The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning pro...The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .展开更多
In order to improve the computational accuracy and efficiency,it is necessary to establish a reasonable 3D FEM model for multi-pass spinning including not only spinning process but also springback and annealing proces...In order to improve the computational accuracy and efficiency,it is necessary to establish a reasonable 3D FEM model for multi-pass spinning including not only spinning process but also springback and annealing processes.A numerical model for multi-pass spinning is established using the combination of explicit and implicit FEM,with the advantages of them in accuracy and efficiency. The procedures for model establishment are introduced in detail,and the model is validated.The application of the 3D FEM model to a two-pass spinning shows the following：The field variables such as the stress,strain and wall thickness during the whole spinning process can be obtained,not only during spinning process but also during springback and annealing processes,and the trends of their distributions and variations are in good agreement with a practical multi-spinning process.Thus the 3D FEM model for multi-pass spinning may be a helpful tool for determination and optimization of process parameters of multi-pass spinning process.展开更多
Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency an...Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.展开更多
A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw ...A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw resonance. The results show that for shear thin fluids, the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning. When the power index approaches zero, the critical draw ratio points at unity, indicating no melt spinning can be processed stably for such fluids. For shear thick fluids, the critical draw ratio increases in a more rapid way with increasing the power index.展开更多
During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly...During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly, the backward roller paths of hemispherical parts with aluminum alloy 2024-O are analyzed. Finite element model with parameterized conventional spinning roller paths, which are based on quadratic Bezier curves, is developed to explore the evolution of the stress, strain and thinning during the backward processes. Analysis of the simulation results reveals stress and strain features of backward pass spinning. According to the findings, the application of the backward pass can obviously improve the uniformity of wall thickness. Furthermore, references of the parameters in future backward path design are provided.展开更多
Based on simplified axisymmetrical forming model, a elasto-plastic FEM simulation system of multi-pass conventional spinning is developed. Taking the typical draw-spinning as the study object, and establishing reasona...Based on simplified axisymmetrical forming model, a elasto-plastic FEM simulation system of multi-pass conventional spinning is developed. Taking the typical draw-spinning as the study object, and establishing reasonable mechanics model, research on the first pass of spinning process is carried out with FEM system developed. The distributions of the stress and strain are obtained by three types of roller-trace curves: straight line, involute curves and quadratic curves. The results are as follows: (1) The values of equivalent stress and strain are the lowest under involute curve compared to other two curves, and they change relatively small and decrease with the increase of radius. The values of equivalent stress and strain is the highest under quadratic curves, and increase with the increase of radius. (2) The value of radial stress is smallest under involute curve, and is the largest under straight line. Value of radial stress is often used as the criterion of cracking limit, so its distribution laws can provide references for studying the condition of cracking in multi-pass conventional spinning under different roller-trace. (3) Tangential stress is compressive stress. Absolute value of tangential stress is the smallest under involute curve, and values of tangential stress are close between other two curves. The distribution laws of tangential stress can serve as a significant guide to research the critical condition of wrinkling in multi-pass conventional spinning under different roller-trace. (4) The reduction of thickness is the smallest under involute curve. The distribution of the thickness strain is very unequal under quadratic curves. The results obtained can provide references for selecting reasonable roller-trace in multi-pass conventional spinning.展开更多
The spinning flow of Boger fluids and the gravity-drawing extrusion flow of a Newtonianas well as a Boger fluid have been simulated by using the stream-line finite element method and thetechnique of matching the finit...The spinning flow of Boger fluids and the gravity-drawing extrusion flow of a Newtonianas well as a Boger fluid have been simulated by using the stream-line finite element method and thetechnique of matching the finite element solutions with those of one-dimensional spinning equations.The recoverable shear strain is proved not to be a basic parameter in characterising thespinning flow of Boger fluids.For Newtonian fluids this technique predicts the experimental jetshape accurately.For Boger fluids,the numerical simulation agrees with the experimental data of spin-ning flow reported by Sridhar et al.,but seems to give an insufficient swelling and over contractionof the jets when drawn by its own weight,compared with the experimental results of Trang andYeow.It implies that the Oldroyd-B model fitting the viscometric-flow data fails to describeaccurately the elasticity and extensional viscosity in the extrusion flow of Boger fluids with gravi-ty-drawing.展开更多
Direct difference methods have been used to solve the simultaneous non-linear partial differential equations formelt spinning without recourse to linearisation or perturbation approximation.The stability of each diffe...Direct difference methods have been used to solve the simultaneous non-linear partial differential equations formelt spinning without recourse to linearisation or perturbation approximation.The stability of each difference schemes wasstudied by error analysis using the Taylor series,and by comparison of the results obtained from numerical simulation withthe logical value in melt spinning.It is found that computation with 19 digit long double precision has significantlysimplified the stability problem of difference equations.Using this method,the precise critical draw ratio of draw resonancein an isothermal and uniform tension spinning of Newtonian fluids can be obtained in between 20.218 and 21.219,a figureconsistent with 20.218 which was obtained by a linear perturbation approximation method by Kase and Denn.It thus haspaved the way to computation of full information for unsteady melt spinning processes using the difference method.展开更多
文摘The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .
