Capitanias hereditárias: herança colonial sobre desigualdade e instituições

Este trabalho tem como objetivo analisar em que aspectos a desigualdade histórica de formação dos municípios brasileiros foi determinante para as suas condições atuais de desigualdade de terra e renda e sobre qualidade das instituições. Em particular, emprega-se área, latitude, longitude e a data de fundação das Capitanias Hereditárias como determinantes históricos para as instituições atuais dos municípios brasileiros. Considerando controles, tais como área proporcional da capitania, ano de fundação do município, distância de Portugal, tipo de solo, quantidade de chuva, altitude, temperatura média, e variáveis sócio-econômicas municipais, os resultados sugerem que a herança colonial deixada pelas Capitanias Hereditárias foi maior concentração de terras. O resultado é robusto à inclusão de variáveis que capturam o ciclo da cana-de-açúcar, do ouro e efeitos estaduais. Além disso, estima-se efeito ambíguo sobre instituições para os municípios do país.

Development of an instrumentation system embedded on FPGA for real time measurement of mechanical vibrations in rotating machinery

The real-time monitoring of events in an industrial plant is vital, to monitor the actual conditions of operation of the machinery responsible for the manufacturing process. A predictive maintenance program includes condition monitoring of the rotating machinery, to anticipate possible conditions of failure. To increase the operational reliability it is thus necessary an efficient tool to analyze and monitor the equipments, in real-time, and enabling the detection of e.g. incipient faults in bearings. To fulfill these requirements some innovations have become frequent, namely the inclusion of vibration sensors or stator current sensors. These innovations enable the development of new design methodologies that take into account the ease of future modifications, upgrades, and replacement of the monitored machine, as well as expansion of the monitoring system. This paper presents the development, implementation and testing of an instrument for vibration monitoring, as a possible solution to embed in industrial environment. The digital control system is based on an FPGA, and its configuration with an open hardware design tool is described. Special focus is given to the area of fault detection in rolling bearings. © 2012 IEEE.

Fiscal policy and the economic cycle in Chile

Includes bibliography

Medida da difusividade térmica de um solo incorporado com resíduo industrial de silicato

Pós-graduação em Física - IGCE

Problemas ambientais e relações de trabalho no Porto de Belém: perspectivas para um projeto de educação ambiental

