# Bearing Severity Fault Evaluation Using Contour Maps--Case Study
## 2 Method
### Experimental Data
#### 2.2.2 Design of Experiment (DoE)  
The DoE was based on the development of a combined outer race (OR) and three rolling elements (RE) failures in the test bearing. For this, a \"Factorial 5 \(\times\) 3\" design was considered, to study the influence of five fault levels (F0, F1, F2, F3 and F4) on ORRE, under three operating regimes (200, 350 and 500 rpm). Table 5 describes the factors and levels considered in the test.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**6304-2R**} & \multirow{2}{*}{**Frequency**} & \multicolumn{3}{c}{**Regime**} & \multicolumn{2}{c}{**Units**} \\ \cline{3-6}  & & **200** & **350** & **500** & **rpm** \\ \hline BPFO & 2.5783 \(\times\) F\({}_{\text{r}}\) & 8.59 & 15.04 & 21.49 & Hz \\ BPFI & 4.4398 \(\times\) F\({}_{\text{r}}\) & 14.80 & 25.90 & 37.00 & Hz \\ BSF & 1.7590 \(\times\) F\({}_{\text{r}}\) & 5.86 & 10.26 & 14.66 & Hz \\ FTF & 0.3687 \(\times\) F\({}_{\text{r}}\) & 1.23 & 2.15 & 3.07 & Hz \\ \hline \hline \end{tabular}
\end{table}
Table 4: Fundamental frequencies of the 6304-2R bearing (Sensor 2) under different regimes [16].  
Figure 4: Test bench.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**22205E1 KC3**} & \multirow{2}{*}{**Frequency**} & \multicolumn{3}{c}{**Regime**} & \multicolumn{2}{c}{**Units**} \\ \cline{3-6}  & & **200** & **350** & **500** & **rpm** \\ \hline BPFO & 6.1852 \(\times\) F\({}_{\text{r}}\) & 20.62 & 36.08 & 51.54 & Hz \\ BPFI & 8.8148 \(\times\) F\({}_{\text{r}}\) & 29.38 & 51.42 & 73.46 & Hz \\ BSF & 5.4030 \(\times\) F\({}_{\text{r}}\) & 18.01 & 31.52 & 45.03 & Hz \\ FTF & 0.4123 \(\times\) F\({}_{\text{r}}\) & 1.37 & 2.41 & 3.44 & Hz \\ \hline \hline \end{tabular}
\end{table}
Table 3: Fundamental frequencies of the 22205E1 KC3 bearing (Sensors 1 and 3) under different regimes [16].  
The depth of the fault is expressed as the absolute magnitude of the difference between the geometry of the normal state and the induced fault. The development of the flaws was generated by milling the surface of each component, their quantification was carried out using a DML IP54 micrometre.  
The ISO 13373-1 [14] standard indicates that the load is one of the most influential factors in vibration; therefore, the fault generated in OR must be positioned in the load zone of its support. As indicated by [PERSON] et al. [16], a threaded tightening tower was used in this experiment, which allows for a vertical load of 1.4 kN to be applied.  
The type of lubricant used in the bearing is the one recommended on the official Schaeffler website (ISO VG 220) for the operating conditions. Considering the influence of a correct lubricant film on the friction level and heat dissipation between the bearing components, a protocol was executed prior to the start of the record capture at each failure level. This ensures correct lubrication and maintains the same working conditions at each record capture. This protocol considered the change the lubricant at each fault level generated and the preheating of the bearing, for which two stages of operation were carried out, starting with 10 min of operation at a rotational speed of 200 rpm and then continuing with 10 min of work at a rotational speed of 500 rpm. After these operations, the engine turns to the speed test (200 rpm). Each event was repeated three times, where the most representative replica was obtained through the geometric mean of the correlation, covariance and coherence estimators. These estimators analyse the relationship between replicas in the frequency domain. The most representative replicas will also be used in this work.  
The records were acquired with a sampling frequency of 45 kHz in three of its channels, for 45 s. These, in turn, were resampled at 40 kHz to guarantee a constant sample rate throughout the record.