Journal articles: 'EXTRUSÃO DE TUBOS'

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Souza, Shamon H. F., Fernando A. Silva, and Eliane C. Vilela. "Uso de Carbonato de Cálcio na Formulação de Tubos de PVC Rígido." Revista Processos Químicos 3, no. 6 (July 1, 2009): 42–47. http://dx.doi.org/10.19142/rpq.v03i06.p42-47.2009.

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O trabalho consistiu em avaliar o desempenho de dois tipos de carbonato de cálcio (um de origem mineral e outro de origem cretácea) utilizados na formulação de tubos de PVC rígido. Os tubos foram produzidos pelo processo de extrusão e o desempenho do material foi analisado com a realização de testes de controle de qualidade propostos pela ABNT. Os resultados dos testes de qualidade foram bem mais satisfatórios nos tubos que possuíam em sua composição o carbonato de origem cretácea. Para verificar as diferenças existentes entre os carbonatos foi realizada uma análise de difratometria de raios-X, que indicou conformações cristalinas romboédrica e monoclínica para os carbonatos de origem cretácea e mineral, respectivamente. A possível existência de “cantos vivos” na conformação monoclínica do carbonato mineral e consequentemente a formação de espaços vazios na estrutura do polímero teriam causado os resultados negativos nos testes de qualidade do produto final.

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Alves, Juliana P. D., and Antonio Rodolfo Jr. "Análise do processo de gelificação de resinas e compostos de PVC suspensão." Polímeros 16, no. 2 (June 2006): 165–73. http://dx.doi.org/10.1590/s0104-14282006000200018.

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Este artigo busca analisar a relação existente entre o grau de gelificação de compostos de PVC rígido (U-PVC) durante seu processamento e as propriedades mecânicas finais dos produtos obtidos através do processo de extrusão de tubos. Para tanto, a morfologia das resinas de PVC é analisada a fim de se entender seu desenvolvimento ao longo da extrusão e entender sua influência na gelificação já que o desempenho do produto dependerá dessa influência. O desenvolvimento morfológico, devido às condições de processamento e ambiente termo-mecânico, bem como alguns testes como microscopia eletrônica de varredura para monitorar esse desenvolvimento são descritos. O grau de gelificação e sua quantificação são analisados utilizando reometrias de torque, rotacional e capilar, utilizando análises térmicas (DSC) e utilizando imersão em solvente (cloreto de metileno).

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Wruck, Emerson, Lidiane J. Michelini, Pedro H. S. de Paula, Carlos A. S. Júnior, Danilo M. dos Santos, and Ítalo L. Fernandes. "Aplicação da Metodologia “Medidor R&R” em processos de extrusão." Revista Processos Químicos 3, no. 5 (January 2, 2009): 73–82. http://dx.doi.org/10.19142/rpq.v3i5.89.

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O trabalho consistiu em avaliar a capacidade do sistema de medição de um processo de extrusão de tubos de PVC pela metodologia medidor R & R, apoiado pelas cartas do controle estatístico do processo. No experimento realizado, foi constado que grande parte da variabilidade total do processo estava associada à capacidade de medição dos operadores. Foram identificados através da metodologia quais os operadores apresentavam mais dificuldades, além de hábitos de medição inadequados. Dessa forma sugeriu-se um programa de treinamento em medição direcionado, aferição periódica de equipamentos e avaliação constante da capacidade de medição pela metodologia exposta, visando à redução da variabilidade, como conseqüência a diminuição das perdas.

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Rodrigues, A. M., and E. S. Loureiro. "CONFECÇÃO DE UMA COLEÇÃO DE FUNGOS ENTOMOPATOGÊNICOS COM ISOLADOS ENCONTRADOS EM CULTURAS AGRÍCOLAS E AMBIENTES DE PRESERVAÇÃO AMBIENTAL EM MATO GROSSO DO SUL." Arquivos do Instituto Biológico 76, no. 2 (June 2009): 303–6. http://dx.doi.org/10.1590/1808-1657v76p3032009.

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RESUMO Com o avanço do desmatamento, a prática de culturas agrícolas não planejadas e a utilização de defensivos agrícolas tóxicos ao meio ambiente, estima-se que grande parte da diversidade de fungos entomopatogênicos presente no meio ambiente esteja sendo alterada. A preservação na forma de coleção de culturas é uma prática de fundamental importância para a manutenção da biodiversidade destes micro-organismos. Este trabalho objetivou a coleta sistematizada de amostras de solo e de insetos mortos e moribundos que apresentassem a extrusão do patógeno ou com características da doença, em culturas agrícolas e área de preservação ambiental. Os insetos coletados foram identificados e levados para o laboratório, onde se isolou o patógeno em meio de cultura BDA. As placas foram mantidas em B.O.D. a 25± 1° C, 70 ± 10% UR e fotofase de 12 horas, durante 7 dias. Após a obtenção de culturas puras, os conídios foram retirados por meio de raspagem com alça metálica, armazenados em tubos plásticos do tipo Eppendorf, e mantidos em freezer a -4º C. Até o momento foram isolados os fungos entomopatogênicos: Beauveria bassiana, parasitando Lagria villosa (UFGD 01), Hypothenemus hampei (UFGD 06 e UFGD 11), um inseto da família Crisomellidae (UFGD 02) e do solo (UFGD 16); o fungo Metarhizium anisopliae parasitando Zulia entreriana (UFGD 05), Mahanarva fimbriolata (UFGD 03), M. posticata (UFGD 07) e do solo (UFGD 12); Paecilomyces fumosoroseus atacando um inseto da família Scarabaeidae (UFGD 04), Lagria villosa (UFGD 13) e do solo (UFGD 09 e 15); P. farinosus isolado a partir do solo (UFGD 08) e o fungo Nomuraea rileyi parasitando a lagarta Anticarsia gemmatalis (UFGD 14).

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Hu, Hong Jun, Zhao Sun, and Ding Fei Zhang. "Effects of Extrusion-Shear and Direct Extrusion on the Plastic Deformation of AZ31 Magnesium Alloy." Materials Science Forum 913 (February 2018): 176–81. http://dx.doi.org/10.4028/www.scientific.net/msf.913.176.

