Mechanics of Materials Commons^™

Microstructural Characterization And Heat Treatment Of A-286 Turbine Buckets, Christopher Michael Bradley

Open Access Theses & Dissertations

A-286 is an iron-based superalloy used extensively in land-based gas turbines for 2nd stage (low pressure) buckets and 1st and 2nd stage wheels. Although A-286 may appear to some as just another austenitic stainless steel, its elevated temperature properties are attributed to ' precipitate structures, effective distributions of alloy carbides in the forms of M23C6, M6C and MC, and solid solution strengthening. Unfortunately over the course of these components service lives microstructural degradation develops in the form of η-phase formation. The presence of η-phase, especially in large quantities, can have a negative effect on stress rupture properties. Resistance to creep …

Spectroscopic Characterizations Of Organic/Inorganic Nanocomposites, Jayesh Rasikalal Govani

Open Access Theses & Dissertations

Inorganic potassium dihydrogen phosphate (KDP) is widely known for its value as a nonlinear optical material. In this study, pure and l-arginine-doped KDP single crystals were grown by the slow solvent evaporation technique and further subjected to infrared absorption and Raman studies for the confirmation of chemical group functionalization and possible bonding between the organic and inorganic materials. The appearance in the infrared absorption spectra of additional vibrational lines, which mostly originate from disturbed N-H, C-H, and C-N bonds of the l-arginine-doped salt, confirm the interaction between KDP and the organic material. This affirmation is supported by more evidence from …

Effects Of Build Orientation, Aging, And Pre-Conditioning On Mechanical Properties For Stereolithography-Manufactured Astm Type I Specimens Using A Design Of Experiments Approach, Karina Puebla

Open Access Theses & Dissertations

With industry's growing focus on the rapid manufacturing (RM) of end-use products, rapid prototyping (RP) or layered manufacturing (LM) machines that were originally designed to build prototypes may now be required to build functional end-use products. To successfully accomplish the transition, the available materials utilized in RP must provide the performance required for RM. The specific technology used must also be capable of producing repeatable and reproducible parts in regards to mechanical and dimensional properties.

A design of experiments approach was performed to determine the effects of build orientation, aging, and pre-conditioning on the mechanical properties. To perform the investigations, …

Computational Modeling Studies Of The Structures And Properties Of Organotin(Iv) And Stannyl-Thioether Systems With Comparisons To X-Ray Crystallography, Michelle R. Stem Joseph

Open Access Theses & Dissertations

Controlling the toxic effects of organotin(IV) compounds involves engineering the structure of the molecules to optimize their properties. Molecular engineering, coupled with improved capabilities to generate reliable computational optimization models (COMs), will enable researchers to have greater success at harnessing the highly specific cytotoxicity of organotins. For example, as the thio_n ligand phenyl groups were replaced with Cl atoms, the S-Sn intramolecularity was strengthened, the bond distance decreased, and the stannyl tetrahedral structure was deformed from its triphenyl conformation. With each substitution, conformation deformations lowered the damaging bioactivity levels of thio_n. Bonding various ligands to organotin(IV) compounds …

High Temperature Oxidation Behavior Of Nb-20mo-15si-5b-20cr Alloy, Julieta Angelica Ventura

Open Access Theses & Dissertations

Materials for high temperature applications, such as jet engines, gas turbines and turbine blades, require a balanced combination of physical and chemical properties to withstand the aggressive environments in which they are utilized. Some of the properties required are high strength, low density, high melting point and good oxidation resistance at elevated temperatures [1-3]. For this reason, the microstructure and oxidation behavior of the Nb-20Mo-15Si-5B-20Cr alloy (at.%) has been studied as a potential candidate to replace Nickel-based alloys currently used in the aerospace industry.

Short term oxidation (STO) and long term oxidation (LTO) studies have been performed in air for …

Exploring Poly(Ethylene Glycol) As A Suitable Material For Peripheral Nerve Regeneration Scaffolds Manufactured By Stereolithography, Nubia Zuverza

Open Access Theses & Dissertations

One of the challenges in tissue engineering is to have spatial and temporal control over the biological elements within a scaffold used to guide regeneration for example of transected nerves. Some of the physical and chemical characteristics to regulate include incorporation of bioactive domains and release of chemical signals. This study presents the use of stereolithography (SL) to incorporate localized domains for cell adhesion in addition to include releasable nerve growth factor (NGF) in the process of building poly(ethylene glycol)diacrylate (PEGda) hydrogel scaffolds. Besides providing sites for cell attachment, an ideal nerve guidance conduit (NGC) should be able to release …

Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.

Department of Engineering Mechanics: Faculty Publications

We introduce here adaptive refinement algorithms for the non-local method peridynamics, which was proposed (in J. Mech. Phys. Solids 2000; 48:175–209) as a reformulation of classical elasticity for discontinuities and long-range forces. We use scaling of the micromodulus and horizon and discuss the particular features of adaptivity in peridynamics for which multiscale modeling and grid refinement are closely connected. We discuss three types of numerical convergence for peridynamics and obtain uniform convergence to the classical solutions of static and dynamic elasticity problems in 1D in the limit of the horizon going to zero. Continuous micromoduli lead to optimal rates of …

Comparison Of Fuzzy Clustering Methods And Their Applications To Geophysics Data, David J. Miller, Carl A. Nelson, Molly Boeka Cannon, Kenneth P. Cannon

Department of Mechanical and Materials Engineering: Faculty Publications

Fuzzy clustering algorithms are helpful when there exists a dataset with subgroupings of points having indistinct boundaries and overlap between the clusters. Traditional methods have been extensively studied and used on real-world data, but require users to have some knowledge of the outcome a priori in order to determine howmany clusters to look for. Additionally, iterative algorithms choose the optimal number of clusters based on one of several performance measures. In this study, the authors compare the performance of three algorithms (fuzzy c-means, Gustafson-Kessel, and an iterative version of Gustafson-Kessel) when clustering a traditional data set as well as real-world …

Experimental Investigation Of A Novel Blast Wave Mitigation Device, Zhenbi Su, Wen Peng, Zhaoyan Zhang, George Gogos, Reed Skaggs, Bryan Cheeseman, Chian Fong Yen

Department of Mechanical and Materials Engineering: Faculty Publications

A novel blast wave mitigation device was investigated experimentally in this paper. The device consists of a pistoncylinder assembly. A shock wave is induced within the cylinder when a blast wave impacts on the piston. The shock wave propagates inside the device and is reflected repeatedly. The shock wave propagation process inside the device lengthens the duration of the force on the base of the device to several orders of magnitude of the duration of the blast wave, while it decreases the maximum pressure over an order of magnitude. Two types of experiments were carried out to study the blast …