Variable gauge rolling （VGR） is a new technology to produce flat products with different thicknesses （FDT）, which could be used to replace conventional fiat products in order to save metals and reduce structure ma...Variable gauge rolling （VGR） is a new technology to produce flat products with different thicknesses （FDT）, which could be used to replace conventional fiat products in order to save metals and reduce structure mass. The method of VGR was introduced for investigating new problems in rolling theory of VGR, and the new formulas for calculating parameters of VGR were proposed. Besides, some results of numerical simulation by finite elemen~ method were described. As an example, the products applications of FDT in bridge construction, ship building and auto manufacturing were presented. Finally, the prospects for VGR and FDT were discussed.展开更多
The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension w...The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension was set up, and the deformation formulae for the thinner side and for the thicker side were derived to quantify the deformation of TRB. On this basis, uniaxial tension tests on TRB and ordinary blanks （the thinner side and the thicker side of TRB） were conducted. Lagrange polynomial interpolation method was adopted to construct the stress-strain fields of unannealed and annealed TRBs for solving TRB material parameters, and then, uniaxial tension simulation on TRB was completed. Deformations and properties of unannealed TRB were compared with those of annealed TRB, and the thinner side and the thicker side were also compared. Finally, the research results were explained by metallurgical structure. The results show that nonuniform deformation happens in TRB during uniaxial tension, and the necking occurs on the thinner side. The agreement of analysis, test and simulation confirms the correctness of the analytical model and the deformation formulae. The findings of this paper can lay the foundation for the future study on TRB stamping formability and provide a way for TRB modeling.展开更多
Variable gauge rolling （VGR） is a new technology for producing the materials which have the advantage of lightweight due to optimized thickness according to load distribution. The new progresses in the theoretical r...Variable gauge rolling （VGR） is a new technology for producing the materials which have the advantage of lightweight due to optimized thickness according to load distribution. The new progresses in the theoretical research and application of VGR are reviewed in this paper. Two basic equations, VGR-f and VGR-s, were deduced. The former is a new differential equation of force equilibrium, and the latter is a new form of formula for the law of mass conservation. Both of them provide a new base for the development of VGR analysis. As the examples of VGR＇s application, tailor rolled blank （TRB） and longitudinal profile （LP） plate are introduced. Now TRBs are only produced in Germany and China, and have been used in the automotive manufacturing to play an important role in lightweight design. LP plates have been used in shipbuilding and bridge construction, and promised a bright prospect in reducing construction weight. In addition, new technologies and applications of VGR emerge constantly. Tailor welded strips and tailor rolled strips with variable thickness across the width can be used for progressive die and roll forming. The 3D profiled blank can be obtained by two-step rolling process. Tailor tubes witli the variable wail thickness are an efficient way to reduce the weight. The blank with tailored thickness and mechanical property is also under development. Above products based on the tailored ideas provide a new materials-warehouse for the designers to select so as to meet the needs of weight reducing and material saving.展开更多
Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the d...Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.展开更多
The process of automobile lightweight can be promoted by the application of tailor rolled blank（TRB）in the automobile industry.Therefore,research on the formability of TRB is of good practical significance and appli...The process of automobile lightweight can be promoted by the application of tailor rolled blank（TRB）in the automobile industry.Therefore,research on the formability of TRB is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight.Aiming at the present condition of lack of researches on the influence of characteristic parameters on TRB drawing process,the drawing formability of TRB was studied with a combination method of simulation and experiment by taking square box as the research object.Firstly,drawing simulation and experiment of TRB were carried out.Then,effects of thickness transition zone（TTZ）position and blank size on the drawing formability of TRB were analyzed.Forming limit and TTZ movement for TRB square box during the drawing process were respectively discussed,when transition zones of TRB were located at different positions and blanks were of different sizes.The results indicate that lubrication condition exerts greater influence on TRB forming limit in comparison with TTZ movement,and the smaller blank size and TTZ being located at the blank center or slightly offset to the thinner side are preferable for acquiring greater forming limit and smaller TTZ movement.展开更多
The Brillouin gain properties in a double-clad As2Se3 photonic crystal fiber（PCF）are simulated based on the finite-element method（FEM）.The results indicate that the Brillouin gain spectrum（BGS）of our proposed ch...The Brillouin gain properties in a double-clad As2Se3 photonic crystal fiber（PCF）are simulated based on the finite-element method（FEM）.The results indicate that the Brillouin gain spectrum（BGS）of our proposed chalcogenide PCF exhibits a multipeaked behavior and has a high Brillouin gain coefficient.We also find that a larger size of inner cladding air holes will lead to a more pronounced second peak in the BGS.On the other hand,the size of the outer cladding has nearly no effect on the BGS behavior.Through these results,one can tailor the Stimulated Brillouin scattering effect in PCFs for a wide range of applications.展开更多
