In order to extract the time domain of gear contact stiffness, I model gear pair with Machinery Gear/Gear AT, but I haven't found the corresponding channels through post-processing. The unit of similar ones such as ST_Stiff are Newton. Is there a way to obtain this kind of data?
there is no direct way to get the stiffness plot however you can plot the Stiffnes.TZ vs. Kinematics.Gear_1_TE_Angle or Kinematics.Gear_1_TE_Length to get time history of the gear contact stiffness. Just make sure to start simulation with closed gap in a gear pair, i.e. run static with light preload to define TE zero point.