Determinação da fragilidade ambiental de bacia hidrográfica em relação à atividade suinícola utilizando SIG

The intensified use of natural resources started after the industrial revolution, with increasing the disorderly occupation of watersheds and environmental degradation over the past century. Studies of environmental fragilities helps to identify areas with greater or lesser fragility regarding to certain aspect or activity analyzed, contributing to the decision making and adoption of strategies to minimize such impacts. The objective of the study was to evaluate the environmental fragility of Lajeado Erval Novo Watershed front the swine farming in order to subsidize the support of the decision taken for the environmental licensing system. Therefore, was held an integrated environmental assessment of the basin from data processing in Geographic Information System using a model based on qualitative and quantitative variables and adding socio-environmental characteristics to hierarchize areas with higher and lower environmental fragility for swine effluents. The areas to the southwest and northeast of the studied watershed were diagnosed as points of high environmental fragility. This fragility was, mainly, related to higher generation of swine effluent load and the conditions that contribute to the process of environmental embrittlement of areas, such as the use and soil type, slope and proximity to water resources. The mapping of environmental fragilities, by addressing the specifics variables and conditions of areas, proved to be a very important tool for decision-making and the maintenance of swine activities and the environmental balance of the watershed.

Tensile Properties of Recrystallized and Unrecrystallized Tungsten at Elevated Temperatures

Tungsten has higher melting point than any other metals. Therefore, tungsten is applied to the electrode for resistance welding. The electrodes for resistance welding of tungsten are mainly used for fusing joining because they have high heat resistance and are hard to be alloyed with work metal pieces. However, the cracks on electrode surface occur during cyclic welding processes. In this study, to reveal the relationship between the elevated temperature deformation characteristics and fracture mechanism of recrystallized and unrecrystallized tungsten, tensile tests were carried out with varying strain rate and testing temperature. At 400°C, the total elongation at a strain rate of 1.4×10-1 s-1 in the recrystallized tungsten decreased more than the total elongation at the other strain rate. At 600°C, total elongation increased by approximately 10%, if the strain rate was increased from 1.4×10-3 s-1 to 1.4×10-1 s-1. Then, the recrystallized tungsten at the strain rate of 1.4×10-1 s-1 had more necking than that of 1.4×10-3 s-1. The may be caused by an environmental embrittlement due to oxygen in the high temperature atmosphere.

Corrosion Behaviour of Ti-48Al-2Nb-2Cr Alloys

γ-TiAl intermetallics are attractive materials for high-temperature structural applications in the aerospace and automobile industries. However, they show environmental embrittlement at elevated temperatures that is mainly related to their low high-temperature corrosion resistance. One way how to improve the high-temperature corrosion resistance is the deposition of protective coatings on the surface of the base material. In this study, samples of a Ti-Al alloy with the chemical composition Ti-48Al-2Cr-2Nb (at.%) were covered by physically vapour deposited (PVD), by metalorganic chemically vapour deposited (MOCVD) and by high-velocity oxy-fuel (HVOF) sprayed coatings. All coatings were based on the Ti-Al alloys and contained different amounts of alloying elements. The corrosion experiments were performed in molten salts containing 75 wt.% Na2SO4and 25 wt.% NaCl at 850°C up to 336 h. Both, PVD and CVD protected coatings reduced the changes in the mass of the samples over the corrosion time. Still, the formation of TiO2could not be avoided, as it was confirmed by glancing-angle X-ray diffraction experiments.