Resumo em Inglês:

Among all Predictive Maintenance techniques the oil analysis and vibration analysis are the most important for monitoring some systems. The integration of these techniques has the potential to revolutionize industrial practices and provide a large economic gain for industries. To study the integration of both techniques a bench test was set up and put to work to the extreme limit of use. Tests were carried out with the lubricant recommended by the manufacturer of the equipment, using lubricants supplemented with various percentages of liquid contaminant and lubricants supplemented with several percentages of solid contaminant. This paper presents the results of the first test, that is, with the oil recommended by the manufacturer in extreme conditions. From the results it was observed that if in a system an abnormal occurrence takes place, for example an extra load during a certain period of time, the lubricant analysis can be used together with the vibration analysis to complement it.

Resumo em Inglês:

Natural convection heat and mass transfer along a vertical plate embedded in a doubly stratified power-law fluid saturated non-Darcy porous medium with uniform heat and mass flux is presented. The governing partial differential equations are transformed into ordinary differential equations using similarity transformations and then solved numerically. The effects of magnetic parameter, stratification parameter and power-law index on the velocity, temperature and concentration are illustrated graphically.

Resumo em Inglês:

One of the greatest challenges in today's industrial robotics is the development of off-line programming systems that allow drastic reduction in robots' reprogramming time, improving productivity. The article purpose is to pave the way to the construction of generic calibration systems easily adapted to any type of robot, regardless their application, such as modular robots and robot controllers specifically designed for non-standard applications. A computer system was built for developing and implementing a calibration system that involves the joint work of computer and measurement systems. Each step of this system's development is presented together with its theoretical basis. With the development of a remote maneuvering system based on ABB S3 controller experimental tests have been carried out using an IRB2000 robot and a measurement arm (ITG ROMER) with 0.087 mm of position measurement accuracy. The robot model used by its controller was identified and the robot was calibrated and evaluated in different workspaces resulting in an average accuracy improvement from 1.5 mm to 0.3 mm.

Resumo em Inglês:

This paper presents a brief review on Lagrangian-Hamiltonian Mechanics and deals with the several developments and extensions in this area, which have been based upon the principle of D'Alambert or the other. It is not the intention of the authors to attempt to provide a detailed coverage of all the extensions of Lagrangian-Hamiltonian Mechanics, whereas detailed consideration is given to the extension of Noether's theorem for nonconservative systems only. The paper incorporates a candid commentary on various extensions including extension of Noether's theorem through differential variational principle. The paper further deals with an extended Lagrangian formulation for general class of dynamical systems with dissipative, non-potential fields with an aim to obtain invariants of motion for such systems. This new extension is based on a new concept of umbra-time, which leads to a peculiar form of equations termed as 'umbra-Lagrange's equation'. This equation leads to a simple and new fundamental view on Lagrangian Mechanics and is applied to investigate the dynamics of asymmetric and continuous systems. This will provide help to understand physical interpretations of various extensions of Lagrangian-Hamiltonian Mechanics.

Resumo em Inglês:

Grinding is one of the most widely used manufacturing processes and, in the last few decades, has developed considerably. An example of these developments is hardening by grinding, an operation that is being studied to provide an option to the conventional hardening processes. This study presents the use of a cylindrical grinding process to produce a martensitic structure on the surface of SAE 4340 steel workpieces, and aims at adjusting the parameters of this process. To do much, a set of experiments were carried out using three cycles of grinding: the first one just to obtain a workpiece with regular diameter; the second cycle is that which will provide heating and cooling of the ground workpiece; and the last cycle is to provide corrections to the dimensions and roughness. Results of the experiments showed that hardening by grinding is possible and that the workpiece achieved hardness levels compatible to those provided by the conventional hardening processes. The use of such a process for surface hardening purposes has been researched and developed with a view to increasing the productivity of the process, ensuring dimensional and surface quality, in addition to mechanical resistance.

