Finite Element Analysis Of Thermal Stress And Crack In EDM Surface Strengthening

Titanium alloy has many excellent features, such as high specific strength, impact resistance,high temperature resistant, corrosion resistance and so on, and it has been widely used in manyfields, for example, aerospace, chemical industry, automobile, medical and some corrosiveenvironment, etc. Titanium alloy has the high rebound characteristics, chemical activity andlower coefficient of thermal conductivity of materials properties, using traditional machiningmethod of titanium is very difficult, and the production cost is high, the emergence of EDMtechnology solve the problem of traditional processing met. Electrical discharge machining is away of non-traditional machining, this method has the advantages of energy saving, fast andefficient, green environmental protection, can be a good way to instead of traditional machining,and get the attention of the researchers at home and abroad.This paper using TC4titanium alloy workpiece as research object, finite element software isadopted to establish the mixed powder medium mathematical model of single pulse EDMsurface strengthening process, calculate the change of the temperature field and structure field, inthe EDM process. Analysis EDM process parameters impact on the temperature field, structurefield and surface quality of workpiece.EDM surface strengthening technology with traditional strengthening technology has abiggest difference: using pulse of heat discharge on the surface of the molten heavy caster, makethe strengthening layer and substrate well together. This paper studies the electric spark surfacestrengthening technology, analyses the discharge mechanism, pulse discharge channel and heatdistribution in the single pulse EDM surface strengthening process, writes heat source modelclose to heat sources of gauss.Through the research in the powder mixed dielectric EDM discharge process of physicalchemistry change，it is concluded that not only exist thermal shock in the process of EDMsurface strengthening but also involves the change of the chemical composition in thestrengthening layer, and strengthening layer’s chemical composition change will produce largermismatch stress. Considering the above situations, this paper using JMatPro software fittingmaterial parameter, using sequential coupling method to analysis and solve the workpiece’stemperature field and structure field under the action of single pulse EDM surface strengthening.Using Abaqus finite element software to build artifacts heat transfer mathematical modeland simulate in the heating pulse discharge process, the change of the workpiece’s temperaturefield, calculate the strengthening layer depth; using workpiece’s temperature field load in theprocess of pulse discharge to simulate the stress field variation law of workpiece surface; using workpiece’s discharge heating load at the end of the temperature field to simulate the heattransfer process in the cooling process, get the change of the temperature field; using theworkpiece’s temperature field load in the process of cooling and the stress field load at the end ofthe discharge to simulate workpiece surface structure change rule in the cooling process.Finally, analysis of EDM process parameters’ influence on the workpiece surfacetemperature field, structure field and surface quality, concluded that the process parameters onthe thermal stress and residual stress and the influence regularity of the surface crack.