Abstract
This work proposed a computationally efficient analytical modeling strategy to calculate the product porosity in laser powder bed fusion (LPBF) induced by a lack-of-fusion defect, with the consideration of cap area in solidified molten pools, influence of powder bed characteristics on material properties, and un-melted powders in the lack-of-fusion portion. The powder packing pattern and powder bed void fraction were estimated by an advancing front method and the technique of image analysis. The effects of powder bed characteristics on the material properties were considered by analytical models with solid properties and powder bed void fraction as inputs. A physics-based thermal model was utilized to calculate the temperature distribution and molten pool size. The molten pool cross section in transvers direction was assumed to be dual half-elliptical. Based on this assumption and molten pool size, the geometry of the molten pool cross section with cap area was determined. The overlapping pattern of molten pools in adjacent scan tracks and layers was then obtained with given hatch space and layer thickness. The lack-of-fusion area fraction was obtained through image analysis of the overlapping pattern. The lack-of-fusion porosity was the multiplication of the lack-of-fusion area fraction and powder bed void fraction. The predictions of porosity under different process conditions were compared with experimental results of 316L stainless steel and showed a better predictive accuracy than the predictions that did not consider cap area. The proposed analytical modeling method has no numerical calculations, which ensures its low computational cost. Thus, the proposed model can be a convenient tool for the fast computation of lack-of-fusion-induced porosity and can help the quality control in LPBF.
Highlights
Laser powder bed fusion (LPBF) metal-additive manufacturing has the potential to be widely used by different industries due to its strengths in developing new alloys and producing products with more complex geometries than other traditional manufacturing techniques such as machining and casting [1,2]
The consideration of cap portion and powder bed material properties causes the prediction of solidified molten pool geometries to be closer to experimental observations, which leads to a better estimation of the overlapping pattern of adjacent molten pools
This study proposed a physics-based analytical modeling method to predict the lackof-fusion-induced porosity in LPBF
Summary
Laser powder bed fusion (LPBF) metal-additive manufacturing has the potential to be widely used by different industries due to its strengths in developing new alloys and producing products with more complex geometries than other traditional manufacturing techniques such as machining and casting [1,2]. Crystals 2021, 11, 1568 an analytical strategy to calculate the lack-of-fusion porosity in LPBF, by analyzing the overlapping pattern of the adjacent molten pools in a transverse cross-sectional area of a part. The effects of powder bed void fraction were not considered in the calculation process of lack-of-fusion porosity. A physics-based analytical modeling approach was presented to correlate the lack-of-fusion porosity in LPBF directly with process conditions, characteristics of the powder bed, and material properties, without relying on any iteration-based numerical calculations. The consideration of cap portion and powder bed material properties causes the prediction of solidified molten pool geometries to be closer to experimental observations, which leads to a better estimation of the overlapping pattern of adjacent molten pools. The predicted lack-of-fusion porosity under various process conditions was validated against experimental data of 316L stainless steel and predictions without cap area
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