پديد آورنده :
سعيدي، نويد
عنوان :
ارزيابي مكانيزم آسيب در فولادهاي دوفازي استحكام بالا
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد
صفحه شمار :
سيزده،122ص.: مصور،جدول،نمودار
يادداشت :
ص.ع.به فارسي و انگليسي
استاد راهنما :
فخرالدين اشرفي زاده، بهزاد نيرومند
استاد مشاور :
محمدرضا فروزان، فردريك بارلات
تاريخ نمايه سازي :
8/6/93
استاد داور :
عبدالكريم سجادي، سعيد ضيايي راد، محمدرضا طرقي نژاد
كد ايرانداك :
ID651 دكتري
چكيده انگليسي :
Investigation of damage mechanisms in high strength dual phase steels Navid Saeidi n saeidi@ma iut ac ir Date of Submission June 10 2014 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran 1st Supervisor Fakhreddin Ashrafizadeh Professor ashrafif@cc iut ac ir 2nd Supervisor Behzad Niroumand Associate Professor behzn@cc iut ac ir Department Graduate Program Coordinator Dr Keyvan Raeissi Abstract The needs for new advanced high strength steels AHSS with high ductility and strength has been growing rapidly in recent years to satisfy the world demand for the development of energy ef cient automobiles Large plastic deformation during forming of such materials however involves some deficiencies in terms of unpredicted ductile fracture In the present study ductile fracture mechanisms during room temperature uniaxial tensile testing of a modern high strength dual phase steel namely DP780 steel in two geometries of notched and un notched specimens were studied Detailed microstructural characterization of the strained and sectioned samples was performed by scanning electron microscopy SEM The results revealed that regardless of the specimen shape interface decohesion especially at martensite particles located at ferrite grain boundaries as well as martensite necking and fracturing were the most probable mechanisms for void nucleation EBSD analysis revealed that void nucleation was predominantly promoted by the increase of ferrite ferrite grain boundary misorientation with strain especially at the boundaries incorporating adjacent martensite particles Moreover EBSD study of grain average misorientation grain orientation spread and Kernel average misorientation of the deformed microstructures revealed that voids nucleation initially happened at ferrite martensite interfaces neighboring rather large ferrite grains Void growth kinetics was studied via microscopic observations as well as statistical analysis of different microstructural regions along longitudinal direction from the fracture surfaces Examining different proposed models for the prediction of void growth behavior showed that neither the empirical Agrawal model nor Rice Tracey RT family models could accurately predict the void growth behavior in the DP steel studied Therefore a modified model based on the RT family models was proposed which showed much lower prediction error compared with those of other models studied Keywords dual phase steel ductile fracture mechanisms EBSD analysis DIC analysis ultra fine grained dual phase steel 1
استاد راهنما :
فخرالدين اشرفي زاده، بهزاد نيرومند
استاد مشاور :
محمدرضا فروزان، فردريك بارلات
استاد داور :
عبدالكريم سجادي، سعيد ضيايي راد، محمدرضا طرقي نژاد
