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The aim of this study was to evaluate and compare the fracture resistance of definitive zirconia dioxide restorations obtained using a computer-aided design and manufacturing (CAD/CAM) system. Methods: Two groups of ten samples were analyzed for each material (n: 20); the first group was Zolid Gen X Amann Girrbach (ZGX) and the second group was Cercon HT Dentsply Sirona (CDS). The restorations were designed with identical parameters and milled with a CAD/CAM system. Each specimen was load tested at a speed of 0.5 mm/min, with a direction parallel to the major axis of the tooth and with an initial preload of 10 N until fracture using a universal testing machine (Universal/Tensile Testing Machine, Autograph AGS-X Series) equipped with a 20 kN load cell. The results obtained were recorded in Newtons (N), using software connected to the testing machine. Results: Statistically significant differences were found, and the fracture resistance of the monolithic zirconia crowns was lower in the CDS group (1744.84 ± 172.8 N) compared to the ZGX group (2387.41 ± 516 N). Conclusions: The monolithic zirconia CAD-CAM zirconia crowns showed sufficient fracture resistance when used in posterior molar and premolar zones with either material, as they withstood fracture loads greater than the maximum masticatory force.

Corrosion phenomena are usually difficult to recognize without a deep knowledge of the electrochemical properties of materials, this creates difficulties in the analysis of corrosion in practice, control measures are developed through image processing to solve these problems. This article describes a methodology for the analysis of the inner surface of steam pipelines by means of digital image processing (DIP). A classification algorithm is presented that is able to detect four levels of corrosion on the inner surface of steam pipelines. Gray-level co-occurrence matrix GLCM, which analyzes all the attributes of each image texture was employed. The performance of the classification algorithm was evaluated by using a confusion matrix, which showed very reliable classification results by comparing with experimental tests.

In this article, an experimental investigation was conducted to study the effects of 3D printed structured fabrics on the tensile strength of two additive manufacturing technologies: (i) fused deposition modeling (FDM); and (ii) stereolithography (SLA). Three types of structured fabrics were designed in a linked fabric structure, which resembled the main characteristics of a conventional textile. Through computer-aided design (CAD), the textile structures were sketched, which, in a STL format, were transferred to 3D printing software, and consequently, they were printed. The specimens were subjected to tensile tests to analyse the behaviour of the linked structures under tensile loads. The results obtained indicated that the elements structured in a linked fabric pattern showed a statistically significant effect between the design of the 3D printed structured fabric and its tensile strength. Some important properties in textiles, fabric areal density, fineness (tex) and fabric flexibility were also analysed. This study opens an important field of research on the mechanical resistance of textile structures manufactured by 3D printing, oriented for applications in wearables that have a promising future in the fields of medicine, aerospace, sports, fashion, etc.

En la presente investigación se determinaron las propiedades mecánicas atracción del material biocompuesto de polipropileno(PP)isotáctico reforzado conhaces defibras cortas de bambú orientadas al azar. Se prepararon muestras del material con diferentes contenidos de refuerzo (20, 30 y 40%), empleando como agente de acople el polipropileno con injertos de moléculas de anhídrido maleico (MAPP). Un grupo de estas muestras fueron sometidas a un tratamiento de envejecimiento térmico acelerado para evaluar el efecto de dicho tratamiento sobre las propiedades a tensióndel biocompuesto. Se realizaron ensayos de tracción a diferentes velocidades de deformación (10 y 50 mm/min) y se obtuvo un aumento de la resistencia a la tracción(de 29a 45 MPa)y del módulo de elasticidad(de 1 a 3GPa)del PP con el contenido de fibras. Para diferentes velocidades de estiramiento, se obtuvo una mejor resistencia a altas velocidades. El envejecimiento térmico durante 24 horas a 100ºC aumentó la resistencia del PP puro. Para los biocompuestos, se obtuvo una baja resistencia en las muestras envejecidas en mayor tiempo (98ºC, 10 días). A través de la microscopia electrónica de barrido se realizó unacaracterización microestructural que permitió explicar el mejoramiento de la resistencia del PP reforzado con fibras, y en algunos casos, la pérdida de resistencia debido al tratamiento térmico

