Thesis (M.S.)--University of Michigan, 1977.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Christopher H. M. Jenkins. Includes bibliographical references (leaves 59-61).

Thesis (M.S.)--University of Michigan, 1977.

Orientador: Jose Roberto Lovadino / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-13T11:05:09Z (GMT). No. of bitstreams: 1 Alexandre_RodrigoSversutde_M.pdf: 5656736 bytes, checksum: 13f53feb57ad1569d4d4d53ef1d4e6b6 (MD5) Previous issue date: 2009 / Resumo: O objetivo deste estudo foi avaliar a influência da temperatura do adesivo na resistência à microtração (µT) de um convencional de frasco único, Primer &Bond NT(PBNT) e dois adesivos autocondicionante,Clearfil SE Bond (SEB) e Adper Prompt L-Pop (PLP). Adicionalmente, foram analisados o padrão de condicionamento (PC) e a interface resina-esmalte (IRE). Foram utilizados 63 dentes bovinos divididos em 3 grupos (n=21) de acordo com o adesivo. Cada grupo foi subdividido em 3 sub-grupos de acordo com a temperatura do adesivo (NORM = 20°C; FRIO = 5°C; QNT = 40°C). Os dentes tiveram sua face vestibular média planificada com lixas de granulação 320, 400 e 600 de SiC e abrasionada com uma ponta diamantada por 10s. Os sistemas adesivos foram aplicados segundo as instruções do fabricante e a resina composta em incrementos 2mm de espessura. Cada incremento foi polimerizado por 40s. Em seguida, os espécimes foram cortadas no sentido mésio-distal, sendo a metade cervical destinada a análise da interface e a incisal destinada ao teste de µT , realizado em máquina de ensaio universal. Para cada espécime, 4 amostras do tipo "Hour Glass" foi testado e o padrão de fratura avaliado. Para o PC foram confeccionados 2 blocos para cada subgrupo (14), os quais receberam o mesmo tratamento de superfície dos espécimes utilizados para o teste de µT, porém as superfícies foram lavadas após a aplicação da solução ácida . Para a análise da interface, estas foram polidas e limpas através da aplicação de plasma de argônio e foram, juntamente com os espécimes do padrão de condicionamento, preparados para visualização em MEV. Os valores de resistência à µT foram analisados pelo teste ANOVA/Tukey (p<0,05). Na temperatura NORM não houve diferença estatística entre os adesivos, porém no FRIO a resistência à µT dos adesivos PBNT e PLP foram menores que a do SEB. Na temperatura QNT houve uma redução na resistência à µT dos adesivos SEB e PLP. Dentro de cada adesivo, o SEB aquecido, foi o único que reduziu sua resistência. O padrão de fratura mostrou maior incidência de fraturas coesivas em esmalte para o adesivo PBNT. Porém, os adesivos autocondicionantes mostraram uma predominância de fraturas adesivas/ coesivas e adesivas. O aspecto da interface e do padrão de condicionamento foi dependente da temperatura e do adesivo. O grupo PLP foi o que mais se aproximou do grupo com condicionamento ácido prévio, porém apenas na temperatura ambiente. Através dos resultados deste estudo, pode-se concluir que os adesivos autocondicionantes apresentam menor agressividade de desmineralização em relação ao ácido fosfórico e são influenciados pela alteração da temperatura. / Abstract: This study evaluated the influence of adhesive temperature on microtensile (µT) bond strength of a total-etch adhesive, Primer&Bond NT (PBNT) and two self-etching adhesives, Clearfil SE Bond (SEB) and Adper Prompt L-Pop (PLP). Additionally, the etch patterns (EP) and resin-enamel interface were analyzed. Sixty-three bovine incisors were randomly divided into 3 experimental groups (N=21) according to the adhesive. Each group was subdivided into 3 sub-groups according to the temperature (NORM = 20°C; FRIO = 5°C; QNT = 40°C). The buccal enamel surfaces were flattened with 320, 400, 600-grit SiC paper and abrasioned with a diamond bur for 10s under water coolant. The adhesive were applied according to the manufacturers' instructions and resin was incrementally placed in 2mm thick. Each resin increment was light cured for 40s. The specimens were sectioned in the middle. For the µT test was used incisal center, accomplished in a universal testing machine, 4 "hour glass" type specimens were tested, after was fractures type classified. The cervical middle was used for interface analyze. The sections were polished and cleanned with Argon Plasma. For the EP, 24 fragments received the same treatment of the specimens used for µT, but the surface was rinsed off after the application of the acidic solutions. EP and interface analyze were examined under a scanning electron microscope (SEM). The bond strength data were analyzed by ANOVA/Tukey test (p<5%). No significant differences were found for NORM adhesives. However, for FRIO, PBNT and APLP presented the lower bond strength means significantly differing from SEB. For QNT, the SEB and PLP presented the lowest bond strength means. Within each adhesive, the SEB used in a QNT, was the only one to present a reduction in a bond strength. There was a more enamel cohesive fracture type to PBNT. However, the self-etching adhesive presented adhesive/cohesive fracture types. The interface aspect was temperature and adhesive depended. When the APLP was applied in normal temperature there was greater similarity with the group PBNT. The result of this study was concluded that the self-etching showed a least aggressive etch patterns in relation to the Phosphoric acid and temperature change influenced adhesive µT bond strength and EP. However, they were adhesive and temperature dependent. / Mestrado / Dentística / Mestre em Clínica Odontológica

