Due to manufacturing flaws or cyclic loading, cracks frequently appear in a rotating spindle system. These
cracks markedly affect the dynamic characteristics in higher modes of the rotating machinery. For faster rotational speeds,
especially for super-high-speed cutting, a spindle with magnetic bearings is necessary. However, most investigations into
spindle system dynamic characteristics have been confined to ball-bearing-type spindles. The dynamic response of
rotating cracked spindle systems with magnetic bearings is examined in this article. A Euler-Bernoulli beam of circular
cross section is used to approximate the spindle and the Hamilton principle is employed to derive the equation of motion
for the spindle system. The effects of crack depth, rotation speed and bearing length on the dynamic response of a rotating
magnetic bearing spindle system are studied.