Analysis of gear dynamics of a helical gear pair with faults

This paper presents the dynamic responses of a helical gear pair. The goal of the research provides information for diagnosing the gear faults through examining dynamic signals. Gear faults including crack and spalling on one tooth were considered. A finite element software, ANSYS, was chosen to calculate the gear mesh stiffness for both an undamaged gear pair and gear pairs with faults. A dynamic, lumped-parameter model of gear pairs was then developed for the system responses. The presented model considers not only the gear with fault, but also an unbalanced gear. Two signal processing methods, fast Fourier analysis and cepstrum analysis, were introduced to find the characteristics of the dynamic responses of an undamaged gear pair and gear pairs with various faults. The difference between two types of responses was then identified. An experiment was conducted to obtain data for comparison. This paper concludes that a fault in the gear can result in small components in the frequency domain with the interval equal to the rotating speed of the faulted gear. This feature can be further clearly identified in the cepstrum domain and can provide a good evidence of a gear pair with faults.