Lucilene de Oliveira Rodrigues

Otimização do processo de soldagem FCAW usando o erro quadrático médio multivariado

The optimization of welding processes is not a trivial task, mainly due to the great number of exigible and desirable characteristics that must be analyzed. Moreover, the optimization of a welding process with multiple characteristics without to consider the variance-covariance structure, may lead to inadequate optimum. To help in this task, a method of multiobjective optimization based in the Multivariate Mean Square Error applied in the study of multiple correlated characteristics of a FCAW (Flux Cored Arc Welding) welding process will be presented. This method characterized by a combined approach based in the Response Surface Methodology, Design of Experiments and Principal Components Analysis consisted in an attempt to achieve the nearest values to specific targets, for each studied characteristic (penetration, deposition rate, deposition efficiency, convexity index of the weld bead and dilution) considering the welding variables expressed in function of welding voltage (V), wire feed speed (Va) and the contact tip to workpiece distance (d). The results point out a good adequacy of the proposed method.

Optimization of the FCAW process by weld bead geometry analysis

The flux cored arc welding process has grown in use in recent times as a function of its characteristics of high rate of deposition, associated with suitable mechanical properties in the welded joint. However, many aspects still remain obscure in regard to greater utilization of this process. As a result, the intention of this work is the analysis and optimization of the voltage, wire feed speed and contact tip part distance welding parameters, in a process using tubular wire with shielding gas, on the penetration and convex index of the weld. By means of statistical techniques, a mathematical model was developed with subsequent optimization of the responses. Based on the results obtained, the strong influence of the wire feed speed on the process was seen, followed by the voltage and, with less intensity, the contact tip to workpiece distance (CTWD). Statistical analyses indicated that the best condition for the parameters analysed was obtained with voltage values between 32 and 34 V, associated with a wire feed speed of 12 m/min and a CTWD of 20 mm. On the other hand, tensions at around 36 V caused surface defects that prejudiced the quality of the weld. Later tests showed an acceptable forecast of the results of the mathematical models when compared to the actual results.

FCAW process optimization using the multivariate mean square error

Optimization of welding processes is not a trivial task, mainly due to the great number of required and desirable characteristics that must be analysed. Moreover, the optimization of a welding process with multiple characteristics without considering the variance–covariance structure may lead to inadequate optimum. To help with this task, a method of multi-objective optimization based on the multivariate mean square error applied in the study of multiple correlated characteristics of a flux-cored arc welding process is presented. This method characterized by a combined approach based on the response surface methodology, design of experiments, and principal components analysis consisted of an attempt to achieve the nearest values to specific targets, for each characteristic (penetration, deposition rate, deposition efficiency, convexity index of the weld bead, and dilution), considering the welding variables expressed as a result of welding voltage (V), wire feed speed (Va), and contact tip to workpiece distance (d). The results point, to a good adequacy of the proposed method.

Aerodynamic Analysis Using CFD for Gas Turbine Combustion Chamber

In the past few years, with the development of advanced numerical computational codes, numerical simulation became a promising option to developing and improving the technology in different fields. The obtained results by simulations are used to get important information during the design phase or optimization of industrial equipment. Its employment generates reliable results at low cost due to the reduced number of experiments as well as the opportunity to develop new products and perform many simulations before its production. However, the numerical simulation credibility can only be verified when compared to the obtained results by experiments. This work aims to present and evaluate different aerodynamics models applied to combustion chambers using a CFD tool. In addition, aerodynamic analysis is made in a model of combustion chamber, where the flow is simulated with successive refining of the mesh as part of its validation process. For it, it is used a Low Nox Emission Combustion Chamber from Floxcom project as reference to validate turbulence models. Once that it is done, the selected turbulence model with satisfactory precision is used to describe the aerodynamic behavior of an annular combustion chamber from velocity and pressure distribution, which are important parameters to set load losses and recirculation intensity, which can affect the complex phenomenon of combustion.Copyright