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Articles 1 - 30 of 274
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Machine Learning Framework For Predicting Reliability Of Solder Joints, Robert Lee Jones
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
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
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
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
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
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
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
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. …
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 …
Pulse Modulation In Braided Pneumatic Actuators Mimics Contractile Behavior Of Biological Muscles, Mohamad Elzein
Pulse Modulation In Braided Pneumatic Actuators Mimics Contractile Behavior Of Biological Muscles, Mohamad Elzein
Student Research Symposium
Advancements in robotics and bioengineering aim to emulate biological muscle systems through robotic actuators, blending mechanical strength with biological adaptability. A lesser-explored aspect is mimicking the pulse-like control characteristic of biological muscles, which contract in response to action potentials from motoneurons, with muscle contractile force relying heavily on the timing between these potentials. This study explores the effect of pulse lengths and the gaps between pulses on braided pneumatic actuators (BPAs), which mimic the nonlinearity and dynamic response of biological muscles. It hypothesizes that artificial muscles utilizing pulse-based control will exhibit a similar force dependency on the intervals between pulses …
Comparative Life Cycle Assessment Of Recycling Processes For Perovskite Solar Cells, Juan P. Herrera, Jules Freeman, Achyuth Ravilla, Ilke Celik
Comparative Life Cycle Assessment Of Recycling Processes For Perovskite Solar Cells, Juan P. Herrera, Jules Freeman, Achyuth Ravilla, Ilke Celik
Student Research Symposium
Perovskite solar cells (PSCs) have emerged as a promising option for solar energy generation. However, it is essential to consider the environmental impact of these innovative photovoltaic (PV) technologies as the industry moves towards commercialization. Researchers are currently exploring ways to recycle PSCs to recover valuable materials and reduce their environmental impact at the end of their life. To ensure the sustainability of PSCs, this study evaluates and compares the environmental impacts of five recently developed recycling approaches. The Tool for Reduction and Assessment of Chemicals (TRACI) method was utilized to measure environmental impacts in categories such as acidification (kg …
Deriving Analytical Design Constraints For Absolute & Relative Encoding Schemes In Functional Subnetworks, Cody W. Scharzenberger-Braet, Alexander Hunt
Deriving Analytical Design Constraints For Absolute & Relative Encoding Schemes In Functional Subnetworks, Cody W. Scharzenberger-Braet, Alexander Hunt
Student Research Symposium
As neural networks have become prolific solutions to modern problems, there has been a congruent rise in the popularity of the numerical machine learning techniques used to design them. While they are highly generalizable, numerical methods tend to produce networks that act as inscrutable “black boxes,” making it difficult to interpret their behavior. One solution to the problem of network transparency is to use analytical techniques, but these methods are underdeveloped compared to their numerical alternatives. In order to enhance the viability of analytical techniques, this work extends previous efforts to quantify the impact that non-spiking neural encoding schemes have …
Electron-Phonon Interaction Mediated Gigantic Enhancement Of Thermoelectric Power Factor Induced By Topological Phase Transition., Zhi Li, Koushik Pal, Huiju Lee, Chris Wolverton, Yi Xia
Electron-Phonon Interaction Mediated Gigantic Enhancement Of Thermoelectric Power Factor Induced By Topological Phase Transition., Zhi Li, Koushik Pal, Huiju Lee, Chris Wolverton, Yi Xia
Mechanical and Materials Engineering Faculty Publications and Presentations
We propose an effective strategy to significantly enhance the thermoelectric power factor (PF) of a series of 2D semimetals and semiconductors by driving them toward a topological phase transition (TPT). Employing first-principles calculations with an explicit consideration of electron-phonon interactions, we analyze the electronic transport properties of germanene across the TPT by applying hydrogenation and biaxial strain. We reveal that the nontrivial semimetal phase, hydrogenated germanene with 8% biaxial strain, achieves a considerable 4-fold PF enhancement, attributed to the highly asymmetric electronic structure and semimetallic nature of the nontrivial phase. We extend the strategy to another two representative 2D materials …
