Evolution of artificial defects during shape rolling

Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs. The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.

Tribology in Metal Working

This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest. The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers. The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.

Impactos econômicos, tecnológicos e sociais do desenvolvimento das pessoas na TV Amazonas, pela Fundação Rede Amazônica - a percepção de diretores, gerentes e funcionários

This research has the objective to present the economic, technological and social impacts on the TV Amazonas' employees development. The study was made based on the perception of directors, managers and old employees of the organization, since the creation of the Rede Amazonica Foundation. The methodical procedures were based on the phenomenologic-hermeneutic approach, using theoretical study, text analysis, documents and interviews. The theoretical referential was based on publications about the history of the television in the world, Brazil and Amazon. It looked at digital television, the importance of the education on people's development and the society, as a whole changes in the labor market, professional qualification; professional education and social responsibility. The results show that employees qualification has contributed directly to the economic, technological and social growth of TV Amazonas.

Estudo do perfil térmico de fornos do tipo "caipira" utilizados pelo setor de cerâmica vermelha em parelhas na região Seridó-RN

The present study aimed to characterize the thermal profile of wood fired oven used by the red ceramic industry in Parelhas, in the Seridó region/RN, aiming to propose structural interventions that can contribute to increasing productivity and product quality, optimize wood consumption and mitigate existing losses during the burning process. The study was conducted at Cerâmica Esperança in the city of Parelhas -RN, Brazil, during the period from August 2012 to September 2013. Four treatments were performed with three replicates, ie, with, a total of 12 experimental units (burnings). In the first stage 4 treatments were performed with three replicates, totaling 12 experimental units (firings). In the second stage 2 treatments were performed with three replications, totaling 6 experimental units (firings). The physical characteristics of the wood were analyzed using standard NBR 11941 and NBR 7190 for basic density and moisture, respectively. The clay was used as a reference parameter for distinguishing treatments. For both the analysis and characterization was carried out using techniques of fluorescence X (XRF) rays, X-ray diffraction (XRD) analysis, particle size analysis (FA). In the first and second stages were monitored: the time during the firing process, the amount of wood used at each firing, the number of parts enfornadas for subsequent determination of the percentages of losses, but also product quality. To characterize the thermal profile of the oven, we measured the temperature at 15 points scored in the surface charge put into the oven. Measurements were taken every 30 minutes from preheat until the end of burning, using a pyrometer laser sight sighting from preheating until the end of burning. In the second step 12 metal cylinders distributed on the oven walls, and the cylinder end walls 8 of the furnace 2 and rollers on each side walls are installed equidistant to 17 cm from the soil and the surface 30 of the wall are installed. The cylinders distributed on the front were placed 50 cm above the furnace, and the base of the oven 20 cm distant from the ground. 10 also thermocouples were installed, and five thermocouples distributed 1.77 cm above the combustion chambers, and one thermocouple on each side, and three thermocouples in front of the oven. We carried out the measurements of the temperatures every 1 hour during the burning two hours in cooling the cylinders with a pyrometer and thermocouples for dattaloger. These were fixed with depth of 30 cm from the wall. After statistical analysis it was found that: the thermal profile of the furnace surface and at different heights was heterogeneous; and the ranges of density and moisture content of wood are within recommended for use as an energy source standards. We conclude that even at low temperatures reached during firing there was a significant production of good quality products, this is due to high concentrations of iron oxide and potassium oxide found in clay, which lowers the melting point of the piece. The average burn time for each step varied 650-2100 minutes wood consumption was on average 20 m3, product quality was on average 16% of first quality, 70% second, third and 5% to 10% loss . The distance between the wire and the surface of the oven was a significant parameter for all treatments, but with different variations, meaning that the wire should not be so generic and unique form, used as a criterion for completion of the burn process. The central part of the furnace was the area that reached higher temperature, and in a unified manner, with the highest concentration of top quality products. The ideal temperature curve, which provided the highest quality of ceramic products was achieved in the central part of the furnace

Influência da corrente de pulso, do tempo de pulso e diâmetro de gota sobre a estabilidade da transferência metálica no processo MIG-P

