Heat-assisted rotary draw bending(HRDB)is a promising technique for manufacturing difficult-to-form tubular components comprising high-strength titanium tubes(HSTTs)with small bending radii.However,as a multidie const...Heat-assisted rotary draw bending(HRDB)is a promising technique for manufacturing difficult-to-form tubular components comprising high-strength titanium tubes(HSTTs)with small bending radii.However,as a multidie constrained and thermomechanical coupled process with many uncertainty factors,a high risk of several defects,such as cross-section distortion,over wall thinning,or even cracking,is present.Achieving the robust design optimization(RDO)of complex forming processes remains a nontrivial and challenging scientific issue.Herein,considering a high-strength Ti-3Al-2.5V titanium alloy tube as a case material,the five significant uncertainty factors in HRDB,i.e.,temperature distribution,tube geometrical characteristics,tube material parameters,tube/tool friction,and boost velocity had been analyzed.Subsequently,considering the preheating and HRDB of HSTT,a whole-process thermomechanical three-dimensional finite element model was established and validated for virtual experiments.Further,considering the maximum section distortion Q and maximum wall-thickness thinning t as the optimization objectives and the mean and variance of material and forming parameters,an RDO model was established.Finally,the Pareto optimal solutions were obtained using the nondominated sorting genetic algorithm II,and a minimum distance selection method was employed to obtain the satisfactory solution.Results show that the optimized solutions considering the uncertainty factors reduce the maximum section distortion rate of HSTT after bending by 38.1%and the maximum wallthickness thinning rate by 27.8%.展开更多
For the titanium tube industry in 2016,the widespread loss in the industry in 2015 will quicken the adjustment pace of product structure in the tube market,and create new industrial situation;furthermore,the'One B...For the titanium tube industry in 2016,the widespread loss in the industry in 2015 will quicken the adjustment pace of product structure in the tube market,and create new industrial situation;furthermore,the'One Belt,One Road'plan in the'Thirteenth Five Year'Plan will also boost demand in the tube market.Meanwhile,due to the tremendous base in capacity and output,and excessively long absorption time;coupled with heavy展开更多
Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of exp...Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of explicit and implicit is preferred to predict the springback. This simulation strategy includes several numerical parameters, such as element type, number of elements through thickness （NEL）, element size, etc. However, the influences of these parameters on spring- back prediction accuracy are not fully understood. Thus, taking the geometrical specification 9.525 mm × 0.508 mm ofa HSTT as the objective, the effects of numerical parameters on prediction accuracy and computation efficiency of springback simulation of HSTT RDB are investigated. The simulated springback results are compared with experimental ones. The main results are： （1） solid and continuum-shell elements predict the experimental results well; （2） for C3DSR elements, NEL of at least 3 is required to obtain reliable results and a relative error of 29% can occur as NEL is varied in the range of 1-3; （3） specifying damping factor typically works well in Abaqus/Emplicit simulation of springback and the springback results are sensitive to the magnitude of damping factor. In addition, the explanations of the effect rules are given and a guideline is added.展开更多
The anisotropic tensile mechanical properties of pure titanium(TA2)tubes were studied by means of theoretical analysis,finite element simulation and tensile tests.Based on the stress analysis of circumferential tensil...The anisotropic tensile mechanical properties of pure titanium(TA2)tubes were studied by means of theoretical analysis,finite element simulation and tensile tests.Based on the stress analysis of circumferential tensile of TA2 tube,an equation for calculating the tangential force of circumferential tensile specimen was established,and the relationship among tangential force,friction and position of ring specimen was analyzed.The finite element simulation analysis of circumferential tensile process of TA2 ring specimen was carried out,which verified the tangential force equation derived from theoretical analysis.The effect of gauge length and friction on necking and tensile load was analyzed,and the optimal gauge length was selected for the ring hoop tensile test.Finally,the axial and circumferential tensile digital image correlation experiments were carried out to verify the theoretical and finite element simulation results.The friction coefficient between TA2 tube and D-blocks(using Teflon lubricant)was determined by the inverse finite element method and the friction experiment,and the true stress-strain curve of TA2 tube was obtained.The results show that the axial and circumfere ntial mechanical behaviors of TA2 tubes are significantly different and an isotropic.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51775441).
