# Analysis of the Chip Geometry in Dry Machining of Aeronautical Aluminum Alloys
## 3 Results and Discussion
### Height of Peaks (\(h_{c}\)) and Valleys (\(h_{\mathrm{p}}\))  
Figure 8 shows the evolution of the \(h_{c}\) and \(h_{\mathrm{p}}\) mean values of the chip specimens analyzed, as a function of \(f\). As can be observed, \(h_{c}\) and \(h_{\mathrm{p}}\) values increase with \(f\), in agreement with the arguments  
Figure 6: SOM images of the chip’s longitudinal (200\(\times\)) and transverse (100\(\times\)) section.  
Figure 7: SOM images (200\(\times\)) of the chip longitudinal section of UNS A92024 alloy as a function of \(L\), for some of the \(f\) values tested.  
exposed above. This trend is common for both alloys. Furthermore, the largest percentage increase takes place for low feed values (from 0.05 mm/r to 0.1 mm/r). For higher feed values (from 0.1 mm/r to 0.3 mm/r), the percentage increase is lower. As previously commented on, once the shear limit is reached, the changes are less noticeable.  
In general, the mean values are very similar for each alloy. Only for \(f\) = 0.3 mm/r can a slightly lower value of \(h_{v}\) for the UNS A97075 alloy be observed. Due to this, the height difference between \(h_{c}\) and \(h_{v}\) is higher for the UNS A97075 alloy, than for the UNS A92024 alloy, for this feed value. In addition, the mean value of \(h_{v}\) shows a trend to remain constant when \(f\) increases from 0.2 mm/r to 0.3 mm/r, for the UNS A97075 alloy. All of these observations can be explained by taking into account that the UNS A97075 alloy withstands larger deformations before breaking, due to its higher plasticity. This effect is more noticeable for high feed values, when the cutting forces are higher. Finally, no significant changes were observed for these parameters as a function of \(L\), in a similar way to that observed for the chip morphology. The mean value variation of \(h_{c}\) and \(h_{v}\) along \(L\) is around 10%, which is within the standard deviation of the measurement process.  
From these experimental results for \(h_{c}\) and \(h_{v}\), a segmentation ratio (\(SR\)) can be calculated, Equation (3). The obtained results for \(SR\) are shown in Table 4.  
\[SR\ =(h_{c}-h_{v})/h_{c}, \tag{3}\]  
In general, a higher segmentation ratio has been obtained for the UNS A92024 alloy in the range of lower \(f\) values (0.05-0.01 mm/r), in accordance with the results for \(h_{c}\) and \(h_{v}\), due to the higher fragility that Cu provides to this alloy. These values slightly decrease when \(f\) increases but, practically, a constant trend can be considered. The reasons are similar to those discussed above, for \(h_{c}\) and \(h_{v}\). For the UNS A97075 alloy, the segmentation ratio is lower when \(f\) changes from 0.05 mm/r to 0.02 mm/r, with a general trend remaining constant. However, the segmentation ratio increases for \(f\) = 0.03 mm/r, until it has almost doubled its value. This is due to the lower value of \(h_{v}\) at this point, due to the reasons previously exposed.  
Therefore, the segmentation ratio shows a trend to remain constant in a wide range of \(f\), for both alloys, so it does not provide excessively relevant information, due to the high ductility of these alloys.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \(f\) **(mm/r)** & 0.05 & 0.1 & 0.2 & 0.3 \\ \hline \multirow{2}{*}{\(SR\)} & **UNS A92024** & 0.32 & 0.32 & 0.26 & 0.28 \\ \cline{2-6}  & **UNS A97075** & 0.21 & 0.21 & 0.24 & 0.45 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Segmentation Ratio.  
Figure 8: Height of peaks (\(h_{c}\)) and valleys (\(h_{v}\)) as a function of feed for (**a**) UNS A92024 and (**b**) UNS A97075.