A High Damping Gas Foil Bearing With Negative Poisson’s Ratio Structure Manufactured By 3D Printing

In the field of high-speed rotating machinery,gas foil bearings(GFBs)are self-adaptive hydrodynamic gas bearings with compliant supporting structure.GFBs have advantages such as simple structure,convenient processing,environmentally friendly,high-speed,and long service life,and have received widespread attention from the industry.As the GFBs uses less viscous gas as lubricant and relies on the friction between the foils to dissipate energy,it leads to poor damping performance of the GFBs,which seriously limits the further promotion and development of gas foil bearings.In order to solve the deficiency of poor damping of conventional GFBs,a high damping foil gas bearing is proposed,which is based on negative Poisson’s ratio structure manufactured by 3D printing.The main work is as follows:The supporting structure of the bearing is designed,and the working mechanism of the damping performance of this structure is analyzed.The unit of the supporting structure consists of a double-arrow structure(DAS)with negative Poisson’s ratio characteristics and viscoelastic damping material.Firstly,the supporting structure is machined using 3D printing technology.Then,the bearing structure is assembled by filling the DAS with viscoelastic damping material.By relying on the negative Poisson’s ratio of the DAS,the damping material is compressed in two directions to improve the overall damping performance of the bearing.Subsequently,a mechanical model of the DAS is established by using the force method,and a mechanical model of the double-arrow structure filled with damping material(DASD)is deduced.Finally,the static and dynamic performance experiments that can test the DASD,the DAS and the damping materials are established to verify the correctness of the mechanical model of the DAS and the speculation of high damping performance of DASD.The Reynolds equation in finite difference form is used to describe the discretized gas film between the bearing and the rotor.Based on the theoretical model of DASD,the deformation equations of the supporting structure are obtained.At the same time,the mechanical model of the top foil is constructed using the finite element method,and the global stiffness matrix of the DASD-GFB is finally constructed.By using the Newton-Raphson iterative method,the steady-state Reynolds equation is solved to obtain the information about the distribution of the gas film pressure,thickness,and the position of the rotor.A parametric analysis of the DASD-GFB is carried out by varying the rotor speed and load,and the variations of the static performance of the DASD-GFB and the bearing based on the DAS unit(DAS-GFB)are investigated.The dynamic performance of the DASD-GFB has been investigated on the basis of the theory of its static characteristics.Based on the small disturbance method and the finite difference method,the dynamic stiffness coefficients and dynamic damping coefficients of the bearings are solved by the transient Reynolds equation and the equilibrium equations of the support structure.In terms of the speed of the rotor and the load,a comparative analysis of the dynamic characteristics of the DASD-GFB and the DAS-GFB have been presented,and it is found that the DASD-GFB has better damping performance and load carrying capacity.The effect of different negative Poisson’s ratios on the performance of the DASD-GFB is studied by adjusting the geometrical parameter of the DASD unit,and the results showed that the reduction of the negative Poisson’s ratio contributed to the damping performance of the bearings.In addition,the variation in the performance of the DASD-GFB is studied in terms of both the number of DASD units and their circumferential distribution position in the bearing to provide a reference for the subsequent optimization for the DASD-GFB.Finally,by varying the number and circumferential distribution of DASD units within the bearing,the change in DASD-GFB performance was investigated and it was found that high performance DASD units could be placed centrally in the load area of the bearing to optimize the performance of the bearing.