6301

5889

كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1390

ده،89ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمد مشايخي

محمود كدخدايي

4/8/90

سعيد ضيايي راد، محمود فرزين

مهندسي مكانيك

ID5889

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Investigation of Low Cycle Fatigue Damage of Al 7075 T6 by Experimental and Numerical Methods Saeed Masih s masih@me iut ac ir Date of Submission 2011 07 9 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Mashayekhi Mashayekhi@cc iut ac irAbstractOne of the most important and widely used alloys of aluminum in aerospace structures is 7075 T6 On theother hand many aviation parts are under low cycle fatigue loading Therefore the analysis of 7075 T6alloy under low cycle fatigue loading is very important In this thesis prediction of failure of 7075 T6aluminum alloy in the low cycle fatigue loading with damage mechanics approach is applied by numericaland experimental methods A fully coupled constitutive elastic plastic damage model is developed andimplemented inside the finite element commercial FORTRAN code for ABAQUS VUMAT subroutines The main advantage of developing a user subroutine inside a commercial FE code is the access to a widerange of element types material models and other facilities such as efficient equation solvers First damage parameters and coefficients for 7075 T6 aluminum under three dimensional stress conditionsconsistent with actual state are obtained from experimental results Therefore an experimental procedure toidentify the damage parameters under triaxial stress conditions is proposed To identify and extract theparameters three tests are developed and regulated The experiments included tensile tests for simple andnotch tensile specimens measuring damage test and low cycle fatigue test To measuring damage thevoltage drop and measuring Young s modulus methods for specimen under tensile test are used Modulusmeasured by strain gauges and extensometer Various experiment and measuring methods have beencompared and parameters are obtained from the average results Extensometer data are very similar to thestraingage data while electrical data have an offset to the straingaige data Then by introducing the damage basic definitions of damage mechanics are discussed Lemaitre s damagemodel and the constitutive equations based on small deformation are introduced The next step isintroducing two algorithms for solving the equations In one of the algorithms the stress updates neglectingthe kinematic hardening by solving one non linear scalar equation In the complete algorithm thecombination of the isotropic and kinematic hardenings is considered all variable update by solving twoscalar nonlinear equations The discussed algorithm can be able to trace the different loadings and low cyclefatigue The non linear obtained equations are solved by Newton Raphson iterative procedure Thecompound algorithm is able to model the material s behavior in accordance to the experimental results while the simplified algorithm does not predict these behaviors under the non uniform and fatigue loading Keywords Damage mechanics Al 7075 T6 Low cycle fatigue Kinematic hardening

محمد مشايخي

محمود كدخدايي

سعيد ضيايي راد، محمود فرزين