Potential of bamboo organosolv pulp as a reinforcing element in fiber-cement materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nonlinear formulation based on FEM, Mazars damage criterion and Fick's law applied to failure assessment of reinforced concrete structures subjected to chloride ingress and reinforcements corrosion

Structural durability is an important design criterion, which must be assessed for every type of structure. In this regard, especial attention must be addressed to the durability of reinforced concrete (RC) structures. When RC structures are located in aggressive environments, its durability is strongly reduced by physical/chemical/mechanical processes that trigger the corrosion of reinforcements. Among these processes, the diffusion of chlorides is recognized as one of major responsible of corrosion phenomenon start. To accurate modelling the corrosion of reinforcements and to assess the durability of RC structures, a mechanical model that accounts realistically for both concrete and steel mechanical behaviour must be considered. In this context, this study presents a numerical nonlinear formulation based on the finite element method applied to structural analysis of RC structures subjected to chloride penetration and reinforcements corrosion. The physical nonlinearity of concrete is described by Mazars damage model whereas for reinforcements elastoplastic criteria are adopted. The steel loss along time due to corrosion is modelled using an empirical approach presented in literature and the chloride concentration growth along structural cover is represented by Fick's law. The proposed model is applied to analysis of bended structures. The results obtained by the proposed numerical approach are compared to responses available in literature in order to illustrate the evolution of structural resistant load after corrosion start. (C) 2014 Elsevier Ltd. All rights reserved.

Avaliação de juntas soldadas em tubos de aço carbono submetidos a altas temperatura e pressões

The welding process in industrial piping is still the most effective way to ensure the durability and quality of the wide range of industrial process, although because of the high demand for energy and quality of the produced products, the piping has been constantly tested for high pressure applications and still high temperature. The welding method analyzed is the TIG (Tungsten Inert Gas) welding or GTAW (Gas-Shielded Tungsten Arc Welding), which ones have as principal feature the utilization of a not consumable tungsten electrode in the torch extremity , in this process is necessary a protective atmosphere of inert gas. The welding TIG advantage is the obtaining of a welded seam clean and with quality for not has slag after the welding. This work has as objective show the variability in the carbon steel piping welding parameters and by the tests in four proof bodies will be shown the influence of the variation of the welding methods in a welded seam. The tests will vary since the piece to be welded preparation, till penetrating liquid tests, welding macrography, welding x-ray and traction tests. Even been a clean and with quality welding is necessary a final inspection in the seam welded looking for defects almost inevitable resulted of the welded process, the obtained results have the objective of indicate and minimize the defects to ensure quality and durability of the welded seam

Durabilidade da argamassa mista de revestimento interno contendo dregs-grits em substituição à areia

This paper concerns about the durability of new material in construction. It is noteworthy the fact that increases increasingly searching for alternative materials that do not depend only of natural resources and at the same time be an alternative for reuse of industrial waste. Since the construction materials have a long life and a high cost of civil works and maintenance, it is crucial to estimate the behavior of a new product. Thus , this work discuss the durability of mixed mortar lining , made with waste from the process Kraft pulp production , known as dregs and grits , in partial replacement of sand. Tests were conducted to simulate conditions as adverse environments of constant heat and fire, with the aim of analyzing the behavior of mortar mixed matched the behavior of standard mortar

Biodegradação de materiais poliméricos por fungos filamentosos

The use of polymeric materials has grown in recent years due to its high durability features, atoxicity, shaping versatility and environment resistance. However, while these features represent good advantages to several industry sectors, it results in one of the most serious environmental problems of contemporary society: the rising accumulation of these material, mainly due to the inadequate disposal of waste. Meanwhile, in order to minimize this problem, some mitigation techniques comes up (arises), among which the use of biodegradable polymers has been gaining attention. Because of their easily action of microorganisms, such material degrade more rapidly, becoming integrated to nature. Furthermore, due to the fact of biodegradation is a natural process, occurring through the action if micro-organisms in the environment itself, it is considered the “cleaner” alternative found so far to plastic components reincorporation in the nature. Among the micro-organisms capable of biodegradation process are the filamentous fungi. These micro-organisms have many advantages over the others, the major one being the capacity to produce a range of enzymes capable of degrading different materials. In this context, the present review made it possible to see the importance of this process as an agent of environmental preservation, suggest the use of blends to minimize the problems of cost and flexibility of biodegradable polymeric materials, as well as noting the lack of studies related to this subject nowadays