Eco-Efficient Coatings For Healthy Indoors: Ozone Deposition Velocities, Primary And Secondary Emissions, Alessandra Ranesi, Paulina Faria, M. Rosario Veiga, Elliott T. Gall
Eco-Efficient Coatings For Healthy Indoors: Ozone Deposition Velocities, Primary And Secondary Emissions, Alessandra Ranesi, Paulina Faria, M. Rosario Veiga, Elliott T. Gall
Mechanical and Materials Engineering Faculty Publications and Presentations
Volatile organic compounds (VOCs) and ozone (O3) are harmful pollutants present in indoor air. Indoor concentrations of VOCs are typically higher than outdoors, due to the presence of indoor sources like building materials and ozone-surface reactions. The study aims to identify and quantify the ozone reactivity and primary and secondary emissions of different indoor coatings. The coatings selected for the study were three gypsum-based plastering mortar, with and without the addition of a bio-waste from Acacia dealbata (raw bark, BA, and bark heated at 250°C, BA250), two clay plasters (one with sand and the other with seashells as additional aggregate), …
Inertial Particle Clustering Due To Turbulence In An Air Jet, Bianca Viggiano, Kris Gish, Stephen Solovitz, Raul Bayoan Cal
Inertial Particle Clustering Due To Turbulence In An Air Jet, Bianca Viggiano, Kris Gish, Stephen Solovitz, Raul Bayoan Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Explosive volcanic eruptions create turbulent plumes of fine ash particles. When these particles collide in the presence of moisture and electrostatic fields they combine into larger aggregates, which can significantly change the atmospheric residence time of the airborne cloud. Previous studies have suggested that turbulence may lead to preferential concentration—also known as clustering—of particles within the flow, increasing the likelihood of collisions and aggregation. Few experimental studies have quantified these processes for volcanic plumes. This behavior was investigated using a particle-laden air jet. By systematically varying the exit speed and the size, density, and concentration of particles, flows were produced …
Comparison Of Conventional And Adaptive Acoustic Beamforming Algorithms Using A Tetrahedral Microphone Array In Noisy Environments, Megan Brittany Ewers
Comparison Of Conventional And Adaptive Acoustic Beamforming Algorithms Using A Tetrahedral Microphone Array In Noisy Environments, Megan Brittany Ewers
Dissertations and Theses
In situ acoustic measurements are often plagued by interfering sound sources that occur within the measurement environment. Both adaptive and conventional beamforming algorithms, when applied to the outputs of a microphone array arranged in a tetrahedral geometry, are able to capture sound sources in desired directions and reject sound from unwanted directions. Adaptive algorithms may be able to measure a desired sound source with greater spatial precision, but require more calculations and, therefore, computational power. A conventional frequency-domain phase-shift algorithm and a modified adaptive frequency-domain Minimum Variance Distortionless Response (MVDR) algorithm were applied to simulated and recorded signals from a …
Machine Learning A Universal Harmonic Interatomic Potential For Predicting Phonons In Crystalline Solids, Huiju Lee, Yi Xia
Machine Learning A Universal Harmonic Interatomic Potential For Predicting Phonons In Crystalline Solids, Huiju Lee, Yi Xia
Mechanical and Materials Engineering Faculty Publications and Presentations
Phonons, as quantized vibrational modes in crystalline materials, play a crucial role in determining a wide range of physical properties, such as thermal and electrical conductivity, making their study a cornerstone in materials science. In this study, we present a simple yet effective strategy for deep learning harmonic phonons in crystalline solids by leveraging existing phonon databases and state-of-the-art machine learning techniques. The key of our method lies in transforming existing phonon datasets, primarily represented in interatomic force constants, into a force-displacement representation suitable for training machine learning universal interatomic potentials. By applying our approach to one of the largest …
