Nonlinear dynamic analysis of bi-directional porous aero-thrust bearing systems

For some years, bi-directional porous aero-thrust bearing systems have been receiving much attention. They are now applied extensively where there is a need for rigidity in high-precision instruments and mechanisms that run at high speed. Although the carrying capacity of gas bearings is not as good as that of oil film bearings, the heat generated at high speed is lower and does not cause spindle deformation. Under certain conditions, the shaft will display unstable non-periodic movement, and this can even become chaotic. This irregular behavior, when serious, can even damage the mechanical parts, cause a breakdown, and stop production. The aim of this study was to gain an understanding of this phenomenon and the conditions under which it might arise and to find a means for avoiding irregular vibrations and eliminating the air hammer effect that accompanies them. A detailed examination of the related characteristics of a gas bearing shaft system was carried out using numerical value analysis such as the finite difference and differential transformation methods. An analysis of the nonlinear dynamic behavior of the main axis was then carried out using bifurcation diagrams, Poincare sections, and spectral response.