Avaliação da colagem de suportes utilizados para fixar cabos elétricos em aeronaves

The most usual method to fix supports that hold the vast majority of electrical cables on an aircraft is accomplished by using, for this purpose, rivets. However, this procedure may some cause some inconveniences such as the need of effecting holes in the structure that is intended to fix these supports, thus decreasing resistance of the structure. In order to have an alternative to seek an increase in the performance of structured materials, the aircraft industry, like other industries, have been studying the use of collage as a method of replacing this usual forms. Against this backdrop, this paper aims to assess the strength and durability of a joint bonded using the adhesive EA9394, manufactured by company Henkel Corporation, and perform a careful survey of the mechanical performance of riveted structures, taking into account different types of conditioning environment and thus create a database that can be used by the aerospace industry

Desenvolvimento de um equipamento para análise de desgastes em prótese de articulação total de quadril

Pós-graduação em Engenharia Mecânica - FEG

Análise do comportamento do desgaste de dressadores de ponta única confeccionados com diamantes naturais e sintético piramidais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Transmission enhancement in chalco-halide glasses for multiband applications

The potential of clear Ga2S3-GeS2-CsCl based sulfide glasses transparent up to 11.5 μm to be used as new optical material for multispectral applications has been investigated. The addition of large amount of chlorine ions – above 40 mol.% of CsCl – into the chalcogenide vitreous network in order to produce colorless glasses results in a drastic increase of their water contamination. We report for the first time, to the best of our knowledge, the purification of cesium chloride CsCl by dynamic distillations under vacuum in order to reduce water and hydroxyl group contamination before complete melting of the glass. Besides, sulfur purification by dynamic and static distillations was also performed in the implemented method. The obtained glasses were then characterized by UV-visible and infrared (FTIR) spectroscopies, by electron probe microanalysis (EPMA), thermal analysis (DSC), and their refractive indices in the visible and near infrared ranges were also measured. A large improvement of the glass transmission spectrum has been achieved with an estimated reduction of about 45 times of the OH and H2O content and 60 times of the SH content. The glass thermal molding ability and chemical durability with and without protective coating have been tested to probe their potential for fabrication of complex optics.

Concreto com adição de cinza de bagaço de cana-de-açúcar

Pós-graduação em Engenharia Civil - FEIS

Identidade e estudos organizacionais: em direção a um novo paradigma?

This paper aimes to contribute to the analyzes of Caldas and Wood Jr (1997) concerning to the concept of identity. That concept has been developed in Organization Studies under the propositions of Albert and Whetten (1985). In that way, identity concept has been defined by the following characteristics: centrality, distinctiveness and continuity. Nevertheless, a new paradigm has been emerging within social science. In this paper, we present a synthesis on how the concept of identity has been discussed in Social Psychology and Cultural Studies. For both theoretical perspectives, the ideas of centrality and durability are put into doubt, as identity is seen as dynamic and fragmentary. Besides that, we intend to show how the new paradigm is getting formed within Organizational Studies, especially considering international context. Considering that the emerging organizational ideas concerning identity show proximity with those proposed by Social Psychology and Cultural Studies, we raise possible questions that the new paradigm will have to face.

Redução do medo durante o tratamento odontológico utilizando pontas ultrassônicas

Over the last few years, new technologies have been developed to making cavity preparations, among which the diamond burs CVDentus® (CVDentus, São José dos Campos, Brazil) are outstanding. These points are produced by chemical deposition from the vapor phase, forming a single diamond stone, with greater durability than the conventional diamond burs. Coupled to the ultrasound appliance, they have several clinical applications in Dentistry with advantages over conventional rotary instruments, such as lower pressure, noise, vibration and heat, as well as reducing the need to use local anesthesia, contributing to minimize patient’s fear and anxiety. The aim of this study was to present the complete restorative dental treatment performed with this system in a child patient with a prior history of non-cooperative behavior. The use of this new technology offered the patient greater comfort, making it possible recondition the patient’s attitude to dental treatment, in addition to favoring conservative cavity preparations to be made.

