The perturbation method is often used when calculating the oil film stiffness and damping coefficients of journal bearings. The oil pressure is divided into two parts, steady-state pressure and dynamic pressures. Proper boundary conditions are needed in solving the differential equations for the pressures. The paper presents a new pressure starting boundary condition, which is based on oil continuity condition, for those dynamic pressure terms. Then the film stiffness and damping coefficients, the critical mass and angular speed are computed by using two starting pressure conditions, Δp (θ10) = 0 and θp (θ10) ≠ 0 (θp (θ10) is the starting boundary value of the perturbed pressure terms). Significant differences of the results of these parameters between the two conditions are found. The paper also presents a method of how to determine the starting pressure boundary in numerical computation.

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