Previous work on DBD PAs documented thrust generation at high voltages and frequencies, thrust in varying fluid compositions, and vortex generation. However, certain arrangements hinder flow magnitudes, limiting the use of multiple DBD PAs in close proximity. …

Collaborative Robotics: Application Of Delphi Method, Jean-Marc Salotti, Ephraim Suhir

Mechanical and Materials Engineering Faculty Publications and Presentations

In the domain of collaborative robotics, it is often needed to make complex multiparametric choices or assessments that combine heterogeneous criteria, such as task performance, reliability, safety, and ergonomics. The Delphi method, a process of arriving at group consensus by providing experts with rounds of questionnaires, as well as the group response before each subsequent round, can be applied to solve this type of problems. The following Delphi method efforts are addressed in our analysis with application to finding appropriate criteria and their relative weights for the evaluation of the teleoperation task of a robotic platform: (1) Contribution of experts; …

Evaluating The Multi-Valued Bartlett Processor, Daniel Robert Frister

Dissertations and Theses

A variety of approaches exist to track targets in the ocean using acoustic sensors, and the complex mix of source characteristics, environmental effects, and sensor array limitations can make the selection of an appropriate algorithm challenging. This thesis models in simulation a recently proposed signal processing method that is intended for use with a large rectangular sensor array to track the bearings of multiple sources. The method, referred to as the Multi-Valued Bartlett (MVB) processor, is an eigenvector beamformer that leverages the capabilities of large arrays to locate in bearing multiple sources simultaneously. The analysis of this thesis details the …

Evaluating Diy Air Cleaner Variability And Potential For Post-Construction Emission Of Aromatic Vocs During Wildfire Events, Brett W. Stinson, Amity L. Deters, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

While do-it-yourself (DIY) air cleaners such as the Corsi-Rosenthal Box (CR Box) are an increasingly popular choice for low-cost, accessible air cleaning during a wildfire event, construction and performance variability remains a concern. Using the same set of instructions, materials, and location of assembly, seven CR Boxes are constructed by individuals with no prior DIY air cleaner experience and clean air delivery rates (CADRs) are experimentally determined for each of the devices. Against a challenge aerosol consisting of fresh smoke generated via pine needle combustion, average number-based, PM2.5 CR Box CADRs range from 313–396 m3/h (relative standard deviation = 7.6 …

Active Grid Turbulence Anomalies Through The Lens Of Physics Informed Neural Networks, Sofía Angriman, Sarah E. Smith, Patricio Clark Di Leoni, Pablo J. Cobelli, Pablo D. Mininni, Martín Obligado

Mechanical and Materials Engineering Faculty Publications and Presentations

Active grids operated with random protocols are a standard way to generate large Reynolds number turbulence in wind and water tunnels. But anomalies in the decay and third-order scaling of active-grid turbulence have been reported. We combine Laser Doppler Velocimetry and hot-wire anemometry measurements in a wind tunnel, with machine learning techniques and numerical simulations, to gain further understanding on the reasons behind these anomalies. Numerical simulations that incorporate the statistical anomalies observed in the experimental velocity field near the active grid can reproduce the experimental anomalies observed later in the decay. The results indicate that anomalies in experiments near …

Bipolar Ionization Did Not Reduce Airborne Bacteria In A Lecture Hall, David A. Kormos, Nishit J. Shetty, Elliott T. Gall, Aaron J. Prussin, Amy Pruden, Linsey C. Marr

Mechanical and Materials Engineering Faculty Publications and Presentations

Ionization treatment of indoor air has attracted attention for its potential to inactivate airborne pathogens and reduce disease transmission, yet its real-world effectiveness remains unverified. We evaluated the impact of an in-duct, bipolar ionization system on airborne particles, including culturable bacteria, in a lecture hall. The ionizer was off with variable fan speed for 1 week, on with variable fan speed for a second week, and on with high and constant fan speed for a third week. We measured ion concentrations and aerosol particle concentrations, and we collected bioaerosol samples for analysis of 16S rRNA gene copies representing total bacteria …

The Hydraulically Smooth Limit Of Flow Over Surfaces With Spanwise Heterogeneity, Haosen Xu, George Ilhwan Park, Xiang Yang, Xiaowei Zhu