基金Selected from Proceedings of the 7th International Conference on Frontiers of Design and Manufacturing(ICFDM' 2006)This project is supported by National Natural Science Foundation of China(No.50405039,No.50575186)National Natural Science Foundation of China for Distinguished Young Scholor(No.50225518).
文摘In order to improve the computational accuracy and efficiency,it is necessary to establish a reasonable 3D FEM model for multi-pass spinning including not only spinning process but also springback and annealing processes.A numerical model for multi-pass spinning is established using the combination of explicit and implicit FEM,with the advantages of them in accuracy and efficiency. The procedures for model establishment are introduced in detail,and the model is validated.The application of the 3D FEM model to a two-pass spinning shows the following：The field variables such as the stress,strain and wall thickness during the whole spinning process can be obtained,not only during spinning process but also during springback and annealing processes,and the trends of their distributions and variations are in good agreement with a practical multi-spinning process.Thus the 3D FEM model for multi-pass spinning may be a helpful tool for determination and optimization of process parameters of multi-pass spinning process.
基金supported by National Natural Science Foundation of China(Grant Nos.50905137,50975222)China Postdoctoral Science Foundation(Grant No.2012M521757)Natural Science Foundation of Shaanxi for Youths,China(Grant No.2012JQ7032)
文摘Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.
文摘A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw resonance. The results show that for shear thin fluids, the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning. When the power index approaches zero, the critical draw ratio points at unity, indicating no melt spinning can be processed stably for such fluids. For shear thick fluids, the critical draw ratio increases in a more rapid way with increasing the power index.
基金Project(2014CB046601)supported by the National Basic Research Program of ChinaProject(51675333)supported by the National Natural Science Foundation of China
文摘During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly, the backward roller paths of hemispherical parts with aluminum alloy 2024-O are analyzed. Finite element model with parameterized conventional spinning roller paths, which are based on quadratic Bezier curves, is developed to explore the evolution of the stress, strain and thinning during the backward processes. Analysis of the simulation results reveals stress and strain features of backward pass spinning. According to the findings, the application of the backward pass can obviously improve the uniformity of wall thickness. Furthermore, references of the parameters in future backward path design are provided.
文摘Based on simplified axisymmetrical forming model, a elasto-plastic FEM simulation system of multi-pass conventional spinning is developed. Taking the typical draw-spinning as the study object, and establishing reasonable mechanics model, research on the first pass of spinning process is carried out with FEM system developed. The distributions of the stress and strain are obtained by three types of roller-trace curves: straight line, involute curves and quadratic curves. The results are as follows: (1) The values of equivalent stress and strain are the lowest under involute curve compared to other two curves, and they change relatively small and decrease with the increase of radius. The values of equivalent stress and strain is the highest under quadratic curves, and increase with the increase of radius. (2) The value of radial stress is smallest under involute curve, and is the largest under straight line. Value of radial stress is often used as the criterion of cracking limit, so its distribution laws can provide references for studying the condition of cracking in multi-pass conventional spinning under different roller-trace. (3) Tangential stress is compressive stress. Absolute value of tangential stress is the smallest under involute curve, and values of tangential stress are close between other two curves. The distribution laws of tangential stress can serve as a significant guide to research the critical condition of wrinkling in multi-pass conventional spinning under different roller-trace. (4) The reduction of thickness is the smallest under involute curve. The distribution of the thickness strain is very unequal under quadratic curves. The results obtained can provide references for selecting reasonable roller-trace in multi-pass conventional spinning.
基金Subject supported by the National Natural Science Foundation of China and Natural Science Foundation of Zhejiang Province
文摘The spinning flow of Boger fluids and the gravity-drawing extrusion flow of a Newtonianas well as a Boger fluid have been simulated by using the stream-line finite element method and thetechnique of matching the finite element solutions with those of one-dimensional spinning equations.The recoverable shear strain is proved not to be a basic parameter in characterising thespinning flow of Boger fluids.For Newtonian fluids this technique predicts the experimental jetshape accurately.For Boger fluids,the numerical simulation agrees with the experimental data of spin-ning flow reported by Sridhar et al.,but seems to give an insufficient swelling and over contractionof the jets when drawn by its own weight,compared with the experimental results of Trang andYeow.It implies that the Oldroyd-B model fitting the viscometric-flow data fails to describeaccurately the elasticity and extensional viscosity in the extrusion flow of Boger fluids with gravi-ty-drawing.
文摘Direct difference methods have been used to solve the simultaneous non-linear partial differential equations formelt spinning without recourse to linearisation or perturbation approximation.The stability of each difference schemes wasstudied by error analysis using the Taylor series,and by comparison of the results obtained from numerical simulation withthe logical value in melt spinning.It is found that computation with 19 digit long double precision has significantlysimplified the stability problem of difference equations.Using this method,the precise critical draw ratio of draw resonancein an isothermal and uniform tension spinning of Newtonian fluids can be obtained in between 20.218 and 21.219,a figureconsistent with 20.218 which was obtained by a linear perturbation approximation method by Kase and Denn.It thus haspaved the way to computation of full information for unsteady melt spinning processes using the difference method.
