Engineering Science and Materials Commons^™

The Examination Of Stress Corrosion Cracking In High Strength Carbon Steel Through Combined Mechanical-Electrochemical Testing, Jacob Sines

Williams Honors College, Honors Research Projects

Through the analysis of materials and environments seen in industry a better understanding of the fundamentals behind degradation mechanisms can be observed. The scope of this project was to better understand the fundamentals behind the degradation of high strength pipeline steels in a lab setting to simulate an environment seen in industry. Specifically the degradation mechanisms of high and nearly neutral pH stress corrosion cracking were examined in environments that simulated oil and gas pipelines buried in soil. Experimentation was carried out utilizing X65 carbon steel specimen, a Gamry potentiostat, a CORTEST proof ring, a CORTEST slow strain rate machine, …

Parametric Study Of Self-Centering Concentrically-Braced Frames In Response To Earthquakes, Nicholas F. Roth

Williams Honors College, Honors Research Projects

This research project consisted of the use of computer aided numerical software to test the response of an earthquake resistance system within various buildings when exposed to various design-level earthquakes. This research project is an extension of an existing NSF research project. The relevant questions and investigations of this and the greater project surround the performance of an earthquake resistance system with the intentions of better understanding its abilities and limitations. This project has been aided by Dr. David Roke, the faculty sponsor, in order to perform the research and collect, organize, and analyze the data. This research was performed …

Novel Endohedral Derivatives Of Sc3n@C2n (N = 34, 40) And Unique Tether Controlled Bis-Functionalization Of Fullerenes, Maira Raquel Ceron Hernandez

Open Access Theses & Dissertations

Since the discovery of fullerenes in 1985, their exohedral functionalization has been necessary to increase their solubility and explore their properties and potential applications in materials science and medicinal chemistry. This Thesis provides a short overview of the importance of electronic, size and shape complementarity in determining the structures of specific endohedral fullerene compounds. This is followed by a description of a new method for the separation of scandium nitride endohedral fullerenes Sc3N@C2n (n = 34, 39 and 40), and their monofunctionalization.

We also present the regioselective synThesis of easily isolable bis-derivatives of C60, C70, and M3N@Ih-C80 (M = Sc, …

Transition States And Modeling For Co9s8/Mos2 Catalysis, Gabriel Angel Gonzalez

Open Access Theses & Dissertations

Transition state computational studies of the sulfur removal from dibenzothiophene (DBT) molecule have herein been performed considering the Co9S8/MoS2 interface existing on unsupported Co/MoS2 catalysts. The linear synchronous transit (LST) and quadratic synchronous transit (QST) methods integrated in a density functional theory (DFT) program such as Dmol3 were used for the calculations of energy barriers of the transition states. Three different configurations present on the Co9S8/MoS2 interface have been envisaged as possible catalytic sites: sulfur-sulfur (S, S) sites, and molybdenum-sulfur (Mo, S) and molybdenum-molybdenum (Mo, Mo) edge sites. This study revealed that the (Mo, Mo) edge site is the most …

An Improved Sin-Hyperbolic Constitutive Model For Creep Deformation And Damage, Mohammad Shafinul Haque

Open Access Theses & Dissertations

Inspection and maintenance of industrial gas turbines (IGTs) cost millions of dollars. Growing demand of obtaining higher IGT efficiency leads to higher temperature and pressure operating conditions. Long exposure of turbine components at elevated temperature and pressure

makes creep damage critically important to consider during planning, designing and operating conditions. Effective and economic maintenance requires accurate creep deformation, damage

evolution and rupture life prediction information. Creep prediction models are used to determine the state of the turbine components and to schedule the inspection, maintenance and replacement time periods. The more accurate the prediction model, the less is the overall cost …

Transition Metal Carbide (Tmc) Novel Materials For Novel Catalytic Applications, Svetlana Lagoykina

Open Access Theses & Dissertations

Transition metal carbides (TMC) constitute a diverse class of materials and traditionally have many technological applications. TMC became a subject of extensive research since 1973, when their platinum -like properties were discovered. They demonstrated high catalytical activity and selectivity in a variety of chemical reaction and have potential for some novel catalytic application.

This research is an effort to design new high effective, selective and stable bimetal or alkali promoted TMC catalyst. After extensive theoretical research a wide range of TMC, including bimetal and alkali promoted carbides, were synthesized by different methods. All solids were characterized by XRD and microscopy. …

Thermal Shock Studies On Carbon-Carbon Composites: Experimentation And Analysis, Alma Lucia Leanos

Open Access Theses & Dissertations

The oxidation behavior of C/C composites under thermal shock conditions in air is understood and predicted experimentally and by computational efforts. In Chapter. 1, both compressive properties and oxidation behavior of pristine and thermal shock exposed 2D C/C composite specimens were examined. Pristine test specimens were exposed to thermal shock conditions with temperatures ranging from 400°C to 1000°C in an oxidizing environment, followed by compression tests on pristine and thermal shock exposed specimens to obtain their compressive responses.