To obtain a process stability and a quality weld bead it is necessary an adequate parameters set: base current and time, pulse current and pulse time, because these influence the mode of metal transfer and the weld quality in the MIG-P, sometimes requiring special sources with synergistic modes with external control for this stability. This work aims to analyze and compare the effects of pulse parameters and droplet size in arc stability in MIG-P, four packets of pulse parameters were analysed: Ip = 160 A, tp = 5.7 ms; Ip = 300 A and tp = 2 ms, Ip = 350 A, tp = 1.2 ms and Ip = 350 A, tp = 0.8 ms. Each was analyzed with three different drop diameters: drop with the same diameter of the wire electrode; droplet diameter larger drop smaller than the diameter of the wire electrode. For purposes of comparison the same was determined relation between the average current and welding speed was determined generating a constant (Im / Vs = K) for all parameters. Welding in flat plate by simple deposition for the MIG-P with a distance beak contact number (DBCP) constant was perfomed subsequently making up welding in flat plate by simple deposition with an inclination of 10 degrees to vary the DBCP, where by assessment on how the MIG-P behaved in such a situation was possible, in addition to evaluating the MIG-P with adaptive control, in order to maintain a constant arc stability. Also high speed recording synchronized with acquiring current x voltage (oscillogram) was executed for better interpretation of the transfer mechanism and better evaluation in regard to the study of the stability of the process. It is concluded that parameters 3 and 4 exhibited greater versatility; diameters drop equal to or slightly less than the diameter of the wire exhibited better stability due to their higher frequency of detachment, and the detachment of the drop base does not harm the maintenance the height of the arc

Radiografia digital para inspeção de soldas de dutos - melhor sensibilidade

The conventional radiographic technique using industrial radiographic films is with the days finishing. The Digital Radiography is taking place in several sectors, e.g., the medical, aerospace, security, automotive, etc. In addition to representing a technological trend, it has been demonstrated that digital radiography offers a series of benefits in terms of productivity, sensitivity, environmental aspects, image treatment tools, cost reduction, etc. If one weld seam to be inspected is from a serried product, as example a pipe, the best option to be implemented is the Flat Panel Detector with this equipment is possible to reduce the obtaining digital radiographic images in place of films and reducing the inspection cycle time due to its high degree of automation. In the experiments described in this paper this new technique was tested and the results were compared with those obtained by the conventional radiography. The welded specimens were prepared using the submerged-arc welding process and small artificial cracks of the most varied dimensions, present in the specimens, were used to establish a comparison of the sensitivities presented by the techniques employed After conducting several experiments, the digital method presented the highest sensitivity to the wire-type Image Quality Indicator (IQI) and in the detection of small defects, leading to the conclusion that the use of digital radiography using the flat-panel detector offers advantages over the conventional technique [1, 2]. This work was carried out based on the API 5L Edition 2004 [3] and ISO 3183 Edition 2007 [4] specifications.

Debris, Roughness and Friction of Stainless Steel Archwires Following Clinical Use

Objective: To investigate the degree of debris, roughness, and friction of stainless steel orthodontic archwires before and after clinical use.Materials and Methods: For eight individuals, two sets of three brackets (n = 16) each were bonded from the first molar to the first premolar. A passive segment of 0.019- x 0.025-inch stainless steel archwire was inserted into the brackets and tied by elastomeric ligature. Debris level (via scanning electron microscopy), roughness, and frictional force were evaluated as-received and after 8 weeks of intraoral exposure. Mann-Whitney, Wilcoxon signed-rank, and Spearman correlation tests were used for statistical analysis at the .05 level of significance.Results: There were significant increases in the level of debris (P = .0004), roughness of orthodontic wires (P = .002), and friction (P = .0001) after intraoral exposure. Significant positive correlations (P < .05) were observed between these three variables.Conclusion: Stainless steel rectangular wires, when exposed to the intraoral environment for 8 weeks, showed a significant increase in the degree of debris and surface roughness, causing an increase in friction between the wire and bracket during the mechanics of sliding. (Angle Orthod. 2010;80:521-527.)

