A multi-scale finite element contact model for seal and assembly of twin ferrule pipeline fittings

As the seal and connection piece of pipeline, assembly method and the seal characteristics of pipeline fittings are important for the safety and reliability of hydraulic system of aircraft. According to measured data of roughness of the target surfaces, a multi-scale model for considering the rough surfaces is established and the assembly process of the pipeline fittings is simulated. In the process of simulation, the seal status and seal characteristics of fittings, as well as the influence of fluid pressure on the seal performance are studied in detail. The results show that the change in stress distribution extends around two high stress regions, and multi-scale model could really reflect seal characteristics during the assembly process of pipeline fittings. Moreover, the variation of contact area between front ferrule and pipeline can be described in the linear relations of three stages, and with the increase of fluid pressure, the rate of change of contact area will also increase.