Resumo em Inglês:

In the present work, the Digital Image Correlation (DIC) measurement method is used to obtain the displacement field of specific regions of a cantilever beam under bending. These fields are used within an inverse analysis scheme in order to obtain the elasticity modulus of the beam material. The parameter estimation is performed by means of the minimization of an error function comprising of the difference between the displacement fields obtained from the experiment and from an appropriate mathematical model. The inverse problem is solved by means of the classical Levenberg-Marquardt nonlinear parameter estimation technique. The estimate obtained for the elasticity modulus is validated taking into account new experimental data obtained through modal analysis of another beam-like specimen which, in turn, is made of the same material as the original one.

Resumo em Inglês:

A phase-field model is proposed for the simulation of microstructure and solute concentration during the solidification process of Fe-C-P ternary alloys. A relation between material properties and model parameters is presented. Two-dimensional computation results exhibit dendrites in Fe-C-P alloys for different phosphorus concentrations. Alterations in the phosphorus concentration appear to affect the advance speed of the solid-liquid interface. Such an alteration is due to the small diffusivity of phosphorus during the solidification process.

Resumo em Inglês:

One of the main competitive moves observed in the last two decades was the change in product pricing, evolving from a cost plus margin paradigm to a market-driven one. In the present days, the customer defines how much he or she is willing to pay for a given product or service. As a result, traditional cost accounting procedures and their related pricing formulas cannot accommodate that kind of change without significant turnaround in practices and concepts. Taking that into consideration, this paper proposes a procedure tool based on the contribution margin concept as well as on cutting process economic analysis to be applied to small and medium size (SMS) machining service companies. To improve the reader's comprehension, a numerical simulation is also presented. All the figures have been calculated taking into account the Brazilian currency (Reais). At this moment (2009), the exchange rate is approximately R$2.40 to US$1.00. The numerical simulation presented herein was developed mainly to allow the reader to follow the proposed procedure and not to consider the numeric results as actual data.

Resumo em Inglês:

The problem of flow inside a square cavity whose lid has constant velocity is solved. This problem is modeled by the Navier-Stokes equations. The numerical model is based on the finite volume method with numerical approximations of second-order accuracy and multiple Richardson extrapolations (MRE). The iterative process was repeated until the machine round-off error achievement. This work presents results for 42 variables of interest, and their discretization errors estimates, on the 1024 x 1024 nodes grid and the following Reynolds numbers: 0.01, 10, 100, 400 and 1000. These results are compared with sixteen sources in literature. The numerical solutions of this work are the most accurate obtained for this problem to date. The use of multiple Richardson extrapolations reduces the discretization error significantly.

Resumo em Inglês:

Turbulent natural convection of air that happens into inner square cavity with localized heating from horizontal bottom surface has been numerically investigated. Localized heating is simulated by a centrally located heat source on the bottom wall, and two values of the dimensionless heat source length ? are considered in the present work. Solutions are obtained for several Rayleigh numbers with Prandtl number Pr = 0.70. The horizontal top surface is thermally insulated and the vertical surfaces are assumed to be the cold isothermal surfaces whereas the heat source on the bottom wall is isothermally heated. In this study, the Navier-Stokes equations are used considering a two-dimensional and turbulent flow in unsteady state. The Finite Element Method (FEM) with a Galerkin scheme is utilized for solving the conservation equations. The formulation of conservation equations is carried out for turbulent flow and the implementation of turbulent model is made by Large-Eddy Simulation (LES). The distributions of the stream function and of the temperature are determined as functions of thermal and geometrical parameters. The average Nusselt number Num is shown to increase with an increase in the Rayleigh number Ra as well as in the dimensionless heat source length ?. The results of this work can be applied to the design of electronic components.

Resumo em Inglês:

Vibration absorbers, also called vibration neutralizers, are mechanical systems to be attached to another mechanical system, or structure, called the primary system, with the purpose of reducing vibration and sound radiation. The simplest form of a vibration absorber is that of a single degree of freedom system, where the "spring" is made of a viscoelastic material, perhaps with some metallic inserts. This paper sets out to describe how to design a best possible system of viscoelastic vibration absorbers for an available viscoelastic material, known by its four fractional parameter model, by using a novel objective function, defined through a Frobenius norm. A real example is presented and discussed.

Resumo em Inglês:

In upsetting process, an initial block of metal (billet) is compressed between two or more dies to produce a complex part. Geometry of the final product is strongly dependent on the shape of initial work piece as well as on the perform shapes at each of the subsequent forming stages. Design of the optimum preform for near net shape manufacturing is a crucial step in the designing of many upsetted products of mild steel. In this study, the same is realized by using profile map, which is generated using the results of FE simulations of varying geometrical and processing parameters. The map is further verified experimentally using a mild steel specimen. It is shown that preform designed on the basis of profile map results in near net shape manufacturing. Such map offers a powerful tool for near net shape upsetting.

