Hiroki Ueda

Development of a composite boring bar

A composite boring bar, whose stability against chattering is superior to not only conventional steel bars but also cemented carbide bars, has recently been developed. The main material of this composite bar is pitch-based carbon fiber reinforced plastic. Carbon fibers aligned unidirectionally in the longitudinal direction of the bars give high bending stiffness. Four types of bar having different shaped steel cores were designed by FEM analysis and produced for actual testing. A bar having a cross-shaped steel core shows the best cutting capability and stability amongst all bars designed. This bar can be used when the length (L) and diameter (D) ratio L/D is 7 or even at severe conditions while a cemented carbide bar cannot control the chatter vibration even if the L/D is less than 6. Emphasis should be placed on the fact that the cross-shaped steel core can increase the bending stiffness of the bar in both tangential and radial directions by constraining the shear deformation of the fiber layers without sacrificing the increase of resonant frequencies.

Study for Improvement of Inner Cutting Tool. Development of a CFRP Boring Bar.

A new boring bar whose stability against chatter is superior to not only conventional steel bars but also cemented carbide bars, has been successfully developed. A high-modulus carbon-fiber reinforced plastic was used as the material of the bar. Four types of bar having different shapes of steel core were tested while carbon fibers were aligned unidirectionally in the longitudinal direction to give high bending stiffness for all cases. The bar with a cross-shaped steel core shows the best cutting capability and stability among all CFRP boring bars. It can be used when the ratio between length (L) and diameter (D) is 7 even under severe conditions, whereas a cemented carbide bar sometimes chatters even at L/D=6. The cross-shaped steel core can increase the bending stiffness of the bar in both tangential and radial directions by constraining the shear deformation of fiber layers without sacrificing resonant frequencies significantly.

Active vibration control of a free-free beam by the use of a tendon mechanism.

This paper is concerned with the active vibration control of a free-free beam. The beam is reduced to a finite-degree-of-freedom system by the modal analysis, in which the mode function is derived from the transfer matrix method. An active control force is produced by a pair of tendons and a DC servo motor attached to the beam. The state of the beam is presumed by the minimal order state observer and the control force is determined by the digital optimum regulator theory. It is found that the active tendon control method is effective for suppressing the vibration of the free-free beam.