Chatter analysis of machine tool systems in turning processes

Chatter of a machine tool system consisting of a flexible workpiece and a cutting tool flexibly mounted on a guided bed in turning process is investigated in this thesis. Chatter onset conditions are accurately determined using combinations of the finite element method, the modal analysis method, and the Laplace transform technique. Stability charts separating stable and unstable cutting operations are determined using the Nyquist criteria and provided for conventional lathes and workpieces of various shapes subjected to different boundary constraints simulating the effects of chuck and center. These charts can be conveniently used in industry to select an appropriate set of cutting parameters for a chatter-free turning operation.; Four dynamical models are proposed in this thesis to handle chatter of machine tool systems. The first model is applicable to machine tool systems having workpieces of very large stiffness compared to the cutting tool mounting stiffness. The second model is developed for workpiece of relatively small stiffness. The third model handles general machine tool systems in which motions of the workpiece and cutting tool structure are truly coupled. The fourth model is applicable to turning processes involving the novel use of two cutting tools.; In chatter analysis, the tool structure is considered as a mass-spring-damper system having two degrees of freedom; the workpiece is considered a spinning beam structure whose displacement-strain relationships obey the Timoshenko theory. The finite element method and Lagrange equations are employed to formulate the system equations of motion for the workpiece. In all cases studied, the cutting force may be applied at any locations along the workpiece.; The procedure for determining the chatter onset conditions of machine tool systems represented by the four dynamical models is programmed into a computer code written in the Matlab language. Chatter-flee cutting conditions may now be easily established for any machine tool system in turning process by simply providing a few input parameters and running the computer program.