Similarly, in Chapter. 2, the influence of thermal shock conditions on both, the extent of carbon materials decomposition and the through-thickness compressive …

Experimental Validation Of The Calphad Approach Applied To Multi-Principle Element Alloys, Nathan J. Bryant

Browse all Theses and Dissertations

High entropy alloys (HEAs) are a recent area of research in materials science. Their namesake is because their high entropy of mixing due to multiple metallic elements in a near equimolar ratio. The high entropy of mixing is supposed to suppress unwanted, brittle, ordered intermetallic phases, and form a single, randomly mixed solid solution phase. This phenomena makes HEAs a good candidate for structural applications. However, this entropy of mixing may not be enough to suppress all intermetallic phases. For this reason, the CALculation of PHAse Diagrams (CALPHAD) approach is being explored to predict phase equilibrium in HEAs. This study …

Efficiency Enhancement In Polymer Solar Cells With A Polar Small Molecule Both At Interface And In The Bulk Heterojunction Layer, Zhengguo Xiao, Qingfeng Dong, Qi Wang, Wenjing Tian, Hui Huang, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The polar molecules, including ferroelectric materials with large dipole moments, have been applied as interfacial layers to increase the efficiency of organic solar cells by increasing the bounded charge separation, tuning the energy levels, etc. Here, we report a small polar molecule 2-cyano-3- (4-(diphenylamino) phenyl)acrylic acid (TPACA) that can be either blended in the active layer or at the polymer/electrode interface to increase the efficiency of organic solar cell devices after poling. It is found that the built-in potential of the device is increased by 0.2 V after poling under negative bias. Blending TPACA into the active layer has shown …

Electron-Hole Diffusion Lengths >175 Μm In Solution-Grown Ch3Nh3Pbi3 Single Crystals, Qingfeng Dong, Yanjun Fang, Yuchuan Shao, Padhraic Mulligan, Jie Qiu, Lei Cao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH₃NH₃PbI₃ are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH₃NH₃PbI₃ single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in …

Towards Tuning The Mechanical Properties Of Three-Dimensional Collagen Scaffolds Using A Coupled Fiber-Matrix Model, Shengmao Lin, Lauren A. Hapach, Cynthia Reinhart-King, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold was simulated by a Voronoi network embedded in a matrix. The computational model was validated using published experimental data. Results indicate that both non-enzymatic glycation-induced matrix stiffening and fiber network density, as regulated by collagen concentration, influence scaffold behavior. The heterogeneous stress patterns of the scaffold were induced by the interfacial mechanics between the collagen fiber network …

Development And Preliminary Evaluation Of A Spray Deposition Sensing System For Improving Pesticide Application, Melissa A. Kesterson, Joe D. Luck, Michael P. Sama

Department of Mechanical and Materials Engineering: Faculty Publications

An electronic, resistance-based sensor array and data acquisition system was developed to measure spray deposition from hydraulic nozzles. The sensor surface consisted of several parallel tin plated copper traces of varying widths with varying gap widths. The system contained an embedded microprocessor to monitor output voltage corresponding to spray deposition every second. In addition, a wireless module was used to transmit the voltage values to a remote laptop. Tests were conducted in two stages to evaluate the performance of the sensor array in an attempt to quantify the spray deposition. Initial tests utilized manual droplet placement on the sensor surface …

Multiscale Modeling Of Skeletal Muscle Active Contraction In Relation To Mechanochemical Coupling Of Molecular Motors, Jiangcheng Chen, Xiaodong Zhang, Shengmao Lin, He Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, a mathematical model was developed to relate the mechanochemical characterizations of molecular motors with the macroscopic manifestation of muscle contraction. Non-equilibrium statistical mechanics were used to study the collective behavior of myosin molecular motors in terms of the complex conformation change and multiple chemical states in one working cycle. The stochastic evolution of molecular motor probability density distribution during the contraction of sarcomere was characterized by the Fokker-Planck Equation. Quick muscle contraction was demonstrated by the collective dynamic behavior of myosin motors, the muscle contraction force, and the muscle contraction velocity-force relation. Our results are validated against …

Inducing Persistent Flow Disturbances Accelerates Atherogenesis And Promotes Thin Cap Fibroatheroma Development In D374y-Pcsk9 Hypercholesterolemic Minipigs, Ryan M. Pedrigi, Christian Bo Poulsen, Vikram V. Mehta, Niels Ramsing Holm, Nilesh Pareek, Anouk L. Post, Ismail Dogu Kilic, Winston A.S. Banya, Gianni Dall'ara, Alessio Mattesini, Martin M. Bjorklund, Niels P. Andersen, Anna K. Grondal, Enrico Petretto, Nicolas Foin, Justin E. Davies, Carlo Di Mario, Jacob Fog Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva

Department of Mechanical and Materials Engineering: Faculty Publications

Background—Although disturbed flow is thought to play a central role in the development of advanced coronary atherosclerotic plaques, no causal relationship has been established. We evaluated whether inducing disturbed flow would cause the development of advanced coronary plaques, including thin cap fibroatheroma (TCFA).