Esta pesquisa mostra o olhar que trabalhadores e passageiros da Companhia das Docas do Pará – Porto de Belém têm do cotidiano do porto em relação aos problemas ambientais. Nossa motivação para o desenvolvimento deste estudo pautou-se na identificação de qual a situação ambiental na área portuária das Docas de Belém e se as ações de Educação Ambiental desenvolvidas em seu interior contribuem para a construção de melhorias socioambientais? Para a realização da pesquisa utilizamos como forma de análise a abordagem qualitativa, na qual buscamos priorizar não apenas a quantidade de dados referentes ao objeto de estudo, mas principalmente compreender o fenômeno em foco. No estudo desenvolvemos as seguintes etapas: a) levantamos dados sobre o entorno, destacando a ocupação urbana na área de influência do Porto; b) elaboramos um diagnóstico ambiental, por intermédio da visão de trabalhadores e usuários do Porto de Belém, visando suas expectativas quanto ao ambiente; c) Buscamos compreender o desenvolvimento de ações relacionadas à preservação ambiental, necessárias ao processo de educação para a sustentabilidade, desenvolvidas no Porto de Belém. Neste sentido, inicialmente realizamos uma ampla revisão da literatura sobre a temática, conjuntamente com a pesquisa documental, onde analisamos textos escritos por pesquisadores na área de meio ambiente, e da educação Ambiental, como: Loureiro (2004, 2009), Lima (2007), Silva (2009), Teisserenc (2010), Tapia (2005), Campanhola (2000), Gadotti (2008), Becker (2008), Antunes (2002). Assim como documentos oficiais relacionados ao meio ambiente e a outras iniciativas voltadas a Ações de Preservação e de Portos como: Constituição da Republica Federativa (1988); Decreto Lei 9.795 que dispõe sobre a educação ambiental, institui a Política Nacional de Educação Ambiental; Decreto Lei 8.630 que dispõe sobre o regime jurídico da exploração dos portos organizados e das instalações portuárias; Lei nº 8.630, de 25/02/1993 (antiga Lei dos Portos). A partir da construção do texto ampliamos nosso conhecimento, o que nos deu suporte teórico para iniciarmos a pesquisa empírica. Nesta etapa fizemos um levantamento da área edificada em parte da orla de Belém para identificar o percentual de ocupação urbana na faixa exclusiva selecionada, às proximidades do lócus da pesquisa, o levantamento realizado visou identificar alguma provável influência externa na área de movimentação de navios, o que foi descartado, pois o percentual de ocupação urbana (45,0830 %) encontrado foi considerado dentro dos padrões aceitáveis. Na segunda etapa do estudo foi feita a coleta de dados junto às pessoas que vivenciam o cotidiano da área portuária como: trabalhadores e usuários, objetivando obter informações sobre sua visão e opinião sobre o foco da pesquisa, utilizamos primeiramente a entrevista semiestruturada, objetivando esclarecer sobre as reais condições atuais do meio ambiente de trabalho, vivido cotidianamente por seus atores, nas questões profissionais, sociais e ambientais na área do Porto de Belém e, para que tivéssemos um diagnóstico do momento em que se encontra a ambientalização do Porto, realizamos entrevistas com sujeitos que trabalham diariamente naquele ambiente portuário. Culminando o estudo, utilizamos questionários, os quais foram aplicados a 80 (oitenta) sujeitos trabalhadores e 149 (cento e quarenta e nove) aos usuários/passageiros. O resultado da pesquisa revelou como principais problemas apontados, tanto pelos usuários como pelos trabalhadores os impactos ambientais causados pelas atividades portuárias como a emissão de resíduos sólidos, líquidos, derrame de produtos perigosos e os riscos de contaminação do rio. Assim como lixo em excesso e sua coleta indevida, que tem ocasionado frequentes entupimentos dos esgotos. Assim como a inexistência de continuidade do trabalho de limpeza e manutenção com a prática necessária da dragagem retirada de entulhos do rio e do canal das docas. Constatamos também, que existe a intenção pela gestão da CDP em realizar o trabalho de utilização correta de sistemas de carga e descarga, armazenagem, pesagem, acomodação e movimentação de cargas no porto, bem como realizar de forma correta controle de matérias que chegam e que saem, e que é perceptível a eficiente vigilância da movimentação na área de embarque e desembarque de passageiros, o fazem com que o Porto de Belém permaneça dentro dos padrões estabelecidos na Constituição, o processo de gestão portuária ocorre regularmente obedecendo a um sistema de atividades previamente determinadas e que se encontram de acordo com a Lei dos Portos. O grande ganho que se observa no estudo e esclarecimento das questões investigadas é a apresentação do conceito que os atores envolvidos têm da realidade ambiental existente.

Avaliação mecânica da colagem estrutural entre compósitos poliméricos e materiais metálicos utilizados em dutos petroquímicos

The development of technology for structural composites has as one of its ends form a set of materials that combine high values of mechanical strength and stiffness and low density. Today, companies like Embraer and PETROBRAS and research institutions like NASA, working with these materials with recognized advantages in terms of weight gain, increased performance and low corrosion. We have developed a systematic study to determine the bond strength between composite carbon fiber / epoxy and fiberglass / epoxy laminate both bonded to a carbon steel which are widely used in the petrochemical industry and repair. For morphological evaluation and bonding between materials of different natures, ultrasound analysis, optical microscopy and stereoscopy were performed. To simulate actual conditions, the composites were subjected to conditioning by using heat shock temperatures from -50 to 80 ° C for 1000 cycles for composite carbon fiber / epoxy composites and 2000 cycles for fiberglass / epoxy . The use of composites studied here proved to be efficient to perform repairs in metallic pipes with application petrochemical, as when exposed to sudden changes of temperature (-50 ° to 80 ° C) cycling at 1000 to 2000 times, its mechanical properties (shear and tensile) practically do not change

Melhoria do nível de serviço no atendimento ao cliente por meio da estrutura direta de distribuição Transit Point

Increasingly competitive markets have driven the search for companies in many different ways to win and keep customers. The service level is basically the performance of companies in fulfilling the orders made, or how companies demonstrate to their clients efforts in their behalf. This work aims to solve the difficulties faced by a multinational company present in Brazil, in the distribution of its products in the category Ice Cream in order to improve the service level of their customers. Review the logistics network and concepts related to the distribution system of products is one of several ways to achieve this goal, as well as the use of IT and tools to assist in planning and programming of the physical distribution of products. In this study we used the concept of direct distribution system called Transit Point (TP). The TP provides at the same time, a strategy of rapid response, flexibility, low transportation costs and no inventory. A router - software capable of simulating the actual conditions experienced in the daily distribution - was used to assist in calculations. Results showed reductions of up to 47.5% in transportation costs and better conditions were provided in the distribution of products, positively impacting on service levels and in the maintenance of products quality, with a reduction of 1.6% of the total costs involve