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Based on characteristics of direct extrusion for magnesium alloy seamless tube and continuous equal channel angular pressing (ECAP) of tubes, a new composite extrusion process of tubes including direct extrusion and many steps ECAP was invented firstly, which are shorten for TES process in this paper. A three-dimensional finite element thermo-mechanical coupled model and conditions for TES process were established. The extrusion process and cumulative strains evolution during TES process were simulated. The results show that TES process can improve the cumulative strains significantly. The microstructures observations of longitudinal sections for tubes fabricated by direct extrusion and TES process were carried out. It was found that when the extrusion temperature was 400°C, and extrusion ratio was 8.4 and the channel angle was 150°, TES process can refine the microstructures of tubes effectively.

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Gibb, Alan G., and Ian J. Mackenzie. "The Extrusion Rate of Grommets." Otolaryngology–Head and Neck Surgery 93, no. 6 (December 1985): 695–99. http://dx.doi.org/10.1177/019459988509300601.

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A prospective study was performed to determine the factors Influencing the extrusion rate of tympanostomy tubes. Nine hundred thirty-nine tubes were inserted In 589 patients and the extrusion of these tubes was reviewed up to a period of 27 months. The eight tubes used in the survey were the Shepard, Exmoor, Bobbin, Armstrong, Paparella, Shah, Arrow, and collar button. These tubes were inserted In strict rotation, the operator using the designated tube. The position, type of incision, presence of fluid, quality of tympanic membrane, and degree of difficulty of insertion were all recorded at operation. The sex, age, side of operation, and any simultaneous operative procedures were also recorded. The patients were reviewed the day after operation and then every 3 months thereafter until the tube was extruded. A definite pattern was Identified for the extrusion of each type of tube. At one end of the spectrum, Exmoor and Shepard tubes were, for the most part, extruded between 6 and 9 months after Insertion, while at the other end, most of the collar button tubes were still functioning at 18 months. The design of the tube was the only factor found to be a significant determinant of the extrusion of the tube, although the experience of the surgeon affected the extrusion rate of the Arrow tube. The different dimensions of the Exmoor and collar button tubes are examined and compared.

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Wang, Ying Xin, Xiao Qin Zeng, Wen Jiang Ding, Alan A. Luo, and Anil K. Sachdev. "Development and Validation of Extrusion Limit Diagram for AZ31 and AM30 Magnesium Alloys." Materials Science Forum 546-549 (May 2007): 327–32. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.327.

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Uniaxial hot compression tests were performed at constant temperature (T) and strain rate (ε& ) in the ranges of 200-500 °C at an interval of 50 °C and 0.001-20 s-1. The flow stress data were used to develop the extrusion limit diagram for AZ31 and AM30 magnesium tubes. The extrusion limit diagram shows a wide region available for extruding AZ31 and AM30 seamless tubes, and comparison of the two extrusion limit diagrams shows that, the extrudability of AM30 alloy is better than that of AZ31 alloy. Actual extrusion trials validated the predicted temperature rise limit curve corresponding to the occurrence of surface cracking during the extrusion process. Magnesium tubes were successfully extruded according to the safe regions identified by the extrusion limit diagram.

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Furushima, Tsuyoshi, Tetsuhide Shimizu, and Kenichi Manabe. "Grain Refinement by Combined ECAE/Extrusion and Dieless Drawing Processes for AZ31 Magnesium Alloy Tubes." Materials Science Forum 654-656 (June 2010): 735–38. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.735.

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Grain refinement processing by severe deformation, combined equal-channel angular extrusion (ECAE) processing and conventional tube extrusion, is applied to AZ31 magnesium alloy. By a combination of ECAE processing and tube extrusion, a fabricated tube, with outer and inner diameters of 2 mm and 1 mm, respectively, has fine, homogeneous, and equiaxed grain structure with an average grain size of 1.5m. Tensile test results indicate that the fine-grained tubes exhibited a superplasticity potential m value of 0.55.The maximum elongation (688%) is obtained at a temperature of 673K. Furthermore, the tubes fabricated by combined ECAE/extrusion process is applied to dieless drawing process without using any tool and die.As a result, dieless drawing limit is enhanced due to high m value achieved by combined ECAE/Extrusion process. From these results, the effectiveness of new grain refinement processing for fabricating fine-grained tubes and its application for dieless drawing process to fabricate the fine tubes was demonstrated experimentally.

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Hussain, S. S. M. "Extrusion Rate of Shah and Shepard Ventilation Tubes in Children." Ear, Nose & Throat Journal 71, no. 6 (June 1992): 273–75. http://dx.doi.org/10.1177/014556139207100606.

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Shah and Shepard ventilation tubes are the two most commonly used ventilation tube in current practice. In some centres these two tubes are used interchangeably, in others the Shepard is often used as the first ‘grommet’ of insertion and the Shah for subsequent insertions. A study was undertaken of extrusion rate of these ventilation tubes in 180 children who had surgery for Serous otitis media in 1987. Extrusion time was found to be very significantly different between these tubes. The Shah ventilation tube remains in situ 3 months longer than the Shepard. A case is made for the use of Shah ventilation tubes as the first “grommet” of insertion. Otorrhoea following insertion of ventilation tube did not affect the extrusion rate of ventilation tubes in this study. Nor has otorrhoea a predilection for any particular ventilation tube.

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Sahmel, Olga, Stefan Siewert, Klaus-Peter Schmitz, Daniela Arbeiter, Niels Grabow, Christine Friederike Kreiner, and Rudolf Guthoff. "Extrusion as a manufacturing process for polymer micro-tubes for various bio-medical applications." Current Directions in Biomedical Engineering 5, no. 1 (September 1, 2019): 489–91. http://dx.doi.org/10.1515/cdbme-2019-0123.

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AbstractIn various biomedical applications extrusion represents a common manufacturing process for polymeric semi-finished products. Extrusion allows the processing of a wide range of biomaterials, as well as different cross-sectional geometries. The present work focuses on the development of an extrusion process for polymer micro-tubes used for medical devices manufacturing, e.g. microstents for minimally invasive glaucoma therapy. Semi-finished products were manufactured by means of extrusion and dip-coating. Morphology was investigated using biaxial laser measurement and scanning electron microscopy (SEM). For the analysis of mechanical and thermal properties of the specimens uniaxial tensile testing and differential scanning calorimetry (DSC) were performed. While dip-coated micro-tubes reveal a smooth and homogeneous surface, SEM micrographs of extruded micro-tubes exhibit some longitudinal grooves. Mechanical properties of extruded and dip-coated micro-tubes are comparable, so that the presented extrusion process can be regarded suitable for the manufacturing of polymer microtubes in a sub-millimeter scale. A future improvement of nozzle design will allow for a smooth surface of extruded semi-finished products.

