Research On Hydroforming Of LF2M Aluminum Alloy Thin-wall Five-way Tube

LF2M aluminum alloy five-way tube has a special use in the field of aerospace.In order to meet the needs of lightweight and integrated parts,the research of internal high-pressure forming five-way tube has become very meaningful.In this paper,the forming of five-way tube with a diameter of 40 mm and a wall thickness of 1 mm is studied.A 32 mm diameter reducing branch tube and two 40 mm diameter equal branch tubes symmetrically distributed about the center at the upper side and the lower side of the expanding part of the internal high pressure forming are used.The forming scheme of the five way tube is designed and the forming height of the branch tube is improved and the wall thickness distribution is more uniform by optimizing the test parameters.The specific research contents,methods and results are as follows:Based on the shape and structural characteristics of the five-way tube,three different forming methods are designed:(1)one-step forming method of five-way tube is to form three branch tubes at one time;(2)the step-by-step forming scheme of four-way tube and five-way tube is to pre form the four-way tube with one branch tube on the upper side and the lower side,and then form the other branch tube on the lower side;(3)three-way tube and then The five way step-by-step forming scheme is to first form the three-way tube with the upper branch tube,and then finally form the two lower branch tubes.DYNAFORM software is used to establish the finite element model of the above forming method,and the forming process of the five-way tube is simulated by finite element method.Then the simulation results are verified by experiments.The results show that the wall thickness distribution and the height of each branch tube can be effectively improved by adopting the scheme of three-way before five-way step forming.Based on the above research,the forming quality of the preformed tee in the step-by-step forming scheme with the middle state of the tee is optimized.Through the simulation and experiment of the three-way tube pre forming process,the influence of the lubrication mode and the shape of the push head on the pre forming effect of the three-way tube is studied.The results show that the surface wrinkling of the preformed tee tube can be effectively avoided by using the differential lubrication method,that is,increasing the lubrication degree of the upper half ring area of the tube blank;the forming height of the branch tube can be effectively increased by using the extended push head;meanwhile,the branch tube height and the wall thickness distribution of the preformed tee tube can be the highest and the most uniform by using the semi-ring differential lubrication method and the 38 mm diameter extended push head.The final forming simulation and experiment of the preformed tee are carried out.The final forming of the tee is easy to produce the defects of low height and low depression on the outer side of the lower branch tube.The influence of lubrication mode and pressure feed loading path on the forming quality of tube end forming parts was studied.The results show that the differential lubrication method can promote the material flow to the branch tube and make the wall thickness distribution more uniform,and the pressure feed loading path can reduce the degree of depression on the outer side of the branch tube.