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Coupled Field Modeling of Gas Tungsten Arc Welding

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dc.contributor.authorSen, Debamoyen
dc.contributor.committeecochairBall, Kenneth S.en
dc.contributor.committeecochairPierson, Mark A.en
dc.contributor.committeememberTafti, Danesh K.en
dc.contributor.committeememberBattaglia, Francineen
dc.contributor.committeememberHendricks, Robert W.en
dc.contributor.departmentMechanical Engineeringen
dc.date.accessioned2014-03-14T21:16:14Zen
dc.date.adate2012-08-08en
dc.date.available2014-03-14T21:16:14Zen
dc.date.issued2012-07-03en
dc.date.rdate2012-08-08en
dc.date.sdate2012-07-17en
dc.description.abstractWelding is used extensively in aerospace, automotive, chemical, manufacturing, electronic and power-generation industries. Thermally-induced residual stresses due to welding can significantly impair the performance and reliability of welded structures. Numerical simulation of weld pool dynamics is important as experimental measurements of velocities and temperature profiles are difficult due to the small size of the weld pool and the presence of the arc. From a structural integrity perspective of welded structures, it is necessary to have an accurate spatial and temporal thermal distribution in the welded structure before stress analysis is performed. Existing research on weld pool dynamics simulation has ignored the effect of fluid flow in the weld pool on the temperature field of the welded joint. Previous research has established that the weld pool depth/width (D/W) ratio and Heat Affected Zone (HAZ) are significantly altered by the weld pool dynamics. Hence, for a more accurate estimation of the thermally-induced stresses it is desired to incorporate the weld pool dynamics into the analysis. Moreover, the effects of microstructure evolution in the HAZ on the mechanical behavior of the structure need to be included in the analysis for better mechanical response prediction. In this study, a three-dimensional model for the thermo-mechanical analysis of Gas Tungsten Arc (GTA) welding of thin stainless steel butt-joint plates has been developed. The model incorporates the effects of thermal energy redistribution through weld pool dynamics into the structural behavior calculations. Through material modeling the effects of microstructure change/phase transformation are indirectly included in the model. The developed weld pool dynamics model includes the effects of current, arc length, and electrode angle on the heat flux and current density distributions. All the major weld pool driving forces are included, namely surface tension gradient, plasma drag force, electromagnetic force, and buoyancy. The weld D/W predictions are validated with experimental results. They agree well. The effects of welding parameters (like welding speed, current, arc length, etc.) on the weld D/W ratio are documented. The workpiece deformation and stress distributions are also highlighted. The transverse and longitudinal residual stress distribution plots across the weld bead and their variations with welding speed and current are also provided. The mathematical framework developed here serves as a robust tool for better prediction of weld D/W ratio and thermally-induced stress evolution and distribution in a welded structure by coupling the different fields in a welding process.en
dc.description.degreePh. D.en
dc.identifier.otheretd-07172012-073156en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07172012-073156/en
dc.identifier.urihttp://hdl.handle.net/10919/38820en
dc.publisherVirginia Techen
dc.relation.haspartSen_D_D_2012.pdfen
dc.relation.haspartSen_D_D_2012_Copyright.PDFen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectResidual Stressen
dc.subjectThermal Stressen
dc.subjectBuoyancyen
dc.subjectElectromagnetic Forceen
dc.subjectPlasma Induced Shearen
dc.subjectMarangoni Convectionen
dc.subjectMaterial Modelingen
dc.subjectStructural Analysisen
dc.subjectWeld Pool Dynamicsen
dc.subjectGas Tungsten Arc Weldingen
dc.titleCoupled Field Modeling of Gas Tungsten Arc Weldingen
dc.typeDissertationen
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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