كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1396

ده، 89ص.: مصور، جدول، نمودار

ص. ع. به فارسي و انگليسي

صالح اكبرزاده

محمد مشايخي

محمدرضا فروزان، مهدي سلماني تهراني

1396/05/04

كتابنامه

مكانيك

مهندسي مكانيك

ID11515

91 Theoretical and Experimental Analysis of Relation between Tension Compression Fatigue of Aluminium 6061 T6 and Entropy Elahe Azizan Farsani e azizian@me iut ac ir Date of Submission 2017 06 21 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Saleh Akbarzadeh s akbarzadeh@cc iut ac irAbstract Nowadays engineering structures are often subjected to repeated loading so the evaluation of fatiguelimit is definitely necessary One of the most effective methods for fatigue life prediction is by applying thethermodynamics equations In fatigue process entropy is generated because of plastic deformation heattransfer and other reversible factors This study is intended to estimate the thermodynamic entropy of metalsunder cyclic loading that reaches a constant value at the point of fracture Then by using the relation betweenentropy and fatigue life we could estimate the number of cycles to fracture Most of the energy in fatigueprocess is wasted in form of heat transfer Therefore with use of temperature evolution during fatigueprocess fatigue fracture entropy of metals can be calculated An empirical correlation of the formN f c1 R c2 with constants c1 and c 2 is derived for tension compression fatigue loading that relates the rate N f Since axialof temperature rise R at the beginning of the test to the number of cycles to failure fatigue tests are expensive and time consuming they are replaced by a finite element analysis In this study Abaqus software was used for numerical simulation Temperature evolution is obtained by subjecting analuminum alloy 6061 T6 specimen to fully reversed tension compression cyclic loading that is simulated byelastic plastic finite element analysis Since hardening parameters of Aluminum alloy 6061 T6 are notaccessible a combined hardening model of Chaboche is applied for estimating the material parameters Fromstress strain hysteresis loops results which are obtained from experimental tension compression fatiguetests hardening parameters of material can be calculated An infrared thermographic technique is used tomeasure the temperature increase of the specimen due to hysteresis heating during the fatigue tests and tovalidate of finite element results Also a universal curve for prediction of fatigue failure based on initialslope of temperature evolution for tension compression fatigue loading was presented Then the numericalresults of stress strain hysteresis loops temperature evaluation and entropy were in a good agreement withthe experimental results Finally by using defined relation between entropy and temperature the fatiguefracture entropy was achieved Moreover the numerical and experimental results indicated that the fatiguefracture is constant at different frequencies and stress amplitudes Also it was shown that the coolingoperation during fatigue process increases the fatigue life Keywords Fatigue life Entropy Tension compression fatigue loading Combined hardening Numerical simulation

صالح اكبرزاده

محمد مشايخي

محمدرضا فروزان، مهدي سلماني تهراني