Numerical Analysis Of Dynamic Characteristics Of Micro Self-Acting Bearing Using Slip Models

Because of Micro self-acting bearing unique advantages of high speed,high precision,and high reliability,Micro self-acting bearing have been applied to practical industrial manufacturing in the fields of micro-mechanical,micro-electronics and ultra-precision machining.With the rapid development of micro-electromechanical system,the micro-size bearing technology has attracted the attention of various industry experts,but because of the small size of micro-precision equipment structure,the scale effect will have a great influence on the design and development of micro-bearing.At present,the steady-state theory of the gas bearing will appear error in the actual processing,which makes the continuous model under the macroscopic dimension fail in the analysis of the dynamic characteristics of the bearing,it is necessary to study the variation of dynamic characteristics of micro-bearing under slip effect.In view of the above problems,the relationship between the slip models and the dynamic characteristics of micro-gas bearing under micro-gap is studied and compared.Firstly,the steady-state mathematical model of micro self-acting bearing without slip boundary condition is calculated based on Newton-Raphson iterative method,and the numerical simulation results are compared with the literature to verify the accuracy of this static program when the influence of slip effect was not considered.Then,the steady-state mathematical model considering the first-order slip and Wu's new slip correction is established,and the mathematical model is solved by using the program of slip correction,and the static characteristics of the micro bearing under the slip flow are analyzed numerically.Secondly,based on the steady state mathematical model of micro bearing,the dynamic mathematical models of continuous model,first-order sliding model and Wu new sliding model was established.The dynamic equations of model's was calculated by the finite difference method and SOR iteration method.Under the continuous model,the numerical simulation results and literature data are compared to verify the accuracy of the dynamic program in this paper.The relationship between the disturbance frequency of journal and the dynamic stiffness coefficient and damping coefficient of gas bearing under the sliding effect and the influence of the sliding effect on the stability of the bearing rigid rotor was analyzed.The results show that the pressure and bearing capacity of the traditional continuous model are significantly higher than that of the bearing considering the first-order slip and the new slip of Wu in the gas film clearance of less than 1 ?m.With the decrease of the gas film clearance,the result deviation among the three models becomes larger,and the other two models have larger deviation than that of the Wu's new slip calculation.It is necessary to analysis the static characteristics of gas bearing under the condition of small clearance by Wu's new slip.The dynamic main stiffness coefficient of bearing increases with the increase of disturbance frequency,and the dynamic main damping coefficient of bearing first increasesand then decreases.Under the influence of slip effect,with the increase of disturbance frequency,the dynamic characteristic coefficient of Wu new slip model is the smallest compared with the other two models.