Methods for detecting fatigue cracks in gears

A crack in the tooth root is the least desirable damage caused to gear units and it often causes failure of gear unit operation. For fault analyses presented in this article, gear units with real damages or faults produced on the basis of numerical simulations of real operating conditions are usedtests were carried out in a laboratory test plant. Damages in gear units can be identified by monitoring vibrations. The influences of a crack in a single-stage gear unit on produced vibrations are presented. Significant changes in tooth stiffness are caused by a fatigue crack in the tooth root whereas, in relation to other faults, changes of other dynamic parameters are more expressed. Non-stationary signals are analysed, using the family of Time Frequency Analysis tools, which include Wavelets and Joint Time Frequency Analyses