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Huang, Song Jeng, Yeong-Maw Hwang, and Y. S. Huang. "Grain Refinement of AZ61/SiCp Magnesium Matrix Composites for Tubes Extruded by Hot Extrusion Processes." Key Engineering Materials 528 (November 2012): 135–43. http://dx.doi.org/10.4028/www.scientific.net/kem.528.135.

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Magnesium (Mg) alloys are gaining more recognition as a lightest structural material for light-weight applications, due to their low density and high stiffness-to-weight ratio. Nevertheless, their ductility is still not good for further metal forming and their strength is not large enough for real structure applications. The aim of this paper is to develop new magnesium metal matrix composites (Mg MMCs) reinforced with SiC particles by the stir-casting method for the hot extrusion processes to produce tubes. AZ61/SiCp MMCs ingots reinforced with 1, 2, and 5 wt% SiC particles are fabricated by the melt-stirring technique. AZ61/SiCp MMCs tubes are manufactured by hot extrusion using a specially designed die-set for obtaining uniform thickness distribution tubes. Finally, the mechanical properties of the reinforced AZ61/SiCp MMCs and Mg alloy AZ61 tubes are compared with those of the billets to manifest the advantages of extrusion processes and addition of SiC particles. The microstructures of the billet and extruded tubes are also observed. Obvious grain size refinement both by addition of particles and extrusion process are discovered.

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Ge, Qiang, and Maurizio Vedani. "Processing of Wrought Magnesium Alloys to Produce Small Tubes for Biomedical Applications: Investigation about the Extrusion Process by a Laboratory Test Rig." Key Engineering Materials 491 (September 2011): 75–80. http://dx.doi.org/10.4028/www.scientific.net/kem.491.75.

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Two commercial ZM21 and AZ31B alloys were extruded into small-size tubes at 410°C and strain rate 2.78·10-3 s-1 by a laboratory hot-extrusion system. The series of tubes, with outer diameter in the range of 8-4 mm and inner diameter from 6 to 3 mm were investigated considering microstructure and texture analysis. The tubes featured a homogeneous and refined equiaxed grain structure since dynamic recrystallization was clearly observed during the extrusion process. A typical ‘basal’ type texture was detected in extruded tubes by using EBSD technique.

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Sun, Fasen, Jia Guo, Yijun Li, Shibing Bai, and Qi Wang. "Preparation of high-performance polyethylene tubes under the coexistence of silicone cross-linked polyethylene and rotation extrusion." Royal Society Open Science 6, no. 5 (May 2019): 182095. http://dx.doi.org/10.1098/rsos.182095.

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In this study, the silicone cross-linked polyethylene (Si-XLPE) powder with better thermoplastic performance and abundant cross-linked network points was attained by using solid-state shear mechanochemical (S 3 M) technology and it was added into high-density polyethylene (HDPE) matrix to prepare Si-XLPE/HDPE tubes by a rotation extrusion rheometer. SEM and 2D-SAXS experiments showed that the presence of Si-XLPE and rotation extrusion facilitated the formation of stable shish-kebabs which deviated from the axial direction in polyethylene (PE) tubes. This result was interpreted that introduction of Si-XLPE in PE tubes provided abundant molecular cross-linked network structures, which suppressed the thermal movement and relaxation of oriented molecular chains owing to intermolecular interaction. Moreover, the axial and hoop flow field further promoted orientation of the permanent cross-linked network entanglement points and formation of more stable cluster-like shish structures in the off-axial direction during the rotation extrusion process. Besides, our experimental results had also ascertained that molecular orientation and shish-kebabs in off-axial direction should be the primary responsibility for the remarkable enhancement of hoop torsional strength in PE tubes. Hoop torsional strength of PE tubes adding Si-XLPE reached 19.58 MPa when the mandrel rotation rate was 30 r.p.m., while that of conventional extruded PE tubes was only 9.83 MPa. As a consequence, PE tubes with excellent performance were prepared under the combined effect of Si-XLPE and rotation extrusion.

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Hsiang, Su-Hai, and Chao-Shun Liao. "Study on hot extrusion of tubes." Journal of Materials Processing Technology 63, no. 1-3 (January 1997): 254–59. http://dx.doi.org/10.1016/s0924-0136(96)02632-5.

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Kalnins, Christopher A. G., Kyle J. Bachus, Andrew Gooley, and Heike Ebendorff-Heidepriem. "High precision extrusion of glass tubes." International Journal of Applied Glass Science 10, no. 2 (December 3, 2018): 172–80. http://dx.doi.org/10.1111/ijag.13092.

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Zhao, P., and R. A. Holt. "Microstructural Evolution and Micro-Texture in Zr-2.5Nb Tubes." Materials Science Forum 475-479 (January 2005): 1421–24. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1421.

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Both small experimental extruded tubes and full-size pressure tubes were examined using scanning electron microscope/electron backscattered diffraction (SEM/EBSD) and transmission electron microscope/selected area diffraction (TEM/SAD). The final microstructures and textures vary with billet microstructure, extrusion temperature and extrusion ratio. Three components in {0002} pole figures were determined. The first component (radial) is produced by a and c+a slip in a-grains during extrusion. The second component (transverse) is associated with the elongated a- grains with their c-axes parallel to their long dimension. The third component (axial) is produced by b-a phase transformation after extrusion with a preferred variant of the Burgers relationship.

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Li, Xiao Wei, Kai Kun Wang, Jin Long Fu, and Fei Yin. "Numerical Simulation of Thixo-co-Extrusion of 7075/AZ91D Double-Layer Tubes." Solid State Phenomena 256 (September 2016): 119–25. http://dx.doi.org/10.4028/www.scientific.net/ssp.256.119.

