Resumo em Inglês:

A direct optimization study was performed to produce a preliminary evaluation of the potential benefits of a mission adaptive wing employing variable camber technology in typical jet transport aircraft missions, in terms of fuel efficiency increase directly obtainable from airfoil viscous drag reduction alone. A 2-D airfoil analysis approach was adopted, associated with an idealized variable camber mechanism based on elastic deformation and surface extension. Using a direct function optimization program coupled to a viscous-inviscid airfoil analysis routine, optimized variable camber configurations were obtained for several weight conditions of a typical transport aircraft along a sub-critical cruise mission leg. Independent runs were executed considering only trailing and both leading and trailing-edge camber variation and, for each of them, an integrated range parameter has been obtained, proportional to the maximum possible aircraft range. Results indicate that the range increases up to 7.03% over the base airfoil that could be reached with camber variation in the trailing edge region only, and up to 24.6% when leading edge adaptation was considered simultaneously. However, pressure distribution results indicate that the high leading-edge curvatures required for that would probably decrease cruise critical Mach. On other hand, the trailing-edge only approach may offer better conditions for supercritical cruise.

Resumo em Inglês:

This work describes an experimental technique for obtaining, simultaneously, the thermal diffusivity and thermal conductivity of polymer materials. This technique uses experimental data from only one of the sample surfaces. It means functions using experimental and calculated temperature are defined. An objective function representing the eigenvalue phase angle is used to determine thermal diffusivity, while a least square error function is used for the thermal conductivity estimation. The sequential unconstrained optimization technique BFGS is used to calculate the search direction. In each case the golden section method is used in a one-dimensional search, followed by a polynomial approximation. A comparison with the flash method and the guarded hot plate method gives a deviation of 2.97 % and 0.63 % for thermal diffusivity and thermal conductivity, respectively, for a Polychloroethylene (PVC) sample. An uncertainty analysis is also presented.

Resumo em Inglês:

This paper proposes a new model for the representation of design processes based on the evolutionary aspect of this activity. Also this work presents an innovative approach to object-oriented design processes and a new pragmatic view of the Design Problem Space (DPS). Furthermore, the principles underlying the model are derived from a working CAD system in furnace design developed during the present research work. The information related to the artifact form (space representation), as well as those associated to the functions (rules and nature laws) that the form should attend to, are incorporated by the model. The proposed model is structured in terms of a small number of object types which are capable of building an efficient and robust hierarchical tree. This tree incorporates all the requirements associated with the artifact from the conceptual stage up to the stage of the artifact complete specification.

Resumo em Inglês:

This work aims to apply the disturbance theory to accomplish sensitivity computations in problems of pollutant transported in liquid media modeled through the advection-diffusion-reaction equation. The numerical solution of the differential equation that describes the behavior of the system was found via the SUPG ("Streamline Unwinding Petrov Galerkin") finite element technique. Simulations were done for different Péclet numbers. Then, the adjoint equation of the advection-diffusion-reaction equation was derived for the one-dimensional case and the expression of the coefficient of sensitivity of a generic functional related to a generic parameter was obtained. The sensitivities of the mean and instantaneous pollutant rates were analyzed with relation to the following parameters: drag speed of the flowing current and Péclet number. Results of the sensitivity coefficient obtained with first and second order perturbation methodology satisfactorily matched the same values calculated by the direct method, that is, by means of the direct solution of the advection-diffusion-reaction equation by changing the values of input data parameters.

Resumo em Inglês:

In this paper, three-dimensional boundary integral computer simulations of emulsions in shear flows are described. Results for ordered BCC emulsions with dispersed-phase volume fractions below the critical concentration are presented. Complex rheological features including: shear-thinning viscosities, normal stress differences, and a nonlinear frequency response are also explored. For deformable drops, pairwise collision produces net cross-flow displacements that govern self-diffusion of drops. We compute trajectories of two interacting drops in shearing and present interesting numerical simulations of three dimensional gravity-induced motion of two drops. The results also demonstrate the feasibility of simulating high-volume-fraction emulsions and foam.

Resumo em Inglês:

This work concerns the application of a mesoscopic scale fatigue criterion to predict the initiation of cracks in components under fretting conditions. A verification of the analysis is carried out by considering available experimental data for fretting fatigue in a high strength Aluminium alloy commonly used in the aerospace industry. These experiments revealed there is a contact size effect in fretting fatigue life. The results show that the mesoscopic scale fatigue criterion can correctly predict the initiation of fretting cracks for larger contact configurations. It is concluded that the reason for the poor performance of the criterion in predicting failure at smaller contacts may well be related to the effect of the stress gradient, a variable not accounted for in the mesoscopic criterion here assessed.

