Goutam Nandi

Solution of Correlated Multi-Response Optimization Problem: Case Study in Submerged Arc Welding

This paper highlights an integrated approach to solve the correlated multi-response optimization problem through a case study in submerged arc welding (SAW). The proposed approach has been presented to overcome different limitations and drawbacks of existing optimization techniques available in literature. Traditional Taguchi optimization technique is based under the assumption that quality responses are independent to each other; however, this assumption may not always be valid. A common trend in the solution of a multi-objective optimization problem is to convert these multi-objectives into an equivalent single objective function. While deriving this equivalent objective function, different weightage are assigned to different responses according to their relative priority. In this regard, it seems that no specific guideline is available for assigning individual response weighs. To avoid this, Principal Component Analysis (PCA) has been adopted to eliminate correlation among individual desirability values and to calculate uncorrelated quality indices that have been aggregated to calculate overall grey relational grade. This study combines PCA, Desirability Function (DF) approach, and grey relation theory to the entropy measurement technique. Finally, the Taguchi method has been used to derive optimal process environment capable of producing desired weld quality related to bead geometry.

Effect of Process Parameters on Bead Geometry, Quality and Performance of Submerged Arc Weldment - Experimental and Statistical Analyses

Submerged arc welding (SAW) is one of the chief metal fabrication processes in industry. It works with high current density and can affect high metal deposition rate. The present work emphasizes the influence of process parameters on quality and performance of submerged arc weldment by incorporating one of the traditional methods of statistical data analysis i.e. ANOVA. This approach aims to reveal the main and interactive effects of process parameters on different response variables associated with the weldment. Based on factorial design without replication, experiments were conducted with three different levels of process parameters like voltage, welding current and electrode stick out to obtain butt joints from mild steel plates. Experimental results were examined by exploring Analysis of Variance Method, using statistical software package MINITAB. liased on ANOVA, several graphical plots are shownhistogram of residuals, normal plot of residuals, residual verses order and residual verses specified variables etc. ANOVA delivers feasible data to justify the significance of process parameters on different response variables of submerged arc weldment in terms of their main effects and interactive effects. The effects due to variation of process parameters on (i) bead geometry in terms of bead width, depth of penetration, reinforcement, and (ii) bead quality as well as performance of the welded joint in terms of hardness, impact value and tensile strength are represented graphically. Graphical representations of the experimental data are supposed to contribute

Metaheuristic Based Parametric Optimization of TIG Welded Joint

Abstract Martensitic stainless steels are hard, brittle and notch sensitive; crack formation during welding is frequent. Selection of the levels of welding parameters i.e. the input variables seems to be important and useful in the context of achieving optimum/maximum strength of the welded joint. In the present work, focus is given on identification of the proper combination of input parameters in TIG welding of martensitic stainless steel AISI 420. Welding current, gas flow rate and welding speed have been taken as input parameters. Ultimate tensile strength (UTS) and Ductility or Elongation of the welded joint obtained from tensile test is taken as response parameter. Initially, response surface methodology based face-centered central composite design has been used for mathematical model building and regression analysis. Next, several recently proposed metaheuristics are applied for parametric optimization of TIG welding process to maximize the response parameters. From, the simulated results, a critical operating region for efficient TIG welding is identified in term of maximum UTS and Ductility. Confirmatory tests are also performed to validate our proposed methodology.

Electro-Discharge Machining of Inconel 825 Super alloy: Effects of Tool Material and Dielectric Flushing

Aspects of machinability of Inconel 825 super alloy during electro-discharge machining was attempted in this work. The extent of machinability was investigated in purview of process performance (i.e. material removal rate), surface integrity (morphology as well as topography) of the EDMed work surface including surface roughness, surface crack density, white layer thickness, and micro-indentation hardness. Effects of variation of tool material (graphite, tungsten, brass and copper) were analyzed in this work. Metallurgical characteristics of the EDMed work surface were studied in view of phase information (matrix and precipitates), grain refinement (crystallite size, micro-strain and dislocation density) etc. Results were further interpreted in support of EDS, and micro-hardness test data. Additionally, effects of flushing condition (with and without flushing) of the dielectric medium were examined on influencing EDM performance on Inconel 825 work material. Moreover, effects of peak discharge current on EDM responses were discussed.

