Browsing by Subject "curvature"
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Item Curvature-Based Segmentation of Powder Bed Point Clouds for In-Process Monitoring(University of Texas at Austin, 2018) Law, Andrew Chung Chee; Southon, Nicholas; Senin, Nicola; Stavroulakis, Petros; Leach, Richard; Goodridge, Ruth; Kong, ZhenyuThis paper presents a curvature-based analysis of point clouds collected in-process with fringe projection in a polymer powder bed fusion process. The three-dimensional point clouds were obtained from outside of the build chamber with a fringe projection measurement system which was provided with access through an observation window. The curvature-based thresholding of powder bed point clouds demonstrates the ability to separate consolidated areas from the powder bed effectively. This segmentation of the point clouds with masks enables the detection of changes in the outline of consolidated areas between layers, computation of average drop due to the consolidation of the powder bed and separate analysis of both powder bed and consolidated areas. The high-level insights extracted from the analysis of the point clouds could improve process control strategies, such as in-line defect detection during an additive manufacturing build as well as an in-process feedback system for tuning the optimal values of additive process parameters. In summary, we show curvature-based thresholding as an effective segmentation for fringe projection point clouds, which can be further applied to detect defects, such as geometric defects and dimensional inaccuracy.Item Effects of convex curvature on adiabatic effectiveness for a film cooled turbine vane(2013-05) Winka, James R; Bogard, David G.A series of experiments were carried out to measure the effects of convex surface curvature on film cooling. In the first series of experiments cooling holes were positioned along the vane such that their non-dimensional curvature parameter, 2r/d, was matched. Single row of holes with the same diameter were placed at high and moderate curvature position along a turbine vane resulting in 2r/d = 28 and 40, accordingly. A third row of holes was installed on the vane at the same location as the moderate curvature row with a larger hole diameter, resulting in 2r/d = 28, matching the high curvature row. Adiabatic temperature measurements were then carried out for blowing ratios of M = 0.30 to 1.60 tested at a density ratio of DR = 1.20. The results indicated that there was some scaling of performance present with matching 2r/d, but there was not an exact matching of performance. The second series of experiments focused on the effects of a changing surface curvature downstream of injection. Two row of holes were positioned along the vane surface such that the local radius of curvature and hole diameters were equivalent, with one row positioned upstream of the maximum curvature point and the other downstream of the maximum curvature point. Adiabatic temperature measurements were carried out for blowing ratios of M = 0.30 to 1.60 and tested at a density ratio of DR = 1.20. The results show that the change in curvature downstream plays a significant role in the performance of film cooling and that the local surface curvature is insufficient in capturing its effects. Additional experiments were carried out to measure the effects of the approaching boundary layer influence on film cooling as well as the effect of injection angle at a weakly convex surface.