## 3 Results
### Determination of a Time Interval for Measurement Evaluation
Based on these analyses, an evaluation interval of 15 s was determined for directly measured contact forces (CFs) as follows: If the measurements identify a change in contact forces (CFs), the evaluation of whether it is a failure and of what kind will be carried out during the measurement that follows after the next 15 s.  
Determination of Minimal Value Differences in Contact Forces (CFs) between a Failure-Free Operation and a Failure, and the Difference in Contact Forces (CFs) between Individual Failures  
Considering the fact that the largest difference in contact forces (CFs) for a steady condition was at position ID11 CF90s \(-\) ID11 CF15s = 16.3 N (Table 6), a minimum acceptable difference in contact forces (CFs) for failures identification was defined as 20 N.  
Determination of Measuring Positions to Measure Contact Forces (CFs) on Rollers So That Defined Failures Can Be Identified on the Basis of Measured Contact Force (CF) Values  
We set the following criteria for measuring roller positions that are suitable for ongoing measurements to classify failures:  
* A minimum number of differences in contact forces (CFs) (between a failure-free state and failures and also between failures) smaller than 20 N.
* The combination of roller positions must ensure that, for every difference (between a failure-free state and a failure and between failures), there is a roller position for which the difference is more than 20 N. To meet these criteria, the following procedure was used:  
1. Calculate the mutual differences between the average contact forces (CFs) at each roller's position in a failure-free state, and for each failure, in accordance with the following procedure: ID7 CFm200 \(-\) ID7 CFm207 (is empty), ID7 CFm200 \(-\) ID7 CFm208 = 44.4 N,..., and ID7 CFm212 \(-\) ID7 CFmWOMA0 = 32.0 N, as listed in Table 7. Mutual differences are given only once. For the type of failure with a missing roller at the measuring point, the difference in measurement is not considered, and the cell is empty. Differences that are unaccepted (their value is smaller than 20N) are displayed in red. 2. Determine the number of unsatisfactory measurement differences (smaller than 20 N) for each roller position. These values are the red cells in Table 7. The number of unsatisfactory differences was obtained for each roller position (Table 8). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Time from Tensioning** & & & \multicolumn{3}{c}{**CF Difference (N)**} & \\
**Termination (s)** & **ID7** & **ID8** & **ID9** & **ID10** & **ID11** & **ID12** \\ \hline
20 & 1.2 & 0.2 & \(-\)1.0 & 0.4 & 2.0 & \(-\)0.8 \\
30 & 2.4 & 0.9 & 0.5 & 0.3 & 5.2 & \(-\)3.4 \\
60 & 0.7 & 0.2 & 1.1 & 3.3 & 12.0 & \(-\)5.0 \\
90 & 1.1 & 0.3 & 1.2 & 4.0 & 16.3 & \(-\)7.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Calculated differences in contact forces (CFs) at 20, 30,..., and 90 s and 15 s from the tensioning termination. Table 8 makes it clear that the best positions to classify a failure are ID7, ID10, and ID11, where the smallest number of unsatisfactory differences is equal to four. 3. Select the roller position combinations that meet the criterion (for each difference, the roller's position exists with a difference larger than 20 N). The validity of this criterium was verified for roller positions chosen in the previous procedure step, i.e., ID7, ID10, and ID11. Table 9 presents the positions for given pairs of the states (without a failure, with a failure), which, based on the differences in contact forces (CFs) on the roller, cannot be distinguished from each other. These are the red cells in Table 9.  
The pair of states m200 and TWOMA0 that cannot be distinguished from each other, occur (Table 9) at roller positions ID7 and ID11 (red cells). For the ID10 roller position, this pair of states meets the difference in contact force (CF) value, i.e., both criteria are met for the selected combination of ID7, ID10, and ID11.