Construindo laços entre o serviço social e a educação: acesso e permanência na educação de jovens e adultos

Pós-graduação em Serviço Social - FCHS

Recovery Tests of an Hybrid Current Limiter Composed of a SFCL in Parallel to an Air-Core Power Reactor

The resistive-type superconducting fault current limiters (RSFCL) prototypes using YBCO-coated conductors have shown current limitation for medium voltage class applications for acting time up to 80 ms. By connecting an air-core reactor in parallel with the RSFCL, thus making an hybrid current limiter, one can extend the acting time for up to 1 s. In this work, we report the performance of a hybrid current limiter subjected to an AC peak fault current of 2 kA during 1 s for which within the first 80 ms the SFCL limits the current concurrently with the air-core reactor, and for the remaining 920 ms, only the air-core reactor limits the current. In order to evaluate the actual conditions for subsequent reconnection of RSFCL to the power grid, the hybrid fault current limiter was tested varying the time interval for recovery from 900 ms and 1.2 s, followed again by the concurrent operation of the hybrid limiter during 1 s (SFCL during 80 ms). From this evaluation test, the recovery time can be measured and compared using the voltage peak generated in superconducting module from the first and second fault test. The recovery time was also determined through the pulsed current method (PCM) on short-length sample test. The results showed that the fault current was limited from 1.9 kA down to 514 A after 1 cycle of 60 Hz frequency, with recovery time lower than 1.2 s for two subsequent fault current tests.

Análise do desempenho térmico de habitações populares da microrregião de Guaratinguetá - SP

Pós-graduação em Engenharia Mecânica - FEG

Low-carbon operations and production: putting training in perspective

The purpose of this paper is mainly to show how training may support low-carbon operations and production management in a more sustainable organizational context. Design/methodology/approach – A conceptual framework to facilitate the integration between training and low-carbon operations and production is presented. Findings – To accomplish better training in a low-carbon organization, some steps should be followed. Challenges may occur, including the necessity of collaboration across the supply chain. Research limitations/implications – The proposed framework should be applied and improved based on the actual conditions in organizations.

The impact of mortality from external causes on human development in the Brazilian borderland

This article estimates the impact of mortality from external causes on the human development index (HDI) along the Brazilian borderland from 2000 to 2005. Data obtained from Brazilian government agencies were combined using the methodology defined by the United Nations Development Program, revealing the HDI according to actual conditions. Subsequently, deaths from external causes were excluded in order to estimate their impact on the index, recalculating life expectancy using the technique of competing causes. HDI showed a gradual increase from North to South, with the most developed regions concentrated in the South, consistent with studies using other sets of economic indicators. By excluding mortality from external causes, the highest gains appeared in regions where the HDI (under actual conditions) were lower, and the magnitude of gains declined towards the South.

Thermoelectric performance of p-type TiCoSb half-Heusler compounds - Intrinsic phase separation and charge carrier concentration optimization as key to high efficiency

The world's rising demand of energy turns the development of sustainable and more efficient technologies for energy production and storage into an inevitable task. Thermoelectric generators, composed of pairs of n-type and p-type semiconducting materials, di¬rectly transform waste heat into useful electricity. The efficiency of a thermoelectric mate¬rial depends on its electronic and lattice properties, summarized in its figure of merit ZT. Desirable are high electrical conductivity and Seebeck coefficients, and low thermal con¬ductivity. Half-Heusler materials are very promising candidates for thermoelectric applications in the medium¬ temperature range such as in industrial and automotive waste heat recovery. The advantage of Heusler compounds are excellent electronic properties and high thermal and mechanical stability, as well as their low toxicity and elemental abundance. Thus, the main obstacle to further enhance their thermoelectric performance is their relatively high thermal conductivity.rn rnIn this work, the thermoelectric properties of the p-type material (Ti/Zr/Hf)CoSb1-xSnx were optimized in a multistep process. The concept of an intrinsic phase separation has recently become a focus of research in the compatible n-type (Ti/Zr/Hf)NiSn system to achieve low thermal conductivities and boost the TE performance. This concept is successfully transferred to the TiCoSb system. The phase separation approach can form a significant alternative to the previous nanostructuring approach via ball milling and hot pressing, saving pro¬cessing time, energy consumption and increasing the thermoelectric efficiency. A fundamental concept to tune the performance of thermoelectric materials is charge carrier concentration optimization. The optimum carrier concentration is reached with a substitution level for Sn of x = 0.15, enhancing the ZT about 40% compared to previous state-of-the-art samples with x = 0.2. The TE performance can be enhanced further by a fine-tuning of the Ti-to-Hf ratio. A correlation of the microstructure and the thermoelectric properties is observed and a record figure of merit ZT = 1.2 at 710°C was reached with the composition Ti0.25Hf0.75CoSb0.85Sn0.15.rnTowards application, the long term stability of the material under actual conditions of operation are an important issue. The impact of such a heat treatment on the structural and thermoelectric properties is investigated. Particularly, the best and most reliable performance is achieved in Ti0.5Hf0.5CoSb0.85Sn0.15, which reached a maximum ZT of 1.1 at 700°C. The intrinsic phase separation and resulting microstructure is stable even after 500 heating and cooling cycles.