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Due to the excellent thermal conductivity and high strength of aluminum alloy and unique advantages containing shock absorbing, vibrations dampening and corrosion resistant of magnesium alloy, Al/Mg double-layer tubes have been widely utilized in household appliances, automobiles, aerospace industries, and high-speed trains in recent years. Conventionally, double-layer tubes are produced by welding, extrusion, hydroforming, magnetic pulse cladding. These processes are either complex or highly energy-consuming. To improve efficiency and reduce energy consumption, a new technology, thixo-co-extrusion (TCE), is put forward for production of double-layer tubes. In this paper, the thixo-co-extrusion of a 7075/AZ91D double-layer tube is investigated by numerical simulation. This study assesses the influences of extrusion velocity, the thickness ratios of two layers, the reheating temperatures of billets and the preheating temperature of die on the flow behaviors. The results show that the extrusion velocity and the thickness ratios significantly influence the contact pressures on the interface as well as the velocity fields. Besides, the reheating temperatures of billets and the preheating temperatures determine the distribution of temperature fields. Under the contact pressures and a certain temperature, atomic diffusion takes place on the interface between inner and outer layer, which leads to metallurgical bonding of the interface. The paper contributes to a better understanding of the thixo-co-extrusion technology for the production of double-layer tubes with desirable mechanical properties.

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Knutsson, J., and M. von Unge. "Five-year results for use of single-flanged tympanostomy tubes in children." Journal of Laryngology & Otology 122, no. 6 (August 1, 2007): 584–89. http://dx.doi.org/10.1017/s0022215107009942.

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AbstractAims:To assess the five-year outcome of the use of single-flanged tympanostomy tubes in children, including the time to extrusion, rate of retained tubes and rate of persistent perforation.Materials and methods:The medical records relating to 640 single-flanged tympanostomy tubes intended for short-term use in paediatric patients were retrospectively reviewed.Results and analysis:We found that 36.4 per cent of the tubes had extruded within 12 months and 71.0 per cent within 24 months. Results showed that 14.1 per cent of the tubes had been removed because of prolonged retention, with a mean time to removal of 38.9 months. The time to extrusion was longer and the rate of retained tubes was higher than those reported for several other short-term tubes. We found that 4.5 per cent of tube insertions had resulted in a persistent perforation, a higher percentage than previously reported for other tubes intended for short-term use. Within five years of tube insertion, 70.5 per cent of the tympanic membranes had normalised.

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Liang, Hai Cheng, Jian Zhong Cui, and Zhong Tang Wang. "Effects of Hot Extrusion Processes on Grain Size of ZK60 Alloy Tubes." Advanced Materials Research 418-420 (December 2011): 1560–63. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.1560.

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Effects of hot extrusion processes on grain size of ZK60 alloy tubes was researched by combining numerical simulation with experimental research. The results show that grain size varies inversely as extrusion ratio and extrusion speed, with extrusion temperature being constant. In order to get the finer and homogeneous microstructure, higher extrusion ratio, higher extrusion speed and lower billet temperature should be chosen in the equipment's rated load. Isothermal extrusion is conducive to tube forming , and the smallest grain size and the better microstructure can be obtained at temperature of 300°C when other deformation conditions are constant.

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Li, Yang, and Ren Shu Yuan. "Forming Analysis of AZ80 Magnesium Alloy Thick-Walled Tube Fabricated by Hydrostatic Shrinkage Extrusion." Materials Science Forum 950 (April 2019): 80–84. http://dx.doi.org/10.4028/www.scientific.net/msf.950.80.

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In order to obtain high performance magnesium alloy thick-walled tubes, the magnesium alloy ingot was extruded by hydrostatic shrinkage extrusion technology. Through a series of experiments, it was found that the magnesium alloy tube was not formed in the extrusion ratio that is smaller than 2.11 . Deform-3D software was used to simulate the tube forming process under different extrusion ratios. It was noting that at the condition of the extrusion ratio of 2.11, the equivalent stress and strain of the extruded tube at the fixed sizing zone were obviously unevenly distributed, which was disappeared with the increase of the extrusion ratio. Compared with the homogenized magnesium alloy , the yield strength, the tensile strength and the elongation were improved when the tensile test was carried out on the extruded magnesium alloy thick-walled tube. These results clearly showed that the mechanical properties of magnesium alloy tubes were improved after hydrostatic extrusion.

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Kay, David J., Magalie Nelson, and Richard M. Rosenfeld. "Meta-Analysis of Tympanostomy Tube Sequelae." Otolaryngology–Head and Neck Surgery 124, no. 4 (April 2001): 374–80. http://dx.doi.org/10.1067/mhn.2001.113941.

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OBJECTIVE: To estimate the incidence of tympanostomy tube sequelae based on systematic review of published case series and randomized studies. DATA SOURCES: English-language MEDLINE search from 1966 through April 1999 with manual reference search of proceedings, articles, reports, and guidelines. STUDY SELECTION: Cohort studies with otitis media as the primary indication for tube placement. DATA EXTRACTION: Two reviewers independently extracted data from 134 articles. DATA SYNTHESIS: Transient otorrhea occurred in 16% of patients in the postoperative period and later in 26%; recurrent otorrhea occurred in 7.4% of patients and chronic otorrhea in 3.8%. Sequelae of indwelling tubes included obstruction (7% of ears), granulation tissue (5%), premature extrusion (3.9%), and medial displacement (0.5%). Sequelae after tube extrusion included tympanosclerosis (32%), focal atrophy (25%), retraction pocket (3.1%), cholesteatoma (0.7%), and perforation (2.2% with short-term tubes, 16.6% with long-term tubes). Meta-analysis showed that long-term tubes increased the relative risk of perforation by 3.5 (95% CI, 1.5 to 7.1) and cholesteatoma by 2.6 (95% CI, 1.5 to 4.4). Similarly, intubation increased the relative risk of tympanosclerosis by 3.5 (95% CI, 2.6 to 4.9) and focal atrophy by 1.7 (95% CI, 1.1 to 2.7) over nonintubated control ears (baseline tympanosclerosis and atrophy rates of 10% and 14%, respectively). CONCLUSIONS: Sequelae of tympanostomy tubes are common but are generally transient (otorrhea) or cosmetic (tympanosclerosis, focal atrophy). Nonetheless, the high incidence suggests a need for ongoing otologic surveillance of all patients with indwelling tubes and for a reasonable time period after tube extrusion. Long-term tubes should be used on a selective and individualized basis.

