Análise das propriedades da madeira de estrutura de telhado após a ocorrência de um incêndio

The present study evaluated the mechanical properties of pieces of wood coming from the roof structure of a residence subject fire in the rural area of Itapeva/SP. The structure was built 25 years ago using wooden beams of the species Guarucaia (Peltophorum vogelianum), where the specimens were removed. The research methodology included qualitative evaluation of the samples, estimating the layer pyrolysis and carbonization of the wood, measuring of density and mechanical tests of compression parallel to grain, tension parallel to grain and shear. The mechanical properties of wood were analytically correlated with the layers carbonization and pyrolysis that are influenced by the temperature and time of fire; these values were estimated at 1000 °C and two hours for the case in question. The results indicate that the strength properties of degraded wood are different from a healthy wood. The level of thermodegradation, in general, can be measured by density, result in weight loss due to decomposition of the wooden components.

Avaliação do comportamento mecânico sob deformação da liga Ti- 30Ta visando aplicações biomédicas

Titanium and its alloys have been used for biomedical applications due their excellent properties such as high corrosion resistance, biocompatibility and mechanical properites. In this study, microstructural and mechanical properties of Ti-30Ta alloy was evaluated during its processing. Ti-30Ta alloy ingots were produced from sheets of commercially pure titanium (99.9%) and tantalum (99.9%). Its melting was realized in arc melting furnace in an argon atmosphere. After homogenizing at 1200ºC, ingots were cold worked by swaging. Samples with 13 mm in diameter were obtained. They were forging at the reduction ratios of 15%. After deformation, microstructure was evaluated by optical microscopy in each condition. Also, Vickers microhardness of samples was measured and phase constitution was evaluated using XRD analysis

Obtenção de constantes elásticas da madeira de duas espécies de Pinus sp

There are many studies about longitudinal modulus of elasticity of wood, but you can´t say the same of transverse modulus, especially for conifers. The study aimed to characterize and compare the species Pinus elliottii var. elliottii and Pinus elliottii var. elliottii x Pinus cariabeae hondurensis (hybrid), and the longitudinal modulus of elasticity (E) and lateral (G) in bending, to analyze the modulus of elasticity in different spaces and to verify the species studied the ideal range is equal to 21 times the height of the specimen, as prescribed in the normative document NBR 7190/1997, as well as analyzing the relationship G = E/20 defined in the normative document NBR 7190/1997. The wood came from the farm located in Paranapanema, split at the mill São José and the rest of the work was conducted at the Experimental Itapeva Campus - UNESP. Were removed fourteen specimens of each species. The average values of the modulus of elasticity and cross were, respectively, 5828 MPa and 452 MPa for Pinus elliottii var. elliottii and 6407 MPa and 320 MPa for the species of Pinus elliottii var. elliottii x Pinus cariabeae hondurensis (hybrid). The trend lines for the plotted graphs showed an exponential behavior to near linear 21he will equal the constant after this value. We have found the relationship G = E/13, for Pinus elliottii var. elliottii and G = E/20 for hybrid. The results of the modulus and strength for Pinus elliottii var. elliottii and the hybrid were lower than those reported in the literature, showing that this batch inferior quality to apply to structures

Vitrocerâmicas para blindagens balísticas

The use of ceramic materials in ballistic armor is considerable. Such materials can be very harder and lighter than metallic materials commonly used and it presents advantages to replace metallic materials when necessary toughness can be achieved. However, as SiC and Al2O3 ceramic, traditionally used for shielding, still have high manufacturing cost or low density do not have enough to shield applications such as aircraft. An alternative is the glass-ceramics, ceramics obtained by controlled crystallization of glasses, whose properties can be adjusted by choosing the chemical composition of glass, heat treatment of crystallization and special treatments such as ion exchange on the surface, resulting in increased mechanical strength . The objective of this project is to study the kinetics of crystallization of a glass composition based on cordierite (2MgO.2Al2O3.5SiO2), low density and high hardness, for the manufacture of glass-ceramics for ballistic tests. Shown in this report are results of heat treatment of crystallization and characterization by thermal analysis (DSC) glass obtained previously, indicating uneven distribution of crystals, and drying, weighing, mixing of raw materials and a new fusion of glass, the same composition

