VISCOELASTIC EFFECTS IN MIL-L-7808-TYPE LUBRICANT .2. EXPERIMENTAL-DATA CORRELATIONS

Viscoelastic behavior of the MIL-L-7808-type lubricant is modeled by correlating experimental traction data to rheological models based on lubricant viscosity, shear modulus and a critical or limiting shear stress. The two types of traction models used respectively employ a hyperbolic sine and inverse hyperbolic tangent function between the viscous shear strain rate and shear stress in the lubricant. While the viscosity-pressure-temperature relation is determined from viscosity measurements on a high-pressure viscometer, estimates of shear modulus and critical or limiting shear stress are derived by curve-fitting the model predictions to actual traction data obtained from a rolling-disk traction machine.