تحليل تجربي و عددي خستگي بسيار كم‌چرخه در فولاد دوفازي

چكيده انگليسي :

Experimental and numerical analysis of extremely low cycle fatigue in dual phase steel Student s Full Name Manizheh Aghaei Email address Manizheh aghaei@me iut ac ir Date of Submission 2021 22 01 Department of mechanical engineeringIsfahan University of Technology 84156 83111 Isfahan IranSupervisor Saeed Ziaei Rad szrad@iut ac ir1st Advisor Mostafa Jamshidian2nd Advisor Navid SaeidiDepartment Graduate Program Coordinator Mechanical Engineering Department Mechanical engineering department Isfahan University of Technology Isfahan Iran Material engineering department Isfahan University of Technology Isfahan IranAbstractIn this thesis DP600 steel was investigated under extremely low cycle fatigue ELCF loading Byperforming uniaxial tensile test the main properties of the material used in the thesis were determined asfollows yield stress 382 MPa ultimate strength 648 MPa and elongation of 30 Extremely low cyclefatigue tests were performed for displacement 0 22 to 0 4 mm The average value obtained from theperformed tests showed that the fatigue life of the samples varies from 198 to 1999 cycles Simulations were performed in ABAQUS software by writing a user subroutine VUMAT In this way afterchoosing an appropriate representative volume element RVE the behavior of martensite phase was definedby means of Rodrigues equations and a combined hardening coupled with modified Lemaitre damage modelwas used for ferrite phase The loading and meshing were defined on a 2D plane strain model At the end the life strain and the hysteresis diagrams and damage mechanisms that were obtained from the simulation were compared with experimental results Very good matching of simulation and experimental results wasobserved with an error of less than 5 Key WordsDual phase steel extremely low cycle fatigue combined hardening Lemaitre damage model FEM experiment IntroductionDual phase steels can be considered as one of the most important advanced high strengthsteels that have entered the market since 1975 and have recently been developed forvarious industries especially in the automotive industry Other advantages of this type ofsteels include low yield stress high hardness ratio and no discontinuity in yield Dual phase steels consist of two different phases soft ferrite phase and hard martensitephase which are scattered like islands in the ferrite phase Extremely low cycle fatigue ELCF loading is a kind of fatigue loading in which thenumber of cycles to fracture is less than 100 in some references less than 1000 lifecycles This kind of loading is important in earthquake and automobile science So far relatively few research has been carried out on the fatigue of dual phase steels Li et al 2015 Ramazani et al Ramazani et al 2019 investigated tensile and flexural loads indual phase steel They used Rodriguez equations for both ferrite and martensite phases With this choice of material model and defining damage via XFEM in ABAQUS theyachieved a good agreement between results obtained from simulations and experiment Anbarlouei et al Anbarlouei et al 2017 considered high cycle fatigue of dual phasesteels by means of Rodriguez equations for both ferrite and martensite phases and a simpledamage model which defined for damage parameter They observed both ductile andfatigue fracture Hadianfard in 2009 Hadianfard 2009 investigated low and high cyclefatigue of dual phase steels experimentally In this study he investigated the mechanism of

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تحليل تجربي و عددي خستگي بسيار كم‌چرخه در فولاد دوفازي

فولاد دوفازي , سخت شوندگي تركيبي , مدل آسيب لمتر اصلاح شده , خستگي بسيار كم¬چرخه , مكانيزم آسيب و شكست