Research On Numerical Simulation Of Friction Hydro-Pillar Processing Of 7075 Aluminum Alloy

The friction hydro-pillar processing(FHPP)is a new kind of solid-phase joining technology,which belongs to friction welding technology.It is invented by British Welding Institute(TWI)and has wide application prospects.There are abundant resources in the ocean,many countries have paid attention to the research and exploitation of marine resources and the ways of repairing underwater structures are becoming more and more important.FHPP has the advantages of good weld joint performance and insensitivity to the water depth.It is rapidly becoming a new method for repairing marine structures.At the same time,the common method for repairing aircraft crack defects is to drill holes and rivets.However,when the aircraft crack is longer,only through the form of drill hole has been unable to meet the crack repair requirements.Riveting in the vicinity of the crack easily form a new stress concentration area.FHPP can make up for the shortcomings of the above repair methods due to its own characteristics,and get high welding quality.The numerical simulation of FHPP is still in the early stage of development,so in this paper,the forming process of FHPP is taken as the research object.The temperature field and stress field of the whole welding process is analyzed by numerical simulation technology.In the numerical simulation of the complex thermo-mechanical coupling process of FHPP,the dimensional axisymmetric model is selected and analyzed with FRIC subroutine and grid remesh technique.The 7075 aluminum alloy is selected as the research object,the finite element model of FHPP is established by selecting proper friction model,heat production model,material model,and so on.The boundary conditions and constraints are imposed on the model.The friction welding process is simulated.The effect of the shapes of the specimen on the quality of the welding process are studied with different shapes of welding rods and welding holes,analyze the causes of welding defects,and study the evolutions of the temperature field and the stress field under different combinations of specimens.The cylindrical specimen is selected as the research object,and the cylindrical specimen is simulated by setting different process parameters,including rotational speed and axial welding pressure.The temperature field,stress field and axial feed rate are analyzed,and the influence of different process parameters on the forming of FHPP was obtained.The research work in this paper will provide the theoretical basis for the study of FHPP,and lay a solid foundation for the application of FHPP.