Effect of disk tilt angle on critical speed variation in unbalanced rotor systems: The probabilistic approach

This study investigates the combined effects of disk tilt angle and mass unbalance on rotor dynamics through probabilistic analysis. While mass unbalance is widely recognized as one of primary sources of vibration in rotating machinery, its interaction with disk tilt presents complex dynamic behavior that remain relatively unexplored. Using Monte Carlo simulation techniques implemented in MSC Adams/View, we analyzed a Laval/Jeffcott rotor model with fixed unbalanced mass and variable disk tilt angle, along with bearing parameters including damping factors and clearances. Numerical model was validated against experimental data measuring shaft orbital trajectories. Results reveal that disk tilt angle significantly influences system dynamics, producing a wider critical speed range compared to mass unbalance effects alone. Tilt angle demonstrates strong positive correlation with both critical speed and shaft radius of rotation. Orbital analysis shows distinct patterns, with tilt angle producing more diffuse pattern compared to the more concentrated orbital pattern from mass unbalance. Bearing parameters showed minimal direct influence on critical speed, suggesting system design should focus on tilt angle management. Probabilistic approach provides new insights into the interactions between geometric imperfections and rotor dynamics. This enables better prediction of critical speed ranges and orbital boundaries.