Two-Phase Flow In Microchannels: Morphology And Interface Phenomena

The existence and morphology, as well as the dynamics of micro-scale gas-liquid interfaces is investigated numerically and experimentally. These studies can be used to assess liquid management issues in microsystems such as PEMFC gas flow channels, and are meant to open new research perspectives in two-phase flow, particularly in film deposition on non-wetting surfaces. For example the critical plug volume data can be used to deliver desired length plugs, or to determine the plug formation frequency. The dynamics of gas-liquid interfaces, of interest for applications involving small passages (e.g. heat exchangers, phase separators and filtration systems), was investigated using high-speed microscopy - a method that also proved useful for the study of film deposition processes. The existence limit for a liquid plug forming in a mixed wetting channel is determined by numerical simulations using Surface Evolver. The plug model simulate actual conditions in the gas flow channels of PEM fuel cells, the wetting of the gas diffusion layer (GDL) side of the channel being different from the wetting of the bipolar plate walls. The minimum plug volume, denoted as critical volume is computed for a series of GDL and bipolar plate wetting properties. Critical volume data is meant to assist in the water management of PEMFC, when corroborated with experimental data. The effect of cross section geometry is assessed by computing the critical volume in square and trapezoidal channels. Droplet simulations show that water can be passively removed from the GDL surface towards the bipolar plate if we take advantage on differing wetting properties between the two surfaces, to possibly avoid the gas transport blockage through the GDL. High speed microscopy was employed in two-phase and film deposition experiments with water in round and square capillary tubes. Periodic interface destabilization was observed and the existence of compression waves in the gas phase is discussed by taking into consideration a naturally occurring convergent-divergent nozzle formed by the flowing liquid phase. The effect of channel geometry and wetting properties was investigated through two-phase water-air flow in square and round microchannels, having three static contact angles of 20, 80 and 105 degrees. Four different flow regimes are observed for a fixed flow rate, this being thought to be caused by the wetting behavior of liquid flowing in the corners as well as the liquid film stability. Film deposition experiments in wetting and non-wetting round microchannels show that a thicker film is deposited for wetting conditions departing from the ideal 0 degrees contact angle. A film thickness dependence with the contact angle theta as well as the Capillary number, in the form h_R ~ Ca^(2/3)/ cos(theta) is inferred from scaling arguments, for contact angles smaller than 36 degrees. Non-wetting film deposition experiments reveal that a film significantly thicker than the wetting Bretherton film is deposited. A hydraulic jump occurs if critical conditions are met, as given by a proposed nondimensional parameter similar to the Froude number. Film thickness correlations are also found by matching the measured and the proposed velocity derived in the shock theory. The surface wetting as well as the presence of the shock cause morphological changes in the Taylor bubble flow.