Mechanical and Materials Engineering Faculty Publications and Presentations

Wall slip is conventionally obtained through riblets or grooves. As riblets are macroscopic objects, it is usually not practical to discuss slip patterns at the hydraulically smooth limit. Per Nikuradse, the smooth limit is when the characteristic length of the surface pattern is comparable to the viscous length scale. Recent studies show the possibility of slip at the microscopic scale, making slip patterns at the hydraulically smooth limit relevant. In this study, we leverage a high-fidelity pseudo-spectral code and study flow over surfaces featuring alternating strips of slip and no-slip wall conditions. The wavelength of the surface pattern, denoted as …

Improved Parameters Of Anand Model And Advanced Fea Technique For Low-Cycle Fatigue Life: Finite Element Analysis Models For Pb-Free Solder And Pb Solder In Real Life Ball Gird Ally Package, Hamidreza Nahavandi

Dissertations and Theses

The present study uses the finite element method to evaluate the fatigue life of solder joints of plastic ball grid array packages (PBGA) under thermal-cycling conditions. A Series of precise 3D FE models for solder joints of plastic ball grid array packages is created to improve reliability prediction accuracy. Damage parameters are obtained from the FEA results and used to estimate solder balls’ thermal fatigue life. The Coffin-Manson equation is employed. The predicted thermal fatigue lives are discussed in detail.

Due to marketing and legislative pressures, Pb-free solder is fast becoming a reality in electronic manufacturing. The industry has concluded …

Machine Learning Framework For Predicting Reliability Of Solder Joints, Robert Lee Jones

Dissertations and Theses

This paper presents the techniques and framework to produce an explainable machine learning model for predicting the reliability of solder joints exposed to thermal cycle testing. While machine learning techniques have become prevalent for many engineering and data analysis tasks, the complexity of the model occludes valuable information which can be used to refine the data, tune model parameters, and aid in scientific discovery. By exposing the relationships within the model, users can have greater confidence in the use and employment of it. The purpose of this study is to show how useful relationships can be obtained from a traditional …

Layered Naba2m3q3(Q2) (M = Cu Or Ag; Q = S Or Se) Chalcogenides And Local Ordering In Their Mixed-Anion Compositions, Ayat Tassanov, Huiju Lee, Yi Xia, James M. Hodges

Mechanical and Materials Engineering Faculty Publications and Presentations

Three new NaBa2M3Q3(Q2) (M = Ag or Cu; Q = S or Se) chalcogenides were prepared by using solid-state methods and structurally characterized by using single-crystal X-ray diffraction. NaBa2Ag3Se3(Se2) and NaBa2Cu3Se3(Se2) crystallize in monoclinic space group C2/m and have a two-dimensional structure composed of edge-sharing MSe4/4 tetrahedra separated by Na+ and Ba2+ cations, along with (Se2)2– dimers at the center of the spacings between [M3Se3]3– slabs. NaBa2Ag3S3(S2) adopts a related structure with space group C2/m but has additional, crystallographically distinct Ag atoms in the [Ag3S3]3– layer that are linearly coordinated. NaBa2Ag3Se3(Se2) and NaBa2Ag3S3(S2) have indirect band gaps measured to be …

Hierarchy Of Exchange-Correlation Functionals In Computing Lattice Thermal Conductivities Of Rocksalt And Zinc-Blende Semiconductors, Jiacheng Wei, Zhonghao Xia, Yi Xia, Jiangang He

Mechanical and Materials Engineering Faculty Publications and Presentations

Lattice thermal conductivity (𝜅L) is a crucial characteristic of crystalline solids with significant implications for thermal management, energy conversion, and thermal barrier coating. The advancement of computational tools based on density functional theory (DFT) has enabled the effective utilization of phonon quasiparticle-based approaches to unravel the underlying physics of various crystalline systems. While the higher order of anharmonicity is commonly used for explaining extraordinary heat transfer behaviors in crystals, the impact of exchange-correlation (XC) functionals in DFT on describing anharmonicity has been largely overlooked. The XC functional is essential for determining the accuracy of DFT in describing interactions among electrons/ions …

Improving Biomimetic Passive Dynamics Of A Quadruped Robot Hind Leg Hip Joint With A 3d Printed Torsion Spring, Haonan Zheng

Dissertations and Theses

The Agile and Adaptive Robotics Lab is interested in researching the neuromuscular control network of legged animal locomotion. To validate the lab's understanding of biological neural control, synthetic neural networks are developed and applied to biologically inspired legged robots. For a synthetic neural network to operate in the same manner as a biological neural network and produce the same locomotor behavior, the robot that the synthetic neural network is controlling must also mimic its biological counterpart. Previous research produced a quadruped robot hind leg designed with biomimetic passive dynamics by installing spring and damper pairs at each joint, however, an …

