복합변형변수를 사용한 회전 드릴의 모델링 및 진동해석

Abstract

In this paper, modeling and vibration analysis of a rotating drill was conducted based on the Euler-Bernoulli beam theory and Winkler-type elastic foundation theory. The drill was idealized as a rotating pre-twisted beam, and the hybrid deformation variable modeling method was employed to consider the effect of compression due to axial force on the bending stiffness of the drill. The time-varying penetration depth of workpiece was modeled using the Winkler-type elastic foundation theory and unit-step function. Finally, the equation of motion is derived using the Rayleigh-Ritz assumed mode method and Kane's method. From the numerical results, it was found that the natural frequency abruptly dropped at the moment of contact between the drill and workpiece. It was also found that the 1st natural frequency of the drill depends on the rotation speed, pre-twisted angle and axial force.