Wavelength-Induced Shedding Frequency Modulation Of Seal Whisker Inspired Cylinders, Trevor Dunt, Kirby S. Heck, Kathleen Lyons, Christin Murphy, Raul Bayoan Cal, Jennifer A. Franck
Wavelength-Induced Shedding Frequency Modulation Of Seal Whisker Inspired Cylinders, Trevor Dunt, Kirby S. Heck, Kathleen Lyons, Christin Murphy, Raul Bayoan Cal, Jennifer A. Franck
Mechanical and Materials Engineering Faculty Publications and Presentations
The spanwise undulated cylinder geometry inspired by seal whiskers has been shown to alter shedding frequency and reduce fluid forces significantly compared to smooth cylindrical geometry. Undulation wavelength is systematically investigated in order to explore its effect on unsteady lift force and shedding frequency. Prior research has parameterized the whisker-inspired geometry and demonstrated the relevance of geometric variations on force reduction properties. Among the geometric parameters, undulation wavelength was identified as a significant contributor to forcing changes. To analyze the effect of undulation wavelength, a thorough investigation isolating changes in wavelength is performed to expand upon previous research that parameterized …
Droplet Jump From A Particle Bed, Karl Cardin, Facundo Cabrera-Booman, Raúl Bayoán Cal
Droplet Jump From A Particle Bed, Karl Cardin, Facundo Cabrera-Booman, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Drop tower experiments have been performed to study droplet jump from a particle bed across a wide range of fluid viscosities. Here the droplet jumps from the particle bed in response to the apparent step reduction from terrestrial gravity to microgravity when the experiment is dropped and enters free fall. The presence of a particle layer has been found to affect contact line dissipation and the overall jumping behavior of droplets. Additionally, the study has identified the impact of the Ohnesorge number (Oh) on droplet morphology. The investigation has yielded results that not only validate a modified version of the …
Path Instabilities And Drag In The Settling Of Single Spheres, Facundo Cabrera-Booman, Nicolas Plihon, Mickael Bourgoin
Path Instabilities And Drag In The Settling Of Single Spheres, Facundo Cabrera-Booman, Nicolas Plihon, Mickael Bourgoin
Mechanical and Materials Engineering Faculty Publications and Presentations
The settling behavior of individual spheres in a quiescent fluid was studied experimentally. The dynamics of the spheres was analyzed in the parameter space of particle-to-fluid density ratio (Γ) and Galileo number (Ga), with Γ ∈ (1.1,7.9) and Ga ∈ (100,340). The experimental results showed for the first time that the mean trajectory angle with the vertical exhibits a complex behavior as Ga and Γ are varied. Numerically predicted regimes such as Vertical Periodic for low Γ values, and Planar Rotating for high Γ values were validated. In particular, for the denser spheres, a clear transition from planar to non-planar …
Experimental And Modeled Assessment Of Interventions To Reduce Pm2.5 In A Residence During Awildfire Event, Chrissi Argyro Antonopoulos, H. E. Dillon, Elliott T. Gall
Experimental And Modeled Assessment Of Interventions To Reduce Pm2.5 In A Residence During Awildfire Event, Chrissi Argyro Antonopoulos, H. E. Dillon, Elliott T. Gall
Mechanical and Materials Engineering Faculty Publications and Presentations
Increasingly large and frequent wildfires affect air quality even indoors by emitting and dispersing fine/ultrafine particulate matter known to pose health risks to residents. With this health threat, we are working to help the building science community develop simplified tools that may be used to estimate impacts to large numbers of homes based on high-level housing characteristics. In addition to reviewing literature sources, we performed an experiment to evaluate interventions to mitigate degraded indoor air quality. We instrumented one residence for one week during an extreme wildfire event in the Pacific Northwest. Outdoor ambient concentrations of PM2.5 reached historic …
Floating Wind Farm Experiments Through Scaling For Wake Characterization, Power Extraction, And Turbine Dynamics, Juliaan Bossuyt, OndˇRej FercˇÁk, Zein Sadek, Charles Meneveau, Dennice Gayme, Raúl Bayoán Cal
Floating Wind Farm Experiments Through Scaling For Wake Characterization, Power Extraction, And Turbine Dynamics, Juliaan Bossuyt, OndˇRej FercˇÁk, Zein Sadek, Charles Meneveau, Dennice Gayme, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
