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no abstract provided by author / Master of Science

This investigation was made in an attempt to compare the casting properties of various commercially used grid-metal alloys and to study other alloys that promise to be of value in the battery manufacturing industry. In previous publications (1) it has been shown that zinc has a very market effect in raising the surface tension of type metals when it is present even in small amounts. A more recent publication (2) has shown that zinc in small amounts (which increases (1) the surface tension of type metals) and sodium in small amounts (which decreases the surface tension of type metals) does not impair the ability of type metal to flow in molds all parts of which are above capillary in size. As neither zinc nor sodium have any appreciable effect on runnability it is concluded that surface tension is a negligible factor in determining the runnability of an alloy in molds which are in all parts of above capillary size. Since the molds used in casting grid plates are above capillary size in all parts, and from evidence cited, it is concluded that surface tension does not enter this problem, and the procedure as outlined in the following section was chosen as the most logical for this study. (1) The Surface Tension of Type-Metal Alloys, by H.V. White, Bulletin of Virginia Polytechnic Institute, January 1993, Engineering Experiment Station Serious No. 13. The Effect of Impurities on the Surface Tension o Type-Metal Alloys, Bulletin of Virginia Polytechnic Institute, by H.V. White, June, 1934, Engineering Station Series No. 17. 2) "The Effect of Zinc and Sodium on the Relative Runnability of Type-Metal Alloys," by H.V. White and F.O. Reese: Bulletin of Virginia Polytechnic Institute, September, 1935, Engineering Experiment Station Series No. 21. / M.S.

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To minimize the production cost and time of the heat treatment of critical application aluminum castings within the automotive industry a combined hot isostatic pressing (HIP)/solution heat treat process is desired. A successfully combined process would produce parts of equal quality to those produced by the individual processes of HIP and subsequent heat treatment with increased efficiency in time and energy. In this study, an experimental combined process was designed and implemented in a production facility. Industrially produced aluminum castings were subjected to the combined process and results were quantified via tensile and fatigue testing and microscopic examination. Comparisons in fatigue and tensile strength were made to raditionally HIPed and heat treated samples, as well as un-HIPed samples in the T6 condition. Results show that castings produced with the combined process show fatigue properties that are equal in magnitude to castings produced with the independent HIP and heat treatment processes. Furthermore, an order of magnitude improvement in the fatigue life in those castings that were produced with the combined process exists compared to the castings that were only heat treated. This study shows no difference in the tensile properties that result from any of the processing routes compared. Also, microstructural comparison of the castings processed show no difference between the process routes other than porosity, which is only evident in the un-HIPed samples. Dendrite cell size and dendritic structure of the samples that were solutionized for the same time is identical. Theoretical examination of the combined process was also completed to quantify the energy consumption of the combined process compared to the independent processes. Thermodynamic calculations revealed that the energy consumed by the combined process for a typically loaded HIP vessel is fifty percent less than the energy required to process the same quantity of castings with the two individual processes. However, it was determined that a critical ratio of the volume occupied in the HIP vessel by castings to the total HIP vessel volume exists that ultimately determines the efficiency of the combined process. This critical ratio was calculated to be approximately fifteen percent. If the volume ratio is less than fifteen percent then the combined process is less energy efficient then conventional processing. These thermodynamic calculations were experimentally verified with power consumption process data in a production facility. In addition, the time required for the combined process of HIP and solution heat treatment was calculated as thirty-percent less than the conventional two-step process. This calculation was verified via the comparison of data compiled from the experimental combined process.

