# Image-Based Analysis of Plate Separation and Clearance Distribution in Wet Clutches
## 3 Results
### Results Operating Mode 1  
Figure 7 shows the result of the Reference Test 1-R. The plates were in the end position at the start of the test. As the rotation started, the plates separated immediately, and the gaps formed (see Figure 7c).  
The plates separated further with increasing differential speed and reached their final position regarding their main movement before reaching the maximum differential speed (see Figure 7b). From the variation of the clearances, it can be deduced that the plates performed non-periodic oscillations even at a constant differential speed. There were no significant main movements during the constant differential speed and subsequent decrease in differential speed. The drag torque measurement shows the characteristic behavior with a clear maximum value and a drop to a constant value (see Figure 7a). The difference in the maxima at the increase and decrease in differential speed results from the difference between acceleration and deceleration torque. However, the maximum drag torque decrease during the subsequent speed ramps is conspicuous. It is assumed that this is due to the increasing oil temperature caused by the ongoing energy input.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **Corresponding Figure** & **Corresponding Video** \\ \hline
1–R & Figure 7 & Video S1 \\
1–1 & Figure A3 of Appendix B & Video S2 \\
1–2 & Figure A4 of Appendix B & Video S3 \\
1–3 & Figure A5 of Appendix B & Video S4 \\
2–R & Figure 10 & Video S5 \\
2–1 & Figure A6 of Appendix B & Video S6 \\
3–R & Figure 12 & Video S7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Figures and videos associated with individual tests.  
Figure 8a shows the mean clearances during the sections of constant differential speed (i.e., Sections 1-3, see markings in Figure 7a) of Reference Test 1-R. The values show that the clearances are quite uniform in all sections and prove the repeatability of the separation behavior. The mean utilized total clearance and utilization factor are given in Table 3. The set total clearance was utilized by approx. 80%. Figure 8b shows the clearances' standard deviation during Section 1. The variation of the clearances represented by the error bars indicate minor plate oscillations even at constant differential speed.  
Figure 8: Reference Test 1–R: (**a**) mean clearances \(\overline{h}_{i}\) during Sections 1–3; (**b**) mean clearances \(\overline{h}_{i}\) and standard deviation during Section 1.  
Figure 7: Result of Reference Test 1–R: (**a**) differential speed and torque; (**b**) positions; (**c**) clearances.  
Figure 9 compares the mean clearances during Section 1 of Tests 1-R, 1-1, 1-2, and 1-3. The mean utilized total clearances and utilization factors are given in Table 3. The full results of Tests 1-1, 1-2, and 1-3 are provided in Appendix B.  
When increasing the clearance (Test 1-1) and using dip lubrication (Test 1-2), the set total clearance was not utilized. The utilization factor ranged between 80% and 89%. In addition, the clearances were distributed less uniformly than during the Reference Test 1-R. The drifting off of the outermost plate O5 (numbering according to Figure 4c) and the resulting large clearance of gap \(i=8\) is conspicuous. The larger mean clearances during Test 1-1 caused a lower drag torque. Despite different flow characteristics in the gaps, dip lubrication led to a separation behavior similar to injection lubrication.  
In the case of a clutch pack with 16 gaps, the set total clearance was distributed less uniformly compared to the Reference Test 1-R with 8 gaps. Noticeably, the outermost plates (\(i\geq 11\)) separated more, resulting in larger clearances. However, the set total clearance was not utilized; the utilization factor was approx. 93%. Compared to the Reference Test 1-R, the final positions were reached at a higher differential speed.