Page 84 - ESAM-1-2

Engineering Science in
Additive Manufacturing Porous structure performance improvement

Table 3. Design porosity and measurement porosity of the specimen in this study
Specimen Design porosity (%) Measurement porosity (%) Deviation (%)
O_99.5_65 65.00 66.28±0.18 1.96
O_109.5_65 65.00 65.62±0.09 0.95
O_119.5_65 65.00 65.63±0.23 0.97
R_99.5_65 65.00 66.19±0.05 1.02
R_109.5_65 65.00 65.05±0.27 0.08
R_119.5_65 65.00 65.46±0.16 0.71
Note: All the porosity data were measured and calculated using Equation III.

discs can be measured by caliper. Then, the weights of A B
the upper and lower small discs were subtracted, and the
density was calculated to determine the actual porosity of
the specimens. A comparison between the experimental
porosity and the computer-designed porosity is shown in
Table 3. According to Table 3, it can be observed that the
experimental porosity is within 2% of the design porosity,
indicating a close match.
Image analysis software such as ImageJ was used to Figure 5. Demonstration of the angle between the struts in (A) CAD
observe whether the angle of the printed structure is model and (B) analysis by ImageJ
Abbreviation: CAD: Computer-aided design.
consistent with the design. The demonstration of the
measurement method is shown in Figure 5. Under the
optical microscope, a large amount of unmelted powder
adhered to the structure can be observed, causing
roughness on the surface of the struts.
3.2. Impact of chamfer design on mechanical
properties
According to the experimental results in
Table 4 and Figure 6, it can be observed that structures
with rounded corners have higher yield strength and
compressive strength compared to structures without
rounded corners. Specifically, the yield strength was
39
increased by approximately 8% and the compressive
strength by about 6%. However, the improvement was only
marginal compared to the effect of manipulating the angle
between the struts, indicating that the influence of node
with chamfer or not on mechanical properties was less
significant. Figure 6. Compressive stress–strain curves of uniform porosity
materials with different angles between the struts and with the rounded
Analyzing the specimens under a microscope and corner or not
using ImageJ, we can measure the depth (d) and curvature
radius () of the strut notches. By applying the stress corners, with values exceedingly twice as much. Moreover,
concentration formula, we can calculate the maximum as the stress concentration factor (k) increases, the strength
strength of the notch. The depth and curvature radius of has to stand for more strength by the notch. Therefore, it
the notch with and without rounded corners are depicted can be inferred that structures without rounded corners
in Figure 7. experience higher strength at the notch, leading to an
The results based on Equation II are summarized earlier occurrence of the first load drop and premature
in Table 5. For structures without rounded corners, the crack initiation from the notch. Consequently, the crack
strength stand by the notch ( max ) under a force of F was propagation path became shorter, resulting in early fracture
significantly higher compared to structures with rounded and a decrease in both ductility and strength.

Volume 1 Issue 2 (2025) 6 doi: 10.36922/ESAM025170009