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چكيده انگليسي :

Prediction of Behavior of Selective Laser Melting Materials Using Continuum Damage Mechanics Younes Sorori Mirazizi y sorori@me iut ac ir Date of Submission 2015 01 11 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Mashayekhi Mashayekhi@cc iut ac irAbstractSelective Laser Melting SLM is one of the Additive Manufacturing AM methods that has been used widely inrecent decades Due to the widespread use of thee materials in many fields such as aerospace turbine blades theautomotive and medical industry it is essential to prepare a appropriate way to predict their behavior under differentloading conditions On the other hand many parts in aircraft structures turbine blades etc are under cyclic fatigueloading Therefore the analysis of these materials in cyclic fatigue loading is very important Continuum DamageMechanics CDM provide an efficient tool to predict material behavior and lifetime of components under differentloading conditions Damage mechanics is concerned with the representation or modeling of damage of materials thatis suitable for making engineering predictions about the initiation propagation and fracture of materials withoutresorting to a microscopic description that would be too complex for practical engineering analysis Damage ofmaterials means the progressive or sudden deterioration of their mechanical strength because of loadings or thermalor chemical effects From a physical point of view damage can originate from multiple causes debonding ofatoms nucleation or growth and coalescence of microcracks and microcavities Despite the discontinuous natureof such processes at the microscale continuous damage means a homogeneous modeling in which microcracksand microvoids are represented by a continuous variable in the sense of the mechanics of continuous media The current thesis presents a numerical and experimental study of the behavior of 316L stainless steel produced bySLM process in Low Cycle Fatigue LCF loading using CDM According to experimental observation because ofhigh thermal gradient and prosity of the samples in production process 316L samples produced this way show asemi brittle behavior A ductile brittle damage model is implemented inside the finite element commercialFORTRAN code for ABAQUS UMAT subroutine First mechanical properties and damage parameters and coefficients for 316L SLM samples are obtained fromexperimental results Therefore an experimental procedure to identify the damage parameters is proposed Toidentify and extract the parameters two tests are developed and regulated The experiments included tensile testsand LCF tests Various experiment and measuring methods have been compared and the parameters are obtainedfrom the results Comparisions between the experimentally obtained results and their numerically simulated showthat there is a good agreement between numerical simulation and experimentally results in lifetime prediction of316L steel samples Therfore the ductile brittle damage model can be used in prediction of behavior of materialswhich produced by SLM process in cyclic loading Keywords Selective laser melting Continuum damage mechanics Ductile brittle damage model Low cyclefatigue

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