In this study, wind and water tunnel experiments of turbulent wakes in a scaled floating wind farm are performed. Scaling of a floating wind farm with a scaling ratio of 1:400 is made possible by relaxing geometric scaling of the turbine platform system, such that the dynamic response can be correctly matched, and to allow for relaxing Froude scaling such that the Reynolds number can be kept large enough. Four dimensionless parameters, describing the relative importance of wind and wave loads compared to turbine inertia, are used to guide the scaled floater design. Free decay tests of the pitch and …
Impact Of Material And Tunnel Barrier Quality On Spin Transport In A Cvd Graphene Non-Local Spin Valve Device Array, Samuel T. Olson, Daniel Still, Kaleb Hood, Otto Zietz, Jun Jiao
Impact Of Material And Tunnel Barrier Quality On Spin Transport In A Cvd Graphene Non-Local Spin Valve Device Array, Samuel T. Olson, Daniel Still, Kaleb Hood, Otto Zietz, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
Wafer-scale graphene films produced via chemical vapor deposition (CVD) are now commercially available, however these films inherently contain randomly distributed defects such as adlayers and grain boundaries. This report discusses the impact of these defects on the signal integrity of an array of graphene-based non-local spin valves (NLSVs). It was found that critical spin parameters fluctuate drastically between adjacent identical devices. Investigation of the channel quality indicated that adlayers do not affect spin signal significantly even when located directly in the spin transport region of the device. In contrast, grain boundary defects within the spin transport region have significant impact …
Multicolor Dye-Based Flow Structure Visualization For Seal-Whisker Geometry Characterized By Computer Vision, Ondřej Ferčák, Kathleen Lyons, Christin T. Murphy, Kristina M. Kamensky, Raul Bayoan Cal
Multicolor Dye-Based Flow Structure Visualization For Seal-Whisker Geometry Characterized By Computer Vision, Ondřej Ferčák, Kathleen Lyons, Christin T. Murphy, Kristina M. Kamensky, Raul Bayoan Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Pinniped vibrissae possess a unique and complex three-dimensional topography, which has beneficial fluid flow characteristics such as substantial reductions in drag, lift, and vortex induced vibration. To understand and leverage these effects, the downstream vortex dynamics must be studied. Dye visualization is a traditional qualitative method of capturing these downstream effects, specifically in comparative biological investigations where complex equipment can be prohibitive. High-fidelity numerical simulations or experimental particle image velocimetry (PIV) are commonplace for quantitative high-resolution flow measurements, but are computationally expensive, require costly equipment, and can have limited measurement windows. This study establishes a method for extracting quantitative data …
A One-Dimensional Volcanic Plume Model For Predicting Ash Aggregation, D. W. Hoffman, L. G. Mastin, Alexa R. Van Eaton, Stephen Solovitz, Raul Bayoan Cal, J. K. Eaton
A One-Dimensional Volcanic Plume Model For Predicting Ash Aggregation, D. W. Hoffman, L. G. Mastin, Alexa R. Van Eaton, Stephen Solovitz, Raul Bayoan Cal, J. K. Eaton
Mechanical and Materials Engineering Faculty Publications and Presentations
During explosive volcanic eruptions, volcanic ash is ejected into the atmosphere, impacting aircraft safety and downwind communities. These volcanic clouds tend to be dominated by fine ash (μm in diameter), permitting transport over hundreds to thousands of kilometers. However, field observations show that much of this fine ash aggregates into clusters or pellets with faster settling velocities than individual particles. Models of ash transport and deposition require an understanding of aggregation processes, which depend on factors like moisture content and local particle collision rates. In this study, we develop a Plume Model for Aggregate Prediction, a one-dimensional (1D) volcanic plume …
Development Of Prediction Method For Dimensional Stability Of 3d-Printed Objects, Kyung-Eun Min, Jae-Won Jang, Jesik Shin, Cheolhee Kim, Sung Yi
Development Of Prediction Method For Dimensional Stability Of 3d-Printed Objects, Kyung-Eun Min, Jae-Won Jang, Jesik Shin, Cheolhee Kim, Sung Yi
Mechanical and Materials Engineering Faculty Publications and Presentations
