## 4 Fabrication and Experimental Verification
### Cutting Experiment  
The cutting experiment was performed to confirm the effectiveness of the ultrasonic-assisted cutting using the fabricated ultrasonic horn. Figure 11 shows the experimental set-up of the cutting experiment. The load cell was used to measure the cutting force and the oscillator was used to resonate the horn to a natural frequency of 28.5 kHz. The cutting work was conducted in the axial direction of the ultrasonic cutter, and the resonance frequency was applied for 0.1 s before and after the contact occurs. Silicon composite materials (8 GPa Vickers hardness, 18-\(\upmu\)m thickness), which are actively used in electronic products, were used as the experimental specimens. The cutting speed was 100 mm/s, in order to cut two specimens per second. The average cutting force of the 10 cutting experiments was measured. The experiments were conducted with and without an ultrasonic vibration excitor. Table 6 shows the cutting force of the 10 cutting experiments with and without an ultrasonic vibration excitor. The output cutting force of the optimized cutter assisted by ultrasonic vibration was 78.5 N and the output cutting force without using ultrasonic vibration was 234.0 N. The cutting force assisted by ultrasonic vibration was reduced to 30% of the conventional cutting force. Figure 12 shows samples of the cutting surface of the specimens photographed using a scanning electron microscope (SEM). As shown in Figure 12a, the cutting surface without an ultrasonic vibration excitor had crack and delamination in which lamination layer being apart or defected. On the other hand, as shown in Figure 12b, the cutting surface with an ultrasonic vibration excitor was clean, with no faults. This can be explained by the fact that the reduced cutting force with the application of the ultrasonic vibration excitor decreases the friction force between the horn and the specimen and improves the quality of the cutting surface.  
Figure 10: Simulated and experimental output displacement of the optimal model.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Displacement [\(\upmu\)m]**} & \multirow{2}{*}{**Axial Mode Frequency [Hz]**} \\ \cline{2-3}  & **Maximum** & & **Minimum** \\ \hline Simulation & 17.55 & 14.76 & 28,478 \\ Experiment & 17.56 & 15.30 & 28,480 \\ Difference [\%] & 0.06 & 3.52 & 0.01 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Simulated and experimental output displacement of the optimal model.  
Figure 11: Cutting experiment set-up.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Test \#**} & \multicolumn{2}{c}{**Cutting Force [N]**} \\ \cline{2-3}  & **Ultrasonic Cutting** & **Conventional Cutting** \\ \hline
1 & 76.3 & 235.6 \\
2 & 77.9 & 240.1 \\
3 & 82.4 & 228.9 \\
4 & 75.5 & 232.5 \\
5 & 76.9 & 234.8 \\
6 & 78.4 & 239.4 \\
7 & 80.4 & 229.8 \\
8 & 81.2 & 234.5 \\
9 & 76.8 & 231.2 \\
10 & 78.8 & 233.0 \\ average & 78.5 & 234.0 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Cutting force measured in the cutting experiment.  
Figure 12: SEM images of cutting surface (**a**) without the application of ultrasonic vibration and (**b**) with the application of ultrasonic vibration.