Selecting Significant Process Parameters of ECG Process Using Fuzzy-MCDM Technique

Selecting Significant Process Parameters of ECG Process Using Fuzzy-MCDM Technique

Goutam Kumar Bose (West Bengal University of Technology, Kolkata, India)
DOI: 10.4018/ijmfmp.2015010103

Abstract

The present paper highlights selection of significant machining parameters during Electrochemical grinding while machining alumina-aluminum interpenetrating phase composites by MCDM techniques. The conflicting responses like higher material removal rate, lower surface roughness, lower overcut and lower cutting force are ensured simultaneously by a single parametric combination. Control parameters like electrolyte concentration, voltage, depth of cut and electrolyte flow rate have been considered for experimentation. VIKOR is one of the multiple criteria decision making (MCDM) models to determine the reference ranking from a set of alternatives in the presence of conflicting criteria. Finally Grey Relational Analysis is performed to optimize multiple performances in which different levels combinations of the factors are ranked based on grey relational grade. Surface roughness is given more importance than other responses, using Fuzzy Set Theory considering basic objective of the process. It is observed that substantial improvement in machining performance takes place following this technique. The study highlights the effects of different process variables on multiple performances for complex process like ECG.
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1. Introduction

Rapid globalization has changed the dynamics of the manufacturing industries across the globe. In order to survive in this complex business environment industries are undergoing several modifications by reorienting the traditional way of manufacturing to non-traditional manufacturing. In order to cope with the changes application of these emerging manufacturing techniques along with the modern materials is becoming popular day by day. Electrochemical grinding (ECG), is a non–conventional machining process, applied for machining difficult–to–machine alloys, hardened, fragile and heat sensitive parts (El Hoffy, 2005). The hybrid machining processes are popularly used now a days mainly to avail the combined advantages and to evade or restrict some adverse effects the basic processes produce when they are separately applied. The material removal takes place by the combined effect of electrochemical dissolution and mechanical abrasion and is found to be superior to its conventional counterpart. Since the process is based on electrochemical dissolution of work material, the machined surfaces are free from burr and residual stress, eliminating costly and time consuming secondary operations and reducing rejection caused by stress and cracks. ECG has high material removal rate as compared to the conventional grinding when working with the tough-to-machine materials, such as high temperature resistant Co-Ni alloys, high tensile strength materials, metal matrix composites etc (Benedict, 1987).

Interpenetrating phase composites (IPC) are a new group of composite materials in which phases are three-dimensionally (3D) continuous and each phase spans or percolates throughout the microstructure. Such materials are envisaged as very promising category of composites since it exhibits multifunctional characteristics - offering improved combinations of mechanical and physical properties and enhanced damage tolerance (Huchler et al, 2004). The alumina-aluminum (Al2O3–Al) system is one of the most considered ceramic–metal IPC systems. Al2O3–Al IPCs produced by these processes have a random, usually isotropic, spatial distribution of phases (Clyne, 2001).

The material removal in the ECG process takes place through the following mechanisms (i) purely mechanical abrasion (ii) electrochemical removal combined with mechanical abrasion with zero over cut (iii) electrochemical removal coupled with mechanical means with over cut greater than zero (iv) absolutely electrochemical reaction (Nobel, 1987). Input variables like voltage, electrolyte flow rate, electrolyte concentration and depth of cut significantly contribute to the responses. Few research works have been carried out to establish the optimal process variables so as to achieve better surface finish (Ra) and higher material removal rate (MRR) (Bhowmick & Mishra, 2000; Reddy et al, 2000). Nevertheless there is hardly any mathematical model involving process variables that can successfully describe all the responses simultaneously. Since the objective being conflicting in nature, it is very difficult to achieve them simultaneously by a single set of process variables. The present work is aimed at optimization of process variables by applying VIseKriterijumsa Optimizacija I Kompromisno Resenje (VIKOR) in regard to high MRR, lower Ra, lower Overcut and lower Cutting force concurrently following Grey Relational Analysis technique during ECG of Al2O3–Al IPC.

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