Fused deposition modeling (FDM), as one of the additive manufacturing processes, is known for strong layer adhesion suitable for prototypes and end-use items. This study used a multiple regression model and statistical analysis to explore the dimensional accuracy of FDM objects. Factors such as inclination angle, layer thickness, support space, and raster angle were examined. Machine learning models (Gaussian process regression (GPR), support vector machines (SVM), and artificial neural network (ANN)) predicted dimensions using 81 datapoints. The mean squared dimensional error (MSDE) between the measured and designed surface profiles was selected as an output for the dimensional accuracy. Support spacing, …
Modeling Yield Strength Of Austenitic Stainless Steel Welds Using Multiple Regression Analysis And Machine Learning, Sukil Park, Myeonghwan Choi, Dongyoon Kim, Cheolhee Kim, Namhyun Kang
Modeling Yield Strength Of Austenitic Stainless Steel Welds Using Multiple Regression Analysis And Machine Learning, Sukil Park, Myeonghwan Choi, Dongyoon Kim, Cheolhee Kim, Namhyun Kang
Mechanical and Materials Engineering Faculty Publications and Presentations
Designing welding filler metals with low cracking susceptibility and high strength is essential in welding low-temperature base metals, such as austenitic stainless steel, which is widely utilized for various applications. A strength model for weld metals using austenitic stainless steel consumables has not yet been developed. In this study, such a model was successfully developed. Two types of models were developed and analyzed: conventional multiple regression and machinelearning- based models. The input variables for these models were the chemical composition and heat input per unit length. Multiple regression analysis utilized five statistically significant input variables at a significance level of …
Role Of Binder On Yield Strength Of Polycaprolactone/Dimethylsulfone Composites For Bio-Applications, Kyung-Eun Min, Jae-Won Jang, Sung Yi, Cheolhee Kim
Role Of Binder On Yield Strength Of Polycaprolactone/Dimethylsulfone Composites For Bio-Applications, Kyung-Eun Min, Jae-Won Jang, Sung Yi, Cheolhee Kim
Mechanical and Materials Engineering Faculty Publications and Presentations
Polycaprolactone (PCL) and dimethylsulfone (DMSO2) composites can tailor the properties of scaffold materials, allowing their use in bone tissue engineering. With an increase in DMSO2 content, the modulus of the material increases but not the yield strength. In order to increase yield strength, a binder was added. However, the optimization of the content and the mixing process of the binder were not optimized in the previous studies. In this study, gamma-methacryloxypropyltrimethoxysilane (A-174) was used as a binder to increase the strength of a composite. Four different mixing processes were employed based on the binder mixing sequence. The binders with content …
Real-Time Length Sensing Of Braided Pneumatic Actuator Using Ir Time-Of-Flight Sensor, Luon B. Chung
Real-Time Length Sensing Of Braided Pneumatic Actuator Using Ir Time-Of-Flight Sensor, Luon B. Chung
Dissertations and Theses
Braided Pneumatic Actuators (BPAs) are used widely in robotics as artificial muscles because of their similar characteristics to biological muscles. When a BPA is pressurized, it expands in the radial direction and contracts in the longitudinal direction. The contraction generates a pulling force that is dependent on the input pressure and BPA length. Biological muscle also behaves in the same way where a pulling force is generated on a contraction. To control BPAs on a robot, the real-time pressure and length measurements are necessary. In this dissertation, I present a new method to measure length of BPAs in real-time using …
Phase Stability Of Lead Phosphate Apatite, Jiahong Shen, Dale Gaines Ii, S. Shahabfar, Zi Li, Dohun Kang, Sean Griesemer, Adolfo Salgado-Casanova, Tzu-Chen Liu, Yi Xia, Multiple Additional Authors
Phase Stability Of Lead Phosphate Apatite, Jiahong Shen, Dale Gaines Ii, S. Shahabfar, Zi Li, Dohun Kang, Sean Griesemer, Adolfo Salgado-Casanova, Tzu-Chen Liu, Yi Xia, Multiple Additional Authors
Mechanical and Materials Engineering Faculty Publications and Presentations
Recently, Cu-substituted lead apatite LK-99 was reported to have room-temperature ambientpressure superconductivity. Here we utilize density functional theory (DFT) total energy and harmonic phonon calculations to investigate the thermodynamic and dynamic stability of two lead phosphate apatites in their pure and Cu-substituted structures. Though Pb10(PO4)6O and Pb10(PO4)6(OH)2 are found to be thermodynamically stable (i.e., on the T=0K ground state convex hull), their Cu-substituted counterparts are above the convex hull. Harmonic phonon calculations reveal dynamic instabilities in all four of these structures. Oxygen vacancy formation …