Modelagem e Simulação Computacional das propriedades estruturais, eletrônicas e constantes elásticas do ZnO

The electronic, structural properties and elastic constants of the wurtzite phase of zinc oxide, ZnO, was investigated using computer simulation at Density Functional Theory level, with B3LYP hybrid functional and Hartree-Fock methodology. The electronic properties as well the band energy was investigated through the analysis of the band structures and density of states (DOS), and the mechanical properties was studied through the calculus of the elastic constants C11, C33, C44, C12 e C13. The results are in good agreement with experimental data found in the literature and in accordance with results obtained by another theoretical methodology

Estudo do efeito do modificador Al-Sr no tratamento de modificação do eutético da liga AA356

The AA356 alloy is an alloy widely used in the automotive industry and aerospace due to its excellent mechanical properties. Refining the structure of eutectic silicon aluminum alloys is a fairly common practice in the foundry through treatment known as modification. This can be achieved by modifying agent adding chemicals such as contained in groups I and IIa of the periodic table and rare earths (europium, céreioi, praseodymium, neodymium, etc.). Has the ability to modify the structure of the eutectic, but only sodium and strontium produce an action modifier strong when used in low concentrations. The modifying effect of the shafts turn silicon into a fibrous form and branched surrounded by metallic matrix in the form of a composite structure that has the highest limit of tensile strength, ductility and machinability. In this work will be obtained ingots with and without the modifier type Al-10% Sr, made in sand molds and are generated and analyzed cooling curves and also the study of the macrostructure and microstructure of the solidified material. It was found that by adding the Al-Sr made shorten the solidification time and lower the grain size

Comportamento fractal de superfície da zona de estiramento em aço 300M temperado

Fracture surfaces are the fracture process marks, taht it is characterized by energy release guieded by failure mode. The fracture toughness express this energy em stress and strain terms in pre-cracked samples. The strectch zone is the characteristic region forms by the transition of fatigue fracture and final fracture and it width demonstrate the relation with failure energy release.The quantitative fractography is a broadly tool uses in failure surfaces characterization that it can point to a material’s aspect or a fracture process. The image processing works like an investigation tool, guinding a lot of studies in this area. In order to evaluate the characterization effectivity and it respectivity studies, it used 300M steel that it was thermal treated by an aeronautical process known and it characterized by tensile test and energy dispersive spectroscopy (EDS). The tensile test of this material, made by ASTM E8, allowed the head treatment effectivity confirmation, beyond of mechanics porperties determination. The EDS confirmed the material composition, beyond of base the discussion about fracture mechanism presence. The fracture toughness test has also made, that it works to obtain the fracture surfeaces studies below self-similarity and self-affinity approaches. In front of all the exposed it was possible to conclude that the fractal dimension works like a study parameter of fracture process, allowinf the relation of their values with changes in thickness, which interferes directly in material’s behaviour in fracture toughness approach

Análise da estabilidade dimensional e resistência mecânica em bambu Guadua angustifolia pós-processos de tratamentos químicos e térmico

Nowadays, bamboo is being studied because of their strength properties according with their specific mass and speed of growth, which makes it an important alternative as a new resource that will help reduce pressure on forests and helpping them favoring the minimization of uncontrolled deforestation in many regions of Brazil. This study aimed, in general, to analyze physical and mechanical properties of the material with the divulgation of its potential for industrial application. To do so, in this research were determined in relation to the physical properties, moisture content, dimensional stability and the apparent densities and the mechanics and basic, just a tension parallel to grain, in order to observe the interference of various kinds of treatments (chemical, thermal and natural) on the strength and modulus of elasticity in this request. The species used was the Guadua angustifolia, a species native of Brazil. All tests were performed at Universidade Estadual Paulista - Campus Experimental Itapeva in the laboratory of Materials Properties. The methodology used for testing of moisture, density and tension parallel to grain were based on NBR 7190/1997 for the wood, and dimensional stability tests were based on much the same as in COPANT 462/1972 (South American) . The preservative treatments conducted followed the recommendation of each manufacturer. The values obtained in tests of physical properties were satisfactory especially with respect to density and dimensional stability analyzed by the coefficient of anisotropy, showed that, compared to wood, excellent quality for the shrinkage test, obtaining a coefficient of 1.2. With respect to parallel tensile tests to fibre results showed, in most cases, that test specimens with the presence of us have lower values of resistance and modulus of elasticity when compared with those without us. In the treatment of thermal-treatment there was an apparent treatment there was an apparent increase in...

