## 3 Results and Discussion
### Influence of Different Roughness Topography and Force Analysis for Leakage Detection  
The first pair of samples (1-2) was selected from the part with surface topography parameters belonging to code group A. When analyzing the stabilization stage of the tightness test for the study of the first test case, for the first pair of samples, i.e., the lowest pressing force equal to 890 \(\pm\) 70 N, a slight pressure drop was noticeable during the test. Figure 7: Contour map and isometric view of samples. (**a,b**) Coded D, (**c,d**) coded E, (**e,f**) coded F.  
It was 0.05 bar, which is 2.5% of the filling pressure value. In the case of increasing the clamping force (which was confirmed by repeated tests), this relationship was not noted. This may indicate that the applied clamping force was in the boundary force area, in which a positive test result was not obtained. When analyzing the test stage, i.e., the course of the leakage curve over time, a decrease in leakage with an increase in the compression force was observed. The minimum value of the required compression force of the samples is 2280 \(\pm\) 70 N. For the indicated force, a leakage of 0.460 \(\pm\) 0.013 cm\({}^{3}\)/min was obtained. The observed initial value of leakage, for the discussed force case, may be related to the switching of the leak detector valve. Increasing the force by almost 82%, i.e., to the value of 4140 \(\pm\) 70 N, made it possible to obtain approximately 7.4 times smaller leakage, i.e., at the level of 0.062 \(\pm\) 0.007 cm\({}^{3}\)/min. On the other hand, increasing the force by a value of 182% in relation to the minimum force made it possible to obtain a significantly smaller improvement in tightness than in relation to the 4140 N force. In this case, the leakage was about 8.1 times smaller than the initial one, i.e., at the level of 0.062 \(\pm\) 0.007 cm\({}^{3}\)/min. By increasing the force to 6420 \(\pm\) 70 N from 4140 N, i.e., almost 55%, the leakage was reduced by 0.05 \(\pm\) 0.007 cm\({}^{3}\)/min, i.e., about 8%. Therefore, the testing of samples was not extended to further test the cases, i.e., increasing the clamping force, as the leakage reduction was negligible. The obtained test results are shown in Figure 8.  
Analyzing the first pair of samples revealed that increasing the force has a very good influence on the tightness of the samples and that increasing the tightness is limited. Therefore, after reaching the appropriate level, there is no need to additionally increase the force. It could be noted that with the force of 4140 N, the leakage was 8.1 times smaller and the result is comparable to the conclusions of the work by [PERSON] et al. The second pair (9-10) had surface parameters belonging to code group B and Figure 9 shows the graph of dependence for a pair of samples 9-10, produced with comparable surface topography parameters for different test cases, i.e., different compressive forces. The forces are leakage values of the second pair (9-10), as shown in Table 6.  
Figure 8: Graph of dependence for a pair of samples 1–2, produced with comparable surface topography parameters for different test cases, i.e., different compressive forces. The next set consisted of parts 17 and 18, which were characterized by surface topography parameters belonging to group code C. The tests of a pair of samples were carried out for various compressive forces. However, filling the chamber between the samples with the set pressure was unsuccessful; therefore, it was not possible to perform the stabilization step of the test. Moreover, the test step was not performed due to the lack of stabilization of the pressure in the chamber between the samples. The maximum force applied to the test set was about 20 kN and was over 2173% greater than the minimum force, which was enough to obtain the leak test result for the previously tested pair of samples 9-10.