No abstract

The life prediction of components built by additive manufacturing process, such as Direct Metal Deposition (DMD), needs a good characterization of their physical states (including metallurgy, residual stresses…). A robust finite element analysis of the DMD process at a macroscopic scale should then include thermal, metallurgical and mechanical aspects. The present paper shows a comprehensive model, where the metallurgical section is developed in strong connection with the physical process. The model is implemented in the Finite Element Code Z-Set and a specific strategy is introduced to progressively activate the elements and follow a given fabrication route.

The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder streams characteristics is essential to control the process and improve its reliability and reproducibly for industrial applications. This paper proposes multiple experimental techniques, such as gas pressure measurement, optical and weighting methods, to analyze the gas and particle velocity, the powder stream diameter, its focal plan position and density. This was carried out for three nozzle designs and multiple gas and powder flow rates conditions. The results reveal that (1) the particle stream follows a Gaussian distribution while the gas velocity field is closer to a top hat one; (2) axial, carrier and shaping gas flow significantly impact the powder stream’s focal plan position; (3) only shaping gas, powder flow rates and nozzle design impact the powder stream diameter. 2D axisymmetric models of the gas and powder streams with RANS turbulent model are then performed on each of the three nozzles and highlight good agreements with experimental results but an over-estimation of the gas velocity by pressure measurements.

No abstract