Resumo em Inglês:

A particulate feeding system based on air flluidization principles was developed at the Thermal and Fluids Engineering Group at EESC-USP. The system is basically formed of a cylindrical chamber comprising two levels of fluid bed distributor plates. The performance of the system was addressed. Repeatability experiments were performed in order to check out for the possibility of solids feeding control through a sphere valve which controls the air feed rate. Silica sand particles of three different size were used, with mean diameters of 152, 287 and 484 µm. Experiments showed that the total particulate discharge depends on the primary air feeding rate, the distance between the exit of the feeding hopper and the primary air distributor plate, and the particulate diameter, but independs on the secondary air feeding rate. The system was observed to be of difficult control and showed poor repeatability. However, the system was found to be an excellent device for distributing the flow of solids throughout several discharge sections. For the operational conditions considered and air volumetric flowrates above 3×10-3 m³/s the deviation on the particulate mass flowrate through a given discharge section related to the average value through the four sections of the injector was always below 5 %.

Resumo em Inglês:

This paper presents the experimental study of pressure and velocity fluctuations and their interdependence, in the turbulent flow impinging on arrangements of yawed circular cylinders simulating inclined tube banks with square arrangement and a pitch to diameter ratio of 1.26. Measurements were performed with hot-wires and a pressure transducer. Behaviour of fluctuating quantities is described by means of dimensionless autospectral density functions and cross correlations. Experimental results indicates the presence of two different phenomena of vortex generation in inclined tube banks.

Resumo em Inglês:

The high percentage of the refrigeration costs (17%) in the operational production costs, the ecological subjects, the lawlegal demands related to the preservation of the environment and the human health justify the recent researches about the restriction towards the use of abundant cutting fluid in machining processes. However, it is important to point out that the use of a minimal mist lubrication (mixture of air and oil) has been possible in production processes for machining, due to the technological development of tool materials and also machine-tools. The objective of this work is to test the minimum quantity of lubricant (MQL) technique (10 ml/h of oil) mixed in a flow of air in the drilling process of aluminum silicon alloy (SAE 323) with a solid carbide drill (K10). The input variables were drill diameter (and consequentelyconsequently, depth of cut) and cutting speed. The results showed that when high depth of cut and cutting speed are used, the operation using abundant fluid is not possible because the drill breaks after a few holes. Moreover, the quality of the holes obtained using MQL is not worse than that obtained for with smaller cutting speed and depth of cut.

Resumo em Inglês:

The main objective of this paper is to use a recurrent neural network (RNN) to determine the trunk motion for a biped-walking machine, based on the zero-moment point (ZMP) criterion. ZMP criterion can be used to plan a stable gait for a biped-walking machine that has a trunk (inverted pendulum). So, a RNN is trained to determine a compensative trunk motion that makes the actual ZMP get closer to the planned ZMP. In this context, an identification scheme is presented to obtain the vector of parameters of the RNN. A first order standard back-propagation with momentum (BPM) is used to adjust free parameters for the network. Artificial neural network brings up important features for function approximation. This was the main reason to use an RNN to determine the trunk motion. The proposed scheme is simulated on a 10-degree-of-freedom biped robot. The results confirm the convergence of the proposed scheme, proving this is a new way to solve this classical problem in the biped-walking machine area.

Resumo em Inglês:

We report herein on a comparison of the performance of two different grinding wheels (conventional and CBN) in the transverse cylindrical grinding of a eutectic alloy. Three cutting conditions were tested: rough, semi-finishing and finishing. The parameters of evaluation were the cutting force, roughness and wheel wear. The optimal cutting force and roughness values were obtained when grinding with the conventional wheel, due to the superior dressing operation performed under every cutting condition tested. Although the CBN wheel presented the best G ratio values, they were lower than expected owing to the inappropriate dressing operation applied. Excessive wheel corner wear was detected in both wheels, caused by the grinding kinematics (transverse grinding) employed. In terms of cutting force and roughness, the conventional wheel proved to be the better choice under the conditions tested. However, in terms of the G ratio, a cost analysis is crucial to determine whether the differences between the wheels justify the use of the CBN wheel, in which case the dressing operation requires improvement.

Resumo em Inglês:

A capital issue in roll-gap control for rolling mill plants is the difficulty to measure the output thickness without including time delays in the control loop. Time delays are a consequence of the possible locations for the output thickness sensor, which usually is located some distance away from the roll gap. In this work, a new model-based predictive control law is proposed. The new scheme is a neural network based predictive control structure which is applied to roll-gap control with outstanding results. It is shown that the neural network based predictive control permits to overcome the existing time delays in the system dynamics. The proposed scheme implements a virtual thickness sensor, which releases an accurate estimate of the actual output thickness. It is shown that the dynamic response of the rolling mill system can be substantially improved by using the proposed controller. Simulation results are presented to illustrate the controller performance.

Resumo em Inglês:

The non-linear dynamics of a pin-ended elasto-plastic beam is discussed in this contribution. Ideal plasticity is in focus. Free and forced responses are considered. An iterative numerical procedure, based on the operator split technique, is developed. This work shows that jump phenomenon and sensitivity to initial conditions imply that the system response may become unpredictable even when a periodic response is expected. Chaotic motion is also associated with the unpredictability of the beam response.

Resumo em Inglês:

The electromagnetic fuel injector (EFI) predominates in almost all electronic spark-ignited engine control systems because of its simple, precise and reliable functioning. A new non-linear general mathematical model to predict the EFI performance and to confront its theoretic response with experimental data is proposed. A confrontation to the Element Finite Method is also done.