Diagnostic indicators of tooth flank wear based on the analysis of tooth spectral component parameters

The wear of gear tooth flanks of aircraft gas turbine engines is the most common and the most dangerous of their defects. Practice shows that vibroacoustic diagnostics is the most effective method for monitoring the technical condition of rotary machines, including gears. It has been shown that, in this case, it is difficult to use a widely applied diagnostic indicator of gear tooth flank wear as the intensity of an n-dimensional vector from a series of tooth harmonics. This is due to the need to measure vibration parameters in a wide frequency range and low intensity of higher tooth harmonics. The factors affecting the kinematic error, such as: technological factors (manufacturing and assembly defects), operational mode-related factors (speed, temperature, transmitted load), design-related factors (flexibility of gearing parts, tooth flank modification), and tooth flank wear, lead to a significant increase in the width of the tooth spectral component. This allowed us to suggest diagnostic indicators of wear based on the analysis of changes in its width. Using the example of a turboprop differential gearbox, we experimentally confirmed that the use of an auto power spectrum with filter width much smaller than the width of the tooth spectral component is ineffective in studying the defect being considered.  The parameters of the spectral component of the first tooth harmonic such as its width at the selected levels relative to the maximum value and their combinations, and the tooth harmonic intensity defined as a function of the power spectrum density are more sensitive to wear. The resulting dependences of the proposed parameters on the amount of wear have a pronounced non-linear nature. These diagnostic indicators allow several-fold reduction of the frequency range being analyzed.