Research On Dynamic Response Of A Typical Hydraulic Pipeline Of The Aircraft In Complex Vibration Environment

The hydraulic system is an important part of modern aircrafts.In order to avoid the vibration damage of the aircraft hydraulic piping system during the working process,it is necessary to comprehensively analyze the dynamic characteristics of the piping system to improve the safety and reliability of the aircraft hydraulic piping system.The vibration analysis of the hydraulic piping system mainly includes the random vibration analysis of the engine in the frequency domain and the hydraulic pump fluid pulsation analysis in the time domain.However,since the response analysis in the frequency domain and the time domain is very complicated at the same time,it is currently studying the vibration problem of the hydraulic pipeline system under a single excitation source.Aiming at the above problems,this paper proposes a dynamic response analysis method for aircraft hydraulic pipelines under the joint excitation of engine random vibration and fluid pulsation,which has important theoretical significance and engineering reference value.The main contents of the study are as follows:(1)The dynamic response analysis of typical simple hydraulic pipelines is studied.The derivation process of the Bernoulli equation of the branch pipeline is given,and the fluidsolid coupling simulation analysis of the T-branch pipeline under constant pressure and constant velocity is carried out.The simulation analysis results are consistent with the theoretical calculation results.The fluid-solid coupling analysis of the The L-bend under constant pressure and constant velocity is studied and the response law of the pipeline and fluid is summarized.The fluid-solid coupling simulation analysis and theoretical calculation comparison study completed in this chapter laid the analytical foundation for the subsequent chapters.(2)The dynamic response analysis of a typical hydraulic pipeline of an aircraft under a single excitation source of random vibration of the engine is studied.The random vibration analysis process of pipeline based on equivalent mass method is summarized.The modal analysis of the typical hydraulic pipeline of the aircraft is carried out by the equivalent mass method.Then,the engine random vibration excitation in the three directions of X,Y and Z is applied to the pipeline structure,and the X-direction response with the largest stress response is determined as the reference dynamic response result.Finally,the ten dangerous points of the pipeline structure with large stress in the random vibration response are screened out.The results show that there is a large stress response on the support members such as the clamp and the pipeline clamp bracket under the random excitation of the engine.(3)The dynamic response analysis of a typical hydraulic pipeline of an aircraft under a single excitation source of fluid pulsation is studied.The fluid-solid coupling simulation analysis steps of the typical hydraulic pipeline of the aircraft under the pulsation of fluid pulsation are summarized.The parameters such as fluid pulsation pressure and structural damping are calculated,and the ten stresses of the pipeline structure in the fluid pulsation response are finally screened out.The results show that there is a large stress response on the pipeline and pipeline connections under fluid pulsation excitation.The response law of the component under fluid pulsation excitation is analyzed with the three-way joint with the largest stress response.Finally,the effects of pressure mean and pressure amplitude on the stress and displacement responses of the branch pipeline under fluid pulsation excitation are investigated.(4)The dynamic response analysis method of a typical hydraulic pipeline of an aircraft under the joint excitation of engine random vibration and fluid pulsation is proposed.The dangerous points of the dynamic response of the typical hydraulic pipeline of the aircraft under two kinds of excitations are comprehensively screened.The 3 paradigm equivalent stress of the superimposed response dangerous point under the random excitation of the engine and the paradigm equivalent stress peak under the fluid pulsation excitation are taken as its stress limit value.By comparing the stress limit value and the yield limit of the material,it is judged that the pipeline structure does not suffer strength damage under the joint action of the two excitations.Finally,the total fatigue life of the clamp bolt with the highest stress limit value under the combined action of the two excitations is estimated and the safety of the clamp bolts was confirmed by comparing the estimated life with the first revision life of the aircraft.