Contribution of acoustic emission into optimal bearing lubrication

This article describes the bases of the acoustic emission analysis to make successful applications in the range of the tribological problems, especially at machinery slide journal bearings. Acoustic emission differs from ultrasonic testing, which actively probes the structure; Acoustic emission listens for emissions from active defects and is very sensitive to defect activity when a structure is loaded beyond its service load. During detecting and analysing the generated acoustic emission we earn information about the behaviour, state or quality of these acoustic emission sources. A lot of different sources are generating acoustic emission (e.g. corrosion processes, fluid friction, cracks, cutting processes). This paper shows the acoustic emission sources, the wave propagation, the mode conversion, the damping, the design of a typical transducer and the whole measurement chain. The piezoelectric disc, the "heart" of a typical acoustic emission transducer, converts the incoming mechanical wave into a corresponding electrical signal. Every transducer has its own characteristic, if this is unknown we can test it with difficult methods e.g. so called reciprocal method. On the end of this paper the signal parameters (burst-count, rise-time, signal-duration, signal peak amplitude, signal energy and root-mean-square) will be discussed.