Pradip Kumar Pal

Desirability Function Approach for Solving Multi-Objective Optimization Problem in Submerged Arc Welding

Like any other welding technique, Submerged Arc Welding (SAW) is also a multi-objective, multi-variable metal processing technology. In general, the acceptability of a weldment depends on various parameters in relation to bead geometry, bead quality, microstructure and mechanical-metallurgical characteristics of the weld, that can fulfill the required goal. The acceptable limits of these parameters are also influenced by the area of application as well as functional requirements of the prepared weld. Therefore, there exists a need to search for an optimal process condition that may achieve the desired purpose. In the present work, it is aimed to search for an optimal solution for the process parameters that would result in maximum depth of penetration, minimum height of reinforcement, minimum bead width, minimum dilution, minimum area of reinforcement and minimum area of penetration, within experimental domain. Data, collected from previous research for four factor-five level central composite design, have been utilized to determine individual desirability of the responses, which have been used further to calculate composite desirability associated with overall features of bead geometry and bead volume of the desired weldment. Desirability function optimization approach, followed by Response Surface Methodology (RSM), has been incorporated to evaluate the optimum parameter setting that would meet * Communicating Author the overall desirability of the weldment. Comparison of optimal parametric combination as determined by the previous researchers to that obtained by using desirability function approach and RSM has also been made. Good agreement has been found. This proves the application feasibility of desirability function approach coupled with RSM for solving multi-objective optimization problems in SA welding.

INVESTIGATION ON SURFACE ROUGHNESS IN CYLINDRICAL GRINDING

Cylindrical grinding is a complex machining process. And surface roughness is often a key factor in any machining process while considering the machine tool or machining performance. Further, surface roughness is one of the measures of the technological quality of the product and is a factor that greatly influences cost and quality. The present work is related to some aspects of surface finish in the context of traverse‐cut cylindrical grinding. The parameters considered have been: infeed, longitudinal feed and work speed. Taguchi quality design is used to design the experiments and to identify the significantly import parameter(s) affecting the surface roughness. By utilization of Response Surface Methodology (RSM), second order differential equation has been developed and attempts have also been made for optimization of the process in the context of surface roughness by using C‐ programming.

An Investigation on Temperature Distribution and Cooling Rate of ERW Pipes during TIG Welding

Abstract The present investigation deals with the determination of temperature profile and subsequent rates of cooling at certain points on the external surface along axis of an ERW pipe, during TIG welding. Two samples of different diameters of pipes of ASTM A 106 Gr. B, seamless type are selected for experimentation. The temperatures on the external surface at different locations on each of these seamless pipes (of different diameters) during welding have been measured with the help of digital pyrometers. The temperature variation along the axis of pipe from the weld arc has been presented. Thereafter, through separate analytical methods the temperature distribution across the external surface of the pipe for a given point heat source is theoretically calculated, and the results are compared with the previously found experimental values of temperatures. They are found to be well in agreement. Further, the rates of cooling of a pre-selected point on the pipe surface are experimentally and analytically determined under varying welding conditions and are compared likewise and are found to be in good agreement too.

A study on quality of weld in flux cored arc welding process

Flux cored arc welding (FCAW) is a semi–automatic or fully automatic welding method that is widely used for welding large and thick sections, especially in the flat position. The welding can be performed with shielding gas (FCAW–G) or without shielding gas (FCAW–S). A tubular filler wire containing mixture of mineral flux and powder in the core of the tube is supplied on reels and fed through the welding gun in metal inert gas (MIG) welding. The process is popularly used in construction and fabrication of carbon steel, low alloy steel weldment in power plant equipment. Hence in this paper effects of the welding parameters on the quality of weldment have been discussed based on the experimental data obtained. The welding was performed on metal plates of boiler quality of steel using a semiautomatic gas metal arc welding (GMAW) machine. To predict the weld quality, experiments were conducted based on three–factor five levels Taguchi orthogonal array design matrix. Parametric optimisation has been done based on radiographic test, visual inspection and tensile test results.

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.

Machining performance optimization in drilling of GFRP composites: A utility theory (UT) based approach

In the 21st century, GFRP composites have been successfully substituted majority of the traditional engineering materials and widely used in manufacturing sectors. As there are a number of favorable properties associated with GFRP composites; but machining of GFRP is significantly different as compared to other engineering materials, because, GFRPs are non-homogeneous in nature (which consist of distinctly different phases), so that their machining operation is characterized by uncontrolled intermittent fiber fracture causing oscillating cutting forces and critical bending stresses, poor surface properties due to crushed fiber or resin pull out. For effective use of any machining process, it becomes important to find optimum parametric setting to achieve improved quality as well as increased productivity. In this present context, a case study on optimal machining parameters selection has been reported to ensure high productivity as well as satisfactory surface quality of machined glass fiber reinforced epoxy composites. Utility function based on Taguchi optimization approach has been proposed in this research. During GFRP drilling, fiber breakage, entry and exit delamination are encountered as the major issues leading to decrease in product quality and overall productivity of manufacturing processes and products. Taguchi L16, 4 level orthogonal array have been used to study the influence of various combinations of process parameters Present work aims to conduct a case experimental research on drilling of GFRP (epoxy) composites in order to select the most appropriate process parameter combination by utility theory based approach to ensure satisfactory process performance yields as well as hole quality.