文摘Heat-assisted rotary draw bending(HRDB)is a promising technique for manufacturing difficult-to-form tubular components comprising high-strength titanium tubes(HSTTs)with small bending radii.However,as a multidie constrained and thermomechanical coupled process with many uncertainty factors,a high risk of several defects,such as cross-section distortion,over wall thinning,or even cracking,is present.Achieving the robust design optimization(RDO)of complex forming processes remains a nontrivial and challenging scientific issue.Herein,considering a high-strength Ti-3Al-2.5V titanium alloy tube as a case material,the five significant uncertainty factors in HRDB,i.e.,temperature distribution,tube geometrical characteristics,tube material parameters,tube/tool friction,and boost velocity had been analyzed.Subsequently,considering the preheating and HRDB of HSTT,a whole-process thermomechanical three-dimensional finite element model was established and validated for virtual experiments.Further,considering the maximum section distortion Q and maximum wall-thickness thinning t as the optimization objectives and the mean and variance of material and forming parameters,an RDO model was established.Finally,the Pareto optimal solutions were obtained using the nondominated sorting genetic algorithm II,and a minimum distance selection method was employed to obtain the satisfactory solution.Results show that the optimized solutions considering the uncertainty factors reduce the maximum section distortion rate of HSTT after bending by 38.1%and the maximum wallthickness thinning rate by 27.8%.
文摘For the titanium tube industry in 2016,the widespread loss in the industry in 2015 will quicken the adjustment pace of product structure in the tube market,and create new industrial situation;furthermore,the'One Belt,One Road'plan in the'Thirteenth Five Year'Plan will also boost demand in the tube market.Meanwhile,due to the tremendous base in capacity and output,and excessively long absorption time;coupled with heavy
基金the National Natural Science Foundation of China (No.51275415)Program for New Century Excellent Talents in University+1 种基金the fund of the State Key Laboratory of Solidifcation Processing in NWPUNatural Science Basic Research Plan in Shaanxi Province (No.2011JQ6004),and the 111 Project (No.B08040) for the support
文摘Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of explicit and implicit is preferred to predict the springback. This simulation strategy includes several numerical parameters, such as element type, number of elements through thickness （NEL）, element size, etc. However, the influences of these parameters on spring- back prediction accuracy are not fully understood. Thus, taking the geometrical specification 9.525 mm × 0.508 mm ofa HSTT as the objective, the effects of numerical parameters on prediction accuracy and computation efficiency of springback simulation of HSTT RDB are investigated. The simulated springback results are compared with experimental ones. The main results are： （1） solid and continuum-shell elements predict the experimental results well; （2） for C3DSR elements, NEL of at least 3 is required to obtain reliable results and a relative error of 29% can occur as NEL is varied in the range of 1-3; （3） specifying damping factor typically works well in Abaqus/Emplicit simulation of springback and the springback results are sensitive to the magnitude of damping factor. In addition, the explanations of the effect rules are given and a guideline is added.
基金the financial supports of the National Natural Science Foundation of China(Nos.51675260 and 51475223)the Six Talents Peak Project of Jiangsu Province(No.20I4-ZBZZ-012).
文摘The anisotropic tensile mechanical properties of pure titanium(TA2)tubes were studied by means of theoretical analysis,finite element simulation and tensile tests.Based on the stress analysis of circumferential tensile of TA2 tube,an equation for calculating the tangential force of circumferential tensile specimen was established,and the relationship among tangential force,friction and position of ring specimen was analyzed.The finite element simulation analysis of circumferential tensile process of TA2 ring specimen was carried out,which verified the tangential force equation derived from theoretical analysis.The effect of gauge length and friction on necking and tensile load was analyzed,and the optimal gauge length was selected for the ring hoop tensile test.Finally,the axial and circumferential tensile digital image correlation experiments were carried out to verify the theoretical and finite element simulation results.The friction coefficient between TA2 tube and D-blocks(using Teflon lubricant)was determined by the inverse finite element method and the friction experiment,and the true stress-strain curve of TA2 tube was obtained.The results show that the axial and circumfere ntial mechanical behaviors of TA2 tubes are significantly different and an isotropic.