Immediate human pulp response to ethanol-wet bonding technique

To evaluate the short-term response of human pulps to ethanol-wet bonding technique. Methods Deep class V cavities were prepared on 17 sound premolars and divided into three groups. After acid-etching, the cavities from groups 1 (G1) and 2 (G2) were filled with 100% ethanol or distilled water, respectively, for 60 s before the application of Single Bond 2. In group 3 (G3, control), the cavity floor was lined with calcium hydroxide before etching and bonding. All cavities were restored with resin composite. Two teeth were used as intact control. The teeth were extracted 48 h after the clinical procedures. From each tooth serial sections were obtained and stained with haematoxylin and eosin (H/E) and Masson's trichrome. Bacteria microleakage was assessed using Brown & Brenn. All sections were blindly evaluated for five histological features. Results Mean remaining dentine thickness was 463 ± 65 μm (G1); 425 ± 184 μm (G2); and 348 ± 194 μm (G3). Similar pulp reactions followed ethanol- or water-wet bonding techniques. Slight inflammatory responses and disruption of the odontoblast layer related to the cavity floor were seen in all groups. Stained bacteria were not detected in any cavities. Normal pulp tissue was observed in G3 except for one case. Conclusions After 48 h, ethanol-wet bonding does not increase pulpal damage compared to water-wet bonding technique. Clinical significance Ethanol-wet bonding may increase resin-dentine bond durability. This study reported the in vivo response of human pulp tissue when 100% ethanol was applied previously to an etch-and-rinse simplified adhesive system.

Análise estrutural de tubos de concreto armado com resíduo de borracha de pneu

Pós-graduação em Engenharia Civil - FEIS

Longitudinal evaluation of bond strength to enamel of dental adhesive systems associated with Nd:YAG laser

Objectives: This study evaluated the durability of bond strength to enamel using total-etch (Single Bond/SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with neody-mium: yttrium-aluminu- garnet (Nd:YAG) laser irradiation through the uncured adhesives.Methods: Bovine incisors were worn to expose an area of enamel and were divided into four groups: group 1 (control) SB + polymerization; group 2 (control) CSEB + polymerization; group 3 (laser) - B + Nd:YAG laser (174.16 J/cm(2)) + polymerization; and group 4 (laser) CSEB + Nd:YAG (174.16 J/cm(2)) + polymerization. Blocks of composite were fabricated and stored for 24 hours or 12 months, sectioned into beams, and submitted to microtensile tests. Results were analyzed by three-way analysis of variance (ANOVA) (adhesive, technique, and storage time) and Tukey tests.Results: ANOVA revealed significant differences for adhesive 3 technique and technique 3 storage time (p<0.05). The mean values (MPa) for interaction adhesive x technique (standard deviation) were as follows: SB/control = 35.78 (6.04)a; SB/laser = 26.40 (7.25)b, CSEB/control = 26.32 (5.71)b, CSEB/laser = 23.90 (7.49)b. For interaction technique x storage time the mean values were as follows: control/24 hours = 32.58 (6.49)a; control/12 months = 29.52 (8.38)a; laser/24 hours = 29.37 (5.71)a; laser/12 months = 20.92 (6.5)b. Groups with the same letters showed no statistically significant differences.Conclusion: Scanning electron microscope analysis showed evident areas of micromorphological alterations in lased samples after 12 months of water storage. Nd: YAG laser irradiation of enamel through unpolymerized totaletch adhesive significantly reduced bond strength compared with the control. Bond strength decreased when enamel samples irradiated with Nd: YAG laser through unpolymerized adhesives were stored in water for 12 months.