Fatigue Strength under High Frequency Loading of Materials Produced by Selective Laser Melting

The mathematical modeling of the selective laser melting process of metallic alloy powders for the construction of metal products has been carried out within the framework of the enthalpy formulation of the three-dimensional non-stationary nonlinear heat conductivity problem for a multi-phase system. The parameters of the geometry of a single track, as well as single-layer and multilayer systems of overlapping tracks, depending on the power and speed of the laser beam have been determined that makes it possible to estimate the structure and types of defects occuring during layer-by-layer printing of specimens. To study the effect of single and multiple defects on the fatigue behavior of printed specimens under high-frequency loading, the previously proposed multi-mode model of cyclic damage has been used. It is shown that the internal heterogeneity of the microstructure of materials printed by selective laser melting can lead to earlier subsurface nucleation of fatigue cracks and significantly reduce the fatigue strength and durability. This effect is more pronounced for systems of multiple defects. The proposed models and calculation algorithms allow us to calculate the fatigue strength and durability of specimens for various systems of microstructure defects corresponding to the specified characteristics of a moving laser beam, as well as to determine the range of parameters of the selective laser melting process, in which the best fatigue strength indicators are achieved under high-frequency loading.