Enhancement Of Mechanical Properties Of Pcl/Pla/Dmso2 Composites For Bone Tissue Engineering, Kyung-Eun Min, Jae-Won Jang, Cheolhee Kim, Sung Yi

Mechanical and Materials Engineering Faculty Publications and Presentations

Bone tissue engineering shows potential for regenerating or replacing damaged bone tissues by utilizing biomaterials renowned for their biocompatibility and structural support capabilities. Among these biomaterials, polycaprolactone (PCL) and polylactic acid (PLA) have gained attention due to their biodegradability and versatile applications. However, challenges such as low degradation rates and poor mechanical properties limit their effectiveness. Dimethyl sulfone (DMSO₂) has emerged as a potential additive to address these limitations, offering benefits such as reduced viscosity, increased degradation time, and enhanced surface tension. In this study, we investigate tailored composites comprising PLA, PCL, and DMSO₂ to enhance mechanical …

Developing And Testing Low-Cost Air Cleaners For Safer Spaces During Wildfires, Brett W. Stinson, Elliott T. Gall

Mechanical and Materials Engineering Faculty Publications and Presentations

Air cleaning reduces indoor exposure to fine particulate matter (PM2.5) during wildfire smoke events. However, resource and cost constraints may limit access to air cleaning during such an event, as both commercial devices and the higher-rated MERV filters that do-it-yourself (DIY) assemblies typically rely upon tend to be expensive and in short supply. With these constraints in mind, we developed and evaluated several configurations of a novel, DIY air cleaner that uses common household fabrics as filtration media. Clean air delivery rates (CADRs) of the devices were experimentally evaluated in two ways: first, with independent measurements of flowrates and single …

Wind Plant Wake Losses: Disconnect Between Turbine Actuation And Control Of Plant Wakes With Engineering Wake Models, Ryan Scott, Nicholas Hamilton, Raul Bayoan Cal, Patrick Moriarty

Mechanical and Materials Engineering Faculty Publications and Presentations

Wake losses from neighboring plants may become a major factor in wind plant design and control as additional plants are constructed in areas with high wind resource availability. Because plant wakes span a large range of physical scales, from turbine rotor diameter to tens of kilometers, it is unclear whether conventional wake models or turbine control strategies are effective at the plant scale. Wake steering and axial induction control are evaluated in the current work as means of reducing the impact of neighboring wind plants on power and levelized cost of electricity. FLOw Redirection and Induction in Steady State (FLORIS) …

Capstone Review: Filament Unit Multiplexing Engine, Gal Cohen

University Honors Theses

The Filament Unit Multiplexing Engine (FUME) is a Mechanical Engineering capstone project sponsored by Portland State University's Electronic Prototyping Lab (EPL). The project addresses the need for an automated system to manage 3D printing operations. The current manual process of selecting and routing a spool of filament to one of the available 3D printers is labor-intensive and limits the efficiency of the lab's 3D printing farm. FUME aims to create a custom solution tailored for a multi-user, multi-spool, and multi-printer environment. The designed system includes key components: a spool holder, an engine, a track and shuttle system, and a funnel. …

On The Transitional Wake Past A Streamwise Rotating Prolate Spheroid, Yuxin Wu, Jianzhi Yang, Helge I. Andersson, Jianyu Chen, Xiaowei Zhu

Mechanical and Materials Engineering Faculty Publications and Presentations

Direct numerical simulations are performed to study the behavior of the wake behind a 5:2 streamwise rotating prolate spheroid. The Reynolds number Re = 1000 under different rotational speeds over a large range of is considered, where Ω is the non-dimensional rotational speed based on the freestream velocity and the volume-equivalent diameter of the prolate spheroid. By successively increasing the rotational speed, seven distinct flow regimes were identified and explored: steady state, low-speed steady rotation state, axisymmetric state, high-speed steady rotation state, twofold rotational symmetrical state (TFRS), quasi-periodic vortex shedding state (QVS), and weakly chaotic state. Among these wake regimes, …

Enhancing Miter Saw Safety: Challenges And Prospects Of Brake Incorporation With An Automatic Blade Retraction System, Derek Cole

University Honors Theses

Miter saws pose significant safety risks with thousands of injuries reported annually. Despite this risk, they are still used every day as they are a necessity for thousands of workers in the United States and globally. This leaves a demand to make these machines safer to mitigate any potential harm. This research addresses the critical need for an automatic safety system for miter saws, aiming to enhance user safety by retracting and stopping the blade upon skin contact. This analysis identified the primary challenge: The large force generated when braking at high speed on a miter saw blade, translates the …