This study investigated the flash temperature rise of an
example spur gear pair under the tribo-dynamic condition. The
interactions between the gear dynamics and the gear tribological
behavior were modeled by coupling a six DOF transverse–torsional
discrete gear dynamics equation set with a thermal mixed EHL
formulation. The flash temperature rises were quantified within a
wide speed range and compared between the tribo-dynamic
condition and the quasi-static condition, showing evident devia-
tions, especially in the vicinities of the resonances. It was very
interesting to observe that not only the LOA direction gear
dynamics, but also the OLOA direction transverse vibratory motion
influences the flash temperature rise. Therefore, the single DOF
torsional gear dynamics model in literature is not sufficient for the
accurate prediction of the gear surface flash temperature. Addi-
tionally, a parametric study was carried out by varying the torque,
the lubricant viscosity and the roughness amplitude from the
baseline condition to examine the influences of these contact
parameters on the flash temperature rise. It was shown the
increase of the load largely increased the flash temperature by
imposing more friction. The flash temperature was reduced by
increasing the lubricant viscosity or decreasing the surface
roughness amplitude. The latter was shown to be more effective in
the reduction of the roughness contact activities and thus reached
the minimum flash temperature rise among the four operating
conditions considered.