The goal of this line of research is to add to the existing body of literature on the effect of heat treatments on the microstructure of chrome-bearing white irons and add bend test data to the literature concerning chrome-bearing white irons. This project was intended to support an existing line of research into cast metal-ceramic lattices using chrome white iron as a substitute for sintered ceramic tiles used to defeat projectiles. Chrome-bearing white irons have a substantial quantity of chromium carbides, giving them high hardness and abrasion resistance. Additionally, tiles cast from white iron proved to be more durable than sintered ceramic tiles, breaking into large chunks rather than a powder following an impact. These properties make tiles cast from chrome-bearing white iron a low-cost alternative to sintered carbides. The alloy investigated contained nominally 14 chromium and 3.2 carbon by weight percent. Three-point bend test specimens were cut from cast plates. These specimens were austenitized, air cooled, then tempered prior to three-point bend and hardness testing. The microstructure of the specimens was evaluated using optical microscopy, SEM, and XRD. This line of research revealed that lower austenitization temperatures resulted in a martensitic matrix with fewer, smaller secondary carbides, resulting in higher strength and hardness. In contrast, higher austenitization temperatures produced an austenitic matrix with coarser carbides, resulting in lower strength and hardness. This research did not reveal an appreciable change in ductility over heat treatment temperature. / Master of Science / This research investigates a hard iron alloy capable of replacing expensive ceramics in situations where the goal is to prevent penetration by a projectile. This iron alloy, known as white cast iron, can be cast using typical foundry practices, making it cost-effective. Additionally, the properties can be changed by heat-treatment, a process that involves heating the material to a given temperature, holding it at that temperature for a given amount of time, then cooling the material at a given rate. The results of this research add to the existing understanding of how heat treatment affects the properties of white cast iron. Additionally, this research generated new data about the strength of white cast irons in a three-point bending test, a test not normally used for white cast irons. The research found that high heat-treatment temperatures resulted in a softer white cast iron with lower strength. The structure of the white cast iron treated at these temperatures was predominantly austenite, a soft iron phase, and large carbides, a hard but brittle phase. Temperatures close to the lower end of the temperature range tested resulted in a harder white cast iron with higher strength. The structure of the iron in these conditions contained martensite, a hard iron phase, some austenite, and smaller but more angular carbides.

There are instances where efficiency and safety may be compromised as a result of wear and tear of fluid transporting pipe systems. Consequently, it is sometimes necessary to shut down the entire operation to fix the problem. Thus, it is worth evaluating other methods that can repair the damage for a temporary period without shutting down the operation while a new pipe is being constructed. The objective was to evaluate the durability of the epoxy bonded steel in aqueous environments that might be the conditions of such a repair. EPON(registered mark)828 was chosen as the epoxy resin, and dicyandiamide and polyamidoamine were two types of curing agent evaluated in this study. The epoxy bonded steels were exposed in either distilled water or 3.4% NaCl solution for various time periods. The mechanical strengths of the bonded joints were evaluated using a three-point flexure test. The neat epoxy samples were also aged under the same conditions, and three-point flexure test and dynamic mechanical analysis (DMA) were performed to evaluate their mechanical properties. The moisture uptake of the neat epoxy increased with exposure time, and the bending modulus of the neat epoxy decreased with aging time and moisture uptake. It was found that the interfacial shear strength decreased with aging time for both epoxy bonded systems. Scanning Electron Microscopy (SEM), optical microscopy, and X-ray Photoelectron Spectroscopy (XPS) were used to determine the locus of failure of the bonded joints. It was concluded that failure occurred cohesively within the oxide layer if oxides were present on the substrate surface prior to the bonding procedure. / Master of Science

Sclerostin, a protein coded for by the SOST gene, is an osteocyte-expressed negative regulator of bone formation. The absence of SOST in the genome may have an effect on bone formation both during skeletal maturation and full maturity. This study attempts to determine significant differences in the mechanical properties of bone that expresses SOST compared to bone that does not. One hundred femur samples from 6, 8, and 12 month old mice were obtained from Lawrence Livermore National Labs and loaded until failure using three-point bending. Results showed significant differences in treatment group effects for cross sectional area, yield force, and ultimate force. SOST knockout (KO) mice were found to have significantly higher values for these properties in comparison to transgenic (TG) and wildtype (WT) littermates. In addition, there was a noted effect dependent on the primary axis of loading, anterior-posterior versus medial-lateral. Lastly, data from this study support the existing hypothesis that there is no systematic side-to-side (left-right) difference in bone formation. This data may aid understanding of the role SOST has in bone formation. If the structural integrity and quality of bone resulting from the removal of the SOST gene is shown to be comparable to that of normal, healthy bone, the use of gene therapy to combat diseases/disorders such as osteoporosis may lead to important contributions to medical therapy.

No description available.

