Research On Forming Limit Of Bulge During Hot Power Backward Spinning For 7075 Cast Aluminum Alloy Tube

7075 cast aluminum alloy thin-walled tube has been widely used in aviation aerospace and other technical fields,because of its light weight,high strength and good corrosion resistance.Multi-pass hot power backward spinning is one of the most effective methods to manufacture this kind of thin-walled tube.However,bulge is one of the common defects in the spinning process of tube,which seriously restricts the improvement of the forming quality and forming limit.In this paper,the numerical simulation of multi-pass hot power backward spinning process has been carried out by using the virtual orthogonal experiment.Then based on the spinning experiment,the forming limit of bulge in multi-pass hot power backward spinning process for tube has been studied.The main research contents and results are as follows:(1)A 3D coupled thermo-mechanical and elastic-plastic FE model in multi-pass hot power backward spinning process for 7075 cast aluminum alloy tube is well built based on ABAQUS/Explicit.(2)The uniform orthogonal experiment data has been analyzed by using variance analysis method.Meanwhile,the relationship model between the process parameters and bulge,and bulge limit forecasting model have been taken into account.Three parameters of each pass that significantly affect bulge height are selected.In the first pass,significant process parameters that affect bulge height are sequentially taken as sv,mT,s?.In the second pass,significant process parameters are mT,mn,(35)t,sequentially.And those of the third pass are(35)t,sv,mT,those of the fourth pass are sv,mn,mT.(3)The uniform orthogonal experiment results have been analyzed by using range analysis method.Compared and analyzed the results of confirmatory tests,and the optimal process parameters are obtained.In the first-pass spinning process,reduction in thickness(35)t is 2.4mm,mandrel preheating temperature mT is 220?,mandrel rotational speed mn is 3.0r·s-1,roller feed rate sv is 0.6mm·s-1,mandrel/tube friction coefficient m? is 0.15,roller/tube friction coefficient s? is 0.35.In the second pass,the values of(35)t,mT,mn,sv,m?,s? are 2.4,200,3.5,0.8,0.15,0.30,respectively.And those of the third pass are 1.9,100,4.0,0.6,0.15,0.35,those of the fourth pass are 1.4,100,4.0,0.6,0.20,0.45.(4)Based on the significant process parameters of bulge,the relationship model between the process parameters and bulge is built,and bulge limit forecasting model of each pass is deduced.The laws of process parameters affecting bulge limit are obtained.In the first pass,as sv rises,bulge limit decreases firstly and then increases,and bulge limit increases with s? increasing.In the second pass,with mn increasing,bulge limit decreases firstly and then changes not much.With the increase of(35)t,bulge limit decreases.In the third pass,as(35)t rises,bulge limit decreases firstly and then increases,and bulge limit increases with sv increasing.In the fourth pass,with sv or mn increasing,bulge limit decreases firstly and then changes not much.In addition,bulge limit diagram of each pass is established.