From Solving Tribology Problems in Rotating Machines
1.6 Instrumentation Details and Techniques
1.6.1 Vibration Signature and Recording System
In all the tests, vibration accelerometers were mounted in four different locations, to record radial and axial vibration signals as shown in Fig. 1.2. Two pick-ups with magnetic bases were mounted radially, one on the outer race and the other on the end shield. In addition, one pick-up with a magnetic base was mounted axially on the end shield, while one pick-up with a stud base was mounted radially on the end shield to assess the attenuation of the signal. The signals from the different pick-ups were recorded on the four-channel B&K tape recorder in acceleration mode, to carry out further detailed analysis of the signatures by using a real-time analyser in the laboratory.
Figure 1.2: Motor with instrumentation details and scheme.
1.6.2 Investigations Using the High-frequency Resonance Technique
A number of resonances can be detected by an accelerometer mounted on the bearing surface. The signal from accelerometer, after some amplification, is tape recorded for high-frequency resonance analysis at a later time. When setting up such an analysis system, the output signal from the accelerometer is directly analysed in the real-time frequency spectrum analyser. This step helps in determining the carrier (resonant) frequencies, which are being most strongly modulated by the defect frequencies. The accelerometer signals are then envelope-detected about these frequencies in order to determine which of them is the best carrier for the particular defect frequency.
Envelope Detection System
The system comprises an input amplifier, a multiplier,...
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1.7 Determination of Defect Frequencies and Energy Levels 1.7.1 Theoretical Defect frequencies at different speeds of operation were theoretically determined for the NU 330 type of bearing by...
1.2 Introduction Normal rolling-element bearings generate an easily identifiable ball or roller pass frequency when operating. Bearing defects amplify the amplitude of these frequencies. By using...
1.9 Conclusions and Recommendations Based on this study and analysis, the following major conclusions are drawn:8,9 Data brought out in this study can be used for appropriate bearing...
The experimental technique I use in the laboratory to measure the vibrational mode shapes, natural frequencies and damping parameters of baseball and softball bats is called Experimental Modal...
1.8 Results and Discussion Tables 1.2 to 1.5 and Fig. 1.4 to 1.13 show the following: In the spectrum of bearing 'A' (new), certain defect frequencies such as RW, ORDFL, RRS, IRWL appear...
