Nonlinear Dynamic Response Analysis And Fatigue Life Prediction Of Aeronautical Thin-walled Structures

The thin-walled structure of aviation bears severe high temperature load,high sound pressure level acoustic load and aerodynamic load caused by high-speed gas flow.Because of the complex load,it is urgent to solve the dynamic response law and fatigue life prediction method of thin-walled components under multi field coupling.1.The theoretical system of dynamic response and life prediction of thin-walled structure under multi field coupling is established.Based on the basic equations of hydrodynamics,the large deflection control equations of thin-walled structure,the coupled thermal fluid solid control equations,the thermal random vibration control equations and the structural dynamic control equations based on the coupling of finite element and boundary element,the theoretical system of dynamic response is established;based on the S-N life curve,the improved rain flow cycle counting method,the average stress model,the fatigue failure criterion and the fatigue accumulation Based on the damage theory,the theoretical method of life prediction is constructed.2.Aiming at the high temperature random vibration response and fatigue problems of typical thin-walled cantilever plate members.The response of the cantilever plate to the axial dynamic stress at the critical point under different temperature and vibration levels is studied.Based on the theory of fatigue cumulative damage,the fatigue life of thin-walled components is estimated.Comparing the high temperature random vibration fatigue test with the simulation results,it is found that the calculated value of response under different temperature and random vibration load is in good agreement with the test value,and the fatigue life of structure is in the same order of magnitude with the test result.3.The thermoacoustic response and fatigue of thin wall plate with four end fixed support under high speed flow are studied.Considering the typical working condition of aeroengine,the temperature distribution and impact load distribution of thin-walled plate under high-speed flow are studied.The response law of stress power spectral density of thin-walled plate under different velocity and temperature is compared and analyzed,and the fatigue life is predicted.The thermoacoustic test of metal thin-walled plate without flow velocity was carried out,and the numerical simulation was carried out to verify the effectiveness of the simulation method.The results show that the effect of high velocity flow on the dynamic response of thin-walled plates is obvious.4.Based on the effective calculation method of thermoacoustic response and fatigue prediction of thin-walled structure under high-speed flow,a simplified turbine rotor blade model is established.Under the action of thermoacoustic flow load,the thermal mode frequency distribution of rotor blade,temperature distribution and thermal shock load distribution under different flow velocity are obtained,and the dynamic response of rotor blade is analyzed by thermoacoustic flow coupling.The fatigue life of the rotor blade under the combined action of thermoacoustic load with or without flow velocity is predicted and calculated,and the effect of high flow velocity on the rotor blade is compared and analyzed.In this paper,the theoretical research,simulation calculation,experimental verification and pre-estimation of the dynamic response and fatigue life of high-temperature alloy thin-walled structures under the combined action of thermal-acoustic-fluid-solid multi-physical fields are carried out.The research conclusion will provide an important basis for strength analysis and stability design of aerospace thin-walled structures.