The signal resulting from the IR-FSE sequence has been thoroughly analyzed in order to improve the accuracy of quantitative T1 mapping of the human brain. Several optimized post-processing algorithms have been studied and compared in terms of their T1 mapping accuracy. The modified multipoint two-parameter fitting method was found to produce less underestimation compared to the traditional multipoint three-parameter fitting method, and therefore, to result in a smaller T1 estimation error. Two correction methods were proposed to reduce the underestimation problem which is commonly seen in IR-FSE sequences used for measuring T1, especially when a large turbo factor is used. The intra-scan linear regression method corrects the systematic error effectively but the RMSE may still increase due to the increase of uncertainty in sequences with large turbo factors. The weighted fitting model corrects not only the systematic error but also the random error and therefore the aggregate RMSE for T1 mapping can be effectively reduced. A new fitting model that uses only three different TI measurements for T1 estimation was proposed. The performance for the three-point fitting method is as good as that of the multipoint fitting method with correction in the phantom simulation. In addition, a new ordering scheme that implements the three-point fitting method is proposed; it is theoretically able to reduce the total scan time by 1/3 compared to the TESO-IRFSE sequence. The performance of the three-point fitting method on the real human brain is also evaluated, and the T1 mapping results are consistent to with the conventional IR-FSE sequence. More samples of true anatomy are needed to thoroughly evaluate the performance of the proposed techniques when applied to T1 mapping of the human brain.

Sandwich beams are composite systems having high stiffness-to-weight and strength-to-weight ratios and are used as light weight load bearing components. The use of thin, strong skin sheets adhered to thicker, lightweight core materials has allowed industry to build strong, stiff, light, and durable structures. Due to the use of viscoelastic polymer constituents, sandwich beams can exhibit time-dependent behavior. This study examines and predicts the time-dependent behavior of sandwich beams driven by the viscoelastic foam core. Governing equations of the deformation of viscoelastic materials are often represented in differential form or hereditary integral form. A single integral constitutive equation is used to model linear viscoelastic materials by means of the Boltzmann superposition principle. Based on the strength of materials approach, the analytical solution for the deformation in a viscoelastic sandwich beam is determined based on the application of the Correspondence Principle and Laplace transform. Finite element (FE) method is used to analyze the overall transient responses of the sandwich systems subject to a concentrated point load at the midspan of the beam. A 2D plane strain element is used to generate meshes of the three-point bending beam. User material (UMAT) subroutine in ABAQUS FE code is utilized to incorporate the viscoelastic constitutive model for the foam core. Analytical models and experimental data available in the literature are used to verify the results obtained from the FE analysis. The stress, strain, and deformation fields during creep responses are analyzed. Parameters such as the viscosity of the foam core, the ratio of the skin and core thicknesses, the ratio of the skin and core moduli, and adhesive layers are varied and their effect on the timedependent behavior of the sandwich system is examined.

Made available in DSpace on 2014-06-11T19:26:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-01-28Bitstream added on 2014-06-13T20:35:09Z : No. of bitstreams: 1 barros_aap_me_sjrp.pdf: 459604 bytes, checksum: 0a23c4af2e8f9afe3807f0dd603a1237 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo desse trabalho é estudar problemas de valor de contorno com três pontos lineares e não ineares, também conhecidos como problemas não Isto é feito, usando as funções de Green, usadas para resolver problemas de valor de contorno com dois pontos. / The aim of this work is to study boundary value problems with three points also known as non-classical problems. This is done using the Green's functions, which are used to solve two-point boundary value problems.

The diploma thesis is focused on the development of a mathematical model of the tractor-tool set in the MSC Adams program enabling analysis of the influence of the position of the upper linkage of the three-point hitch on the load of the driving wheels during the system operation. The measured force effects are analysed with focus on the adhesion load of the drive wheels and the traction properties of the tractor. Based on the calculations made, it determines the optimal setting of the upper link of the hitch for the connected tool.

The objective of this research is to determine how the sandwich's physical characteristics have an impact on the mechanical properties, determine under what conditions the specimens will be lighter and mechanically stronger, and determine if the use of an aluminum honeycomb sandwich as a construction material is feasible. The research has aimed at the use of aluminum sandwiches as light and strong material. The study of the structural layers' damage resistance and tolerance demonstrated that the top and bottom layers play a crucial role. The thesis presents three test results from aluminum honeycomb sandwich compression horizontal, compressive vertical, and bending tests. Also, each group was displayed mechanically and simulated in Abaqus. The study determines the mechanical properties such as maximum elastic stress-strain, ultimate stress-strain, fracture point, density, poison ration, young modulus, and maximum deflection was determined. The energy absorbed by the FEA, such modulus of elasticity, resilience, and toughness, the crack propagation, the test's view shows aluminum honeycomb behaved like a brittle material with both compression test. And the maximum deflection, crack propagation, shear forces, bending moment, and images illustrated that the layers play a crucial role in the 3-point bend test.

Topic: Comparison of three-point shoot trials occurence and effectivity in the aspects of FIBA rule changes in 2010 as well as in a relation with placement of the teams in Czech Women's basketball league Aim: The main aim of the thesis is to find out whether the following four- year-period as a result of rule changes applying to an extension of three- point line was sufficient enough to be able to adapt from the frequency and success in three-point shoot of view in the highest Czech Women's basketball league in the basic part of the Championship in between the selected teams. We take into account eight surveyed seasons in this study, where straight after the period of first four seasons following one after another there was a rule of three-point line extention established. The statistics of three-point shoots in the four seasons mentioned above, which means after establishing the rule, are the main source of data used for this survey and was accomplished according to statistical results and comparing these results. The mail goal is to create statistical analysis that would show how great impact the three-point line extention had during following four seasons of the change, which means the adaptability process applied for three- point shooting within the teams placed in the first, fourth, seventh...