# Compressive Behavior of Inconel 625 and Ti-6 Al-4V Strut Lattices Fabricated by LPBF
## 3 Results  
The theoretical volume and surface of each specimen configuration were determined using the nTop software, and these values were compared with the values obtained for a solid cylindrical specimen (as reference). The obtained results are presented in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Specimen Type**} & \multirow{2}{*}{\
\begin{tabular}{c} **Theoretical** \\ **Volume, cm\({}^{3}\)** \\ \end{tabular} } & \multicolumn{2}{c}{**Volume Reduction**} & \multirow{2}{*}{
\begin{tabular}{c} **Theoretical** \\ **Surface, cm\({}^{2}\)** \\ \end{tabular} } & \multicolumn{2}{c}{**Surface Area Increase**} \\  & & & **Compared with the Solid** \\  & & & **Specimen, \%** & & **Specimen, \%** \\ \hline
1. & Solid specimen & 4.946 & - & 16.72 & - \\ \hline
2. & Octet specimen & 2.545 & 49 & 80.86 & 484 \\ \hline
3. & Truncated octahedron specimen & 2.255 & 54 & 62.17 & 372 \\ \hline
4. & Kelvin cell specimen & 2.016 & 59 & 52.01 & 311 \\ \hline
5. & Re-entrant specimen & 2.125 & 57 & 60.34 & 361 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cylindrical specimens’ characteristics. Based on this simple analysis, a significant volume reduction was determined for all specimens (values between 49-59%) simultaneous with an increase in the specific surface area of the specimens (values between 311-484%). In contrast to solid structures, the integration of lattice structures can lead to a significant decrease in weight and an increase in specific surface area, making them well-suited for applications such as heat exchangers. Figure 5 depicts the results of a comparative static finite element analysis, showcasing the von Mises stress distributions in the case of all four cell types selected, and for both the alloys. Figure 6 depicts the results of a comparative static finite element analysis, showing the resultant displacement in the case of all four cell types selected, and for both the alloys. The simulation results revealed that the highest performance was recorded for the octet specimens, regardless of the material used, followed by the truncated octahedron and Kelvin specimens. The lowest performance was recorded for the re-entrant specimens. The von Mises stress values obtained show similar values for both materials, but a significant difference was observed for displacement. In this case, a similar trend was observed for the cell types as in the case of the von Mises stress, but higher displacement values were obtained for the titanium alloy compared with those registered for the nickel-based alloy; thus, it can be concluded that the specimens manufactured from titanium alloy will present a higher degree of deformation during experimental texting. Figure 7 shows images of specimens under compressive loading during many stages of the experimental tests. Figure 5: Cont. Figure 5: _Cont_. Figure 5: _Cont._  
Figure 5: Static finite element analysis results—von Mises stress comparison for different cell topologies (octet, truncated octahedron, Kelvin, re-entrant) and materials (Inconel 625, Ti-6 Al-4V). Figure 6: Static finite element analysis results—resultant displacement comparison for different cell topologies (octet, truncated octahedron, Kelvin cell, re-entrant) and materials (Inconel 625, Ti-6 Al-4V). Comparing the images from Figures 5 and 6 with those from Figure 7, a slight resemblance can be observed between the simulation and the experimental results, with the highest degree of damage observed in the case of the titanium alloy specimens, mainly on the re-entrant specimens. During the experimental tests, the Inconel 625 specimens exhibited plastic behavior and tended to bend, while the Ti-6 Al-4V specimens exhibited more brittle behavior as the struts tended to break under compressive loads.