This paper presents a 3D transient finite element (FE) model of laser solid freeform fabrication (LSFF) process. The proposed model determines the thermal distribution throughout the workpiece as a function of time and process parameters including laser power, traverse speed, and material properties. Based on the thermal analysis, the clad formation is then predicted. In the proposed method, the thermal domain is numerically obtained, assuming the interaction between the laser beam and powder stream is to be decoupled. Once the melt pool boundary is obtained, the physical domain is discretized in a cross-sectional direction. Based on the powder feed rate, elapsed time, and intersection of the melt pool and powder stream area, layers of additive material are then added onto the non-planar domain. In the numerical simulation, the effects of a non-planar surface on the process parameters such as powder efficiency and absorption factor are taken into account. The model was used to predict the geometrical and thermal properties of a four-layer thin wall of AISI 4340 steel. Numerical results show that the temperatures increase sensibly at the end-segments of layers 2, 3, and 4. Experimental and numerical results are compared to verify the accuracy and reliability of the proposed model.

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