Modeling And Verfication Of Nonlinear Dynamic Of Casing Bolt Connection

During the actual working process of aero engine,casing will withstand extremely complicated loads,such as thermal load,aerodynamic load,pressure load,rotor inertial force and force and bending moment of adjacent components.Casing is connected by the mounting edges of casing,the bolting structure forms the joint surface,so the dynamic characteristics of casing will mostly change due to the nonlinear factors of the joint.At present,the influence of the contact nonlinearity on the dynamic characteristics of the bolt connection is ignored at home and abroad in engineering design.However,the practical application of the bolt connection structure in the casing structure of an engine is much more.If the influence on the dynamic characteristics of the overall structure is not taken into consideration,the numerical calculation results will be greatly inaccurate.With the increasing demand for the precision of complex structure analysis,the traditional modeling method is difficult to meet the needs of modern aero engine design.Therefore,to accurately predict the dynamic characteristics of the casing in complex working conditions,the complex nonlinear behavior must be analyzed and studied to establish its nonlinear dynamic model for accurate dynamic analysis.In this paper,L type flange bolt connection beam and thin-walled casing structure for the study,using finite element software ANSYS to establish finite element model,the modal analysis and test of the comparison and analysis of the impact of pre tightening torque and the rigid connection of the modal.A nonlinear dynamic analytical model was established for the L type flange bolted beam,and the nonlinear dynamic parameters of the joint surface were identified by Force State Mapping method combined with the experiments.A nonlinear model was established for L flange bolt connection beam and thin-walled casing,and nonlinear static calculation was carried out.The influence of preload and friction coefficient on contact stress and contact state was analyzed.At the end,the displacement response and acceleration response of three models of complete bonded,bolt position bonded and complete friction for the L type connection beam and thin-walled casing were compared and analyzed.The nonlinear model of L type flange bolts connection beam and thin-walled casing was verified.Through this study,a reliable analytical nonlinear model of the single freedom flange bolt connection structure and the nonlinear model of the thin-walled casing structure were established.At the same time,model validation was carried out,which can provide valuable reference for the design and development of thin-walled casing,and has a certain reference value for the similar structure's dynamic analysis and research.