Vibration Characteristics and Response of Composite Material Spinning Drill Collar

This paper analyzes and studies the vibration issues of a novel composite material drill string. Based on the Hamiltonian variational principle, dynamic equations describing the vibration of composite rotating drill strings, considering complex downhole conditions are established. Additionally, the influence of nonlinear contact forces is taken into account in formulating these dynamic equations. By using Galerkin discretization, the approximate solutions of the [Formula: see text]th natural frequencies of the drill string with uniform section are derived considering the drilling fluid damping force, stabilizers, the characteristics of fiber composite materials, and the spinning motion. Subsequently, the transient acceleration variations of the drill string under contact forces, as well as the influence of axial compression on these acceleration changes, were analyzed using the Newmark-[Formula: see text] method in conjunction with finite element discretization. In the numerical analysis process, the effectiveness and accuracy of the proposed method were validated through model comparison. The numerical research results indicate that the spinning angular speed, internal flow speed, drilling pressure, fiber orientation of composite materials, and stabilizer position have a significant influence on the dynamic characteristics of the drill collar. During the analysis of dynamic transient variations, the vibrational response of the drill string under contact forces was also examined, and it was discovered that the drilling pressure (i.e. the axial force applied to the drill bit) has a significant influence on the acceleration generated during system collisions.