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Yılmaz Çırakoglu, Neslihan, and Yağız Özbay. "Apically extruded debris associated with ProTaper Next, ProTaper Gold and TruNatomy systems: An in vitro study." Journal of Dental Research, Dental Clinics, Dental Prospects 15, no. 1 (February 13, 2021): 30–34. http://dx.doi.org/10.34172/joddd.2021.006.

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Background. This research aimed to investigate and compare the amount of apically extruded debris after root canal preparation using ProTaper Next, ProTaper Gold, and TruNatomy systems. Methods. Forty-five extracted mandibular premolar teeth with single canals with similar lengths were used. The root canals were prepared using ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold (Dentsply Maillefer, Ballaigues, Switzerland), or TruNatomy (Dentsply Maillefer, Ballaigues, Switzerland) files. Apically extruded debris during preparation was gathered into preweighed Eppendorf tubes. Then the Eppendorf tubes were incubated at 70°C for five days. The Eppendorf tubes were weighed again to determine their final weight plus the extruded debris. Results. The TRN system resulted in significantly less debris extrusion than the PTN system (P<0.05). There was no significant difference between the PTN and PTG groups and between the PTG and TRN groups (P>0.05). Conclusion. All the instrumentation systems caused apical extrusion of debris. However, the TRN system resulted in significantly less debris extrusion than the other systems.

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Hiscocks, Jessica, Lan Jiang, and John J. Jonas. "Longitudinal Seam Failure in Extruded AZ31 Alloy." Advanced Materials Research 15-17 (February 2006): 439–44. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.439.

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Research is currently being conducted on the feasibility of hydroforming extruded magnesium tubes to integrate multiple parts into a single hydroformed section. Among other applications, such sections would reduce the weight of both cars and planes, particularly when used in the vehicle frame. This would lead to either reduced fuel costs, or the ability to carry an increased payload. Magnesium generally has limited ductility, which in the case of the current extruded tubes is even further reduced at the extrusion seams. These are locations where the material flow separates and rejoins during extrusion and are unavoidable when a hollow profile die is used. When the tubes were stressed in a circumferential direction, tube ruptures consistently occurred along the extrusion seams of the tubes. This led to the current project, an inquiry into the exact cause of failure at these locations. The creation of irregularities at the seams, such as precipitate dispersions, local texture changes, grain size changes and entrained material, is discussed. These irregularities are considered together with their roles in producing the failures. The results are summarized and the most fruitful directions for future work are outlined.

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Huang, X., and S. Blackburn. "Extrusion of Ceramic Tubes with Controlled Bends." Key Engineering Materials 206-213 (December 2001): 433–36. http://dx.doi.org/10.4028/www.scientific.net/kem.206-213.433.

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Borghi, N., O. Rossier, and F. Brochard-Wyart. "Hydrodynamic extrusion of tubes from giant vesicles." Europhysics Letters (EPL) 64, no. 6 (December 2003): 837–43. http://dx.doi.org/10.1209/epl/i2003-00321-x.

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Margolius, A. P., B. V. Mandzyuk, and V. T. Pastushkin. "Extrusion of tubes with internal helical fins." Metallurgist 32, no. 5 (May 1988): 185–86. http://dx.doi.org/10.1007/bf00741186.

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Momeni-Khabisi, H., H. Haghighat, and M. J. Momeni-Khabisi. "Upper Bound Analysis and Finite Element Simulation of Bi-Metallic Tube Backward Extrusion." Advanced Materials Research 445 (January 2012): 155–60. http://dx.doi.org/10.4028/www.scientific.net/amr.445.155.

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In this paper, the process of bi-metallic tube backward extrusion through a conical punch, by means of upper bound method and finite element method is investigated. A cylindrical admissible velocity field is developed and by calculating the internal, shear and frictional powers, the extrusion force is estimated. The extrusion process is also simulated by using the finite element code, ABAQUS. Analysis and simulations are done for two types of bi-metallic tubes: aluminum as core, copper as sleeve (Al-Cu) and copper as core, aluminum as sleeve (Cu-Al). The extrusion force from the upper bound method is compared with the Finite Element results. This comparison shows that the upper bound predictions are in good agreement with the Finite Element results. The results also show that, the extrusion force in the case of Al-Cu tube is smaller than Cu-Al tube and in both types of bi-metallic tubes, the aluminum leaves the deformation zone sooner than the copper. Finally the effects of various extrusion parameters, such as the friction factor, reduction in area and semi-punch angle upon the extrusion force are investigated and the optimum semi-punch angle is determined.

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Standley, Matthew R., and Marko Knezevic. "Towards Manufacturing of Ultrafine-Laminated Structures in Metallic Tubes by Accumulative Extrusion Bonding." Metals 11, no. 3 (February 27, 2021): 389. http://dx.doi.org/10.3390/met11030389.

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A severe plastic deformation process, termed accumulative extrusion bonding (AEB), is conceived to steady-state bond metals in the form of multilayered tubes. It is shown that AEB can facilitate bonding of metals in their solid-state, like the process of accumulative roll bonding (ARB). The AEB steps involve iterative extrusion, cutting, expanding, restacking, and annealing. As the process is iterated, the laminated structure layer thicknesses decrease within the tube wall, while the tube wall thickness and outer diameter remain constant. Multilayered bimetallic tubes with approximately 2 mm wall thickness and 25.25 mm outer diameter of copper-aluminum are produced at 52% radial strain per extrusion pass to contain eight layers. Furthermore, tubes of copper-copper are produced at 52% and 68% strain to contain two layers. The amount of bonding at the metal-to-metal interfaces and grain structure are measured using optical microscopy. After detailed examination, only the copper-copper bimetal deformed to 68% strain is found bonded. The yield strength of the copper-copper tube extruded at 68% improves from 83 MPa to 481 MPa; a 480% increase. Surface preparation, as described by the thin film theory, and the amount of deformation imposed per extrusion pass are identified and discussed as key contributors to enact successful metal-to-metal bonding at the interface. Unlike in ARB, bonding in AEB does not occur at ~50% strain revealing the significant role of more complex geometry of tubes relative to sheets in solid-state bonding.

