Evaluation of the performance of α-SiAlON tool when turning Ti-6Al-4V alloy without coolant

Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the most suitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. This necessitates a process optimization when machining superalloys with Si3N4 based ceramic cutting tools. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. This paper evaluates the performance of α-SiAlON tool in turning Ti-6Al-4V alloy at high cutting conditions, up to 250 m min-1, without coolant. Tool wear, failure modes and temperature were monitored to access the performance of the cutting tool. Test results showed that the performance of α-SiAl0N tool, in terms of tool life, at the cutting conditions investigated is relatively poor due probably to rapid notching and excessive chipping of the cutting edge. These facts are associated with adhesion and diffusion wear rate that tends to weaken the bond strength of the cutting tool.

Perfil marítimo de América Latina y el Caribe = Maritime profile of Latin America and the Caribbean

Incluye Bibliografía

Development of ceramic cutting tools for future application on dry machining

Advanced ceramic materials constitute a mature technology with a very broad base of current and potential applications and a growing list of material compositions. Within the advanced ceramics category, silicon nitride based ceramics are wear-resistant, corrosion-resistant and lightweight materials, and are superior to many materials with regard to stability in high-temperature environments. Because of this combination the silicon nitride ceramics have an especially high potential to resolve a wide number of machining problems in the industries. Presently the Si3N4 ceramic cutting tool inserts are developed using additives powders that are pressed and sintered in the form of a cutting tool insert at a temperature of 1850 °C using pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and the mechanical response of this array microstructure was characterized for hardness Vickers and fracture toughness. The results show that Si3N4/20 wt.% (AlN and Y 2O3) gives the best balance between hardness Vickers and fracture toughness. The Si3N4/15 wt.% (AlN and Y 2O3) composition allows the production of a very fine-grained microstructure with low decreasing of the fracture toughness and increased hardness Vickers. These ceramic cutting tools present adequate characteristics for future application on dry machining. © (2010) Trans Tech Publications.

The impact of structural reforms on growth in Latin America and the Caribbean: an empirical estimation

Includes bibliography

La educación de las mujeres: de la marginalidad a la coeducación: propuestas para una metodología de cambio educativo = The education of women: from marginality to coeducation: proposals for a methodology to achieve educational change

Incluye Bibliografía

Use of mathematical and numerical methods in the Latin American Demographic Centre CELADE. Santiago, Chile

Includes bibliography

The origin and magnitude of the recessionary adjustment in Latin America

Includes bibliography

An analysis of the Hygiea asteroid family orbital region

(10) Hygiea is the fourth largest asteroid of the main belt, by volume and mass, and it is the largest member of its family, that is made mostly by low-albedo, C-type asteroids, typical of the outer main belt. Like many other large families, it is associated with a 'halo' of objects, that extends far beyond the boundary of the core family, as detected by traditional hierarchical clustering methods (HCM) in proper element domains. Numerical simulations of the orbital evolution of family members may help in estimating the family and halo family age, and the original ejection velocity field. But, in order to minimize the errors associated with including too many interlopers, it is important to have good estimates of family membership that include available data on local asteroid taxonomy, geometrical albedo and local dynamics. For this purpose, we obtained synthetic proper elements and frequencies of asteroids in the Hygiea orbital region, with their errors. We revised the current knowledge on asteroid taxonomy, including Sloan Digital Sky Survey-Moving Object Catalog 4th release (SDSS-MOC 4) data, and geometric albedo data from Wide-field Infrared Survey Explorer (WISE) and Near-Earth Object WISE (NEOWISE). We identified asteroid family members using HCM in the domain of proper elements (a, e, sin (i)) and in the domains of proper frequencies most appropriate to study diffusion in the local web of secular resonances, and eliminated possible interlopers based on taxonomic and geometrical albedo considerations. To identify the family halo, we devised a new hierarchical clustering method in an extended domain that includes proper elements, principal components PC1, PC2 obtained based on SDSS photometric data and, for the first time, WISE and NEOWISE geometric albedo. Data on asteroid size distribution, light curves and rotations were also revised for the Hygiea family. The Hygiea family is the largest group in its region, with two smaller families in proper element domain and 18 families in various frequencies domains identified in this work for the first time. Frequency groups tend to extend vertically in the (a, sin (i)) plane and cross not only the Hygiea family but also the near C-type families of Themis and Veritas, causing a mixture of objects all of relatively low albedo in the Hygiea family area. A few high-albedo asteroids, most likely associated with the Eos family, are also present in the region. Finally, the new multidomains hierarchical clustering method allowed us to obtain a good and robust estimate of the membership of the Hygiea family halo, quite separated from other asteroids families halo in the region, and with a very limited (about 3 per cent) presence of likely interlopers. © 2013 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.

Informe de la Sexta Reunión de la Mesa Directiva de la Conferencia Regional sobre la Integración de la Mujer en el Desarrollo Económico y Social de América Latina y el Caribe = Report of the Sixth Meeting of the Presiding Officers of the Regional Conference on the Integration of Women into the Economic and Social Development of Latin America and the Caribbean

Documento distribuido inicialmente sin símbolo en la Reunión Regional de América Latina y el Caribe Preparatoria de la Conferencia Mundial para el Examen y la Evaluación de los Logros del Decenio de las Naciones Unidas para la Mujer: Igualdad, Desarrollo y Paz, La Habana, 19-23 noviembre 1984

Current trends and patterns of female migration: evidence from México

Includes bibliography

Informe de la Reunión de Personalidades sobre la crisis mundial y América Latina = Report of the Meeting of Personalities on the world crisis and Latin America

Reunion convocada por la Secretaria Ejecutiva de la CEPAL para analizar el impacto de la crisis economica internacional sobre America Latina y sus posibles soluciones. Las personalidades intervinieron a titulo personal sin compromiso de los gobiernos de sus respectivos paises.

Caribbean and its incomplete class structure: essay on the logic of its negotiations with the metropolitan countries

Publicado también con el símbolo E/CEPAL/SEM.10/R.11

Progresos en América Latina y el Caribe en materia de implementación de las recomendaciones contenidas en el Capítulo 18 del Programa 21 sobre gestión integral de los recursos hídricos = Progress achieved by the Latin American and Caribbean countries in the implementation of the recommendations made in Chapter 18 of Agenda 21 on integrated water resources management

Incluye Bibliografía