Aeroelastic Analysis Of Rudder Structure With Freeplay

For many years,designers have been trying to avoid nonlinear because of the completeness of linear aeroelastic theory.However,the nonlinear phenomenon is everywhere.In some cases,the nonlinear effect has a great influence on the structure,even plays a key role in the structure.According to the linear theory,when the structure exceeds the critical flutter velocity,the response will tend to infinity.However,in practice,due to the influence of nonlinearity,the structure will undergo constant amplitude periodic oscillation,this is,limit cycle motion.Structure damage is mainly caused by fatigue problems.Therefore,it is necessary to use the nonlinear theory to analyze the aeroelasticity.According to the need of nonlinear aeroelastic research,the dynamic equation of multi-degree-of-freedom structure is established,and the nonlinear parameters of the structure are identified by time domain identification method,which is verified by the ground vibration test,a fast time-domain calculation modal of unsteady aerodynamic force is established,forms a complete set of freeplay nonlinear Aeroelastic research,provides theoretical guidance and technical support for nonlinear flutter problems.The specific research contents as follows:The dynamic equation of complex structure with multiple degrees of freedom is established by Fixed-interface Component Mode Synthesis Method.The nonlinear internal force term is extracted from the bi-conforming condition,obtains the nonlinear dynamic model of multi-free complex structure with nonlinear factors.Simulation and theoretical verification of the modal are carried out by a numerical example.The nonlinear dynamic equation of the structure is obtained by Fixed-interface Component Mode Synthesis Method(CMS),based on the Hilbert-transformation method,the damping and stiffness of the structure are obtained respectively with time.Then the corresponding response and restoring force relation are obtained,and the nonlinear parameters are fitted by the optimization algorithm.The effectiveness of the identification method is verified by the simulation of the nonlinear rudder structure with freeplay.The Parameter Identification Test of the self-research rudder structure is carried out,proves the accuracy of the Hilbert time-domain identification method.After the verification is completed,the identification method is used in the parameter identification of an air-rudder structure.Based on the ZONA7 method and time-domain fitting,the steady aerodynamic calculation modal is obtained,and combines with the dynamic equation of the rudder structure with freeplay.The aeroelasticity of the linear rudder structure is analyzed,on this basis,the aeroelastic problem of the nonlinear rudder structure is investigated.The Aeroelastic modeling method of nonlinear rudder structure with freeplay studied in this paper can be widely used in typical structure with nonlinear factor,provides an effective method for nonlinear aeroelastic analysis。...