The purpose of the present study is to determine the effect of three "non-rinse" washing compounds upon the tensile strength of cotton percale, in order to have some basis for recommendation as to use when teaching laundering to homemaking students and homemakers.

OBJECTIVE: To evaluate if the firing cycles and etching conditions have an effect on the tensile bonding strength (TBS) of IPS e.max-CAD and CeltraDUO. METHODS: Lithium-disilicate (IPS e.max-CAD) ceramic blocks and zirconia reinforced lithium-disilicate (CeltraDUO) were sectioned into rectangular tiles. The tiles were randomly assigned to various treatment groups and heat treated (1, 5, or 9 firing cycles) or (0, 1 or 5 firing cycle) respectively. e.max-CAD and CeltraDUO tiles were etched for different times (20,160, 300 seconds) and (20, 50, 80 seconds) respectively with hydrofluoric-acid gel (9.6% or 5%). Titanium-pins were sand-blasted on the flat end and cemented on the etched tiles using self-adhesive resin cement (TheraCem). A vertical load of 12N was placed for 40 minutes. All the cemented specimens were stored in incubator at 37°C for 48 hours. A tensile test was performed using a mechanical testing machine (Instron-5566A). The load at failure was recorded and the TBS was calculated. The same procedure was followed on another set of 18 e.max-CAD (fired for 5 firing cycles) and 21 CeltraDUO tiles (fired for 1 firing cycle). The same cementation procedure was followed and TBS was calculated. RESULTS: The TBS of both CeltraDUO and e.max-CAD was significantly affected by etching duration and firing cycles (p<0.001), but not significantly affected by etchant concentration (p=0.31). The highest load to failure was observed around 50 and 60 seconds of etching respectively. CONCLUSION: The etching time and firing cycle directly affect the TBS of both materials whereas the etchant concentration does not. / 2021-07-15T00:00:00Z

The purpose of this study was to examine the influence of content of a copovidone binder (0%, 5% and 10% w/w) and its addition method on compression and compaction properties of six MCCformulations following dry granulation. Briquetting was used to form dry granules for furthercharacterization. The mean yield pressure and fracture strength of granules were assessed at 300MPa on the basis of “in-die” Heckel and Adams model respectively. Then tablet tensile strengthof manufactured tablets was determined at 100 and 300 MPa. The results demonstrated thatintragranular addition of further binder (10%) to MCC could increase plasticity. However, therewas a drastic reduction in compactibility of dry granules mostly impacted by binding capacity ofthe binder. Generally, 5% intragranular:5% extragranular binder under a compaction pressure of300 MPa had the greatest binder efficacy on strength of pure MCC tablets while 10%extragranular binder improved tensile strength significantly at 100 MPa. PVP in a level of 5%w/w had no significant impact on tensile strength of tablets compacted at 100 and 300 MPa.

