Selective Laser Melting (SLM) is one of the Additive Manufacturing (AM) methods that has been used widely in recent decades. Due to the widespread use of the materials in many fields such as aerospace, turbine blades, the automotive and medical industry, it is essential to prepare a appropriate way to predict their behavior under different loading conditions. On the other hand, many parts in aircraft structures, turbine blades, etc. are under cyclic fatigue loading. Therefore, the analysis of these materials in cyclic fatigue loading is very important. Continuum Damage Mechanics (CDM) provide an efficient tool to predict material behavior and lifetime of components under different loading conditions. Damage mechanics is concerned with the representation or modeling of damage of materials that is suitable for making engineering predictions about the initiation, propagation and fracture of materials without resorting to a microscopic description that would be too complex for practical engineering analysis. Damage of materials means the progressive or sudden deterioration of their mechanical strength because of loadings or thermal or chemical effects. From a physical point of view, damage can originate from multiple causes: debonding of atoms, 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 microcracks and 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 by SLM process in Low Cycle Fatigue(LCF) loading using CDM. According to experimental observation, because of high thermal gradient and prosity of the samples in production process, 316L samples produced this way show a semi-brittle behavior. A ductile- brittle damage model is implemented inside the finite element commercial FORTRAN code, for ABAQUS UMAT subroutine. First, mechanical properties and damage parameters and coefficients for 316L SLM samples, are obtained from experimental results. Therefore, an experimental procedure to identify the damage parameters is proposed. To identify and extract the parameters, two tests are developed and regulated. The experiments included tensile tests and LCF tests. Various experiment and measuring methods have been compared, and the parameters are obtained from the results. Comparisions between the experimentally obtained results and their numerically simulated, show that there is a good agreement between numerical simulation and experimentally results in lifetime prediction of 316L steel samples. Therfore the ductile-brittle damage model can be used in prediction of behavior of materials which produced by SLM process in cyclic loading. Keywords: Selective laser melting, Continuum damage mechanics, Ductile-brittle damage model, Low cycle fatigue.
