Mechanics of Materials Commons^™

Fe Modeling Methodology For Load Analysis And Preliminary Sizing Of Aircraft Wing Structure, Jun Hwan Jang, Sang Ho Ahn

International Journal of Aviation, Aeronautics, and Aerospace

It is a critical part at the basic design phase of aircraft structural design to build a finite element model and it will have a direct impact on time and cost for airframe structure development. In addition, the objective of finite element model will be varied depending on each design review phase and the modelling methodology varied accordingly. In order to build an effective and economic finite element model, it is required to develop adequate level of modelling methodology based on each design phase and its objectives. Therefore, in this paper, the finite element modeling methodology was presented for internal …

Deformation Correlations And Machine Learning: Microstructural Inference And Crystal Plasticity Predictions, Michail Tzimas

Graduate Theses, Dissertations, and Problem Reports (ETD)

The present thesis makes a connection between spatially resolved strain correlations and material processing history. Such correlations can be used to infer and classify prior deformation history of a sample at various strain levels with the use of Machine Learning approaches. A simple and concrete example of uniaxially compressed crystalline thin films of various sizes, generated by two-dimensional discrete dislocation plasticity simulations is examined. At the nanoscale, thin films exhibit yield-strength size effects with noisy mechanical responses which create an interesting challenge for the application of Machine Learning techniques. Moreover, this thesis demonstrates the prediction of the average mechanical responses …

Unveiling The Operation Mechanism Of Layered Perovskite Solar Cells, Yun Lin, Yanjun Fang, Jingjing Zhao, Yuchuan Shao, Samuel J. Stuard, Masrur Morshed Nahid, Harald Ade, Qi Wang, Jeffrey E. Shield, Ninghao Zhou, Andrew M. Moran, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Layered perovskites have been shown to improve the stability of perovskite solar cells while its operation mechanism remains unclear. Here we investigate the process for the conversion of light to electrical current in high performance layered perovskite solar cells by examining its real morphology. The layered perovskite films in this study are found to be a mixture of layered and three dimensional (3D)-like phases with phase separations at micrometer and nanometer scale in both vertical and lateral directions. This phase separation is explained by the surface initiated crystallization process and the competition of the crystallization between 3D-like and layered perovskites. …

Higher-Order Overtone Thickness-Shear Vibrations Of Multilayered Thin-Film Acoustic Wave Resonators And Angular Rate Sensing, Hui Chen, Ji Wang, Jianke Du, Jiashi Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We propose a new structure for piezoelectric gyroscopes. It is made from multilayered thin films of AlN or ZnO with alternating c-axes along the film thickness. It is shown theoretically that when such a film is electrically driven into higher-order overtone thickness-shear vibration in one of the two in-plane directions of the film and is rotating about the film normal, the Coriolis force due to the rotation causes a higher-order overtone thicknessshear vibration in a perpendicular direction with an electrical output that can be used to measure the angular rate of the rotation. Different from existing thickness-shear mode piezoelectric gyroscopes …

Mechanical Stresses Associated With Flattening Of Human Femoropopliteal Artery Specimens During Planar Biaxial Testing And Their Effects On The Calculated Physiologic Stress-Stretch State, Majid Jadidi, Anastasia Desyatova, Jason N. Mactaggart, Alexey Kamenskiy

Department of Mechanical and Materials Engineering: Faculty Publications

Planar biaxial testing is commonly used to characterize the mechanical properties of arteries, but stresses associated with specimen flattening during this test are unknown. We quantified flattening effects in human femoropopliteal arteries (FPAs) of different ages, and determined how they affect the calculated arterial physiologic stress-stretch state. Human FPAs from 472 tissue donors (age 12-82 years, mean 53±16 years) were tested using planar biaxial extension, and morphometric and mechanical characteristics were used to assess the flattening effects. Constitutive parameters for the invariant-based model were adjusted to account for specimen flattening, and used to calculate the physiologic stresses, stretches, axial force, …

Correlation Microanalysis Of Localized Molecular Structure And Nano-Mechanical Property Of Pvdf Based Copolymer, Wen Qian, Shuo Sun, Charles Nguyen, Stephen Ducharme, Joesph A. Turner

Department of Mechanical and Materials Engineering: Faculty Publications

Poly (vinylidenefluoride) (PVDF) and its copolymers, are well-recognized electroactive polymers. The PVDF polymer can crystallize in a quasi-hexagonal close-packed “β-phase” structure with the dipoles of all chains aligned with maximum spontaneous polarization [1-3]. Due to the limited availability of quantitative methods for nanoscale molecular structure and mechanical analysis, the polymer organization has not been fully optimized. For such ferroelectric polymers, the influence of nanoscale molecular structure on mechanical response is not well understood. In this paper, we demonstrate nanoscale characterization and measurement techniques, by comprehensive integrating atomic force microscopy (AFM), X-ray diffraction (XRD), nano-infrared (nanoIR) spectroscopy, nanoindentation, chemical nanoIR mapping, …

Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The objective of this study is to characterize the micromechanical properties of poly-L-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 μm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of …

Hemodynamic Interference Of Serial Stenoses And Its Impact On Ffr And Ifr Measurements, Siyeong Ju, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The hemodynamic interference of serial stenoses poses challenges for identifying the functional severity using the fractional flow reserve (FFR) method. The instantaneous wave-free ratio (iFR), i.e., the distal-to-proximal pressure ratio at 75% of diastole, was recently proposed to overcome the disadvantages of the FFR. However, the underlying mechanism remained ambiguous due to the lack of quantitative definition of hemodynamic interference. The objective of this study is to quantitatively define the hemodynamic interference and then examine its role on the FFR and iFR measurements. Pressure distributions, velocity fields, and Q-criterion which identifies vortices, were obtained through the computational fluid dynamics (CFD) …

Hemodynamics And Wall Mechanics After Surgical Repair Of Aortic Arch: Implication For Better Clinical Decisions, Siyeong Ju, Ibrahim Abdullah, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Graft repair of aortic coarctation is commonly used to mimic the physiological aortic arch shape and function. Various graft materials and shapes have been adopted for the surgery. The goal of this work is to quantitatively assess the impact of graft materials and shapes in the hemodynamics and wall mechanics of the restored aortic arch and its correlation with clinical outcomes. A three-dimensional aortic arch model was reconstructed from magnetic resonance images. The fluid–structure interaction (FSI) analysis was performed to characterize the hemodynamics and solid wall mechanics of the repaired aortic arch. Two graft shapes (i.e., a half-moon shape and …

Interface Facilitated Reorientation Of Mg Nanolayers In Mg-Nb Nanolaminates, Y. Chen, Mingyu Gong, N. A. Mara, Jian Wang

Department of Mechanical and Materials Engineering: Faculty Publications

Mg/Nb nanolaminates synthesized through vapor deposition techniques exhibit high flow strength without conventional twinning in Mg. In this work, we investigated the influence of laminated microstructures on deformation mechanisms of Mg nanolayers. Using molecular dynamics simulations, we explored that (0001)-oriented Mg layers transform or re-orient to {10¯10}-oriented Mg layers through nucleation and growth of {10¯12} twins by atomic shuffling, instead of conventional {10¯12} twinning shear. Such a reorientation accommodates in-plane compressive strain and out-of-plane tensile strain when Mg/Nb laminates are subjected to compression parallel to the Mg/Nb interfaces. The nucleation of {10¯12} twins is promoted at the Mg/Nb interface due …

Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, the peridynamic corrosion model is used for 3D simulation of pitting corrosion in stainless steel. Models for passivation and salt layer formation are employed to predict detailed characteristics of pit growth kinetic in stainless steels, such as lacy cover formation on top of the pit, and the diffusion-controlled regime at the pit bottom. The model is validated against an experimentally grown pit on 316L stainless steel in NaCl solution. Lacy covers in this model are formed autonomously during the simulation process. They are remarkably similar to the covers observed on top of the real pits.

Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen

Department of Mechanical and Materials Engineering: Faculty Publications

In this work, the peridynamic corrosion model is used for 3D simulation of pitting corrosion in stainless steel. Models for passivation and salt layer formation are employed to predict detailed characteristics of pit growth kinetic in stainless steels, such as lacy cover formation on top of the pit, and the diffusion-controlled regime at the pit bottom. The model is validated against an experimentally grown pit on 316L stainless steel in NaCl solution. Lacy covers in this model are formed autonomously during the simulation process. They are remarkably similar to the covers observed on top of the real pits.

Mechanical Properties And Degradation Of High Capacity Battery Electrodes: Fundamental Understanding And Coping Strategies, Yikai Wang

Theses and Dissertations--Chemical and Materials Engineering

Rechargeable lithium ion and lithium (Li) metal batteries with high energy density and stability are in high demand for the development of electric vehicles and smart grids. Intensive efforts have been devoted to developing high capacity battery electrodes. However, the known high capacity electrode materials experience fast capacity fading and have limited cycle life due to electromechanical degradations, such as fracture of Si-based electrodes and dendrite growth in Li metal electrodes. A fundamental understanding of electromechanical degradation mechanisms of high capacity electrodes will provide insights into strategies for improving their electrochemical performance. Thus, this dissertation focuses on mechanical properties, microstructure …

Development And Characterization Of Polyethylene Terephthalate (Pet)-Cotton Natural Fiber-Reinforced Composites From Waste Materials, Israel Alejandro Carrete