Parametric studies of dissimilar welding of AISI 409 ferritic stainless steel to AISI 316L austenitic stainless steel using Taguchi desirability analyses

Abstract In the present work, dissimilar joints between AISI 409 ferritic stainless steel and AISI 316L austenitic stainless steel were made by gas metal arc welding (GMAW) using ESAB AUTO Rod 316L as a filler wire. Welding was conducted as per the L9 orthogonal array using the Taguchi method. Three levels of the input parameters: welding current, gas flow rate and nozzle to plate distance were selected. After welding, visual inspection and an X-ray radiographic test were conducted on the weld specimens to detect surface and sub-surface defects of weld specimens made from dissimilar stainless steels. The quality of the weld was evaluated in terms of yield strength, ultimate tensile strength and percentage of elongation of the welded specimens. The observed data are interpreted, discussed and analyzed using Taguchi desirability analyses.

Parametric Optimization Of Gas Metal Arc Welding Process By Using Grey Based Taguchi Method On Aisi 409 Ferritic Stainless Steel

Abstract Welding input process parameters play a very significant role in determining the quality of the welded joint. Only by properly controlling every element of the process can product quality be controlled. For better quality of MIG welding of Ferritic stainless steel AISI 409, precise control of process parameters, parametric optimization of the process parameters, prediction and control of the desired responses (quality indices) etc., continued and elaborate experiments, analysis and modeling are needed. A data of knowledge - base may thus be generated which may be utilized by the practicing engineers and technicians to produce good quality weld more precisely, reliably and predictively. In the present work, X-ray radiographic test has been conducted in order to detect surface and sub-surface defects of weld specimens made of Ferritic stainless steel. The quality of the weld has been evaluated in terms of yield strength, ultimate tensile strength and percentage of elongation of the welded specimens. The observed data have been interpreted, discussed and analyzed by considering ultimate tensile strength ,yield strength and percentage elongation combined with use of Grey-Taguchi methodology.

Parametric optimization of dissimilar delding of AISI 409 ferritic stainless steel to AISI 316L austenitic stainless steel by using PCA method

Purpose: Taguchi design has been adopted in order to identify optimal parametric combination for desired quality of weld. Microscopy was conducted to study the effect of welding input process parameters (welding current, gas flow rate and nozzle to plate distance) on MIG weld microstructures of AISI 409 ferritic stainless steel and AISI 316L austenitic stainless steel. Design/methodology/approach: A plan of experiments based on Taguchi technique has been used. Findings: The present work is planned to investigate some perspectives of GMAW dissimilar joints between AISI 409, a ferritic stainless steel and AISI 316L a austenitic stainless steel. Research limitations/implications: The main objective of the present study was to apply the Taguchi method to establish the optimal set of control parameters for the welding. The Taguchi method is employed to determine the optimal combination of design parameters, including: current, gas flow rate and nozzle to plate distance. the observed data have been interpreted, discussed and analyzed by considering yield strength , ultimate tensile strength and percentage of elongation combined with use of principal component analyses (pca) method. Practical implications: Dissimilar welding is the joining between two different materials by any welding process. Dissimilar weld has made considerable attention in many fields, such as in ship industries and nuclear power plant. Originality/value: The result computed is in form of contribution from each parameter, through which optimal parameters are identified for maximum tensile strength and percentage elongation. This paper presents new results of optimization using principal component analyses.

Parametric Studies Of Weld Quality Of Tungsten Inert Gas Arc Welding Of Stainless Steel

Effect of current and gas flow rate on quality of weld in tungsten inter gas arc welding of austenitic stainless steel has been studied in the present work through experiments and analyses. Butt welded joints have been made by using several levels of current and gas flow rate. The quality of the weld has been evaluated in terms of ultimate and breaking strengths of the welded specimens. The observed data have been interpreted, discussed and analyzed by using Grey—Taguchi methodology. Optimum parametric setting has been predicted and validated as well.

Effect of process parameters on mechanical properties of submerged arc butt-welding experiments and statistical modelling

Nonlinear mathematical models were developed in order to reveal the direct and interactive effects of process parameters on mechanical properties of butt weldments by Submerged Arc Welding (SAW). Based on factorial design without replication, experiments were conducted with different levels of process parameters ? welding current, electrode stick-out and voltage on mild steel plates ? to obtain butt welds. Various bead quality and performance parameters like hardness, toughness, yield strength and ultimate tensile strength were measured for each of the butt welds made in the experimental runs. All of these data were utilised to develop mathematical models for the prediction of mechanical properties of the weldment for different settings of the factor level. Multiple linear regression method was used to calculate the coefficients of the models. The significance of the coefficients for each of the factors in the models was calculated by Analysis of Variance (ANOVA) Method. The predictions as given by the models have been represented graphically to show the influence of the process control parameters on bead quality in terms of mechanical properties associated with the weldment.