Numerical model of a single stage gearbox under variable regime

Abstract

Condition monitoring of gearboxes running under nonstationary regimes continue to be an important source of interest for industrialists and researchers. Despite the diversity of models in the literature, none allows simulating all cases of machine operations and failures modes in nonstationary regimes. This paper will discuss through a modeling approach how speed and load variations will influence the dynamic response of a single-stage gearbox supported by four rolling-element bearings, in the healthy case and in the case of gear and/or bearing defects. Combining 72 degrees of freedom and taking into consideration meshing and bearing nonlinear excitations, the proposed model allowed to compute the dynamic behavior of the real system for the case of gear tooth crack defect, pinion eccentricity defect, and the three localized bearing defects (outer race, inner race, and ball defects). Fast Fourier transform, Squared envelope spectrum, Short-time Fourier transform, and Kurtogram was used to reveal the vibration signature of the introduced defects under the different operating modes. A special envelope spectrogram was also designed to reveal the bearing defect frequencies variations in the case of a variable-driven speed.