【作者】 李民；

【导师】 翟敬宇；

【作者基本信息】 大连理工大学 ， 机械设计及理论， 2023， 硕士

【摘要】 飞机液压系统是保证飞机正常飞行和安全的关键操纵系统,其中管接头是重要的液压附件之一。据统计,飞机液压系统故障中约35%是由液压管接头失效引起的。与目前国内大型飞机液压系统主要采用28 MPa压力体制相比,35MPa体制在系统减重、性能提升方面具有明显的优势。可拆卸式管路连接结构是35MPa级航空液压管路连接件的重要组成部分,其连接性能直接影响管路连接件的功能实现,对航空液压系统甚至整机的安全性和可靠性有重要影响,因此有必要对其连接与密封性能开展研究。本文面向35MPa液压管路连接件,结合计算分析与试验验证,重点研究了可拆卸式结构的密封与连接性能,主要工作如下:(1)基于35MPa级可拆卸式管接头的结构组成、工作状态以及性能要求分析了其密封机理,提出运用密封接触强度Wa定量评价密封的新方法。对管接头材料进行了单轴拉伸试验并运用幂强化模型进行材料建模,得到了接头密封塑性区的应力应变曲线。(2)研究了 35MPa级可拆卸式管接头拧紧时的运动状态,并从理论方面研究了力矩分配比例。结果表明在施加的全部拧紧力矩中,约41.8%的力矩用于克服螺旋副间摩擦,12.7%的力矩用于产生轴向力,42.3%的力矩用于克服支撑面间的摩擦,3.2%的力矩用于克服锥面间的摩擦。通过有限元分析方法验证了研究结果的合理性和准确性。(3)开展了接头非线性连接密封有限元建模与分析,并运用密封接触强度理论和密封面极限屈服理论评估了连接密封性的极限状态,进而研究了不同拧紧力矩和装配偏差对管接头密封性能的影响。结果表明平均接触应力随着拧紧力矩的增加呈线性增加,密封面宽呈阶段式增加,给出了推荐力矩范围是42-46N·m,密封接触强度Wa的变化幅度随角度偏差φ和径向偏差Δ的增大而更加剧烈。(4)研制了可拆卸式管接头扭矩-轴向力专用试验台。对MJ18× 1.5螺纹规格的管接头进行了试验测试,确定合适扭矩范围为43-47N·m。结合拧紧力矩-时间曲线与力-时间曲线,建立了拧紧力矩与力的数量关系。(5)开展了管接头重复拧紧的理论与试验分析,当管接头重复拧紧时,接触面磨损增加,导致摩擦系数增加。根据试验数据得出重复拧紧8次时,轴向力降低约9.13%,进而建立了轴向力初始损失、使用损失以及摩擦力矩、摩擦系数的计算公式。结果表明初始损失比随拧紧次数的增加而上升,螺纹与钢丝摩擦力矩及其摩擦系数均值随拧紧次数的增加而增大。最后结合有限元仿真,分析了重复拧紧对密封接触强度的影响。更多还原

【Abstract】 Aircraft hydraulic system is the key control system to ensure the normal flight and safety of aircraft,and the pipe joint is one of the important hydraulic accessories.According to statistics about 35%of aircraft hydraulic system failures are caused by hydraulic pipe joint failure.Compared with the 28 MPa pressure system used in the hydraulic system of large aircraft in China,35MPa system has obvious advantages in system weight reduction and performance improvement.Detachable pipeline connection structure is an important part of 35 MPa class aviation hydraulic pipeline connector,and its connection performance directly affects the realization of the function of the pipeline connector,and is crucial to the safety and reliability of the aviation hydraulic system and even the whole machine.Therefore,it is necessary to carry out research on its connection and sealing performance.This paper focuses on the sealing and connection performance of the detachable structure for 35MPa hydraulic pipeline connector,combined with calculation analysis and test verification.The main work is as follows:(1)Based on the structure composition,working state and performance requirements of 35MPa class detachable pipe joint,the sealing mechanism of pipe joint is analyzed,and a new sealing method based on sealing contact strength is proposed for quantitative evaluation.Uniaxial tensile test was carried out on the joint material and the power strengthening model was used to model the material.The stress-strain curve of the joint seal plastic zone was obtained.(2)The motion state of 35MPa class detachable pipe joint during tightening is studied,and the proportion of torque distribution is studied theoretically.That is,among all tightening torques applied,about 41.8%is used to overcome friction between spiral pairs,12.7%is used to generate axial force,42.3%is used to overcome friction between support surfaces and 3.2%torque is used to overcome the friction between the cones.The rationality and accuracy of the research results are verified by finite element method.(3)The finite element modeling and analysis of the joint nonlinear connection seal are carried out,and the sealing contact strength theory and sealing surface limit yield theory are used to evaluate the limit state of the joint sealing.Furthermore,the effects of different tightening torques and assembly deviations on pipe joints are studied.The results show that the average contact stress increases linearly with the increase of tightening torques,and the sealing surface width increases stage-wise.The recommended torque range is 42-46N·m.With the increase of angular deviation φ and radial deviation Δ,the sealing contact strength changes more violently.(4)A special torque-axial force test bench for detachable pipe joint is developed.The fitting torque range of MJ18×1.5 thread is 43-47N·m.Combined with tightening torque-time curve and force-time curve,the quantitative relationship between tightening torque and force was established.(5)The theoretical and experimental analysis of repeated tightening of pipe joints is carried out.When the pipe joints are repeatedly tightened,the wear of contact surface increases,leading to the increase of friction coefficient.According to the test data,when the number of repeated tightening is 8 times,the axial force decreases by about 9.13%.Furthermore,the formulas for calculating the initial axial force loss,service loss,friction torque and friction coefficient are established.The initial loss ratio increases with the increase of tightening times.The friction torque of thread,the friction torque of wire and the mean friction coefficient increase with the increase of tightening times.Finally,combined with finite element simulation,the influence of repeated tightening on sealing contact strength was analyzed.更多还原