In this paper, the one-dimensional tensile behavior of

Different strategies have been used to degrade the molecular structure of lignins in natural fibers. Both chemical and biological processes can obtain different types of lignins for industrial use. In this study, a variation of the spectral intensity of the thermo-mechanical and fungi-modified

El presente artículo analiza las propiedades tensiles de un material compuesto polimérico reforzado con fibras de carbono empleado en la fabricación del monoplaza para competición Fórmula SAE. Para ello se manufacturaron compuestos a partir de preimpregnados con diferentes orientaciones de fibra mediante un proceso de curado al vacío. Se evaluó el efecto de la orientación de las fibras sobre la resistencia y la rigidez de los compuestos formulados. Se instrumentaron las probetas de tracción con extensómetros biaxiales para obtener un registro real de la deformación y posterior determinación del módulo de Young. Los resultados experimentales fueron comparados con los resultados analíticos obtenidos a partir de la Teoría Clásica de Laminados mediante software especializado. Se desarrolló también un análisis microscópico de la región fracturada de las probetas para evaluar el efecto del proceso de manufactura. El conjunto de información generada a partir de los resultados experimentales y analíticos proporciona un entendimiento de la anisotropía de los materiales compuestos Epoxi-Carbono que permitirá tomar decisiones de diseño en futuros desarrollos dentro del proyecto Fórmula SAE.

The present work has been carried out in order to investigate the sliding wear performance of a Ni-Cr based alloy, containing boron, carbon, silicon and iron, deposited onto a SAE 1045 steel substrate. The coatings were thermally sprayed by means of a High Velocity Oxy-Fuel system and post heat-treated for one hour at 760°C in an argon atmosphere. The relative sliding performance was evaluated under unlubricated dry conditions at different applied normal loads and sliding velocities, in order to analyze the influence of these parameters on the wear response. Test results are discussed and interpreted on the basis of both microstructural evaluations and mechanical properties measurements. The surface morphology and topography of the wear scars have been studied through of a Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques. The results have shown an improved wear resistance of the coated steel samples as compared to the uncoated ones.

La presente investigación aborda un análisis del nivel de contaminación producido por los gases generados de monóxido de carbono (CO), dióxido de carbono (CO2) y los hidrocarburos (HC) en la limpieza de láminas metálicas de acero inoxidable AISI/SAE 304 aplicando plasma frío de oxígeno a baja presión para la remoción de los aceites ISO 32, ISO 68 e ISO 220, con diferentes parámetros de control del generador de acuerdo con el aceite lubricante removido de la superficie de la lámina metálica de acero inoxidable. La experimentación se realizó en un primer proceso con una descarga aplicada directamente a la superficie de la lámina impregnada con el aceite colocando con un volumen de 0,1 ml y en un segundo proceso donde la lámina con el aceite impregnado fue sumergida en un desengrasante para aceites y grasas con la finalidad de realizar una limpieza previa a la aplicación del plasma frío a baja presión en la superficie. Para el análisis de los resultados en el nivel de gases generados por cada aceite se aplica un análisis estadístico para determinar si existe una diferencia significativa en el nivel de los gases generados en las dos etapas.//level of contamination produced by gases generated from carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) in the cleaning of metallic sheets of stainless steel AISI / SAE 304 when applying low pressure cold oxygen plasma for the removal of oils ISO 32, ISO 68 and ISO 220, with different generator control parameters according to the lubricating oil removed from the surface of the stainless steel sheet metal. The experimentation was carried out in a first phase in which a discharge was applied directly to the surface of the sheet contaminated with a volume of 0.1 ml of oil, and in a second phase in which the sheet with the oil was immersed in an oil degreaser to perform a pre-cleaning prior to the application of lowpressure cold plasma on the surface. For the analysis of the results in the level of gases generated by each oil, an statistical analysis is applied to determine if there is a significant difference in the level of the gases generated between the two phases.

