1,720,963 research outputs found
Advances in the development of carbidic ADI
Get PDFCarbidic ADI (CADI) is a new type of Austempered Ductile Iron containing free carbides in the microstructure, providing a particular combination of wear resistance and impact toughness. In this work, four CADI variants were evaluated, in which carbides were promoted by alloying with chromium. Tests performed under the low stress abrasion condition imposed by the ASTM G65 standard show that CADI can increase the wear resistance up to ~100 % when compared with conventional ADI austempered at the same temperature. The carbide content must be higher than ~10 % to promote a considerable reinforcing effect. However, at this carbide content level, the impact toughness varies between ~7 and ~11 J/cm2 for unnotched samples. These values are much lower than those of conventional ADI, but higher than those of other abrasion resistant materials, like white irons. Some CADI variants were also evaluated in field tests, producing abrasion under either low stress or high stress conditions. For this purpose, two CADI prototype parts were studied: screw segments for animal food extruders (low stress abrasion) and wheel loader bucket edges (high stress abrasion). The results gathered showed that CADI behaves satisfactorily under low stress abrasion, but the performance is not so good under high stress conditions. To analyze the differences in the abrasion response, scratch tests were performed in order to evaluate the interaction between the abrasive tip and the microstructure.Fil: Laino, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones En Ciencia y Tecnología de Materiales; ArgentinaFil: Sikora, Jorge Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones En Ciencia y Tecnología de Materiales; ArgentinaFil: Dommarco, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones En Ciencia y Tecnología de Materiales; Argentin
Wear behavior of CADI operating under different tribosystems
Get PDFA new type of Austempered Ductile Iron (ADI) containing free carbides in its microstructure, called Carbidic ADI (CADI), has been purposely designed for applications requiring high levels of abrasion resistance, but still keeping impact toughness. Nevertheless, wear resistance is strongly dependent on the tribosystem, and this is clearly noticed for the abrasive wear mechanism. In earlier investigations, the authors used the low stress abrasion condition imposed by the ASTM G 65 standard for laboratory tests. Therefore, this study is intended to evaluate CADI wear resistance by means of field trials under different abrasion conditions. Apart from the additional laboratory tests indicated by the ASTM G 65 standard, two CADI prototype parts were evaluated: screw segments for animal food extruders, whose abrasion severity is considered of low stress type (similar to that imposed in the laboratory), and wheel loader bucket edges, whose abrasion severity is considered of high stress type. The results gathered have demonstrated that CADI behaves satisfactorily under low stress abrasion conditions, though performance is poor under high stress conditions. To justify the differences in wear behavior, the worn surfaces were studied by microscopy, and also scratch tests were performed in order to evaluate the interaction between the abrasive particles and the microstructure. It was found that the good performance is obtained when the groove size is smaller than the average carbide size, and that under this condition abrasion resistance increases with the increase in the carbide content and hardness. Contrarily, when the groove size is greater than that of carbides, the performance is impoverished with the increase in the carbide content.Fil: Laino, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Sikora, Jorge Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Dommarco, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Wear behaviour of carbidic ductile iron with different matrices and carbide distribution
Get PDFJust like other properties, wear resistance is entirely dependent on materials microstructure, which, in turn, is related to the chemical composition and solidification rate that controls phases type, size, amount and dispersion. Depending on the tribosystem, the abrasive wear resistance of ductile iron (DI) may be improved by heat treatment as well as by reinforcing the matrix with hard particles like carbides, typically obtained by alloying with elements such as chromium. The solidification rate mainly depends on wall thickness and mould characteristics. In ductile iron, the solidification rate affects microstructural characteristics, such as nodule size, nodule count, carbide size and distribution and matrix refinement, also including the last to freeze (LTF) amount, size and distribution. This study evaluates the influence of the wall thickness (12.5, 25, 50 and 75 mm) on the abrasion resistance and impact toughness of DI with different matrices reinforced with carbides. Carbidic structures were obtained by alloying the melt with Cr; and the different types of matrices such us pearlitic, martensitic and ausferritc (CADI) were obtained under as cast conditions or by heat treatment. The results reflect the influence of cooling rate on the microstructural characteristics and its relationship with the mechanical properties, particularly the abrasive wear resistance. It was demonstrated that, under the present experimental conditions, the highest carbide content and matrix hardness, obtained from the 12.5 mm thick part with a martensitic matrix, resulted in the highest abrasion resistance.Fil: Basso, Alejandro Daniel. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Laino, Sebastian. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Dommarco, Ricardo. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentin
