Stiffness Characteristics Analysis And Experimental Research Of The Special-shaped Bearing For Elastic Support Structure

In order to reduce the weight and the size of aero engine,the rolling bearing outer ring is often designed as an integrated structure with flange edge.The bearing without housing is fixed on the engine case through the bolt connection,and it is defined as the special-shaped bearing in this paper.The special-shaped bearing acts as the core load-bearing and load-transferring component,its stiffness affects the dynamic properties of rotor system.At present,for the aero engine rotor system dynamics analysis,the stiffness of the rolling bearing is often approximated to be linear,bolted connections are ignored,and the influence of bearing structure,assembly technology and working conditions on the elastic supporting structure stiffness and especially bearing stiffness are not taken into account.The theoretical analysis and experimental research on the special-shaped bearing stiffness characteristics are inadequate.In view of the special-shaped bearing stiffness characteristics,the special-shaped bearing stiffness is analyzed and calculated by establishing the analytical model and finite element model.Considering the elastic supporting boundary condition,bolt connection,speed and load conditions,and the identification method of the bearing dynamic stiffness of the elastic supporting boundary condition is studied.Based on the elastic supporting-single disk rotor tester,the influence analysis test of relevant parameters on the combined elastic supporting structure and the special-shaped bearing stiffness have been carried out,which will provide reference for structural optimization design of elastic supporting structure and main bearing,improvement of the aero engine assembly process.The main results of this paper are as follows:(1)The dynamic and static stiffness analysis of the elastic supporting structure:In view of the mechanical properties of the combined elastic supporting structure,the static stiffness calculation,finite element analysis and experimental study of the cage structure which has the greatest influence on the support stiffness are carried out.In order to analyze the dynamic characteristics of a static structure under rotational excitation conditions,the static and dynamic stiffness of elastic supporting structure are analyzed and compared by static loading method and hammering method respectively.(2)Establish the stiffness model of the special-shaped bearing:Based on the Hertz contact theory and the elastic mechanics,the analytical model of the special-shaped bearing is set up in view of their structural and mechanical characteristics.And the finite element model of special-shaped bearing is established by ANSYS software.The influence of outer ring flange on bearing stiffness is analyzed.Considering the axial pretension,the influence of axial preload on the stiffness characteristics of special-shaped bearings is analyzed.(3)Study on the identifying method of the special-shaped bearing dynamic stiffness:Based on the established radial stiffness model and test platform of combined elastic support structure,the displacement sensor was used to measure the vibration displacement;the rotating dynamic force is obtained by using the squirrel cage strain-load relationship.According to the stiffness series formula and stiffness definition,the dynamic stiffness of the combined elastic supporting structure and special-shaped bearing under different speeds can be obtained.(4)Dynamic stiffness influence analysis test:Based on the identification method of the bearing dynamic stiffness and the elastic supporting-single disc test platform,the fulcrum stiffness and bearing stiffness under different speedss imbalances and bolted connectionsare carried out;the influence of the imbalance and bolt connection on fulcrum stiffness and special-shaped bearing stiffness is obtained.A two fulcrums rotor system with one end elastic supporting and one end fixed supporting is established,and the influence of axial pretension and bolt connection on the dynamic characteristics of the rotor system is analyzed.