The aim of this study was to determine the resistance to fracture of feldspathic restorations with lithium disilicate and crystallized with different ovens and programs. Methods: Sixty monolithic restorations (LD) (EMAX CAD™ LT, Ivoclar-Vivadent™) were designed with the same parameters and milled with a CAD/CAM system (CEREC SW 5.1, CEREC MCXL, Dentsply-Sirona™, Bensheim). Each restoration was randomly assigned by randomization software (RANDNUM) to one of the three groups: (a) (NF) Oven P310 (Ivoclar, Vivadent) normal crystallization program, (b) (FF) Ivoclar P310 oven (Ivoclar-Vivadent™) rapid crystallization program, or (c) (SF) SpeedFire oven (Dentsply-Sirona™). Results: There were statistically significant differences between the groups (ANOVA, p &lt, 0.05). The NF and FF groups showed the highest values of resistance to fracture, with statistically significant differences with the SF group. Conclusions: Using a furnace from the same dental company with predetermined programs from the material manufacturer, as well as using a predetermined program for rapid crystallization, has no effect on fracture resistance, and would save clinical time when performing ceramic restorations with lithium disilicate, while keeping their mechanical properties.

The aim of this study was to evaluate and compare the resistance to fracture of interim restorations obtained through additive techniques (3D impressions) and subtractive techniques (milling) using a computer-aided design and manufacture (CAD/CAM) system of a three-unit fixed dental prosthesis (FDP) to ascertain its clinical importance. (1) Materials and methods: In total, 40 samples were manufactured and divided into two groups (n = 20) using: (1) light-curing micro hybrid resin for temporary crowns and bridges (PriZma 3D Bio Prov, MarketechLabs, São Paulo, Brazil) for the rapid prototyping group (RP) and (2) a polymethylmethacrylate (PMMA) CAD/CAM disc (Vipiblock Trilux, VIPI, São Paulo, Brazil) for the computer-assisted milling (CC). The resistance to fracture was determined with a universal testing machine. (2) Results: The strength and the standard deviation for the computer-assisted milling group were higher (1663.57 ± 130.25 N) than the rapid prototyping (RP) group, which had lower values of (1437.74 ± 73.41 N). (3) Conclusions: The provisional restorations from the computer-assisted milling group showed a greater resistance to fracture than the provisional restorations obtained from the rapid prototyping group.

X-ray computed tomography is a technique that provides a high level of detail in three-dimensional (3D) inspections of composite materials, but the acquisition of phase contrast together with absorption contrast in traditional tomography makes it difficult to obtain information in some composite materials reinforced with natural fibers. In this work, X-ray computed tomography has been used to evaluate an image reconstruction process using the phase-contrast method with three different algorithms (MBA, BAC, PPR). The results of the image reconstructions were compared to traditional methods. Additionally, details of the variation of parameters in each reconstruction method are presented. The phase-contrast image capture technique did not provide an adequate reconstruction of images that showed similar contrast. Finally, the absorption contrast was applied to analyze morphological properties of a bio-based composite showing a significant decrease of fiber length distribution during the manufacturing process.

A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

The present article proposes a method for the estimation of geometrical properties of short natural fibers that act as reinforcing phase in polymeric composites. The extraction of the image attributes is performed based on the analysis of microscopic images taken in different sections of the material, requiring a minimal user intervention. The proposed method estimates the orientation tensor of the short fibers from geometrical characteristics such as inclination, length, width and aspect ratio, using an elliptical covering on each fiber. The method validation was performed on a polypropylene composite reinforced with 30% by weight of bamboo short fibers (guadua angustifolia species), the accuracy and precision of the proposed method proved to be adequate. The \( a_{11} \) element of the orientation tensor was evaluated and the results agree in 98% with respect to the commercial software. This technique is a fast alternative of low cost in characterization of new materials.

