Emerson José de Paiva

Weighted Multivariate Mean Square Error for processes optimization: A case study on flux-cored arc welding for stainless steel claddings

A mathematical programming technique developed recently that optimizes multiple correlated characteristics is the Multivariate Mean Square Error (MMSE). The MMSE approach has obtained noteworthy results, by avoiding the production of inappropriate optimal points that can occur when a method fails to take into account a correlation structure. Where the MMSE approach is deficient, however, is in cases where the multiple correlated characteristics need to be optimized with varying degrees of importance. The MMSE approach, in treating all responses as having the same importance, is unable to attribute the desired weights. This paper thus introduces a strategy that weights the responses in the MMSE approach. The method, called the Weighted Multivariate Mean Square Error (WMMSE), utilizes a weighting procedure that integrates Principal Component Analysis (PCA) and Response Surface Methodology (RSM). In doing so, WMMSE obtains uncorrelated weighted objective functions from the original responses. After being mathematically programmed, these functions are optimized by employing optimization algorithms. We applied WMMSE to optimize a stainless steel cladding application executed via the flux-cored arc welding (FCAW) process. Four input parameters and eight response variables were considered. Stainless steel cladding, which carries potential benefits for a variety of industries, takes low cost materials and deposits over their surfaces materials having anti-corrosive properties. Optimal results were confirmed, which ensured the deposition of claddings with defect-free beads exhibiting the desired geometry and demonstrating good productivity indexes.

Metodologia integrada para mapeamento de falhas: uma proposta de utilização conjunta do mapeamento de processos com as técnicas FTA, FMEA e a análise crítica de especialistas

Abstract Faults are understood as non-conformities in productive activities. Therefore, the study of approaches that aim to eliminate and/or mitigate failures is important and even considered essential. Since the literature on this subject suggests the use of techniques for fault control and prevention, the present article aims to propose integration among process mapping, Fault Tree Analysis (FTA), and the Failure Modes and Effects Analysis (FMEA), as means to reducing and/or eliminating faults. The proposed approach considers process mapping as the starting point, and FMEA, as the concluding stage. The method presented is conducted by means of a proposed technique called Expert Critical Process Analysis. To achieve this goal, bibliographical research was undertaken to enable the conceptualization of each listed technique, followed by an analysis of their integration. The proposed methodology is applied in a case study. Keywords Fault mapping. Extra-juridical services. FMEA. FTA. Oliveira, U. R. et al.

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.

Modeling and Optimization of Multiple Characteristics in the AISI 52100 Hardened Steel Turning

This work aimed to develop a multiple response optimization procedure for the AISI 52100 hardened steel turning process. Optimizing this turning operation is important so that multiple quality characteristics are achieved simultaneously. The considered responses are: total cost, cutting time, total turning cycle time, tool life, material removal rate, and surface roughness. The adjusted process parameters were cutting speed, feed rate and depth of cut. A multi-objective optimization technique based on the Global Criterion Method and Genetic Algorithm were employed to identify the optimal settings for parameters with objective functions built through Response Surface Methodology. This two-fold approach lead up to optimized responses settled near the desired values were obtained with cutting speed = 214 m/min, feed rate = 0.088 mm/rev and depth of cut = 0.33 mm.

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.