Análise estatística da vida em fadiga de compósitos estruturais pela distribuição de Weibull

Nowadays technological trend is based on finding materials that could support low weight with satisfactory mechanical properties and for this reason composite material became a very attractive topic in research projects all over the world. Due to its heterogenic properties, this type of material shows scatter in mechanical test results, especially in cyclic loading. Therefore it is important to predict its fatigue strength behaviour by statistic analysis, once fatigue causes approximately 90% of the failure in structural components. The present work aimed to investigate the fatigue behaviour of the Twill/Cycom 890 composite, which is carbon fiber reinforced with polymeric resin as matrix and manufactured via RTM process (Resin Transfer Molding). All samples were tested in different tensile level in triplicate in order to associate these values. The statistical analysis was conducted with Two-Parameter Weibull Distribution and then evaluated the fatigue life results for the composite. Weibull graphics were used to determine the scale and shape parameters. The S-N curve for the Twill/Cycom composite was drawn and indicated the number of cycles to occur the first damages in this material. The probability of failure was associated with material reliability, as shown in graphics for the different tensile levels and fatigue life. In addition, the laminate was evaluated by ultrasonic inspection showing a regular impregnation. The fractographic analysis conducted by SEM showed failure mechanisms for polymeric composites associated to cyclic loadings ... (Complete abstract click electronic access below)

Comportamento fractal de superfícies de fadiga em ligas aeronaúticas

Fracture surfaces express sequences of events of energy release with crack propagation in metal alloys, the evolution of topographic features can indicate the lines of load action, failures during the use or processing. The quantitative fractography is an important tool in the study of fracture surfaces, because it allows their interpretation and characterization. In order to evaluate the effectiveness of the characterization of fracture surfaces grounded on concepts such as selfsimilarity and self-affinity, it used the 15-5PH steel that was characterized by metallographic and tensile tests. The metallography allows the microstructural characterization of this steel and proved the presence of the martensite phase in the slats form and a fine-grained, both in the radial and in the axial direction of the dowel. The tensile test (ASTM E8) of this material allowed the determination of the mechanical properties, so based on the obtained results it was possible to affirm that the 15-5PH steel has high mechanical properties and a good stretch. Besides, the specimens also underwent testing of crack propagation, standardized by ASTM E647-00, thus it was obtained the fracture surfaces for characterization under monofractal and multifractal approaches. In front of all the exposed it was possible to conclude that in all measurements the correlation between the crack tip position and the fractal dimension was established in accordance with changes in the thickness and in the fracture micromechanisms presents. Furthermore, the multifractal approach was more sensitive to these variations allowing a more detailed characterization of the morphology

Analise mecânica e microestrutural em estruturas tubulares aeronáuticas soldadas de aço ABNT 4130

Airplane Motor Cradles have a complex geometry, since they require different conbinations between different tubes and TIG welded in several angles. In T-25 aircraft and Universal T-27 Tucano (EMBRAER / FAB), besides having to bear the engine balance, these components maintain fixed the nose landing gear in another extremity. They are considered critical to flight safety, and for this reason, the aviation standards are extremely rigid in their production, imposing a zero index” of defects on the final weld metal quality. These structures may be containing an historical of welding repairs, whose effects on their structural integrity are not computed. In this work we analyzed the standardised AISI 4130 steel and the raw steel of tubes to the Airplane Motor Cradles. First of all, microscopy and microanalysis of the base steel, then we analyzed the effects of the TIG weld. Tensile testing was conducted to measure the difference between the mechanical properties of standardised steel and without this treatment

