Study On The Influence Factors Of Hydroforming Of LF2M Aluminum Alloy T-shaped Tube

The T-shaped tubes,being the most typical parts in hollow-structured components,have been a hot topic in research fields from simulation to forming experiments all over the world.In this thesis,by combining simulation and experiments,the research is based on the three factors in the internally high-pressure LF2 M aluminum alloy T-shaped tube forming,namely feed rate and internal pressure,the size of the fillet,and friction and lubrication.The main content is as follows:(1)The technical process and the principle of the T-shaped tube forming are introduced in detail.The three factors influencing the internally high-pressure T-shaped tube forming including internal pressure and feed rate,the size of the fillet,and friction and lubrication are discussed.The three different zones arising from different friction type in the forming process,viz.,guiding zone,transition zone,and growing zone,are mentioned.The theory of CAE analysis and the FEM software are briefly introduced.(2)The FEM model of T-shaped tube forming is established,and the 1/4 model is utilized for analyzing the influence of internal pressure and feed rate,the size of the fillet,and friction and lubrication on the forming process.The simulation shows that when the maximum internal pressure P=20MPa,feed rate S=30mm,the size of the fillet R=4mm,and the friction coefficient ?=0.06,the result is the best.It can be obtained that internal stress is the critical factor for the minimum wall thickness,and the oversized fillet requires the application of back pressure such that the satisfactory components can be formed.The trend of material flow and the forming defects during the internally high-pressure T-shaped tube forming are also analyzed.(3)Since the traditional methods of lubrication are infeasible for the internally high-pressure T-shaped tube forming,a new lubrication method based on partial friction control during the forming process is proposed.The method adopts different ways of lubrication through the analysis of the different friction types in different zones of the formed parts and the influence of the lubrication conditions in different zones on the forming process.The internally high-pressure T-shaped tube forming is carried out based on the proposed method,and it is discovered that satisfactory components can be formed when the lubrication is applied to region 1.(4)The whole process of the internally high-pressure T-shaped tube forming is introduced,which includes experimental objectives,experimental equipment,installation and calibration,the selection of lubricants,tube blank cutting,and conducting experiments.By 1)combining the simulation and experimental results,analyzing the influence of internal pressure,feed rate and size of the fillet on forming quality;2)taking points at critical region and observing how the wall thickness changes during the forming process;3)taking equidistant points on the components and compare the wall thickness distribution in simulation and experiments,it can be obtained that 1)the top of the branch tube has the minimum thickness and it gradually gets thinner during the forming process;2)the bottom of the straight tube has the maximum thickness and it gradually gets thicker during the forming process;3)the wall thickness of the fillet region thickens during the early and middle stages of the forming process,while it gets thinner in the later stage of forming.