Desarrollo de nuevos tratamientos térmicos para aleaciones avanzadas de interés aeroespacial

La corrosión bajo tensiones (SCC) es un problema de gran importancia en las aleaciones de aluminio de máxima resistencia (serie Al-Zn-Mg-Cu). La utilización de tratamientos térmicos sobremadurados, en particular el T73, ha conseguido prácticamente eliminar la susceptibilidad a corrosión bajo tensiones en dichas aleaciones pero a costa de reducir su resistencia mecánica. Desde entonces se ha tratado de optimizar simultáneamente ambos comportamientos, encontrándose para ello diversos inconvenientes entre los que destacan: la dificultad de medir experimentalmente el crecimiento de grieta por SCC, y el desconocimiento de las causas y el mecanismo por el cual se produce la SCC. Los objetivos de esta Tesis son mejorar el sistema de medición de grietas y profundizar en el conocimiento de la SCC, con el fin de obtener tratamientos térmicos que aúnen un óptimo comportamiento tanto en SCC como mecánico en las aleaciones de aluminio de máxima resistencia utilizadas en aeronáutica. Para conseguir los objetivos anteriormente descritos se han realizado unos cuarenta tratamientos térmicos diferentes, de los cuales la gran mayoría son nuevos, para profundizar en el conocimiento de la influencia de la microestructura (fundamentalmente, de los precipitados coherentes) en el comportamiento de las aleaciones Al-Zn-Mg-Cu, y estudiar la viabilidad de nuevos tratamientos apoyados en el conocimiento adquirido. Con el fin de obtener unos resultados aplicables a productos o semiproductos de aplicación aeronáutica, los tratamientos térmicos se han realizado a trozos grandes de una plancha de 30 mm de espesor de la aleación de aluminio 7475, muy utilizada en las estructuras aeronáuticas. Asimismo con el objeto de conseguir una mayor fiabilidad de los resultados obtenidos se han utilizado, normalmente, tres probetas de cada tratamiento para los diferentes ensayos realizados. Para la caracterización de dichos tratamientos se han utilizado diversas técnicas: medida de dureza y conductividad eléctrica, ensayos de tracción, calorimetría diferencial de barrido (DSC), metalografía, fractografía, microscopia electrónica de transmisión (MET) y de barrido (MEB), y ensayos de crecimiento de grieta en probeta DCB, que a su vez han permitido hacer una estimación del comportamiento en tenacidad del material. Las principales conclusiones del estudio realizado se pueden resumir en las siguientes: Se han diseñado y desarrollado nuevos métodos de medición de grieta basados en el empleo de la técnica de ultrasonidos, que permiten medir el crecimiento de grieta por corrosión bajo tensiones con la precisión y fiabilidad necesarias para valorar adecuadamente la susceptibilidad a corrosión bajo tensiones. La mejora de medida de la posición del frente de grieta ha dado lugar, entre otras cosas, a la definición de un nuevo ensayo a iniciación en probetas preagrietadas. Asimismo, se ha deducido una nueva ecuación que permite calcular el factor de intensidad de tensiones existente en punta de grieta en probetas DCB teniendo en cuenta la influencia de la desviación del plano de crecimiento de la grieta del plano medio de la probeta. Este aspecto ha sido determinante para poder explicar los resultados experimentales obtenidos ya que el crecimiento de la grieta por un plano paralelo al plano medio de la probeta DCB pero alejado de él reduce notablemente el factor de intensidades de tensiones que actúa en punta de grieta y modifica las condiciones reales del ensayo. Por otro lado, se han identificado los diferentes constituyentes de la microestructura de precipitación de todos los tratamientos térmicos estudiados y, en especial, se ha conseguido constatar (mediante MET y DSC) la existencia de zonas de Guinier-Preston del tipo GP(II) en la microestructura de numerosos tratamientos térmicos (no descrita en la bibliografía para las aleaciones del tipo de la estudiada) lo que ha permitido establecer una nueva interpretación de la evolución de la microestructura en los diferentes tratamientos. Al hilo de lo anterior, se han definido nuevas secuencias de precipitación para este tipo de aleaciones, que han permitido entender mejor la constitución de la microestructura y su relación con las propiedades en los diferentes tratamientos térmicos estudiados. De igual manera, se ha explicado el papel de los diferentes microconstituyentes en diversas propiedades mecánicas (propiedades a tracción, dureza y tenacidad KIa); en particular, el estudio realizado de la relación de la microestructura con la tenacidad KIa es inédito. Por otra parte, se ha correlacionado el comportamiento en corrosión bajo tensiones, tanto en la etapa de incubación de grieta como en la de propagación, con las características medidas de los diferentes constituyentes microestructurales de los tratamientos térmicos ensayados, tanto de interior como de límite de grano, habiéndose obtenido que la microestructura de interior de grano tiene una mayor influencia en el comportamiento en corrosión bajo tensiones que la de límite de grano. De forma especial, se ha establecido la importancia capital, y muy negativa, de la presencia en la microestructura de zonas de Guinier-Preston en el crecimiento de la grieta por corrosión bajo tensiones. Finalmente, como consecuencia de todo lo anterior, se ha propuesto un nuevo mecanismo por el que se produce la corrosión bajo tensiones