تعيين عمر خستگي جعبه دنده اصلي دستگاه همتراز ساز ورق

چكيده انگليسي :

87 Fatigue Life Determination of the Main Gearbox of Leveler Device Ahmad Amiri Rad ahmad amiri2@gmail com June 19 2011 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiM R Forouzan forouzan@cc iut ac irAbstract In this thesis the lifetime of the main gearbox of the leveler of corrective line I of Mobarakeh steel companyhas been defined In this work two kinds of common failures in gears fatigue fracture at tooth root and pitting ontooth flank have been investigated These two kinds of failure are classified as fatigue fracture There are severaldifferent approaches to study the fatigue phenomenon in this thesis the fracture mechanics approach has been used Fatigue failure is considered as a linear elastic fracture mechanics LEFM problem In this project Paris equationhas been used to evaluate fatigue life Paris equation relates the fatigue crack growth rate to stress intensity factorrange Maximum circumferential stress theory has been used to determine the crack growth direction in each step ofcrack growth In this project first kinematic and force analysis has been done on leveler device and its powertransmission set which consists of seven gearboxes and critical gear and the torque applied to it have been defined Then by a contact analysis the exact load distribution on critical gear teeth has been calculated Since most of theindustrial problems involves complicated geometries and boundary conditions and there are no analytical solutionsfor them using numerical methods for solving these problems is inevitable In this thesis the extended finite elementmethod has been used for simulation of 3D crack growth in gears The extended finite element method has alleviatedmany limitations of conventional finite element method in modeling fracture mechanics problems In theconventional finite element method it is needed to use very fine mesh in the vicinity of crack front to model thesingular stress field Also the mesh should conform to the discontinuity geometry and as a result after each step ofcrack growth the mesh should be updated These two factors increase the modeling and computation timeconsiderably In the extended finite element method crack is not modeled explicitly but is introduced to the finiteelement approximation by using some extra degrees of freedom This procedure is called enrichment In this projectmodeling and computation time has reduced considerably compared to previous works Present study is one of thefew works done on the 3D crack growth in gears Most of the previous works have been limited to 2D cases In thisproject ABAQUS software has been used to simulate fatigue crack growth At the present time ABAQUS does nothave the ability to model fatigue crack growth by extended finite element method Therefore a code has been writtenusing the ABAQUS scripting abilities to provide a tool for simulating 3D crack growth by extended finite elementmethod Two above mentioned failures in gears are modeled using ABAQUS and provided code and the lifetime ofthe main gearbox of leveler device has been defined Final configuration and crack growth shape also have beenidentified In this thesis the crack initiation period length has been calculated using Coffin Manson relation Key WordsFatigue gears fracture Mechanics extended finite element method

اميري راد، احمد

تعيين عمر خستگي جعبه دنده اصلي دستگاه همتراز ساز ورق

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