*2.4. Elliptical Capillary—Influence of Ellipse Aspect Ratio*

Finally, it has to be assessed whether there would be an added-value to using capillaries of elliptical cross section instead of circular cross section. Indeed, these would definitely be more complex to manufacture, but it is deemed that this could have a beneficial impact on the tensile stress level in the initiation region and more significantly on the capillary surface. To that purpose, capillaries of various aspect ratios, ranging from 1 (circular capillary) to 4, but of identical cross sectional area (1 mm2) and constant edge-to-edge distance are considered. These configurations are shown in Figure 5c.

The results of the simulations performed on these lugs is shown in Table 3. It can be seen that the impact on the stress level in the initiation region is negligible. However, as it is expected, the use of an elliptical cross section affects quite significantly the stress level at the capillary surface, as the maximum value of tensile stress attained on the capillary surface drops from 226 MPa (circular capillary) to 174 MPa (ellipse of aspect ratio 4), thus resulting in a 23% decrease on the surface. As a consequence, it indicates that the use of an elliptical cross section could enable to position the capillary closer to the lug hole surface (hence achieving faster detection) while minimizing the risk of initiation at the capillary itself.


**Table 3.** Maximum axial tensile stress values in function of capillary cross section aspect ratio (AR).