Resumo em Inglês:

The atmospheric pressure Tungsten Inert Gas (TIG) arc plasma in argon is studied combining results from emission spectroscopy temperature maps with composition data and transport parameters available from literature. Two arc currents are considered and maps are obtained for the Debye number, the number of particle in the Debye sphere, which shows values of the order of 10 or less in the core region of these arcs. This low number puts into serious question the plasma quasi-neutrality. It is striking that this circumstance occurs where Local Thermodynamical Equilibrium (LTE) is usually assumed in these discharges. It is shown that TIG arcs violate the quasi-neutrality requirements and, as such, these discharges are called 'plasma' quite improperly. Differently from previously published works, the starting point of the discussion is the experimental two-dimensional temperature maps.

Resumo em Inglês:

This paper presents the experimental analysis of the propagation of a disturbance with a fixed frequency in the incidence velocity of the cross flow through a tube bank, and its influence on the velocity fluctuations inside the bank. The disturbance is generated outside the bank by vortex shedding from an obstacle. The tube banks investigated had square arrangement and aspect ratio P/D = 1.60 and 1.26. Air was the working fluid. Measurements were performed with hot wires. Behavior of fluctuating velocities is described by means of autospectral density. The results show that the frequency of the disturbance remains unchanged as it passes through the bank, and subsists until the 4th row in spite of the high turbulence intensities and of the fact that flow velocity inside the bank varies with the position. This fact indicates that external excitations can be transferred to the solid boundaries of the bank maintaining their original frequency. Continuous Wavelet Transforms of the signals show that, in time domain, the frequency of the disturbance has an almost steady behavior.

Resumo em Inglês:

The objective of this paper is to study the vortex shedding from a circular cylinder near a moving ground; this is done using the Vortex Method. A moving ground has been widely used in the field of experimental vehicle aerodynamics, especially of high-performance racing cars, to properly consider the ground effect on the vehicles aerodynamic. In experimental work as well as in numerical simulations, the ground plane develops a boundary layer that interferes with the body viscous wake, leading to not so precise results. A ground moving with the incoming flow velocity, however, does not allow the development of a boundary layer. The results of our numerical simulations show that the critical drag behavior is directly related to a global change in the wake structure of the cylinder in the ground effect. Comparisons with experimental data are encouraging.

Resumo em Inglês:

Biomass derived vegetable oils are quite promising alternative fuels for agricultural diesel engines. Use of vegetable oils in diesel engines leads to slightly inferior performance and higher smoke emissions due to their high viscosity. The performance of vegetable oils can be improved by modifying them through the transesterification process. In the present work, the performance of single cylinder water-cooled diesel engine using methyl-ester of Jatropha oil as fuel was evaluated for its performance and exhaust emissions. The fuel properties of biodiesel such as kinematic viscosity, calorific value, flash point, carbon residue and specific gravity were found. Results indicated that B25 has closer performance to diesel and B100 has lower brake thermal efficiency, mainly due to its high viscosity compared to diesel. The brake thermal efficiency for biodiesel and its blends was found to be slightly higher than that of diesel fuel at tested load conditions and there was no difference between the biodiesel and its blended fuels efficiencies. For Jatropha biodiesel and its blended fuels, the exhaust gas temperature increased with increase in power and amount of biodiesel. But, diesel blends showed reasonable efficiency, lower smoke, CO2, CO and HC.

Resumo em Inglês:

Two non-singular boundary element method (BEM) algorithms for two-dimensional potential problems have been implemented using isoparametric quadratic, cubic and quartic elements. The first one is based on the self-regular potential boundary integral equation (BIE) and the second on the self-regular flux-BIE. The flux-BIE requires the C1,α continuity of the density functions, which is not satisfied by the standard isoparametric elements. This requirement is remedied by adopting the relaxed continuity strategy. The self-regular flux-BIE has presented some poor and oscillatory results, mainly with continuous quadratic elements. This odd behavior has completely disappeared when discontinuous elements, which satisfy the continuity requirement, were applied, and this suggests that the 'relaxed continuity hypothesis' seems to be the main cause of numerical errors in the implementation of the self-regular flux-BIE. On the other side, the potential algorithm has shown very reliable solutions.

Resumo em Inglês:

This work aims at developing a genetic algorithm (GA) to pursue the optimization of hybrid laminated composite structures. Fiber orientation (predefined ply angles), material (glass-epoxy or carbon-epoxy layer) and total number of plies are considered as design variables. The GA is chosen as an optimization tool because of its ability to deal with non-convex, multimodal and discrete optimization problems, of which the design of laminated composites is an example. First, the developed algorithm is detailed explained and validated by comparing its results to other obtained from the literature. The results of this study show that the developed algorithm converges faster. Then, the maximum stress, Tsai-Wu and Puck (PFC) failure criteria are used as constraint in the optimization process and the results yielded by them are compared and discussed. It was found that each failure criterion yielded a different optimal design.