6.4 Experimental setup

Schematic diagram of free vibration of a two DOF rotor system is shown in Fig. 6.3. The experimental setup consists of a rotor with two or three masses mounted on it at certain spans along the length of the rotor as shown in Fig. 6.4. Accelerometers and the sensing devices are placed on each mass present in the system, and are connected to the data acquisition system at the other end. The data acquisition system is connected to a computer having a signal processing software.

The material and geometrical properties of shaft and discs are shown in Tables 1, 2 and 3, respectively.

 

Fig. 6.3: A schematic of the experimental setup of free vibration of 2-DOF rotor system

 

Fig. 6.4: Experimental set up of 2 DOF rotor system

 

An accelerometer (Fig. 6.5) is a sensing element (transducer) to measure the vibration response (i.e., acceleration, velocity and displacement). Data-acquisition systems take vibration signal from the accelerometer and encode it in digital form. Computer acts as a data-storage and analysis system. It takes encoded data from data-acquisition system and after processing (e.g., FFT, filtering), it displays on the computer screen by using the analysis software.

 

Fig. 6.5: Close view of accelerometer mounted on one of discs

 

Data acquisition system (Fig. 6.6) receives voltage signal from the accelerometer and calibrates the data into equivalent accelerometer scale and send it to computer where by using a vibration measurement software these data can be analyzed in time history (Displacement-Time) and in frequency domain (i.e., using FFT).

 

Fig. 6.6: Data acquisition system

 

Table 6.1 Material properties of the system

 

Table 6.2 Geometrical properties of discs

 

Table 6.3 Geometrical properties of shaft