Open Access Theses & Dissertations

Unprecedented levels of production and consumption have caused a rapid exhaustion of the Earth's virgin resources, which is coupled with a fast accumulation of contaminants in the form of solid waste, especially in landfills. Two significant landfill constituents come from textile waste and discarded plastic bottles. Since there is a finite amount of space that can be feasibly used for landfills, solutions that make use of these post-consumer products are imperative. This study presents one possible solution by using surface modifications of cotton fibers to produce a natural fiber-reinforced polymer composite (NFRPC) from post-consumer textile waste and polyethylene terephthalate (PET) …

Understanding Of Deformation And Fracture Behavior In Next Generation High Strength-High Ductility Steels, Venkata Sai Yashwanth Injeti

Open Access Theses & Dissertations

The industrial demand for low density high strength steels without compromising on ductility in is endless. In this regards, grain refinement and austenitic stability considered to the practical approach in order to meet the needs. The concept of phase reversion involving sever cold deformation of metastable austenite to generate strain-induced martensite, followed by time-temperature annealing sequence, was used to obtain varying grain size from nanograined/ultrafine-grained (NG/UFG) to coarse-grained (CG) regime. This concept was used to obtain "high strength-high ductility" combination in nano/ultrafine-grained (NG/UFG) austenite stainless steel. Using this concept, the objective of the study here is to elucidate the dependence …

A Method For Iron Determination During Copper Electrometallurgy And Its Application To The Calculation Of Current Efficiency, Daniel Pedro Cruz

Open Access Theses & Dissertations

With the objective of developing statistical models that describe iron kinetics under typical copper electrolytes as well as its effects on current efficiency and influence in cathodic and anodic behavior, a detailed electrochemical analysis is done in this work as a contribution to implement hydrometallurgical processes in the refining or winning process to produce high purity copper.

This Thesis evaluates the oxidation-reduction potential (ORP) of the Fe3+/Fe2+ couple in the H2SO4-Fe2(SO4)3-FeSO4-H2O and H2SO4-CuSO4-Fe2(SO4)3-FeSO4-H2O systems, with addition of different copper concentrations and temperatures up to 70°, typically employed in the industry. This study further validates and expands a thermodynamic expression developed …

Processing, Structure And Mechanical Behavior Of Advanced Engineering Steels, Bing Yu

Open Access Theses & Dissertations

The concept of low lattice misfit and high-density of nanoscale precipitates obtained through solution treatment was adopted to obtain ultrahigh strength maraging steel without compromising elongation. An "ultrahigh strength-high toughness" combination was successfully obtained in 19Ni3Mo1.5Ti maraging steel with ultimate strength of ~1858 MPa and static toughness of ~110 MJ·m-3. Maraging steel had extremely high density (2.3Ã?1024 m-3) of nanoscale precipitates with minimum lattice misfit of less than 1% at the solutionization temperature of 820 oC. Two kinds of nanoscale precipitates, namely, η-Ni3(Ti,Mo) and B2-Ni(Mo,Fe) contributed to ultrahigh strength. The size of nanoscale precipitates governed the movement of dislocations, cutting …

Investigating Using Titanium Zirconium Molybdenum For Additively Manufacturing Aerospace Components, Justin Hunter Vanhoose

Open Access Theses & Dissertations

Mankind throughout history has possessed an innate characteristic to explore, migrating to new frontiers.The requirement for this travel is most broadly associated with the need to pursue more resources. Rockets have been used as a means of weapons since the Sung Dynasty in the thirteenth empire and have now been integrated for travel/transport. The sophistication of rocketry and propulsion has reached a level to where it is plausible that mankind will be a multi-planetary species. The space industry has grown significantly with the advancement of the sophistication of these rocket technologies. However, a specific challenge to overcome in the space …

Microstructure Evolution Of Chalcogenide Materials Via Molecular Dynamics, Sharmin Abdullah

Open Access Theses & Dissertations

The properties of a material are defined by its granular microstructure which is determined by its grain evolution and the types of grain boundaries present in the structure. For example, the performance of Cadmium Sulfide/Cadmium Telluride (CdS/CdTe) solar cells can be affected by the presence of grain boundaries which makes the study of grain structure evolution a very important part of solar cell performance optimization. Grain boundary mobilities are important properties in material science and engineering as they determine grain structures under given processing and operating conditions.

In this thesis, several computational tools were used to analyze the formation and …

Comparative Study Of Analytical Models Of The Gruneisen Parameter Of Metals As Function Of Pressure, Celia Garcia Amparan

Open Access Theses & Dissertations

Commonly used Gruneisen parameter (γ) models only hold accurate in limited regimes making them inapplicable for use over wide temperature-pressure conditions. The accuracy of these analytical models of γ and of the thermal expansion of solids are of particular interest as these are considered proxies for quantifying anharmonicity, which may be a significant contribution to the thermal pressure at high temperatures. This work reviews various definitions of γ and their relations to the equations of state and apply them to two simple metals: Tantalum (Ta) and Copper (Cu), for which a high body of experimental data exists. Classical Molecular Dynamics …