Stiffness and Damping Reduced Model in EHD Line Contacts

The increasing of operation speed and demand for precision in machinery make lubrication conditions a crucial aspect in order to maximize lifetime of rotor dynamic components. The elastohydrodynamic (EHD) regime more frequently occurs in nonconforming lubricated contacts with local elastic deformation due to high pressure in small contact area. The objective of this work is to analyze the EHD force reduced model applied to line contact based on restitutive and dissipative terms. In restitutive force term, an EHD stiffness approach is evaluated considering an explicit force-displacement relation with two independent parameters - stiffness and a constant surface separation force. Steady-state EHD contact numerical results allow estimating the restitutive parameters. The dissipative force term is composed by linear viscous damping. The damping is characterized by numerical simulation using the principle of energy conservation in transient elastohydrodynamic lubricated system. The influence of load and speed variations in damping fluctuations are investigated.

The EHD reduced force model characterizes the lubricated contact in just three parameters (oil film stiffness, EHD constant surface separation force and viscous damping), simplifying the lubrication problem in comparison of solving EHD system of equations at each work condition and time step. This model can be applied to any nonconforming EHD line contact as cams, gears, needle element rolling bearings and cylindrical roller bearings in dynamic analysis and project stage development. Furthermore, an accurate contact model increases machine reliability, being promising to be used in model-based fault identification.