Sealing Performance Analysis of Memory Alloy Based Flareless Tube Connections Under 35 MPa Pressure

In view of the fact that increasing the pressure grade can improve the response performance of the hydraulic system, reduce the volume of each component, reduce the weight, etc., the current hydraulic system pressure grade of military and civilian aircraft is developing to 35 MPa. Aiming at the current unclear sealing performance of many tube connection forms in the hydraulic system of the current high-pressure system, the flareless tube connections with nominal diameters of 6mm and 8mm were selected for research, and the joints and sleeves were replaced with memory alloys from stainless steel. According to the theoretical analysis of metal-metal sealing, the simulation calculation using finite element software, and the sample test according to the sealing test standard of aircraft hydraulic pipeline connectors, the joint and pipe sleeve made of memory alloy are plastically deformed under the action of preload, the contact area and sealing length are much greater than the required theoretical minimum sealing length, and the sealing performance of the flareless tube connection form is reliable under the 35 MPa pressure system, which meets the requirements of leak-free performance required by engineering applications. It should be noted that the preload required for memory alloy-based flareless tube connections is significantly less than the aviation standard recommendation, which could cause structural failure. For memory alloy-based flareless tube connections with a nominal diameter of 6mm, the recommended preload is 3000–4500 N; For memory alloy-based flareless tube connections with a nominal diameter of 8 mm, the recommended preload is 3000–5000 N. For stainless steel pipe connections with nominal diameters of 6 and 8 mm, the recommended value of preload is about 7000–9000 N according to aviation standards.