Study On Influence Factors Of Hot Extrusion Shrinkable And Thickening Forming Of Thin-walled Aluminum Alloy Tube

Plastic processing of tubes has become an important direction of research and development of advanced plastic processing technology in the 21 st century.It has been widely used in the manufacture of structural parts such as aerospace,national defense,light industry and so on.Aiming at the shortcomings of the design of riveted thread sleeve,unstable connection strength,high manufacturing cost,low service life and complicated assembly of traditional aircraft rod,a design method of aircraft rod with aluminium alloy thickening of shrinkage section is proposed in this paper.By replacing riveted thread sleeve connection with thread connection of shrinkage section,the requirements of good stiffness and strength,light weight and convenient assembly of the rod are realized.At present,the existing reports at home and abroad mainly focus on the process of heat shrinkage forming of the tube,but the direction of tube end thickening is less studied.In this paper,the process of hot extrusion shrinkage and thickening of 5A02thin-walled aluminium alloy tubes with diameter of 22.00 mm and wall thickness of1.00 mm is studied,and the basic theory of shrinkage and thickening forming is analyzed of tube.Finite element software was used to simulate the hot extrusion shrinkage and thickening forming of tube,and the forming device and heating device are designed.The equation for controlling the feed rate of tube was deduced through theoretical research,and the experimental research of hot extrusion shrinkage and thickening is carried out.Therefore,the research results are obtained in the following:The deformation characteristics,forming influencing factors and forming process of thickening were studied theoretically.The forming process and force change of tube hot extrusion shrinkage and thickening are analyzed.The effects of shrinkage coefficient,die cone angle,feed speed,forming temperature and friction conditions on hot extrusion shrinkage and thickening of pipe are description in detail.And a new forming process for shrinkage and thickening of the tube ends is obtained.The finite element model of pipe shrinkage and thickening of the tube is founded by using DEFORM-3D finite element simulation software.A numerical simulation isconducted to wall thickness of tube in the thickening area which increases from 1.00 mm to 3.00 mm.By comparing and analyzing the effects of different process parameters on hot extrusion shrinkage and thickening forming of the tube,the appropriate die cone angle and the range of process parameters are obtained.Since the influence of different process parameters thickening of tubes was studied by orthogonal test,and the primary and secondary relationship which affects each process parameter is determined,as well as the optimum forming process parameters are obtained.The different die structure design schemes are proposed according to the forming process and structural characteristics of an aircraft rod.The experiment research in the structure of die with different die cone angles is carried out.The effects of die structure and mainly process parameters on the experimental forming are analyzed.and the heating device which can be measurable,adjustable and digital display is designed.The feasibility of the new forming process of an aircraft rod was proposed in this paper is verified by experiments.The formed parts of tube wall thickness in the thickening area which is suitable to the experiments are obtained by means of one-time hot extrusion shrinkage and thickening,which simplifies the extrusion forming process of the existing aircraft rod.The experimental forming device is further optimized and improved,and the causes of forming defects are comparative analyzed,what’s more,the solution measures has been put forward.After a material performance test conducted by grain structure testing technology.The microstructures of the optimized tube forming parts in different regions are observed and compared with the original materials.It is found that the grain distribution in the thickening area is uniform and compact of the tube after hot extrusion,and the grain is refined and the stability of the structure is higher.