Dynamics Analysis Of The Aircraft Hydraulic Lines

The aircraft hydraulic pipeline system is an important part of aircraft system, while its strength problems caused by vibration fatigue are always puzzling the hydraulic system designers and accident analysis personnels. With the development of the aircraft hydraulic system, these problems become more and more prominent. These problems may lead to fatigue destructions of the aircraft hydraulic pipelines, even huge economic losses or life casualties, which have certainly put foward a high request for the aircraft hydraulic system design. So it is essential in theoretic and engineering to study vibration characteristics and resonance fatigue testing of aircraft hydraulic system, improve design approach for safety and fatigue reliability.Previous researches on theoretic calculation and finite element simulation technology of pipeline system vibration have achieved great progress. However, the research on vibration of aircraft hydraulic pipe system in our country is mainly focus on the derivation of pipeline mathematical model and the finite element simulation of simple pipelines, so there are still certain gaps from the engineering application. Therefore, based on the practical project, it can provide an important theoretic guidance for vibration fatigue test to carry out finite element simulation on vibration caused by fluid-structure interaction for a typical aircraft hydraulic pipeline.In this paper, numerical analysis and finite element simulation on the fluid-structure interaction of hydraulic pipeline systerm are studied. Moreover, the vibration characteristics analysis of the typical aircraft hydraulic pipeline are studied. The main works can be described as follows:Firstly, the fluid turbulent model and piping model are established respectively. The fluid structure interaction is simulated using both one-way and two-way coupled techniques. The results indicate that it is feasible and reasonable to simulate and analyze the hydraulic pipes using one-way coupled technique in certain condition.Secondly, the FSI vibration of a straight pipe is researched. The simulation examples show that different pipe lengths, fluid flow speeds and fluid pressures impact the pipeline vibration greatly. The calculated results can provide some reference for designers to design and modify their CAD model of hydraulic pipes.Thirdly,the random excitation spectrum of the random vibration analysis has been done on the model, to simulate the vibration condition of pipeline in engine interference. In view of the hydraulic circuit model of aircraft, a briefly and reasonably has been simplified, the random simulation analysis. the results are analyzed and compared with the result of before, The results show that analysis method is reasonable analysis result is reliable.Finally, the dynamics analysis of the aircraft hydraulic pipes based on FSI is carried out using ANSYS-Mechanical. The results show that the response coincides with the actual conditions by comparing with the experimental data. Furthermore, the fatigue analysis of the screw bolt where the maximum von Mises stress exists is done, which demonstrates the screw bolt meets the fatigue strength criterion.