The structural and stress changes in molybdenum/amorphous silicon (Mo/a-Si) EUV reflecting multilayers during annealing at 316��C were studied. The amorphous interlayers, with an Mo:Si stoichiometry of 1:2, grew during annealing. The residual stresses in each component of the multilayer also changed significantly. Through high resolution electron microscopy, selected area electron diffraction, and x-ray diffraction of the crystalline Mo, the biaxial tensile stresses were shown to increase from approximately two to about ten GPa in the lateral direction, parallel to the interface plane. The compressive strains developed in the vertical direction, perpendicular the interface plane, are consistent with a Poisson contraction calculated from bulk elastic properties. Laser deflectometry measurements of thicker (non-EUV, 0.1��m) amorphous silicon showed compressive stress relaxation in the amorphous silicon with annealing, which may also take place in the thin (EUV) silicon. The residual stress in a 40 bilayer EUV film changes from about -0.5 GPa to about +1.5 GPa. / Graduation date: 1996

The successful use of Nickel-Titanium (Nitinol) in biomedical applications requires an accurate control of its unique mechanical properties. The purpose of this study is to analyze the effects of a wide range of heat treatments on the mechanical behavior of hot-rolled and cold-drawn Nitinol. Results comprise an understanding of the effect of heat treatment temperature and time variation on final material response which is imperative for optimization of material properties. Thirty-three heat treatment variations are tested by combining three durations, 10 minutes, 90 minutes, and 8 hours, with eleven different heat treatment temperatures between 200°C and 440°C. Following heat treatment, the Nitinol samples undergo tensile testing with upper plateau strength, lower plateau strength, ultimate tensile strength, strain to failure, and residual elongation compared for all test groups. Heat treatment "power" is used to describe the efficacy of different combinations of heat treatment temperature and duration. When using hot-rolled Nitinol, results show a low heat treatment power does not create significant precipitation hardening or a significant decrease in martensite transformation stress, resulting in a high upper plateau strength, high residual strain values, and evidence of plastic deformation upon unloading. Moderate power treatments lead to sufficient hardening of the material and a decrease in martensite transformation stress resulting in a pseudoelastic response. Increasing to a high treatment power further decreases the transformation stress and increases the martensite transformation temperature leading to a shape-memory response in hot rolled Nitinol. When using cold-drawn Nitinol, low and moderate heat treatment power levels result in the material exhibiting a pseudoelastic response. Increasing heat treatment power shows the same effects on martensite transformation stress and temperature as seen with the hot-rolled material resulting in a material response transition from pseudoelastic to shape memory.

Orientador: Valdemar Silva Leal / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T02:09:31Z (GMT). No. of bitstreams: 1 Carvalho_AntonioRogerioTorres_M.pdf: 2108495 bytes, checksum: 57b748cffef6835e43201549b90022af (MD5) Previous issue date: 2004 / Resumo: Estuda-se a influência da variação da agitação e da severidade de têmpera do meio de resfriamento sobre as curvas e taxas de resfriamento durante o processo de têmpera do aço. Os ensaios foram realizados com amostras dos aços 1045, 8620 e 8640, temperadas em água e salmoura, promovendo-se a variação do estado de agitação do refrigerante. Os dados apontam para variação da taxa de resfriamento máxima de 27,65% a 110,09% e uma diminuição nos tempos de resfriamento de 7,83% a 63,25%, para os três materiais estudados, com o aumento da agitação do meio. Verificam-se ainda, ganhos nas taxas e tempos de resfriamento com a variação da severidade de têmpera pela troca do meio, água por salmoura, da ordem de 73,27%, sem agitação do meio, e diminuição do tempo de resfriamento em aproximadamente 20%. Os dados ainda demonstram ganhos no tempo e nas taxas de resfriamento devido ao aumento do percentual de carbono no aço, quando se compara os dados obtidos para as amostras dos aços 8620 e 8640 / Abstract: Study about the influence of the agitation range and quench severity of the quenchant on cooling times and rates during the quench. The assays were accomplished with samples of steel 1045, 8620 and 8640, water and brine quenched, by increasing the agitation of the quenchant. The data show a rise in the maximum cooling rates of the 27.65% - 110%, and a reduction in the times of cooling of the 7.83% - 63.25%, on the three materials studied, with the increase of the agitation of the quenchant. They were verified too, a gain in the cooling rates and times with the variation of the quenchant severity, water to brine, of 73.27%, without agitation, and reduction of cooling time in approximately 20%. The data still show a gain in the cooling time and rates caused by the percentage of carbon increase on the steel, when be compared with the data scored in the samples of steel 8620 and 8640 / Mestrado / Instrumentação e Controle Industrial / Mestre Profissional em Engenharia Mecanica

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