The effect of initial deflection on nonlinear lateral vibration of drill stem

In the past study of the lateral vibration of drill stem, the effect of the initial deflection was ignored. For this reason, the nonlinear lateral free vibration of drill stem with initial deflection is investigated by the method of perturbation. The first perturbation formulas of the first frequency and vib ration are derived. The influence of the initial deflection on the nonlinear lateral free vibration of drill stem is discussed. The result shows that, the initial deflection is not the effect on linear vibration of drill stem, the first frequency of nonlinear vibration decreases with the initial deflection of the drill stem increased.The effect of initial deflection on the first frequency increased with either the length of drill stem or the axial compressive force on the drill stem increases.It is indicated that, in analyzing the nonlinear lateral vibration of drill stem,the initial deflection should be taken into consideration if the initial deflection is larger and the drill stem is longer or the axial compressive force is stronger.