محاسبه نيروي الكترومغناطيس و شبيه سازي شكل دهي الكترومغناطيسي لوله به طرف داخل

چكيده انگليسي :

Calculating Electromagnetic Force and Simulation of Inward Tube Forming by Electromagnetic Forming Rasoul Shahrokh rshahrokh@gmail com 2011 09 04 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor M Farzin farzin@cc iut ac ir A R Fadaei Tehrani fadaei@cc iut ac ir AbstractElectromagnetic forming EFM is one of the sheet metal forming methods which uses electromagnetic forceto form metallic parts The work piece is formed by the body forces Lorentz forces that results from apulsed magnetic field created by an electic coil In this method an intensive and transient magnetic field isused to push sheets into the die cavity Electromagnetic forming is one of the high velocity forming methodsused for forming and joining metallic sheets without any tool defects or markings on the work piece Thereare many advantages for this type of forming such as having high strain rate decreasing wrinkling and springback and no need of any lubricant Formability can be increased using this high velocity forming techniquedue to the inertial forces and high strain rates However there are many restrictions for electromagneticforming for example complicated shapes cannot be produced by this method and the work piece should havegood electrical conductivity Therefore only metalic parts can be formed such as aluminum copper silver brass and steel with simple shapes In this study governing equations of electromagnetic field and structuralfiled were considered and solved as uncopled problems In this thesis at first governing equations of tube compression were derived from Maxwell equations Magnetic field eddy current electromagnetic force density and magnetic pressure in the tube werecalculated The finite difference method was employed to solve these governing equations The pressureacting on the tube due to the Lorentz forces was estimated neglecting the influence of the tube velocity on themagnetic field Then this pressure was considered as a load in the mechanical problem Numerical simulationof the mechanical problem was performed with the commercial finite element code ABAQUS Explicit Themagnetic pressure distribution was introduced in ABAQUS Explicit to obtain mechanical displacement velocity and thickness distributions Because electromagnetic forming method is performed with highvelocity so the property of material cannot be estimated by conventional equations in plasticity thusequations which consider high strain rate should be used The best formula which could estimate thebehavior of material in high strain rate with work hardening was Johnson Cook equation The material usedin simulation was AA 6061 T6 and its appropriate parameters for Johnson Cook equation were determinedfrom available experiments After getting results from ABAQUS Explicit these had to be validated withexperimental results Displacement of middle of tube and thickness obtained by simulation were comparedwith experimental data of other references There was also an agreement between numerical results gainedfrom governing equations in tube compression and ANSYS software that proves validity of the results TheANSYS results that were used in our validation were obtained from other references In addition there was agood agreement between experimental thickness of the bead center and also its displacement withcorresponding values predicted by numerical method Key wordsElectromagnetic forming Electromagnetic pressure finite difference method ABAQUS Explicit

شاهرخ، رسول

محاسبه نيروي الكترومغناطيس و شبيه سازي شكل دهي الكترومغناطيسي لوله به طرف داخل

تفاضل محدود , ABAQUS , Explicit