Resumo em Inglês:

The AZ31 magnesium alloy tube was used for electromagnetic forming experiment of three kinds of input voltages. The stress-strain state of tube forming was analyzed. It was shown that the cause of oblique crack of tube was σr of axial inhomogeneous distribution and σz, and the cause of longitudinal crack was σr and σè of inhomogeneous distribution in circumferential direction. Moreover, the electromagnetic field and force field during electromagnetic forming was simulated by ANSYS software. The experiment proved the simulation result.

Resumo em Inglês:

Sheet metal bending is one of the most widely applied sheet metal operations. The bending operations present several technical problems in production, such as prediction of spring-back and the punch load. In this paper, the value of the spring-back and bending forces are investigated for a low carbon steel material. Two thicknesses of material (0.95 and 0.75 mm) are applied. Sheet metal components, which are used in the experiments, have oblong holes on their bending surfaces. The influence of the area of the holes, die angles, die widths and punch radius on the value of the spring-back and the bending forces in V-die bending is studied. It is found that all these parameters affect the spring-back and the bending forces, but not in the same way. A new equation is suggested in this paper to predict the bending forces in V-shaped dies for parts with holes on the bending surfaces.

Resumo em Inglês:

Cutting fluids are difficult and expensive to recycle. These drawbacks mentioned can be reduced or eliminated by performing the cutting operations with minimum quantity lubrication or without using any cutting fluid. In this study, the effects of different cutting parameters on performance characteristics are studied empirically during the drilling of Al7075. The work piece surface roughness and the temperature changes due to the incurred heat at the cutting process are taken as performance outputs. In the experiments, HSS tools with a diameter of 8 mm and an angle of 118o were used. Minimum quantity lubrication (MQL), compressed air and dry processing (without the usage of any cooling liquid) techniques are used as the applied cooling technique. In the processing technique with MQL, the cooling liquid is sent pulverized on the interface between the work piece and the tool. Boron oil-water emulsion is used as the cutting liquid. As a result of the experiments, it is determined that better results are achieved with the MQL technique than with other cooling techniques. The best surface roughness is achieved at 20 m/min cutting speed and 0.1 mm/rev feed rate.

Resumo em Inglês:

The well-known CGAM optimization problem was formulated to serve as a benchmark for comparison of different thermoeconomic methodologies. The CGAM cogeneration plant produced 30 MW of power and 14 kg/s of saturated vapor at 20 bar. The objective function was the total cost rate of the system, related to thermodynamic variables and installation costs. Because the CGAM problem originates from an academic viewpoint, its models do not reflect the industrial reality of energy systems, and do not conform to important operational and technological restrictions. The objective of this work is to propose an alternative cogeneration-system optimization problem, denoted the MPCP problem - Maximum Profit Cogeneration Plant, which incorporates functional economic concepts and modern technologies. The objective function is the net present value (NPV) of the monetary gain for the period of plant operation. The optimum (i.e., maximum) NPV value is obtained using two different professional optimization toolboxes appropriate for multivariable nonlinear constrained functions. The optimal operational conditions indicate that the MPCP plant reaches the allowed physical limits of the main equipment, namely, maximum efficiency of the gas turbine generator set and minimum temperature difference inside the heat recovery steam generator. Formal findings like these help to direct efforts to improve current technologies.

Resumo em Inglês:

In the ceramic industry, rarely testing systems were employed to on-line detect the presence of defects in ceramic tiles. This paper is concerned with the problem of automatic inspection of ceramic tiles using Infrared Images and Artificial Neural Network (ANN). The performance of the technique has been evaluated theoretically and experimentally from laboratory and on line tile samples. It has been performed system for IR image processing and, utilizing an Artificial Neural Network (ANN), detecting defected or no defected tile. The system has been applied to detect on-line measurement results achieved at the exit of the press. The above automatic inspection procedures have been implemented and tested on a number of tiles using synthetic and real defects. The results obtained confirmed the efficiency of the methodology defect detection in raw tile and its relevance as a promising approach on-line, as well as included in quality control and inspection programs.