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Milenin, Andrij, Piotr Kustra, Dorota Byrska-Wójcik, Bartłomiej Plonka, Veronika Petráňová, Vladimír Hrbek, and Jiří Němeček. "Numerical Optimization and Practical Implementation of the Tube Extrusion Process of Mg Alloys with Micromechanical Analysis of the Final Product." Key Engineering Materials 716 (October 2016): 55–62. http://dx.doi.org/10.4028/www.scientific.net/kem.716.55.

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The paper is devoted to the development of a process of tubes extrusion from MgCa08 magnesium alloy. For optimization of extrusion process the Qform software was used. The numerical model of flow stress and fracture criterion for MgCa08 were obtained based on tension/compression measurements performed in a universal testing machine Zwick Z250. Predictions of the flow stress and deformations were modeled as well as the ductility of material. The process was optimized according to the plasticity and temperature criterions. In the optimization process, temperature of the billet and the speed of extrusion were determined. Based on the optimal parameters the extrusion of tubes with external diameter of 5 mm was performed in the laboratory press. On top of the macroscopic testing and calculations, investigations of the material microstructure and the micromechanical behavior of the material after the extrusion were performed by a combination of SEM and nanoindentation analyses. Micromechanical properties of the alloy were detected with the aid of statistical nanoindentation. Samples were characterized in terms of their microstructural defects, distribution of elastic modulus and hardness. Good particle dispersion and homogeneous-like distribution of micromechanical properties was found showing the efficiency of the extrusion process.

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Shaqour, Bahaa, Juliana Aizawa, Clara Guarch-Pérez, Żaneta Górecka, Lars Christophersen, Wim Martinet, Emilia Choińska, et al. "Coupling Additive Manufacturing with Hot Melt Extrusion Technologies to Validate a Ventilator-Associated Pneumonia Mouse Model." Pharmaceutics 13, no. 6 (May 21, 2021): 772. http://dx.doi.org/10.3390/pharmaceutics13060772.

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Additive manufacturing is widely used to produce highly complex structures. Moreover, this technology has proven its superiority in producing tools which can be used in different applications. We designed and produced an extrusion nozzle that allowed us to hot melt extrude drug-loaded tubes. The tubes were an essential part of a new mouse ventilator-associated pneumonia (VAP) model. Ciprofloxacin (CPX) was selected for its expected activity against the pathogen Staphylococcus aureus and ease of incorporation into thermoplastic polyurethane (TPU). TPU was selected as the carrier polymer for its biocompatibility and use in a variety of medical devices such as tubing and catheters. The effect of loading CPX within the TPU polymeric matrix and the physicochemical properties of the produced tubes were investigated. CPX showed good thermal stability and in vitro activity in preventing S. aureus biofilm formation after loading within the tube’s polymeric matrix. Moreover, the produced tubes showed anti-infective efficacy in vivo. The produced tubes, which were extruded via our novel nozzle, were vital for the validation of our mouse VAP model. This model can be adopted to investigate other antibacterial and antibiofilm compounds incorporated in polymeric tubes using hot melt extrusion.

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Sendul, Selam Yekta, Halil Huseyin Cagatay, Burcu Dirim, Mehmet Demir, Ali Atakhan Yıldız, Zeynep Acar, Sonmez Cinar, and Dilek Guven. "Comparison of Medpor Coated Tear Drainage Tube versus Silicon Tear Drainage Tube in Conjunctivodacryocystorhinostomy: Problems and Solutions." Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/164834.

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Purpose.This study aims at comparing two different types of drainage tubes in conjunctivodacryocystorhinostomy, which are used for upper lacrimal system obstruction or damage, with respect to their respective postoperative problems and solutions.Methods.Nineteen eyes of 17 patients who underwent conjunctivodacryocystorhinostomy (CDCR) or conjunctivorhinostomy (CR) surgery with a Medpor coated tear drainage tube or silicon tube placement between October, 2010, and February, 2014, were included in this retrospective comparative study.Results.In the initial surgery, Medpor coated tear drainage tubes were used in 11 eyes by CDCR, whereas silicon tear drainage tubes were implanted into 2 eyes by CR and 6 eyes by CDCR. In group 1, proximal and distal obstructions developed postoperatively in 4 eyes, while 1 eye showed tube malposition and 3 eyes developed luminal obstruction by debris 3 times. In group 2, tube extrusion developed in 4 eyes, whereas tube malposition developed in 6 eyes and luminal obstruction by debris developed in 6 eyes at different times, for a total of 20 times.Conclusions.In our study, the most significant complication we observed in the use of silicon tear drainage tubes was tube extrusion,whereas the leading complication related to the use of Medpor coated tear drainage tubes was tube obstruction.

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Luo, Cheng, Xingyuan Huang, Tongke Liu, and Hesheng Liu. "Research on Inner Gas Inflation Improvements in Double-layer Gas-assisted Extrusion of Micro-tubes." Polymers 12, no. 4 (April 13, 2020): 899. http://dx.doi.org/10.3390/polym12040899.

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Micro-tubes have small diameters and thin wall thicknesses. When using double-layer gas-assisted extrusion (DGAE) technology to process micro-tubes, due to the influence of flow resistance, airflow from the inner gas-assisted layer cannot flow into the atmosphere through the lumen. Over time, it will inflate or even fracture the micro-tubes intermittently and periodically. To solve this problem, a new double-layer micro-tube gas-assisted extrusion die was designed in this study. Its mandrel has an independent airway leading to the lumen of the extrudate, with which the gas flow into the lumen of the extrudate can be regulated by employing forced exhaust. Using the new die, we carried out extrusion experiments and numerical calculations. The results show a significant positive correlation between micro-tube deformation and gas flow rate in the lumen of a micro-tube. Without considering the refrigerant distortion of the microtube, the flow rate of forced exhaust should be set equal to that of the gas from the inner gas-assisted layer flow into the micro-tube lumen. By doing this, the problem of the micro-tube being inflated can be eliminated without causing other problems.

