Pneumatic hammer characteristics of the aerostatic thrust bearing with central orifice and pressure-equalizing groove

The introduction of central orifice and central pressure-equalizing groove (PEG) greatly improves the load capacity of aerostatic thrust bearing. However, it is also easier to cause pneumatic hammer vibration which will degrade the bearing performance and requires to be studied urgently. In this paper, a dynamic model is developed to investigate this problem by coupling the bearing dynamic equation and the transient gas film Reynolds equation which is reduced by Galerkin weighted residual method and discretized through finite element method. The flexible sensor is creatively applied to measure the aerostatic force and gas film pressure distribution, which help verify the model correctness. The mechanism of pneumatic hammer is revealed by analyzing the molecular kinetic energy and the phase difference between variations of gas film thickness and aerostatic force. The characteristics of pneumatic hammer are analyzed under different structural parameters and supply pressures. The results indicate the pneumatic hammer vibration tends to happen when the mass and supply pressure are greater than the corresponding critical values.