# Vibration Energy at Damage-Based Statistical Approach to Detect Multiple Damages in Roller Bearings
## 3 Experimental Setup  
This study is based on the experiments performed on a machinery fault simulator (MFS). Experiments testing the vibration energy at damage-based statistical approach in detecting bearing damages were performed on an MFS made by SpectraQuest. This simulator has a three-phase pre-wired electric motor of 1 HP that drives a rotor assembly with a variable frequency AC drive that has a multi-featured, front panel programmable controller. The rotating speed is measured by a built-in tachometer, with an LCD display, that can be varied from 0 to 6000 rpm with a short duration. The motor and rotor shaft is connected with an L-type standard jaw coupling, made of sintered iron, that has a length of 54.6 mm. The rotor assembly consists of a 25.4 mm diameter turned, ground, and polished (TGP) steel rotor shaft supported by two roller bearings. The roller bearings are placed in a horizontal-type split bracket. The accelerometers are placed on inboard and outboard bearing housings in the vertical and horizontal direction, and the vibration data are recorded. These accelerometers can record the vibration with a sensitivity of 10.2 mV and a measurement range of \(\pm\)490 ms\({}^{-2}\). An eight-channel data acquisition card was used to acquire the data from the simulator, which was later analyzed. The complete experimental apparatus is shown in Figure 1.  
This simulator was used in our previous studies to detect: the imbalance caused by using accelerometers at three different operating speeds [25], the misaligned and cracked shafts using order analysis [26], the bearing faults using spectral density analysis [27] and octave analysis [28]. It was also used to detect imbalance using piezoelectric strain sensors [29]. The misaligned and cracked shaft was also analyzed on this simulator, and sensitive locations for transducers were discussed [30]. This study focuses on multiple damages in roller bearings; bearing damages have been analyzed by comparing the intact bearing's histogram and kurtosis values with the following defected bearings: (1) inner race defect; (2) outer race defect; (3) ball defect; and (4) combination defect. All of the above defected bearings in this experimental study were used at 1002, 1500, 2400, and 3000 RPM rotating speeds, with two types of loading conditions: without installing a bearing loader and with installing a bearing loader. In the first type of the loading condition, the vibration data of intact and defected bearings were acquired through the accelerometers, without installing a bearing loader on the rotor assembly. In the second type of loading condition, a bearing loader was installed at a distance of 5 cm from the outboard bearing housing, and the vibration data of intact and defected bearings were acquired through the accelerometers. For both types of loading conditions, the defected  
Figure 1: Experimental setup for evaluating bearing damages. bearing was placed at outboard bearing housing. The intact bearing histograms and kurtosis values are compared with each defected bearing. The inner race, outer race, ball, and combination damage bearings were placed only at the outboard bearing housing. The vibration data were acquired with 12,800 spectral lines and 10 kHz maximum frequency. The overall velocity-RMS values have been collected at no fault condition for both types of loading conditions in order to follow the ISO standard 20816-1 [31]; this was also done in our previous studies [25; 26; 27; 28]. The ISO standard 20816-1 has a vibration severity chart consisting of four categories: A, B, C, and D. Category 'A' means that the machine is in outstanding condition, and category 'D' means that the machine's vibrations are not permissible. The vibration severity chart of ISO standard 20816-1 also classifies all machines into four classes, class I through class IV, depending upon the size of the machine. The simulator had a power of 1 HP and according to the ISO standard 20816-1 vibration severity chart, it belongs to class 1.