14956

1429 دكتري

دكتري

طراحي كاربردي

اصفهان : دانشگاه صنعتي اصفهان

1397

هشت، 121 ص. : مصور، جدول، نمودار

1398/05/29

كتابنامه

مهندسي مكانيك

مهندسي مكانيك

1398/06/02

2552353

Effect of Grain Boundary on Mechanical Properties of Nano Crystalline Iron Using Molecular Dynamics Mohammad Saeed Talaei Pashiri ms talaeipashiri@me iut ac ir Mars 6 2019 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree Doctor of Philosophy PhD Language Farsi Supervisor Prof Saeed Ziaei Rad szrad@cc iut ac ir Abstract In this thesis grain boundary effects on nanoindentation of Fe bicrystal using molecular dynamicwas investigated Particularly mechanical properties of iron bicrystal with 5 grain boundarywere calculated by molecular dynamic simulation of nanoindentation The spherical shapeindenter was used for nanoindentation An embedded atom method interatomic potential for Fewas used for this simulation Grain boundary effect was investigated by performing indentationsimulation at different distances from the grain boundary The effect of grain boundary on theelastic modulus maximum shear stress and hardness of Fe bicrystal was investigated Severalload drops were detected from the obtained loading curves These load drops are the result of theinitiation of dislocation nucleation and so the transition from purely elastic to elastic plasticdeformation The results also indicate that the maximum shear stress on the grain boundary islower than its value far from the grain boundary A brief dislocation reaction analysis isperformed on some simulation snapshots In addition an algorithm was proposed and used forimplementation of EAM force field on GPUs which is faster than its similar CPU codes In the following the grain boundary energy of symmetric and asymmetric iron bicrystals iscalculated for 3 9 boundaries with 110 tilt axis and 5 with 100 tilt axis using moleculardynamics simulations with the embedded atom method potential A modified method for creatinggrain boundary atomic structure is proposed that has sufficient accuracy and its computation costwill be considerably lower than the previously used methods The effect of three parametersnamely rigid body movement overlapping distance and reduction side is investigated andcompared to previous studies and the optimal parameters are introduced which leads to a betterperformance in bicrystal modeling Keywords Iron Grain boundary energy Molecular dynamics Bicrystal Coincidence site lattice Grain Boundary

سعيد ضيايي راد

مهدي جوانبخت

امير لهراسبي، كورش حسن پور، ابوذر طاهري زاده، محمد سيلاني