Marine propulsion shafting: A study of whirling vibrations
Whirling vibration is an important part of the calculations of design of a marine shaft. In fact, all Classification Societies require a propulsion shafting whirling vibration calculation in the scope of the critical speeds i.e. free whirling vibration calculation. However, whirling vibration is a source of fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise and hull vibrations. There are a lot of uncertainties in the calculation of whirling vibration, namely in shafting system modeling, in determination of the excitation and damping forces. Moreover, whirling vibration calculation mathematics is much more complex than torsional or axial. The marine propulsion shaft can be studied as a self-sustained vibration system which can be modeling with de Van der pol equation. In this document, a fashion way to solve the Van der pol equation is presented in a theoretical way.