An approach, for condensing the system matrices of machine-tool structures, based on dynamic condensation, is presented. The selection of the number of degrees of freedom to be retained in the condensed system is based on the accurate representation of the first five modes of the original system. This is illustrated by an example of a lathe spindle-workpiece system. In this example, the system inertia, the damping, and the stiffness matrices, which are originally of the dimension 25×25, are condensed to a dimension of 12×12. Thus, economy in the computation time and computer memory storage is realized. It is shown that this condensation technique is valid for the static case also.
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