# Vibration Energy at Damage-Based Statistical Approach to Detect Multiple Damages in Roller Bearings
## 4 Results and Discussion
### Outer Race Damage  
In order to analyze the outer race damage, an outer race damaged bearing was placed, and the intact bearing was removed from outboard bearing housing. The vibration data were acquired through accelerometers at 1002, 1500, 2400, and 3000 RPM rotating speed. The histograms for all rotating speeds, without installing a bearing loader and with installing a bearing loader, were formulated. The intact bearing and outer race damaged bearing's histogram in the vertical direction of the outboard bearing housing were compared without installing a bearing loader and with installing a bearing loader, and the results are presented in Figures 4 and 5, respectively. The kurtosis was also calculated at each rotating speed, without installing a bearing loader and with installing a bearing loader, in the vertical direction of the outboard bearing housing, as shown in Table 5.  
The vibration data for an outer race damaged bearing are more scattered as compared to those for the intact bearing, since the width and height of the bars for an outer race damaged bearing are greater in Figures 4 and 5. The outer race damage is significantly visible in histograms for all rotating speeds and for both of the loading conditions. The bars are high for an outer race damaged bearing because the damaged bearing produces high vibrations, as it has high damage energy. The kurtosis values are also high for an outer race damaged bearing, as shown in Table 5, except at 2400 RPM without installing a bearing loader; this may be due to nonlinearities of the simulator. The histograms, along with the kurtosis values, revealed that this is an effective approach in detecting an outer race damage in the rolling bearing.  
but only the horizontal direction kurtosis values are shown in Table 6, as this shows the ball damage more clearly.  
Figure 4: Histograms for an outer race damage without installing a bearing loader.  
Figure 5: Histograms for an outer race damage with installing a bearing loader.  
Figure 6: Histograms for ball damage without installing a bearing loader.  
Figure 7: Histograms for ball damage with installing a bearing loader.  
Figures 6 and 7 reveal that the vibrations are high in case of a ball damaged bearing as compared to the intact bearing. Due to the defect, the bearing produces greater vibrations that result in high bars in the histograms, showing that the damage energy can be a good indicator of faults in roller bearings. The histograms for ball damage, without installing a bearing loader and with installing a bearing loader, are almost the same for all rotating speeds, but the histograms with installing a bearing loader have very high bars due to the fact that with the installation of a bearing loader, the load on the damaged bearing increases, which increase the vibrations. Table 6 clearly shows the high kurtosis values for a ball damaged bearing, as the kurtosis is a measurement of the thickness or heaviness of the tails of a distribution, so it can be said that a ball damaged bearing produces high vibration, which results in high kurtosis values. The histograms and kurtosis values revealed that it is an effective method in detecting the ball fault at an early stage in a roller bearing.