Obtenção e caracterização de compósitos via RTM com alta fração de fibras de carbono processados à temperatura ambiente

After confirming the high specific mechanical properties of composite materials by scientific studies conducted over the last decades, one of the challenges of this new class of materials is the ability to achieve mass production at a more affordable cost, which has become indispensable. The Resin Transfer Molding (RTM) is an excellent method for manufacturing composite materials. Despite being a process widely used by international companies in the production of high performance structural composites, only a short time the national aviation industry has shown interest in implementing this type of processing to more complex structures and greater structural responsibility. In aeronautical projects, the reproducibility and the relative low cost of this process, several studies have been performed in Brazil for learning and perfecting this technique. This process is suitable for producing polymer components both simple as complex geometry, and allows to achieve consistent thickness, with high quality finish and without limiting range. Polymeric composite components for the high mechanical stress applications such as aircraft structures, satellites, etc., require a strict control of volume fractions of the composite constituents, beyond the knowledge of their mechanical and thermal properties. Therefore, in this experimental work degree study on the mechanical, thermal and of porosity composites processed by RTM processed characterization was performed. This characterization was performed targeting a possible aerospace application of this composite material. For the production of composites, process equipment (RTM RTM injector Radius 2100cc) was used. The processed carbono/epoxy composites were characterized via flexure tests mechanically and thermally analysis via DMA, DSC and TGA. To determine the volume fraction of fibers, the composite samples were analyzed via matrix digestion (ASTM D3171) ... (Complete abstract click electronic access below)

Propriedades físicas de vidros Sb2O3-P2O5

This work presents experimental results of some physical properties of antimony phosphate glasses with compositions (x) Sb2O3 - (1-x) P2O5 (x = 0.75, 0.85, 0.90). Mechanical, thermal, optical and electrical properties were investigated: density, elastic moduli (Young's moduli and Poisson's ratio), Vickers microhardness, coefficient of thermal expansion, glass transition temperature, refractive index and electrical conductivity (for x = 0.75). There was no evidence of electronic conductivity by bipolaron hopping. Measurements of energy dispersive spectroscopy (EDS) showed that volatilization of Sb2O3 takes place during the glass melting

Desempenho estrutural de vigas em madeira laminada colada armada

The objective of the present work was to evaluate Pinus’ glued laminated timber (glulam) beams and steel reinforced glulam beams, using PU mono-component adhesive in lamination step and epoxy adhesive to bond steel bars. The mechanical performance was verified through bending test, and the adopted method based on homogenized section, to considerate the differences between wood and steel mechanical properties. The homogenization section method proved itself effective in obtaining the stiffness of the parts in MLCA. The stiffness of reinforced beams increased 91% in comparison with glulam beams, differing only 5.5 % from value of stiffness calculated

Análise do comportamento em fadiga de rodas ferroviárias fabricadas pelos processos de forjamento e fundição

Since the beginning of the railway industry until today, rail wheels are important components to the good working of a railway. For being a critical security item, design and maintenance are done with extremely care to avoid failures. Despite de fact of railway components be projected to support a big number of cyclic solicitation during its life, some accidents still occur. These accidents, despite the low frequency, always have great consequences, drawing in great financial, material, and people losses. Nowadays, railway component failure is relatively low, because it’s been projected to work below the materials Fatigue Resistance Limit, however, with the growing demand of faster trains and higher load for each axle, the occurrence probability is even bigger. This work includes a comparative study of two fabrication processes (casting and forging) applied in the production of rail wheels where it was measured the mechanical properties of traction and fatigue. The study also verified through microstructural analysis, hardness, traction and fatigue tests, statistical analysis of fatigue test results and fractographic analysis that forging process lead to better correlations between fatigue life and mechanical properties, providing more security in railroads, less wagon retention caused by corrective maintenance and smaller operational cost with its use