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Xie, Guo Liang, Jing Liu, Jing Tao Han, and Pei Jie Yan. "An Analytical Approach to the Extrusion Pressure of Bimetallic Tube." Key Engineering Materials 443 (June 2010): 87–92. http://dx.doi.org/10.4028/www.scientific.net/kem.443.87.

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In this paper, the extrusion process of bimetallic tubes is discussed, and the extrusion pressure is calculated based on the method of energy conservation, according to the three categories of metal flow that may occur during the process. A number of parameters, geometry of bimetallic tube, mechanical properties of material components and friction conditions, are highlighted in this analytical method. Compared with the data of TP304l/20G bimetallic tubes which were extruded at 1100-1200 °C, the calculated results show a good agreement with the industrial results, with the error less than 10 %. It also proves that the friction between the two layers play an important role in the process.

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Song, Chang Myeon, Min-Hyun Park, Young Ho Kim, and Jun Ho Lee. "Factors Affecting the Extrusion Rate of Ventilation Tubes." Clinical and Experimental Otorhinolaryngology 3, no. 2 (2010): 70. http://dx.doi.org/10.3342/ceo.2010.3.2.70.

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TAKAHASHI, Jun, Yasumasa MAKITA, Sachio NABESHIMA, Taikyoku TEI, Atsushi KEYAKI, and Yoshihisa MIYAMOTO. "Spontaneous Extrusion of Peritoneal Tubes after Ventriculoperitoneal Shunting." Neurologia medico-chirurgica 28, no. 8 (1988): 808–11. http://dx.doi.org/10.2176/nmc.28.808.

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36

Xia, Wei, Bin Wu, Yong Tang, and Bangyan Ye. "On chopping–extrusion of integral-fin copper tubes." Journal of Materials Processing Technology 138, no. 1-3 (July 2003): 385–89. http://dx.doi.org/10.1016/s0924-0136(03)00103-1.

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37

Koutelieris, Antonios, Kyriaki Kioupi, Onoufrios Haralampous, Konstantinos Kitsakis, Nikolaos Vaxevanidis, and John Kechagias. "Simulation of extrusion of high density polyethylene tubes." MATEC Web of Conferences 112 (2017): 04004. http://dx.doi.org/10.1051/matecconf/201711204004.

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38

Ge, Q., M. Vedani, and G. Vimercati. "Extrusion of Magnesium Tubes for Biodegradable Stent Precursors." Materials and Manufacturing Processes 27, no. 2 (July 5, 2011): 140–46. http://dx.doi.org/10.1080/10426914.2011.560231.

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39

Kaya, C., and S. Blackburn. "Extrusion of alumina ceramic tubes with controlled bends." Journal of Materials Science 40, no. 8 (April 2005): 2007–11. http://dx.doi.org/10.1007/s10853-005-1224-4.

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Hsiao, Cheng Hsin, Sen Tian Kao, and Wen Jauh Chen. "Homogenization and Extrudability of 5056 Aluminum Alloy Billet." Key Engineering Materials 801 (May 2019): 233–38. http://dx.doi.org/10.4028/www.scientific.net/kem.801.233.

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Through a series of homogenization and extrusion experiments, the extrusion efficacy of 5056 seamless tubes is improved. Although better extrusion practice was apparent with better homogenization parameters for 5056 alloy, a little over-burning structure and phenomena were found on and in the surface and segregation zone of homogenized billet. The extrudability is worse than theoretical level with no aluminum and magnesium oxide particles on the billet surface. Additional, another quality problem in this study is the segregation zone in 5056 larger billets. The over-heat structure was smoothly flowed into the seamless tube by indirect extrusion, and that makes surface bubbles.

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Zhang, Bao Feng, Shuang Xi Li, Qing Kui Li, and Ai Yun Jiang. "Divided Flow Extrusion of AZ31 Magnesium Alloy with Cerium and Antimony Addition." Applied Mechanics and Materials 66-68 (July 2011): 736–40. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.736.

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Divided flow extrusion deformation behaviors and as-extruded tube properties of AZ31-Ce-Sb alloy were investigated. Addition of Sb and RE in AZ31 could accelerate the nucleation of dynamic recrystallization grains and refine tube microstructure. Compared to AZ31 Mg alloy, higher deformation temperature, extrusion speed and ration were allowed. AZ31-1%Ce-1%Sb alloy tubes had much better comprehensive performance.

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Thürer, Susanne Elisabeth, Julius Peddinghaus, Norman Heimes, Ferdi Caner Bayram, Burak Bal, Johanna Uhe, Bernd-Arno Behrens, Hans Jürgen Maier, and Christian Klose. "Lateral Angular Co-Extrusion: Geometrical and Mechanical Properties of Compound Profiles." Metals 10, no. 9 (August 28, 2020): 1162. http://dx.doi.org/10.3390/met10091162.

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A novel co-extrusion process for the production of coaxially reinforced hollow profiles has been developed. Using this process, hybrid hollow profiles made of the aluminum alloy EN AW-6082 and the case-hardening steel 20MnCr5 (AISI 5120) were produced, which can be forged into hybrid bearing bushings by subsequent die forging. For the purpose of co-extrusion, a modular tooling concept was developed where steel tubes made of 20MnCr5 are fed laterally into the tool. This LACE (lateral angular co-extrusion) process allows for a variation of the volume fraction of the reinforcement by using steel tubes with different wall thicknesses, which enabled the production of compound profiles having reinforcement contents of either 14 vol.% or 34 vol.%. The shear strength of the bonding area of these samples was determined in push-out tests. Additionally, mechanical testing of segments of the hybrid profiles using shear compression tests was employed to provide information about the influence of different bonding mechanisms on the strength of the composite zone.

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Keskar, Nachiket, Vikrant Raizada, Vaibhaw Kumar, Sanjay Kumar Jha, Dinesh Srivastava, Gautam Kumar Dey, and Nudurupati Saibaba. "A Study of the Effect of Extrusion Parameters on the Properties of Extruded Zr-2.5Nb Pressure Tubes." Advanced Materials Research 585 (November 2012): 371–75. http://dx.doi.org/10.4028/www.scientific.net/amr.585.371.