The Influence of Austempering Temperature on the Wear Resistance of Ductile Iron under Two Different Tribosystems
Get PDFThis paper reports the results obtained in a research conducted to evaluate austempered ductile iron(ADI) as a wear resistant material for the production of machine parts processed at intermediate and highaustempering temperatures (Ta). Severe abrasion in actual service performance trials and low stress abra-sion laboratory tests (ASTM G-65) were carried out along with microstructural characterization by optical mi-croscopy and X-ray diffraction. The results derived show that ADI yields excellent abrasion resistance underthe operating conditions resulting from the field tests when Ta is raised. Nevertheless, ADI show an oppo-site trend under the low stress abrasion conditions imposed by the dry sand/rubber wheel abrasion appara-tus (ASTM G-65). The presence of a metastable and ductile ausferrite phase (reacted and unreacted austen-ite ferrite) in ADI microstructure appears to be the most relevant factor influencing the performance ob-served. In addition to a high deformation capability detected at the wear surfaces, an austenite to marten-site transformation took place as determined by X-ray diffraction. These two factors combined make theausferritic microstructure overcome hardness reduction when the austempering temperature is raised, im-proving or sustaining the resistance to severe abrasive wear but, at the same time, increasing impact tough-ness.Fil: Laino, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ortíz, Hugo R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Dommarco, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Influence of chemical composition and solidification rate on the abrasion and impact properties of CADI
Get PDFThe use of CADI, a variant of Austempered Ductile Iron (ADI) containing free carbides, is on the increase thanks to its excellent combination of high abrasion resistance and good impact toughness, when compared to other materials with similar wear resistance. The present work focuses on the study of two CADI variants in which carbides were obtained by a combination of alloying elements and the effect of a cooper chill located in the mould. A detailed microstructural characterization of the material was made; and the content and composition of the carbides as well as their stability during the heat treatment were particularly studied. The abrasion wear resistance as evaluated by testing under the ASTM G 65 standard, and comparing the relative wear resistance of samples taken just beside the cooper chill up to locations where the chill did not affect the solidification rate. The relative wear resistance, determined by using ADI as a reference material, ranged from £=3 to £=2 for samples taken from the different locations, close and far to the chill, respectively. For samples taken from the same locations, the impact toughness ranged from 6.5 to 10J, respectively. The results allow establishing a relationship between the solidification rate, the microstructure and the mechanical properties, thereby enabling to predict their effect on current applications. © 2009 ISIJ.Fil: Laino, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Sikora, Jorge Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Dommarco, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Development of wear resistant carbidic austempered ductile iron (CADI)
Get PDFThe abrasion wear resistance of irons may be improved by the incorporation of an extra phase to the matrix, typically consistent of carbides. Nevertheless, the improvement in wear resistance is generally accompanied by a decrease in the impact toughness. The aim of this work is to study the methodology to obtain a controlled precipitation of carbides in a ductile cast iron that is subsequently austempered, obtaining the so called Carbidic Austempered Ductile Iron (CADI). This material is expected to offer high abrasion resistance but still retaining higher impact toughness than other reinforced irons, thanks to the particular characteristics of the matrix. A plate model with a copper chill allowed to evaluate both, the influence of a high cooling rate and the effect of alloying elements on carbide precipitation. Four different alloys with equivalent carbon close to the eutectic composition were used in order to evaluate the effect of chromium contents ranging from 1 to 2.5%. A detailed microstructural characterisation of the material was made, studying particularly carbide content and composition, besides their stability during the heat treatment. The abrasion wear resistance was evaluated by testing under the ASTM G 65 standard, obtaining relative wear resistance values ranging between 1.02 and 1.95 with respect to conventional ADI samples taken as reference material. The impact toughness decreased from about 138 – 101 J for ADI to about 26 – 7 J for CADI.Fil: Laino, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Sikora, Jorge Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Dommarco, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