en este tipo de aleaciones de aluminio, y que de forma muy resumida se puede concretar lo siguiente: la acumulación de hidrógeno (formado, básicamente, por un proceso corrosivo de disolución anódica) delante de la zonas GP (en especial, de las zonas GP(I)) próximas a la zona libre de precipitados que se desarrolla alrededor del límite de grano provoca enfragilización local y causa el rápido crecimiento de grieta característico de algunos tratamientos térmicos de este tipo de aleaciones. ABSTRACT The stress corrosion cracking (SCC) is a major problem in the aluminum alloys of high resistance (series Al-Zn-Mg-Cu). The use of overaged heat treatments, particularly T73 has achieved virtually eliminate the susceptibility to stress corrosion cracking in such alloys but at the expense of reducing its mechanical strength. Since then we have tried to simultaneously optimize both behaviors, several drawbacks found for it among them: the difficulty of measuring experimentally the SCC crack growth, and ignorance of the causes and the mechanism by which SCC occurs. The objectives of this thesis are to improve the measurement system of cracks and deeper understanding of the SCC, in order to obtain heat treatments that combine optimum performance in both SCC and maximum mechanical strength in aluminum alloys used in aerospace To achieve the above objectives have been made about forty different heat treatments, of which the vast majority are new, to deepen the understanding of the influence of microstructure (mainly of coherent precipitates) in the behavior of the alloys Al -Zn-Mg-Cu, and study the feasibility of new treatments supported by the knowledge gained. To obtain results for products or semi-finished aircraft application, heat treatments were performed at a large pieces plate 30 mm thick aluminum alloy 7475, widely used in aeronautical structures. Also in order to achieve greater reliability of the results obtained have been used, normally, three specimens of each treatment for various tests. For the characterization of these treatments have been used several techniques: measurement of hardness and electrical conductivity, tensile testing, differential scanning calorimetry (DSC), metallography, fractography, transmission (TEM) and scanning (SEM) electron microscopy, and crack growth tests on DCB specimen, which in turn have allowed to estimate the behavior of the material in fracture toughness. The main conclusions of the study can be summarized as follows: We have designed and developed new methods for measuring crack based on the use of the ultrasound technique, for measuring the growth of stress corrosion cracks with the accuracy and reliability needed to adequately assess the susceptibility to stress corrosion. Improved position measurement of the crack front has resulted, among other things, the definition of a new initiation essay in pre cracked specimens. Also, it has been inferred a new equation to calculate the stress intensity factor in crack tip existing in DCB specimens considering the influence of the deviation of the plane of the crack growth of the medium plane of the specimen. This has been crucial to explain the experimental results obtained since the crack growth by a plane parallel to the medium plane of the DCB specimen but away from it greatly reduces the stress intensity factor acting on the crack tip and modifies the actual conditions of the essay. Furthermore, we have identified the various constituents of the precipitation microstructure of all heat treatments studied and, in particular note has been achieved (by TEM and DSC) the existence of the type GP (II) of Guinier-Preston zones in the microstructure of several heat treatments (not described in the literature for alloys of the type studied) making it possible to establish a new interpretation of the evolution of the microstructure in the different treatments. In line with the above, we have defined new precipitation sequences for these alloys, which have allowed a better understanding of the formation of the microstructure in relation to the properties of different heat treatments studied. Similarly, explained the role of different microconstituents in various mechanical properties (tensile properties, hardness and toughness KIa), in particular, the study of the relationship between the tenacity KIa microstructure is unpublished. Moreover, has been correlated to the stress corrosion behavior, both in the incubation step as the crack propagation, with the measured characteristics of the various microstructural constituents heat treatments tested, both interior and boundary grain, having obtained the internal microstructure of grain has a greater influence on the stress corrosion cracking behavior in the grain boundary. In a special way, has established the importance, and very negative, the presence in the microstructure of Guinier-Preston zones in crack growth by stress corrosion. Finally, following the above, we have proposed a new mechanism by which stress corrosion cracking occurs in this type of aluminum alloy, and, very briefly, one can specify the following: the accumulation of hydrogen (formed basically by a corrosive process of anodic dissolution) in front of the GP zones (especially the GP (I) zones) near the precipitates free zone that develops around grain boundary causes local embrittlement which characterizes rapid crack growth of some heat treatments such alloys.