## 3 Results
### Case Study 2--Box Corner
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Initial Cylinder Radius & 1.0 mm \\ Minimal Initial Element Size & 3.0 mm \\ Population & 5000 \\ Node Move Standard Deviation & 0.2 mm \\ Radius Change Standard Deviation & 0.2 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Parameters of feature recognition algorithm used in Case Study 2. Figure 18: **(a,b)** Two different views of the topology optimization output—the input for the features recognition system. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Yellow Boundary** & **Blue Boundary** & **Red Boundary** \\ \hline
**Load Case 1** & Force 200 N, vector Y = \(-1\) & Force 200 N, vector X = 1 \\
**Load Case 2** & Force 200 N, vector Z = 1 & support \\
**Load Case 3** & support & Force 200 N, vector Z = 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Forces and support assignment to boundary areas for load cases in the structural optimization task. Refer to Figure 17 for color-coded boundary areas’ locations. Figure 20: Steps of feature recognition algorithm. **(a)** Structural optimization output mesh with optimization exclusion area. **(b)** Structural optimization output mesh with parts inside optimization exclusion area removed. **(c)** Skeletonized mesh. **(d)** Initial solution—input of heuristic refinement as CAD features. **(e)** Output of heuristic refinement algorithm as CAD features. **(f)** CAD features with parts inside optimization exclusion area re-attached for solution validation. \begin{table}
\begin{tabular}{c c c} \hline  & **Input Mesh** & **Parametric Model** \\ \hline \multirow{2}{*}{**Loss Case 1**} & \multirow{2}{*}{**Mass**} & **64.1 g** & **72.4 g** \\  & Max von Mises stress on surface & \(141\times 10^{6}\) Pa & \(236\times 10^{6}\) Pa \\  & Mean von Mises stress on surface & \(23.1\times 10^{6}\) Pa & \(21.9\times 10^{6}\) Pa \\  & Max Deflection at Force 1 & 0.82 mm & 0.78 mm \\  & Max Deflection at Force 2 & 0.61 mm & 0.62 mm \\ \hline \end{tabular}
\end{table} 
Table 5: Comparison of mass and stress values for input mesh and parametric model for Case Study 2. Figure 21: **(a,c,e)** von Mises stress on a surface calculated for the structural optimization output. **(b,d,f)** von Mises stress on a surface calculated for the mesh reconstructed in CAD; **(a,b)** Load Case 1. **(c,d)** Load Case 2. **(e,f)** Load Case 3. \begin{table}
\begin{tabular}{c c c c} \hline  & & **Input Mesh** & **Parametric Model** \\ \hline  & **Mass** & **64.1 g** & **72.4 g** \\ \hline
**Load Case 2** & & & \\  & Max von Mises stress on surface & \(178\times 10^{6}\) Pa & \(248\times 10^{6}\) Pa \\  & Mean von Mises stress on surface & \(19.98\times 10^{6}\) Pa & \(17.6\times 10^{6}\) Pa \\  & Max Deflection at Force 1 & 0.73 mm & 0.61 mm \\  & Max Deflection at Force 2 & 0.68 mm & 1.0 mm \\ \hline
**Load Case 3** & & & \\  & Max von Mises stress on surface & \(263\times 10^{6}\) Pa & \(436\times 10^{6}\) Pa \\  & Mean von Mises stress on surface & \(28.3\times 10^{6}\) Pa & \(28.9\times 10^{6}\) Pa \\  & Max Deflection at Force 1 & 1.6 mm & 2.29 mm \\  & Max Deflection at Force 2 & 0.96 mm & 1.28 mm \\ \hline \end{tabular}
\end{table} 
Table 5: _Cont._The reconstructed object exhibits both a higher overall mass and worse material properties. Although, for Load Case 1, the parametric model exhibits a lower mean stress and comparable deflection values. For Load Case 2 and Load Case 3, all analyzed measures exceed acceptable values. Details with areas exceeding the allowed surface von Mises stress are visible in Figure 23. Analysis shows that a cylindrical structural element, used to build the parametric model, is insufficient to represent the complex structure of the element optimized using the biomimetic approach. The surface stress exceeds the material's yield strengths in a few different distinct cases: the attachment points to the boundary areas are insufficient, the connection between elements are too weak and the cylinders exhibit poor behavior under bending moments (Figure 24).