Impact of Oil Viscosity on Dynamic Stability and Rub‐Impact Behavior in Magnetic Liquid Double Suspension Bearing

Magnetic liquid double suspension bearing (MLDSB) combines electromagnetic suspension with hydrostatic support to achieve high load capacity and stability under medium‐speed, heavy‐load conditions. When the electromagnetic system fails, the hydrostatic unit temporarily levitates the rotor, but its performance is governed by oil viscosity. This study is aimed at quantifying how viscosity influences rub‐impact dynamics in MLDSB. A three‐degree‐of‐freedom nonlinear model was established and solved by a fourth‐order Runge–Kutta scheme. Parametric bifurcation analyses were performed over speed ratio 0.8–1.05, eccentricity ratio 0.15–0.40, initial pressure 0.1–1.6 bar, and bias current 0.5–2.0 A. Key dynamic features including bifurcation characteristics, phase path, and Poincare mapping were validated on a purpose‐built MLDSB test bench. Results reveal a critical viscosity window ( μ ≈ 3–4 × 10 −3 Pa · s) below which the first period‐doubling bifurcation occurs, followed by alternating multiperiodic and chaotic motion. Higher eccentricity or speed ratio broadens the bifurcation interval, whereas increased initial pressure mitigates chaos. These findings provide design guidelines for viscosity selection and control strategies to enhance the fault‐tolerant performance of MLDSB under rub‐impact conditions.