Resumo em Inglês:

This paper deals with the permutation flow shop scheduling problem with separated and sequence-independent machine setup times. A heuristic method with the objective of minimizing the total time to complete the schedule is introduced. The proposed heuristic is based on a structural property of this scheduling problem, which provides an upper bound on the idle time of the machines between the completion of the setup task and the beginning of job processing. Experimental results show that the new heuristic outperforms two existing ones.

Resumo em Inglês:

This work describes the steps required to construct a hydrodynamic model of the Guajará Bay, using Geographic Information Systems and the Finite Element Method. An overview of the problem that motivates this modelling procedure, i.e., the pollutant dispersion, is presented. The computer software used is then discussed, stressing the links between the data model entities. The calibration procedure is described. The methods used to obtain field data and the results obtained are presented, alongside the main flow patterns of the water. The simulations and applications of the model are discussed at the end of the paper.

Resumo em Inglês:

This work presents a method for numerical simulation of viscous fluid flows based on the use of filtered Lagrangian Navier-Stokes equations. It is based on the hypothesis that the small scale motions are responsible for the homogenization of the physical properties in infinitesimal fluid parcels through a mixing process, mathematically expressed as a spatial filter, which implicitly works as an averaging operator. When the filter was applied to the Navier-Stokes equations for incompressible flows, in the Lagrangian frame of reference, the functional form of the resulting equations was preserved, and the number of unknowns remained the same as the number of available equations, therefore circumventing the need of an explicit subgrid scale model. The method was validated by performing two-dimensional simulations of high Reynolds number wake flows. It was verified that the main large scale characteristics of the flows were properly replicated.

Resumo em Inglês:

In this paper, numerical simulations of incompressible flows around rotating circular cylinders have been performed. The two-dimensional Navier-Stokes equations are solved by using a Cartesian non-uniform grid. The Immersed Boundary Method (IBM) with the Virtual Physical Model (VPM) was used in order to model the presence of the circular cylinder in the flow. The fractional time step method was used to coupling the pressure and velocity fields. The simulations were carried out for Reynolds numbers equals to 60, 100 and 200 for different specific rotations. The effects of rotation on flow characteristics and fluctuating forces were investigated. The Strouhal number, obtained by performing the Fast Fourier Transform (FFT) of the temporal distribution of the lift coefficient, and the pressure coefficients, were also been calculated. Vorticity contours are presented considering different values of the Reynolds number and specific rotation. The numerical results obtained are compared to those obtained by other authors and the usefulness of the numerical methodology composed by the combination of the IBM with the VPM to simulate flows in the presence of mobile bodies is highlighted.

Resumo em Inglês:

The goal of this work is to propose a new methodology to simulate turbulent thermal wall flows using the classical κ - ε model. The focus of this approach is based on the manner used to implement heat flux boundary conditions on the solid walls. In order to explain and to validate this new algorithm, several test cases are presented, testing a great range of flows in order to analyze the numerical response on different physical aspects of the fluid flow. The proposed approach uses simultaneously a thermal wall law, an analogy between fluid friction and heat transfer and an interpolating polynomial relation that is constructed with a data base generated on experimental research and numerical simulation. The algorithm used to execute the numerical simulations applies the classical κ - ε model with a consolidate Reynolds and Favre averaging process for the turbulent variables. The turbulent inner layer can be modeled by four distinct velocity wall laws and by one temperature wall law. Spacial discretization is done by P1 and P1/isoP2 finite elements and the temporal discretization is implemented using a semi-implicit sequential scheme of finite differences. The pressure-velocity coupling is numerically solved by a variation of Uzawa's algorithm. To filter the numerical noises, originated by the symmetric treatment of the convective fluxes, it is adopted a balance dissipation method. The remaining non-linearities, due to explicit calculations of boundary conditions by wall laws, are treated by a minimal residual method.