Research On The Mid-frequency Vibro-acoustic Fatigue Analysis Method Of Structure Based On Hybrid FE-SEA

Aircraft,ship and vehicle are often subject to broadband noise environments,the induced vibration can easily lead to the fatigue failure,such as metal skin of aircraft,ship hull and the white body of vehicle.The broadband vibro-acoustic response analysis is generally divided into low,medium and high frequency bands.For mid-frequency vibro-acoustic response problem,the structure presents significant dynamic mismatches for different parts and the deterministic method or the statistical energy method alone can not work well for the analysis.Aiming at the mid-frequency vibro-acoustic response analysis,the Hybrid FE-SEA method has been proposed and paid much attention in recent years.Up to now,it has been successfully applied to a lot of engineering problems.However,for the important parameters of Hybrid FE-SEA,such as the effective coupling loss factor,deep researches are still needed.So far,the vibro-acoustic fatigue analysis is mainly focused on low frequency part and fatigue analysis in higher frequency band based on the results of Hybrid FE-SEA has not been reported yet.In this dissertation,plate-like structure as the analysis object is used to make further study on the effective coupling loss factor and to explore the mid-frequency vibro-acoustic fatigue analysis method based on Hybrid FE-SEA method.The main contents of this dissertation are as follows:(1)Verification and application of Hybrid FE-SEA methodThe theory of Hybrid FE-SEA method is deducted in detail based on wave approach.Via the group-average idea,the effectiveness of the method is then verified by the Monte Carlo method.At last,using the Hybrid FE-SEA method,the mid-frequency vibro-acoustic response analysis is carried out for the beam-plate built-up structure.(2)Research on the sensitivity of structural parameters for the effective coupling loss factor in Hybrid FE-SEAThe effective coupling loss factor is an important parameter in Hybrid FE-SEA and it can reflect the power flow character between subsystems.In this dissertation,the theory of the effective coupling loss factor is introduced first.And the parameters under condition of line connection are then analyzed.Finally,the influence of structure parameters on the effective coupling loss factor is investigated.The obtained results provide guidances in optimizing the energy transfer between subsystems.(3)Research on the mid-frequency vibro-acoustic fatigue analysis method based on Hybrid FE-SEAPlate-like structure is a kind of typical structure in aircraft,ship and vehicle,which is often subject to broad-band noise environments.The mid-frequency excitation component is commonly rich,and the induced vibro-acoustic fatigue failure can not be ignored.The frequency-domain fatigue analysis needs stress power spectral density of dangerous point.Since the obtained results of Hybrid FE-SEA are displacement,velocity and energy,and which can not be directly used for mid-frequency vibro-acoustic fatigue analysis.In this dissertation,based on the obtained displacement and energy responses by the Hybrid FE-SEA analysis,the stress response in each 1/3 octave is obtained.Combined with the method of zero order moment of stress PSD,the mid-frequency vibro-acoustic fatigue analysis method is then established.The analysis method is verified by the finite element analysis under very fine mesh.At last,the fatigue analysis of stiffened panel under broadband excitation is given.The results show that,the response in mid-frequency band makes important contribution to the fatigue damage under broadband excitation and thus it can not be ignored.