A televisão e a (re)construção do imaginário : as telenovelas e sua ifluência socioespacial em Caicó-RN

Under the perspective of the Cultural Geografhy, this dissetation thoretically discusses about the socio-spatial interference that the Rede Globo's soapoperas have in the construction of the collective imagination of the people who lines in the city of Caicó - RN. Here the social and spatial impacts produced by Rede Globo's main fiction program, the soapoperas, on the collective imagination of the inhabitants of Caicó are the main interest. The main argument here is that this TV program has an anormons influence on the evereday life of the people who live in Caicó and this influence ends up modifying their social, spatial and cultural pratices. This influence has been also working as the main force producing a real spatial impact. In this sense "new spaces of dialogue" are constructed through the influence of television. The main understandig is then that the soapoperas, at least within the context of Caicó, are a great force constructing social and spatial collective imagination of this city's inhabitants.

Analysis in vitro of direct bonding system with cyanoacrylate ester and orthodontic wires

The aim of this study was to evaluate the tensile strength of orthodontic wires bonded onto the enamel with cyanoacrylate ester. To obtain the specimens, 120 human premolars (extracted for orthodontic or periodontal reasons) were included in acrylic blocks of rapid polymerization with three teeth each. Four groups were formed with ten specimens each. In the specimens, a dental splint model was made with cyanoacrylate ester and round stainless steel wire. In groups I, II and III, cyanoacrylate ester was used with round steel wires, with variation in diameter: 0.014 inches; 0.016 inches and 0.018 inches, respectively. In group IV, round steel wire 0.018 inches was used with photo polymerizing resin composite with previous acid etching. The adhesive force of the materials was measured in two points under the action of the tensiometer (ETM-USA). The number of loose wires was counted along with those that remained fixed according to the different levels of force applied because of the direction of the tensile force (vertical or horizontal) and the diameter of the wire used. The data obtained were first submitted to a descriptive analysis and then submitted to a statistical analysis (Friedman's Test and Dunn's Test of Multiple Comparison - Epi-info 3.2). Within the limitations of the experimental conditions presented, the cyanoacrylate ester or 'Super Bonder (R)' maintained bonded to enamel and steel wires (0.016 and 0.018 inches) during the tensile strength tests under different levels of applied forces.

Temperatura e enriquecimento ambiental sobre o bem-estar de coelhos em crescimento

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

Design, manufacturing, and testing of a Nb3Sn coil employing Ti alloy as structural material

We describe the design, manufacturing, and testing results of a Nb3Sn superconducting coil in which TiAIV alloys were used instead of stainless steel to reduce the magnetization contribution caused by the heat treatment for the A-15 Nb-3 Sn phase formation that affects the magnetic field homogeneity. Prior to the coil manufacturing several structural materials were studied and evaluated in terms of their mechanical and magnetic properties in as-worked, welded, and heat-treated conditions. The manufacturing process employed the wind-and-react technique followed by vacuum-pressure impregnation(VPI) at 1 MPa atm. The critical steps of the manufacturing process, besides the heat treatment and impregnation, are the wire splicing and joint manufacturing in which copper posts supported by Si3N4 ceramic were used. The coil was tested with and without a background NbTi coil and the results have shown performance exceeding the design quench current confirming the successful coil construction.

Electrical properties of individual and small ensembles of InAs/InP nanostructures

We investigate electrical properties of InAs/InP semiconductor nanostructures by conductive atomic force microscopy (C-AFM) and current measurements at low temperatures in processed devices. Different conductances and threshold voltages for current onset were observed for each type of nanostructure. In particular, the extremity of the wire could be compared to a dot with similar dimensions. The processed devices were used in order to access the in-plane conductance of an assembly of a reduced number of nanostructures. Here, fluctuations on I-V curves at low temperatures (<40 K) were observed. At these low temperatures and for a suitable range of applied voltages, random telegraph noise (RTN) in the current was observed for devices with dots. These fluctuations can be associated to electrons trapped in dots, as suggested by numerical simulations. A crossover from a semiconductor-like to a metallic transport behavior is also observed for similar parameters. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

O tempo através das mídias: fotografia, cinema, televisão

Pós-graduação em Artes - IA

A digitalização da televisão pública: um estudo do caso da multiprogramação na TV Cultura

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

Televisão digital: interação e usabilidade

Pós-graduação em Comunicação - FAAC