Study of surface integrity and dimensional accuracy in EDM using Fuzzy TOPSIS and sensitivity analysis

(BQ) Surface integrity and dimensional accuracy remain critical concern in Electrical DischargeMachining (EDM). The current research work aims at investigating the influence of various EDM process parameters like pulse current (Ip), pulse-on time (Ton), tool work time (Tw) and tool lift time (Tup) on various aspects of surface integrity like white layer thickness (WLT), surface crack density (SCD) and surface roughness (SR). The dimensional accuracy, characterized by over cut (OC), has also been studied in the similar way.
Nội dung trích xuất từ tài liệu:
Study of surface integrity and dimensional accuracy in EDM using Fuzzy TOPSIS and sensitivity analysisMeasurement 63 (2015) 364–376Contents lists available at ScienceDirectMeasurementjournal homepage: www.elsevier.com/locate/measurementStudy of surface integrity and dimensional accuracy in EDMusing Fuzzy TOPSIS and sensitivity analysisS. Dewangan a, S. Gangopadhyay a,⇑, C.K. Biswas a,babAISI P20 tool steelDepartment of Mechanical Engineering, National Institute of Technology, Rourkela-769008, IndiaDepartment of Petroleum Engineering, Universiti Teknologi Petronas, Ipoh, Malaysiaa r t i c l ei n f oArticle history:Received 28 November 2013Received in revised form 26 September 2014Accepted 27 November 2014Available online 8 December 2014Keywords:Electrical Discharge Machining (EDM)AISI P20 tool steelFuzzy-TOPSISSensitivity analysisa b s t r a c tSurface integrity and dimensional accuracy remain critical concern in Electrical DischargeMachining (EDM). The current research work aims at investigating the influence of variousEDM process parameters like pulse current (Ip), pulse-on time (Ton), tool work time (Tw)and tool lift time (Tup) on various aspects of surface integrity like white layer thickness(WLT), surface crack density (SCD) and surface roughness (SR). The dimensional accuracy,characterized by over cut (OC), has also been studied in the similar way. A response surfacemethodology (RSM) – based design of experiment has been considered for this purpose.The present study also recommends an optimal setting of EDM process parameters withan aim to improve surface integrity aspects after EDM of AISI P20 tool steel. This has beenachieved by simultaneous optimization of multiple attributes (i.e. WLT, SCD, SR and OC)using Fuzzy-TOPSIS-based multi-criteria decision making (MCDM) approach. The optimalsolution was obtained based on five decision makers’ preferences on the four responses(i.e. WLT, SCD, SR, and OC). From this analysis, an optimal condition of process parametersof Ip = 1 A, Ton = 10 ls, Tw = 0.2 s, and Tup = 1.5 s has been determined. Furthermore, sensitivity analysis was also carried out to study the sensitivity or robustness of five decisionmakers’ preference of optimal machining parameters. Form this study, decision makers’preference for surface crack density has been found to be the most sensitive responseand therefore should be chosen first and analyzed very carefully.Ó 2014 Elsevier Ltd. All rights reserved.1. IntroductionElectrical Discharge Machining (EDM) is an erosion process, whereby rapidly recurring spark is generatedbetween the tool and the workpiece in order to removethe materials form the later. EDM is the one of the mostversatile non-conventional machining processes since theeffectiveness of EDM process is absolutely independent ofmechanical properties of the workpiece material. Therefore, very hard and difficult-to-cut materials can be effectively machined into desired complex shape, if the work⇑ Corresponding author. Tel.: +91 9439096336; fax: +91 661 2472926.E-mail address: soumya.mech@gmail.com (S. Gangopadhyay).http://dx.doi.org/10.1016/j.measurement.2014.11.0250263-2241/Ó 2014 Elsevier Ltd. All rights reserved.piece materials are electrically conductive. During the process of EDM, material removal takes place due to meltingand vaporization from the localized zone of the workpiece.Thermal energy liberated during EDM due to generation ofspark leads to formation of thermally affected layers on themachined surface. The properties of such layers are different from parent workpiece material [1]. Therefore, surfaceintegrity in EDM is an issue which requires considerableresearch attention. Surface integrity in EDM is usuallycharacterized by surface roughness, formation of recastlayer or white layer and surface cracks, residual stressand metallurgical modification of parent material [2].Therefore, if the surface integrity is not adequatelyaddressed, the EDMed component would be more prone365S. Dewangan et al. / Measurement 63 (2015) 364–376Table 2Linguistic variable for the important weight of each output.Fuzzy subsetFig. 1. Experimental setup.Table 1Machining parameters and their levels.ParametersSymbolLevelUnit1233800.60.7551501.01.5Control parametersPulse currentPulse on TimeTool work timeTool lift timeIpTonTwTup1100.20.0Fixed parametersDuty cycleVoltageFlashing pressureSensitivityInter electrode gapfVFpSENIEG70450.3690Alsss%VKg f/cm2lmto failure during its intended application. Surface finish inEDM attracted significant research interest. Differentmathematical models have been developed to correlatesurface roughness with various EDM parameters like discharge current (Ip), pulse-on time (Ton), pulse-off time(Toff), duty cycle (Tau), polarity, input power, and thermalphysical and electrical pro ...