Analysis Of Influence Of Assembly Stress On Aircraft Pipeline Sealing Performance And Its Detection Method

As a key connecting component of the aircraft hydraulic system,the pipe joint directly affects the safety and reliability of the aircraft flight.However,the deviations in the actual assembly can cause assembly stresses in the joints,which in turn affects the sealing performance of the entire piping system.Therefore,this paper analyzes the influence of assembly stress on sealing performance for aircraft pipe joints,and studies the intelligent detection technology of installation stress.In this study,there are some discussions as follows:(1)The structural composition and sealing principle of the flared pipe joints are analyzed,the contact finite element model of the pipe joints is established,and the mechanical characteristics of the preloaded state are completed.The results show that the equivalent stress is mainly concentrated in the flaring of the flared pipe,the straight pipe joint and the thread root region of the outer casing nut,basically in line with the actual situation,meet the strength requirements.(2)According to the pipe joints,the influencing factors of the sealing performance were analyzed,the determination conditions of effective sealing were put forward,and the influence of assembly stress on the sealing performance was studied.The results show that as the friction coefficient increases,the sealing performance decreases.The increase of tightening torque will enhance the sealing performance,but beyond a certain limit,the joint may break.The angular deviation and radial deviation during assembly will reduce the area of the seal ring and the sealing performance,and cause stress concentration in some areas.The length deviation is divided into two directions.When the pipe joint is deviated from the flared pipe,the sealing performance will be reduced.When the pipe is deflected,the sealing performance will be enhanced,but larger assembly stress may occur and structural damage may happen.(3)A pipeline installation stress test bench was constructed to study the influence of assembly stress on the inherent characteristics of the pipeline.The results show that there are significant differences in the frequency response function under different assembly stresses,mainly in the magnitude and position of the peak of the resonance peak.A pipeline installation stress detection system was developed and two different detection methods of support vector machine and vector angle were proposed,finally the method was validated by using test bench data.The results show that with the increase of assembly stress,the degree of deviation of the detection results from the normal state is gradually increased,which fully verifies the validity and accuracy of the detection method.