An experimental study of nonlinear oil-film forces of a journal bearing

Hydrodynamic journal bearings under large perturbations go beyond the serviceable range of the linear theory and thus should be treated as nonlinear systems. Three kinds of nonlinear oil-film force models (24-co., 28-co. and 36-co. models) are proposed to denote the oil-film forces by retaining certain terms of Taylor series expansion of the oil-film force. A least-mean squares method in time domain is proposed to identify the oil-film coefficients. The study shows that these three nonlinear models are feasible to describe the oil-film forces and reliable linear oil-film coefficients can be identified from these models.