Research On Springback Law Of Curved Tubes Based On Elasto-viscoplasticity Model

Metal tubes are wide used in aerospace,automotive,marine,chemical and other fields.the tubes are usually processed to people's needs.Bending forming defects such as wall thickness reduction and cross-sectional distortion can be improved by using a mandrel and other process measures,and springback is unavoidable.Springback is the most important index to evaluate the quality of tubes bending.Precisely predicting and controlling the bending back of tubes is of great significance in engineering.The main research contents are as follows:Based on the linear elastic-power-strength constitutive model,the springback model of metal material tubes curved is established.The influence of tubes wall thickness and strain neutral layer offset on the springback angle of the tubes is considered in the derivation formula.The ABAQUS is used to simulate the instantaneous springback process of the tubes curved.The elastoplastic model is used to describe the constitutive relation of the metal unloading springback.The simulation data and theoretical values are compared to verify the accuracy of the springback formula.By comparing the simulation data with the theoretical calculation results,the springback angle of the tubes curved is related to the bending process parameters,and increases with the increase of the tubes wall thickness,the bending radius of curvature and the bending angle,and decreases with the increase of the outer diameter of the tubes.Metals generally have certain viscous mechanical characteristics,and the viscosity of the material during the unloading and springbacking process has a great influence,which leads to the time-dependent springback of the metal tubes after several days after the forming.The two-layer elasto-viscoplasticity model was used to describe the constitutive relationship of the 06Cr19Ni10 tubes during bending and unloading springback.The mechanical properties of the material were obtained by uniaxial tension and stress relaxation tests.The ABAQUS was used to simulate the timedependent springback process of the tubes curved,and the simulated value of the time-dependent springback angle of the tubes curved was obtained within 60 days.The 06Cr19Ni10 seamless tubes was selected for the tubes curved springback test,and the instantaneous springback of the tubes and the time-dependent springback angle data of the nodes at each time in 30 days were obtained.Combined with the theory,simulation and experimental results,the residual stress stored in the tubes section after the bending of the tubes is driven to springback,the residual stress cannot be completely released due to the damping of the material viscosity,and gradually decays to less than the next few days.The experimental tubes continue to deform at a low stress level,forming a Time-dependent springback phenomenon.