磨损颗粒分析

"Trend Analysis is the process by which a change in machine condition is determined from an examination of changes in specific sensors or output.

"Different systems exhibit different trends. For instance, the wear debris generated from a system involving gears and bearings may well be quite high initially, particularly if no attempt has been made to 'run-in' the system. Thus there is a gradually reducing level of debris until the system settles in. Then comes the acceptable very low wear rate associated with well lubricated surfaces, which perhaps increases just slightly. Finally, the machine begins to show signs of fatigue or fracture and particle generation increases at an ever increasing rate. These three stages of wear are shown in the classical 'Bath-tub" curve.

"Another changing feature of wear with time, is that the wear rate begins to fluctuate. After the 'running-in' period, the wear rate is expected to be reasonably uniform, although it may rise slightly. However, as conditions begin to become less favourable wear may be less or more in terms of particle size generation as well as with total quantity. Scatter is thus seen as a trend indicator.

"The third sort of trend indication is that associated with the shape of particle - its morphology. This is less easy to measure than the gravimetric level or 'size' of particulate; but, by using the analysis mentioned later in this chapter for defining particle shape, two or more possible specific indicators of shape may be trended to detect the point at which a serious change in debris particle shape occurs."