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The hot extrusion of Zr-2.5Nb alloy has been simulated using an FEM based software and validated by the experimental measurements during real extrusion process. The flow stress data for Zr-2.5Nb alloy at different temperatures, strain and strain rates were generated by hot compression testing on Gleeble Machine. The flow stress data, obtained both below β transus temperature in two phase α+β region as well as above β transus temperature in β phase region, were directly used in the FEM simulation of extrusion process, eliminating the need for any assumptions regarding material plastic flow law. Two important extrusion parameters, viz. included die angle and reduction ratio, were varied and for each set of conditions, temperature, strain and strain rate at different nodal points of the tube at different stages of extrusion were calculated. The extrusion parameters were optimized to obtain minimum variation in the force, temperature, strain and strain rate in the extruded product. A fair agreement has been found between the measured values of the applied ram force and the temperature profile at the die landing area in a 3780 ton horizontal extrusion press and those obtained through simulations. The effect of the friction and heat transfer coefficient between the die chamber and work piece was also investigated in this study.

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April, Max M., Rafael R. Portella, Peter W. Orobello, and Robert M. Naclerio. "Tympanostomy Tube Insertion: Anterosuperior vs. Anteroinferior Quadrant." Otolaryngology–Head and Neck Surgery 106, no. 3 (March 1992): 241–42. http://dx.doi.org/10.1177/019459989210600306.

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We studied the extrusion rate of Paparella type I tympanostomy tubes in the anterosuperior quadrant compared to those placed in the anteroinferior quadrant in a prospective study. Thirty-five patients were evaluated. The duration (mean ± SEM) in the anteroinferior quadrant was 211 ± 18 days, whereas the duration in the anterosuperior quadrant was 211 ± 11 days. We conclude that placement in the anterosuperior quadrant does not prolong duration of these tympanostomy tubes.

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45

Babaei, A., MM Mashhadi, and F. Mehri Sofiani. "Crystal plasticity modeling of grain refinement in aluminum tubes during tube cyclic expansion-extrusion." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 232, no. 6 (March 4, 2016): 481–94. http://dx.doi.org/10.1177/1464420716634745.

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In the present study, a crystal plasticity finite element model was developed for simulating the microstructure evolution and grain refinement during tube cyclic expansion-extrusion as a severe plastic deformation method for tubular materials. A new approach was proposed for extracting the real deformation history of a representative volume element during severe plastic deformation methods. The deformation history of a representative volume element during four cycles of tube cyclic expansion-extrusion was extracted by the proposed approach. Then, in a crystal plasticity finite element model, the deformation history was applied to a two-dimensional polycrystalline representative volume element with randomly assigned crystalline orientations. The intergranular interactions between grains and the intragranular orientation gradients were successfully simulated by the crystal plasticity finite element model. The distribution of misorientation angles, the evolution of grain boundaries, and the achieved average grain size after different cycles of tube cyclic expansion-extrusion were investigated by the crystal plasticity finite element model. On the other hand, ultrafine grained aluminum tubes were processed by four cycles of tube cyclic expansion-extrusion and the grain size of the processed tubes was studied by scanning electron microscopy observations and X-ray diffraction analyses. The experimental and predicted (by crystal plasticity finite element model) average grain sizes were compared.

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Alfenas, Cristiane Ferreira, Inês de Fátima De Azevedo Jacinto Inojosa, Júlio César De Azevedo Carvalhal, Mariana Teixeira Maneschy Faria, Fernanda Freitas Lins, Lucio De Souza Gonçalves, and Mônica Aparecida Schultz Neves. "Comparison of the amount of apically extruded debris produced by four retreatment techniques: an ex vivo study." Revistas 74, no. 4 (December 27, 2017): 309. http://dx.doi.org/10.18363/rbo.v74n4.p.309.

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Objective: the aim of this study was to compare the amount of apically extruded debris during the removal of root canal filling material using nickel-titanium rotary retreatment instruments and Hedström files. Material and Methods: sixty mandibular incisors with a single canal were instrumented and obturated by cold lateral compaction. For retreatment, specimens were randomly divided into four groups (n = 15): Hedström files with or without solvent; D-RaCe system and Mtwo retreatment system. Debris extruded apically during the removal of canal filling material was collected into preweighed Eppendorf tubes. The tubes were then stored in an incubator at 70°C for 5 days. The weight of the dry extruded debris was established by subtracting the preretreatment and postretreatment weight of the Eppendorf tubes for each group. The mean weights of extruded material were analyzed by one-way ANOVA. Results: the results showed that all retreatment techniques caused apical extrusion of debris, but no statistically significant difference was observed between groups (p>0.05). Conclusion: under the conditions of this study, all retreatment techniques caused apical debris extrusion.

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Park, Kyung Hoon, Bon Jo Koo, Jung Jun Park, Sun Ki Kim, Sun Myung Choi, Soon Uk Kwon, and Sang Won Yoon. "Factors Influencing the Extrusion of Tympanostomy Tubes in Children." Journal of Clinical Otolaryngology Head and Neck Surgery 16, no. 1 (May 2005): 60–65. http://dx.doi.org/10.35420/jcohns.2005.16.1.60.

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48

Afanasyev, Alexander E., Vladimir R. Kargin, and Boris V. Kargin. "Simulation of Extrusion of Tubes with Outer Heavy Ends." Key Engineering Materials 746 (July 2017): 10–15. http://dx.doi.org/10.4028/www.scientific.net/kem.746.10.

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Computer simulation of expansion of tubes by extrusion was performed. Deflected mode analysis was described. Influence of collar taper angle, radius of rounding in interface of conical and cylindrical sections of mandrel, geometry of blank on deformation behavior of tube during expansion was determined.

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Hwang, Yeong-Maw, and Cheng-Nan Chang. "Hot Extrusion of Hollow Helical Tubes of Magnesium Alloys." Procedia Engineering 81 (2014): 2249–54. http://dx.doi.org/10.1016/j.proeng.2014.10.316.

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Rossier, O., D. Cuvelier, N. Borghi, P. H. Puech, I. Derényi, A. Buguin, P. Nassoy, and F. Brochard-Wyart. "Giant Vesicles under Flows: Extrusion and Retraction of Tubes." Langmuir 19, no. 3 (February 2003): 575–84. http://dx.doi.org/10.1021/la026236t.

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Journal articles on the topic 'EXTRUSÃO DE TUBOS'

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