Influences Of Some Parameters On Forming Quality Of High Strength Steel Thin-walled Rectangular Tube In Rotary-draw Bending

For a long time,Metal thin-walled rectangular section elbow is widely used in automobile industry.People gradually pursue lightweight for the development of car body.However,it is a common phenomenon that high-strength steel thin-walled rectangular tube is used in the body frame.It is the most important structural member.There are three main advantages in using this kind of steel:1.The safety strength of the car is guaranteed.2.Reduce body weight.3.Conserve energy and reduce emissions.But the plasticity of high-strength steel is relatively lower than that of other materials.There is a high probability of producing various process defects during bending forming.In order to determine the influence of the change of section size parameters and process parameters of high-strength steel thin-walled rectangular section tube blank on the forming quality of elbow parts.In this thesis,numerical simulation method is used.Firstly,the gap c between the mandrel and the tube blank is analyzed when JAC590Y high-strength steel thin-walled rectangular section bend is bent 180°,Ratio of the average bending radius to billet height R/h₀,Ratio of the average bending radius to average fillet radius of tube blank R/r₀,Ratio of the average bending radius to wall thickness of tube blank R/t₀,The influence of these four parameters on the distortion degree of the cross-section,the thinning degree of the wall-thickness,the wrinkling problem of the bottom plate and the influence of rebound quantity.And when the bending thickness ratio R/t₀ is 120,it bends at different angles.What is the maximum bending angle under the premise of satisfying the mechanical properties of the material itself,Furthermore,it is discussed how many bending angles the bending parts with smaller section distortion and better forming quality can be obtained.The results are analyzed and obtained as follows:?1?The maximum width expansion rate?_maxax of the cross section of the bent pipe is not significantly affected by the wide clearance rate c_w of the core pipe,while the high clearance rate c_h of the core pipe has a significant effect on the reduction rate?of the middle surface height.The maximum wall thickness reduction rate of c_h in the whole bend is about 20°at the section angle,which has no effect on the position of the maximum fluctuation of the bottom plate wrinkling in the pipe section,the rebound angle will increase with its value.?2?The ratio of bending height R/h₀ has no significant effect on?_max.when R/h₀ is larger,it has no effect on?and?_1max.The maximum fluctuation of longitudinal curvature occurs in the pipe section with section angle?=0°?30°.The rebound angle??will increase with the increase of R/h₀.?3?When the bend diameter ratio R/r₀ decreases,?_max will decrease gradually,and the curvature fluctuation will increase,but there is no obvious effect on rebound.When R/r₀<40,?_max and?_1max decreased significantly.?4?When R/t₀ is less than 80,?_max has little change.The reduction of R/t₀ has little effect on the wrinkling of the bottom plate of the bend,?_max and??decrease gradually,while?₁decreases greatly,It shows that the greater the influence on the thinning rate of pipe wall thickness.?5?When the bending thickness ratio R/t₀=120 under different bending angles,with the decrease of bending angle,?_max,?_maxax and?₁ also decrease.Under the premise of meeting the mechanical properties of materials,the maximum limit energy of bending is 120°and the bending quality is better when the bending is less than 30°.