abstract: Materials have been the backbone of every major invention in the history of mankind, e.g. satellites and space shuttles would not exist without advancement in materials development. Integral to this, is the development of nanocrystalline (NC) materials that promise multitude of properties for advanced applications. However, they do not tend to preserve structural integrity under intense cyclic loading or long-term temperature exposures. Therefore, it is imperative to understand factors that alter the sub-features controlling both structural and functional properties under extreme conditions, particularly fatigue and creep. Thus, this dissertation systematically studies the tensile creep and fatigue behaviour of a chemically optimized and microstructurally stable bulk NC copper (Cu)-3at.% tantalum (Ta) alloy. Strategic engineering of nanometer sized clusters of Ta into the alloy’s microstructure were found to suppress the microstructure instability and render remarkable improvement in the high temperature tensile creep resistance up to 0.64 times the melting temperature of Cu. Primary creep in this alloy was found to be governed by the relaxation of the microstructure under the applied stress. Further, during the secondary creep, short circuit diffusion of grain boundary atoms resulted in the negligible steady-state creep rate in the alloy. Under fatigue loading, the alloy showed higher resistance for crack nucleation owing to the inherent microstructural stability, and the interaction of the dislocations with the Ta nanoclusters. The underlying mechanism was found to be related to the diffused damage accumulation, i.e., during cyclic loading many grains participate in the plasticity process (nucleation of discrete grain boundary dislocations) resulting in homogenous accumulation rather than localized one as typically observed in coarse-grained materials. Overall, the engineered Ta nanoclusters were responsible for governing the underlying anomalous high temperature creep and fatigue deformation mechanisms in the alloy. Finally, this study presents a design approach that involves alloying of pure metals in order to impart stability in NC materials and significantly enhance their structural properties, especially those at higher temperatures. Moreover, this design approach can be easily translated to other multicomponent systems for developing advanced high-performance structural materials. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2019

A bonding evaluation that investigated the cryogenic tensile strength of several different adhesives / resins was performed. The test materials consisted of 6061 aluminum test pieces adhered to a wet-wound graphite laminate in order to simulate the bond created at the liner-composite interface of an aluminum lined composite overwrapped pressure vessel. It was found that for cryogenic applications, a flexible, low modulus resin system must be used. Additionally, the samples prepared with a thin layer of cured resin - or prebond - performed significantly better than those without. It was found that it is critical that the prebond surface must have sufficient surface roughness prior to the bonding application. Also, the aluminum test pieces that were prepared using a surface etchant slightly outperformed those that were prepared with a grit blast surface finish and performed significantly better than those which had been scored using sand paper to achieve the desired surface finish. An additional impact investigation studied the post impact tensile strength of composite rings in a cryogenic environment. The composite rings were filament wound with several combinations of graphite and aramid fibers and were prepared with different resin systems. The rings were subjected to varying levels of Charpy impact damage then pulled to failure in tension. It was found that the addition of elastic aramid fibers with the carbon fiber mitigate the overall impact damage and drastically improve the post impact strength of the structure in a cryogenic environment.

Traditionally it was thought that the unidirectional strength in the fiber direction of fiber dominated composites was not influenced by the matrix material. As long as the fiber was not affected then the strength would remain. However this thesis will challange that belief. The unidirectional strength in the fiber direction of fiber dominated composites is influenced by the matrix material. The object of this study was to examine the quasi-static tensile strength of unidirectional polymer composites, and then use current analytic models to predict the experimental results. The different matrix materials were polyphenylene Sulfide (PPS), vinyl ester with two different fiber-matrix interface materials, and polyether ether ketone (PEEK). / Master of Science