Emergence of tangential stiffness through the use of inclined orthotropic material

Abstract

A flexible bearing support structure is effective for stabilizing the self-excited vibration of a bearing, such as oil whirl. The stabilization effect is increased if the structure has static tangential stiffness, where the reaction force is perpendicular to the displacement. In this study, it is shown that a support component made of inclined orthotropic material, which exhibits shear–extension coupling, can have tangential stiffness. The circumferential average of the tangential stiffness was found to vanish with a rotationally symmetric configuration of these components because the tangential forces of each component cancel out. However, the tangential force was recovered by allowing separation on the contact surface. A circular formation of an inclined orthotropic sheet that shows an axisymmetric stiffness matrix is proposed. Theoretical and numerical analyses clarified the effects of the friction coefficient, fitting interference, and degree of anisotropy of the material. Zero interference was found to be the best condition to maximize tangential stiffness.