7101

445 دكتري

دكتري

طراحي كاربري

1391

نه،101ص: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

1397/08/21

كتابنامه

مهندسي برق و كامپيوتر

ID445 دكتري

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Constitutive Equations for Hot Deformation of Polycrystalline and Nano Materials By Reza Jafari Nedoushan r jafari@me iut ac ir June 13 2012 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran1 Mahmoud Farzin farzin@cc iut ac ir Supervisor 2 Mohammad Mashayekhi Advisor AbstractIn the current thesis constitutive models are proposed for dominant mechanisms in hotforming and nano crystalline materials including inter granular deformation grain boundarysliding grain boundary diffusion and grain growth Besides a Taylor type polycrystallineconstitutive model two visco plastic models are used to predict inter granular deformation Previous works on grain boundary mechanisms are extended to drive three dimensionalmacro stress strain rate relationships for these mechanisms The proposed models are firstused to simulate hot forming processes It is shown that the two visco plastic models can beused to predict material behavior for various grain sizes strain stress state and strain rateswith reasonable computational costs Then a model is added to the proposed constitutivemodels to predict void initiation in superplastic forming It is shown that this model spredictions are in excellent agreement with experimental data Finally the proposedconstitutive models are used to predict nano crystalline materials behavior The stressesobtained from these constitutive equations match well with the experimental data for nano crystalline copper for different strains and strain rates Variations of strain rate sensitivity inverse Hall Petch effect tension compression asymmetry and yield locus shape are also wellpredicted by the model Key WordsHot forming Nanocrystalline materials Constitutive equations Crystal plasticity Grainboundary diffusion Grain boundary sliding IntroductionHot forming processes including superplastic forming SPF and quick plastic forming QPF are used to manufacture components with complex shapes which usually cannot beproduced by cold forming Especially superplastically formed parts find many applications particularly in aerospace and transportation industries where weight reduction is critical to

محمود فرزين

محمد مشايخي

احمدكرمانپور، سعيدضيائي راد، عليرضا شهيدي، عباس قائي