Standardization of diagnostic indicators of gearbox teeth wear in aircraft gas-turbine engines

Abstract

The gearboxes of aircraft gas turbine engines are their most stressed parts. One of the main gearbox defects is the tooth flank wear that causes resonant oscillations in engine structure elements. This defect is generally assessed using vibroacoustic diagnostics methods. It is noted that the currently existing recommendations on setting limit values for diagnostic indicators do not take into account the type of mathematical models that describe their dependence on the defect size. This can result in its uncontrolled development. We have shown that for the case under consideration, four kinds of mathematical models were earlier obtained to describe dependences of diagnostic indicators on the wear value: linear, power, exponential and combined (linear and exponential) models. The linear model is characterized by a constant rate of change in the level of a diagnostic indicator with the growth of wear. For power and exponential models the growth of wear leads to an increase of the rate of change in the diagnostic indicator value. The combined model is characterized by the presence of two zones of change in the diagnostic indicator intensity with the growth of wear: the constant rate zone and the zone of increasing rate. The use of diagnostic indicators with a continuous increase in their intensity depending on the growth of wear will require ensuring constant control of the gearbox vibration state, which is not always feasible. We give recommendations for setting standard values of the diagnostic indicator intensity for the considered models.