Numerical Simulation And Experiment Research Of GH4169 Double-layer Tube In Rotary Bending Process

GH4169 has good fatigue,radiation resistance,oxidation resistance and other excellent properties,it can be produced into a variety of specifications of fine diameter tube,in aerospace,petrochemical,automotive industry and other fields have a wide range of applications.Due to the higher strength of the special tube structure,the double-layer clearance tube can adapt to harsher temperatures and more corrosive environments.Therefore,it is particularly important to study the bending and forming law of double-layer gap tube,which can not only enrich modern plastic processing technology,but also provide reference and guidance for the bending of high-strength double-layer tube fittings.In this paper,the process of bending and forming a three-dimensional three-dimensional space tube around the GH4169 double-layer tube is discussed by combining theoretical research,numerical simulation and experimental research.Firstly,through the theory of elastoplastic deformation of the material,combined with the on-site bending conditions,the different deformation stages and force conditions of the double-layer tube in the bending process are analyzed,the relevant stress-strain laws are calculated and the cross-sectional deformation and wall thickness variation are analyzed during the bending of the tube.Using ABAQUS numerical simulation software,combined with the actual bending forming device,establishing a double-layer tube bending and forming finite element model,and numerically simulating the bending and cross-section distortion and wall thickness change process of double-layer tube bending and cross-section distortion and wall thickness change process with different bending process parameters.Through numerical simulation,the cross-section distortion and wall thickness change law of different fillers,bending angles,radius and boost speed on the tube after bending are analyzed,and the stress strain distribution trend under different working conditions and the causes of tube distortion and wall thickness change law are studied.The results show that 1)the bending angle and radius are smaller,the cross-sectional distortion of the inner and outer tubes increases,and the thickening rate and thinning rate of the wall thickness increase;2)The filler material improves the cross-sectional deformation and wall thickness thickening of the inner and outer tubes by supporting the inside of the tube,the pressure in the tube increases,the wall thickness thickening of the two tubes increases,the wall thickness thickening reduces,the internal pressure of the filler reduces the tangential force of the inner and outer sides,and the cross-sectional distortion decreases;the boosting speed has less influence on the cross-sectional distortion and wall thickness change than the other three factors,and 3)under the condition of common bending.The inner tube is fully constrained by the filler,the inner tube wall thickness/outer diameter(t/d)ratio is larger than the outer tube,the tubular structure is more stable,the degree of deformation under the same bending conditions is smaller than the outer tube;4)tangential stress>radial stress>circumferential stress,tangential stress is the first principal stress.As the internal pressure increases,the difference between the stress elongation of the inner and outer tube increases,the total three-way stress elongation of the filled tube is small,corresponding to a lower degree of cross-sectional distortion and wall thickness change rate,and the cross-sectional distortion is composed of wall thickness change and internal compression.Excessive internal pressure will lead to an increase in the cross-sectional distortion rate;5)when the boost speed is greater than the bending die line speed,the tangential tensile stress strain of the tube is reduced and the tangential pressure stress strain increases,and when the boost speed is less than the bending die line speed,the external stress strain rises and the inner stress strain decreases.Through the self-designed bending equipment,the experimental studies corresponding to the numerical simulation were carried out and the results of the simulation and the tests under different working conditions were compared,and the obtained laws were consistent,and the numerical difference was within 5%.The accuracy of the numerical simulation results was verified,and the test results showed that 1)the filler had no effect on the position where the tube began to thicken and thin,and the wall thickness remained stable from 35-70°;2)the gap between the inner and outer tubes decreased with the increase of bending deformation during the bending process,and the gap distribution of the unfilled tube from the outermost to the innermost side showed a trend of first increasing and then decreasing,and the maximum gap appeared in the bending radial direction;3)The difference between the cross-sectional distortion of the inner and outer tubes after the bending of the double-layer tube did not exceed 1%.The maximum distortion rate of the internal and external tube cross-section is not more than 7%,the change rate of the outer tube wall thickness is 8-12%,and the change rate of the inner tube wall thickness is 5-9%.The above research can provide a reference for GH4169 double-layer clearance tube bending forming technology,improve the bending forming quality and forming performance,reduce the design mold cost,and improve the production cycle.