Methods and Results—D374Y-PCSK9 hypercholesterolemic minipigs (N=5) were instrumented with an intracoronary shear-modifying stent (SMS). Frequency-domain optical coherence tomography was obtained at baseline, immediately post-stent, 19, and 34 weeks and used to compute shear stress metrics of disturbed flow. At 34 weeks, plaque type was assessed within serially-collected histological sections and co-registered to …

Self‑Propelled Droplets On Heated Surfaces With Angled Self‑Assembled Micro/Nanostructures, Cory Kruse, Isra Somanas, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

Directional and ratchet-like functionalized surfaces can induce liquid transport without the use of an external force. In this paper, we investigate the motion of liquid droplets near the Leidenfrost temperature on functionalized self-assembled asymmetric microstructured surfaces. The surfaces, which have angled microstructures, display unidirectional properties. The surfaces are fabricated on stainless steel through the use of a femtosecond laser-assisted process. Through this process, mound-like microstructures are formed through a combination of material ablation, fluid flow, and material redeposition. In order to achieve the asymmetry of the microstructures, the femtosecond laser is directed at an angle with respect to the sample …

Quantification Of Ultraprecision Surface Morphology Using An Algebraic Graph Theoretic Approach, Prahalad Rao, Satish T. S. Bukkapatnam, Zhenyu (James) Kong, Omer F. Beyca, Kenneth Case, Ranga Komanduri

Department of Mechanical and Materials Engineering: Faculty Publications

Assessment of progressive, nano-scale variation of surface morphology during ultraprecision manufacturing processes, such as fine-abrasive polishing of semiconductor wafers, is a challenging proposition owing to limitations with traditional surface quantifiers. We present an algebraic graph theoretic approach that uses graph topological invariants for quantification of ultraprecision surface morphology. The graph theoretic approach captures heterogeneous multi-scaled aspects of surface morphology from optical micrographs, and is therefore valuable for in situ real-time assessment of surface quality. Extensive experimental investigations with specular finished (Sa ~ 5 nm) blanket copper wafers from a chemical mechanical planarization (CMP) process suggest that the proposed method was …

Evaluation Of Peritoneal Microbubble Oxygenation Therapy In A Rabbit Model Of Hypoxemia, Nathan D. Legband, Jameel A. Feshitan, Mark A. Borden, Benjamin S. Terry

Department of Mechanical and Materials Engineering: Faculty Publications

Alternative extrapulmonary oxygenation technologies are needed to treat patients suffering from severe hypoxemia refractory to mechanical ventilation. We previously demonstrated that peritoneal microbubble oxygenation (PMO), in which phospholipid-coated oxygen microbubbles (OMBs) are delivered into the peritoneal cavity, can successfully oxygenate rats suffering from a right pneumothorax. This study addressed the need to scale up the procedure to a larger animal with a splanchnic cardiac output similar to humans. Our results show that PMO therapy can double the survival time of rabbits experiencing complete tracheal occlusion from6.6 ± 0.6 min for the saline controls to 12.2 ± 3.0 min for the …

Enhanced Pool-Boiling Heat Transfer And Critical Heat Flux On Femtosecond Laser Processed Stainless Steel Surfaces, Cory M. Kruse, Troy Anderson, Chris Wilson, Craig Zuhlke, Dennis Alexander, George Gogos, Sidy Ndao

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper, we present an experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces. Heat transfer enhancement in metallic surfaces is very important for large scale high heat flux applications like in the nuclear power industry. The multiscale structures were fabricated via a femtosecond laser surface process (FLSP) technique, which forms self-organized mound-like microstructures covered by layers of nanoparticles. Using a pool boiling experimental setup with deionized water as the working fluid, both the heat transfer coefficients and critical heat flux were investigated. A polished reference sample was found to have a critical heat flux …

An Agent Based Approach For Simulating Demo Enterprise Models, Mamadou Seck, Joseph Barjis

Engineering Management & Systems Engineering Faculty Publications

DEMO (design and engineering methodology for organization) is a theoretically grounded methodology for rigorous enterprise modeling. It provides relevant concepts from a construction perspective. As the methodology gains a wider audience, there is a growing interest in simulating DEMO models. Most attempts to develop a simulation approach for enterprise models in general, and the DEMO methodology in particular, are based on process oriented conceptualizations that are typically implementation in a discrete event paradigm. In this paper, we propose a conceptual framework for the translation of DEMO models into an agent based simulation. We will describe the DEMO methodology in some …

Effects Of Forcing Time Scale On The Simulated Turbulent Flows And Turbulent Collision Statistics Of Inertial Particles, B. Rosa, H. Parishani, O. Ayala, L.-P. Wang

Engineering Technology Faculty Publications

In this paper, we study systematically the effects of forcing time scale in the large-scale stochastic forcing scheme of Eswaran and Pope ["An examination of forcing in direct numerical simulations of turbulence," Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynolds …