A Study On The Simulation Of Differential Temperature Push-Bending With Thermo-Mechanical-Elastomer Simulation Of 5A02 Aluminum Alloy Tube

Thin walled tubes with small bending radius are widely used in aerospace,petroleum,electric power and other fields.They are not only used as gas and liquid tubes,but also as metal structures.Therefore,reducing the relative bending radius of the elbow is conducive to reduce the weight of the system components and save the installation space.At present,it is difficult to reduce the relative bending radius of the formed bend with the common tube bending technology in industry.Therefore,the method of differential temperature push-bending with thermo-mechanical-elastomer simulation is adopted in order to push-bending 5A02 aluminum alloy tube.The result shows that this method can form a bend with a relative bending radius of 0.75D,which effectively improves the forming limit of the bend.The mechanical properties of the material in the range of temperature 20℃～400℃and strain rate 0.1S^-1～0.001S^-1were analyzed by using 5A02 aluminum alloy tube.The result showed that the elongation percentage of the material increased with the increase of temperature,and the flow stress decreased with the increase of temperature.When the temperature was higher than 250℃,the material entered the steady state deformation stage from strain-hardening stage,and the elongation of the material increased influenced by the strain rate,and the elongation percentage of the material increased with the decrease of the strain rate.The suitable temperature for bending was obtained by analyzing the heat transfer between the heating rod and the die,and between the die and the tube blank.The theoretical analysis of differential temperature push-bending with thermo-mechanical-elastomer simulation was carried out.The static equilibrium equation was established by force analysis,and the stress-strain in the deformation area of the bend,the defect of the tube blank in the bending process and the critical stress of the wrinkling of the bend were analyzed.The result showed that the reduction of the intrados the axial stress was helpful to prevent the intrados wrinkling,the optimization of the tube blank and the improvement of the rigidity of the material inside the bend could both reduce the axial stress in the inner side of the bend and play a positive role in improving the forming limit of the bend.The finite element model of differential temperature push-bending with thermo-mechanical-elastomer simulation was established.For the first time,the simulation of tube bending with a diameter thickness ratio of 32 and a relative bending radius of 0.75D was carried out.The result showed that the distribution of temperature difference could be controlled by changing the number of heating rods and the length of cooling area.By comparing the results of cold push-bending with that of differential temperature push-bending with thermo-mechanical-elastomer simulation,it was verified that the new method can effectively improve the forming limit of the elbow.As an elastomer,silicone rubber could support the tube wall and reduce the forming defects during the process of bending.The numerical simulation was used to study the influence factors of the differential temperature push-bending with thermo-mechanical-elastomer simulation.The defects of the tube blank in the forming process were predicted,and the influence of the shape,temperature area,lubrication,push speed and reverse thrust forming factors of the tube blank on the forming defects was analyzed.It could be seen from the simulation results that the common forming defects in tube blank forming were the intrados thickening and wrinkling,port distortion and the extrados thickness thinning.Reasonable control of the technological parameters of tube bending could effectively reduce the generation of forming defects and improve the quality of tube blank forming.