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چكيده انگليسي :

Analysis of Forging Process Using Dual Stream Functions DSF Hojat Moosavi s moosavi@me iut ac ir Date of Submission 2012 01 31 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mahmoud Salimi salimi@cc iut ac irAbstractAmong the manufacturing processes metal forming is commonly used for its minimum material waste andbetter mechanical properties Forging is probably the simplest and one of the widely used metal forming processand generally carried out incrementally Open die forging is the process of deforming a metal in order to shape aproduct into the given desired configuration This process is often associated with larger simpler shaped partssuch as shafts bars blocks or rings or early stage of closed die forging In forging operations the prediction ofmetal flow is an important consideration since it will greatly influence the formed configuration mechanicalproperties of the work piece The main factors affecting metal flow are friction yield strength of the metal andthe geometry work piece During forging of a polygonal block between a pair of flat dies the material flowdeveloped is non uniform both in the plane section of the block and along its thickness The non uniformity offlow in the plane section is called bulging and that along the thickness of the block as barreling Both theseeffects are invariably present during forging of any non circular block Analytical solutions are likely to takelong time and even sometimes exact solutions may not be found By using numerical methods estimations withaccuracy and high speed would be made possible by reducing calculation time In this thesis a mathematicalmodel for open die forging of regular polygonal blocks using the dual stream functions and also upper boundmethod has been proposed to examine three dimensional plastic deformation behaviour of the block betweentwo flat dies The velocity field derived from the developed dual stream functions can automatically satisfy theincompressibility condition The non uniform velocity field was employed for simulating the inhomogeneousdeformation and the effect of barreling during the forging In addition in this study an upper bound solution isdeveloped for forging of such blocks using other velocity field in cylindrical coordinate taking into account thebulging of sides Numerical calculations have been carried out to compute the total energy consumption whichconsists of the energy required to overcome the internal deformation and the frictional resistance between thedie The upper bound forging load is determined by minimizing the total power consumption Using these twomodels various effects of forming parameter such as the friction factor reduction etc upon the non dimensionalforging pressure and barrelling of the blocks For the sake of illustration numerical results are given for forgingof triangular square and hexagonal blocks and the results of the velocity field derived from the developed dualstream functions are compared with the results of other velocity field The theoretical predictions of forgingpressure are shown to be in good agreement The results obtained from the present analysis investigations arecompared with the result of the finite element software using Abaqus 6 10 and experimental results Through thecomparison between the results the validity and reliability of the proposed method was verified Experimentswere conducted using copper alloy and showed to be in good correlation with the theoretical analysis by thedual stream functions Keywords Forging Dual stream functions Upper bound method Barreling effect

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