This research work presents an analysis of the injection molding process of a natural fiber-reinforced composite, from the characterization of its rheological properties by the technique of capillary rheometry. Two of the main parameters of injection molding were estimated: the injection pressure and the clamping force. The rheological coefficients obtained were used as inputs in analytical and finite element models, for the prediction of the injection parameters. The results were compared, and it was observed that there is good agreement between them. The percentage errors between the two estimation methods were less than 5% for injection pressure and less than 10% for the clamping force. Also, the behavior of the material using different natural reinforcing contents (compositions of 20%, 30% and 40% fiber with a coupling agent at 4% and 8%) and the effect of its rheological properties on both the injection pressure and clamping force were evaluated. The study is of particular interest given that from the rheological characterization, the experimental values were adjusted to the Cross-WLF viscosity model and the adjustment coefficients, which contain both the reinforcing and coupling agent effects, were fed into the two methods of estimation of the injection parameters. The methodology used and the results obtained allow the prediction of the main parameters of injection molding of new bio-based composites, facilitating their use on an industrial scale.

The research addresses an analysis of the level of contamination generated by the gases produced when applying low-pressure cold plasma in a cleaning process of metal sheets used in the manufacture of white goods. A mixture of argon and oxygen ionized gases at 50% was utilized to break down the lubricating oil molecules deposited on the surface of the sheet metal. A statistically significant number of samples were selected, with different volumes of oil on the surface, between 6 ml and 34 ml. The samples were later subjected to a plasma discharge with a time of 72 s, a gas pressure of 0.6 bar and 50% power to determine the correlation of the oil volume with the levels of gases generated by the discharge, maintaining the degree of surface cleanliness, as given by contact angle values between 67.5 and 79 degrees, constant. For the analysis of results a Pearson correlation was applied for each detected gas. An analysis was later conducted of the relationship between the degree of cleanliness of the metallic surface, as given by contact angles at 16, 36 and 53 degrees, with the levels of the gases generated by the plasma discharge, keeping the volume of the lubricating oil on the surface constant at 5 ml. For the analyses, statistical tests were carried out to find the correlation between the predictor variables and the dependent variable to establish a multivariate linear statistical model. The results allowed the behavior of the level of contamination to be determined, establishing that the volume of oil does not influence the level of the gases generated by the use of low-pressure cold plasma. The results obtained allow us to understand the relationship between the contact angle that represents the quality of surface cleaning of oil-impregnated sheet metal and the level of contamination generated in the process.

Given the growing request for reusing raw material in new manufactured products in the plastics industry, the present study analyzes the effect of the concentration of recycled materials and pigments on the rheological properties of the polymer blend. It was quantified and analyzed in a statistical way the significance of the effects that these components produce in the rheological properties, such as the melt flow index, the maximum torque and the degradation time on high density polyethylene (HDPE). Knowledge of such properties will optimize processing parameters by using polymer blends with recycled materials and pigments. A minimum effect of the components was evidenced on the melt flow index having the pigment content the greatest impact factor.

En este artículo se presenta la determinación de humedad, elementos solubles e insolubles en agua de la fibra de Carludovica palmata (paja toquilla). Para realizar estos ensayos se utilizan las normas ASTM E871-82, ASTM D1110-84 y ASTM D1107-96. Con la finalidad de determinar su uso pontencial como refuerzo en materiales compuestos y la influencia en la resistencia mecánica. El porcentaje de humedad de la fibra analizada corresponde al 5,33% de su peso. El porcentaje de elementos solubles e insolubles en agua es 0,1042% y 0,3589% respectivamente. This paper presents the determination of moisture and water solubles and insolubles of Carludovica Palmata (paja toquilla) fiber. To perform these tests using ASTM E871-82, ASTM D1110-84 and ASTM D1107-96 standars. In order to determine its use pontencial as reinforcement in composite materials and the influence on the mechanical strength. The moisture content of analyzed fiber corresponds to 5,33% by weight. The percentage of soluble and insoluble components in water is 0,1042% and 0,3589 %, respectively.

This research was carried out a comparative analysis of cleaning of sheet steel, for use in forming processes impregnated with a mixture of SAE 40 oil and diesel by means of low-pressure cold plasma. The plasma discharge was generated by radio frequency energy using two types of gases, argon and oxygen. Cleaning of the surface was evaluated by measuring the contact angle with deionized water, diiodo methane and ethylene glycol, for the calculus of the surface free energy by means of the Fowkes theories and Wu and gas chromatography. The results show that the plasma cleaning is more effective when using a previous cleaning, in this case the immersion in solvent (CH3-OH).