Propulsion shafting whirling vibration: case studies and perspective

Since 1869 the main goal of whirling vibration calculations of rotating machinery was to determine critical speeds. Currently, all Classification Societies require a propulsion shafting whirling vibration calculation (also named bending or lateral vibration calculation) in the scope of the critical speeds i.e. free whirling vibration calculation. However, fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise and hull vibrations, generated by shafting, indicate the importance and inevitability of forced whirling vibration calculations. This paper presents some latest results of free and forced whirling vibration calculations obtained using the software intended for shaft design.