The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simu...The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simulation methods have been used to compare and analyze the springback characteristics of equal thickness blanks and tailor rolled blanks in U-channel forming.From the results,the overall springback angles of tailor rolled blanks at thin and thick sides are respectively 106.79° and 99.705°,which are both lower than those of the corresponding equal thickness blanks.Due to the existence of the thickness transition zone,the stress distribution in thin and thick sides of blanks is changed.The location of dangerous region in thin side of tailor rolled blanks is closer to the end of side,and the thick side moved to the middle of straight wall,which are different with the equal thickness blanks.Afterwards,the released quantitles of tangential stress and strain per unit section of blank are adopted to calculate relative springback angles and give novel evaluation criteria for qualitatively analyzing the amount of springback angles.By comparing the results,it shows that the tangential strain method is more suitable for the actual situation.展开更多
BACKGROUND Hallux valgus(HV)is a common foot deformity that manifests with increasing age,especially in women.The associated foot pain causes impaired gait and decreases quality of life.Moderate and severe HV is a def...BACKGROUND Hallux valgus(HV)is a common foot deformity that manifests with increasing age,especially in women.The associated foot pain causes impaired gait and decreases quality of life.Moderate and severe HV is a deformity that is charac-terized by the involvement of lesser rays and requires complex surgical treatment.In this study,we attempted to develop a procedure for this condition.AIM To analyse the treatment results of patients who underwent simultaneous surgical correction of all parts of a static forefoot deformity.METHODS We conducted a prospective clinical trial between 2016 and 2021 in which 30 feet with moderate or severe HV associated with Tailor’s bunion and metatarsalgia were surgically treated via a new method involving surgical correction of all associated problems.This method included a modified Lapidus procedure,M2M3 tarsometatarsal arthrodesis,intermetatarsal fusion of the M4 and M5 bases,and the use of an original external fixation apparatus to enhance correction power.Preoperative,postoperative,and final follow-up radiographic data and American Orthopaedic Foot and Ankle Society(AOFAS)scores were compared,and P values<0.05 were considered to indicate statistical significance.RESULTS The study included 28 females(93.3%)and 2 males feet(6.7%),20(66.7%)of whom had a moderate degree of HV and 10(33.3%)of whom had severe deformity.M2 and M3 metatarsalgia was observed in 21 feet,and 9 feet experienced pain only at M2.The mean follow-up duration was 11 months.All patients had good correction of the HV angle[preoperative median,36.5 degrees,interquartile range(IQR):30-45;postoperative median,10 degrees,IQR:8.8-10;follow-up median,11.5 degrees,IQR:10-14;P<0.01].At follow-up,metatarsalgia was resolved in most patients(30 vs 5).There was a clinically negligible decrease in the corrected angles at the final follow-up,and the overall AOFAS score was significantly better(median,65 points,IQR:53.8-70;vs 80 points,IQR:75-85;P<0.01).CONCLUSION The developed method showed good sustainability of correction 展开更多
The mechanical mismatch effect frequently occurs in the dissimilar materials welded joints, thus leading to plastic gradient at the interface between the weld and heat-affected zone(HAZ). In this work, the boron steel...The mechanical mismatch effect frequently occurs in the dissimilar materials welded joints, thus leading to plastic gradient at the interface between the weld and heat-affected zone(HAZ). In this work, the boron steel and Q235 steel were selected for laser tailor welding,which obtained boron/Q235 steel tailor-welded blanks(TWBs). The method of welding with synchronous thermal field(WSTF) was utilized to eliminate the mismatch effects in TWBs. The WSTF was employed to adjust cooling rates of welded joints, thereby intervening in the solidification behaviors and phase transition of the molten pool. Boron/Q235 steel was welded by laser under conventional and WSTF(300-600 ℃) conditions, respectively. The results show that the microstructure of weld and HAZ(boron) was adequately transitioned to ferrites and pearlites instead of abundant martensite by WSTF. Meanwhile, the discrepancy of microhardness and yield strength between various regions of welded joints was greatly reduced, and the overall plasticity of welded joints was enhanced by WSTF. It is indicated that WSTF can effectively contribute to reducing plastic gradient and achieving mechanical congruity in welded joints by restraining the generation of hardbrittle phase, which could significantly improve the formability of TWBs in subsequent hot stamping.展开更多
The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle...The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle of volume invariance. Based on this assumption, the formula for time step of vertical motion of rolls was proposed and the time-displacement curve of the verti- cal motion of rolls was established. In the preliminary simulation, the time-displacement curve was used as an initial method to control the vertical motion of rolls. Based on the simulation result, the formula for vertical velocity of roll in variable gauge rolling was derived from the common rolling principle. According to the formula, reasonable vertical velocity of rolls in the subsequent simulation was determined. It can accurately control the motion of rolls along the vertical direction. The desired thickness and out- line profile of transition zone were acquired and the formula proved effective by the simulation. Further analysis shows that the di fference of thickness in the thick zone and the thin zone of TRB, length of the transition zone of TRB, radius of work rolls and rota- tion speed of rolls have a significant effect on the vertical velocity of rolls.展开更多
In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation...In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation and stamping experiments.Fundamental theories of springback were analyzed.The stamping and springback processes of annealed 1.2 / 2.0mm TRB , 1.2mm and 2.0mm plates for U-channel were simulated , and the simulation results were compared with the experiments.The results indicate that the springback of TRB falls in between those of the 1.2mm and 2.0mm plates.It is desirable for the TRB U-channel to have die clearance of 1.1times maximum blank thickness and friction coefficient of about 0.12 , and longer thickness transition zone is preferable.The simulation data demonstrate reasonably good agreement with the experiments.展开更多
Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the loc...Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the local carrying capacity of the stamping parts, but also determines the maximum value and variation characteristics of rolling force. How to get the best transitional zone＇s shape is a key problem for production of tailor rolled blank. A double power function is put forward using for transitional curve, which is continuous and smooth at all connection points inde- pendent of its parameters, so the sudden change of mechanical parameters during rolling and forming process can be avoided. At the same time, the velocity formula and restriction for arbitrary transitional curve are derived to preset vertical velocity of the roller and judge whether the curve can be rolled successfully or not. Then, the finite element method （FEM） is used to verify the precision of velocity formula and study the mechanical characteristics of different curves. Finally, a method to obtain the optimal curve equation is put forward and verified.展开更多
In practical engineering, finite element（FE） modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis...In practical engineering, finite element（FE） modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded（FSW） blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone（HAZ）, thermal-mechanically affected zone（TMAZ） and weld nugget（WN）. Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation（DIC） techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50634030,50974039)
文摘Variable gauge rolling （VGR） is a new technology to produce flat products with different thicknesses （FDT）, which could be used to replace conventional fiat products in order to save metals and reduce structure mass. The method of VGR was introduced for investigating new problems in rolling theory of VGR, and the new formulas for calculating parameters of VGR were proposed. Besides, some results of numerical simulation by finite elemen~ method were described. As an example, the products applications of FDT in bridge construction, ship building and auto manufacturing were presented. Finally, the prospects for VGR and FDT were discussed.
基金financially supported by the National Natural Science Foundation of China (Nos. 51105068 and 51475086)the Fundamental Research Funds for the Central Universities (Nos. N130323003 and XNB201413)the Science and Technology Research Project for Higher School of Hebei Province (No. Z2013068)
文摘The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension was set up, and the deformation formulae for the thinner side and for the thicker side were derived to quantify the deformation of TRB. On this basis, uniaxial tension tests on TRB and ordinary blanks （the thinner side and the thicker side of TRB） were conducted. Lagrange polynomial interpolation method was adopted to construct the stress-strain fields of unannealed and annealed TRBs for solving TRB material parameters, and then, uniaxial tension simulation on TRB was completed. Deformations and properties of unannealed TRB were compared with those of annealed TRB, and the thinner side and the thicker side were also compared. Finally, the research results were explained by metallurgical structure. The results show that nonuniform deformation happens in TRB during uniaxial tension, and the necking occurs on the thinner side. The agreement of analysis, test and simulation confirms the correctness of the analytical model and the deformation formulae. The findings of this paper can lay the foundation for the future study on TRB stamping formability and provide a way for TRB modeling.
基金supported by the National Natural Science Foundation of China (Nos. 51034009, 51374069 and 51174249).
文摘Variable gauge rolling （VGR） is a new technology for producing the materials which have the advantage of lightweight due to optimized thickness according to load distribution. The new progresses in the theoretical research and application of VGR are reviewed in this paper. Two basic equations, VGR-f and VGR-s, were deduced. The former is a new differential equation of force equilibrium, and the latter is a new form of formula for the law of mass conservation. Both of them provide a new base for the development of VGR analysis. As the examples of VGR＇s application, tailor rolled blank （TRB） and longitudinal profile （LP） plate are introduced. Now TRBs are only produced in Germany and China, and have been used in the automotive manufacturing to play an important role in lightweight design. LP plates have been used in shipbuilding and bridge construction, and promised a bright prospect in reducing construction weight. In addition, new technologies and applications of VGR emerge constantly. Tailor welded strips and tailor rolled strips with variable thickness across the width can be used for progressive die and roll forming. The 3D profiled blank can be obtained by two-step rolling process. Tailor tubes witli the variable wail thickness are an efficient way to reduce the weight. The blank with tailored thickness and mechanical property is also under development. Above products based on the tailored ideas provide a new materials-warehouse for the designers to select so as to meet the needs of weight reducing and material saving.
基金This work was financiallysupportedbythe Research Grants(NN-8501)from Ministry ofCommerce,Industry and Energyin Republic ofKorea.
文摘Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.
基金Item Sponsored by National Natural Science Foundation of China(51105068,51475086)Fundamental Research Funds for the Central Universities of China(N130323003,XNB201413)Science and Technology Research Project for Higher School of Hebei Province of China(Z2013068)
文摘The process of automobile lightweight can be promoted by the application of tailor rolled blank（TRB）in the automobile industry.Therefore,research on the formability of TRB is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight.Aiming at the present condition of lack of researches on the influence of characteristic parameters on TRB drawing process,the drawing formability of TRB was studied with a combination method of simulation and experiment by taking square box as the research object.Firstly,drawing simulation and experiment of TRB were carried out.Then,effects of thickness transition zone（TTZ）position and blank size on the drawing formability of TRB were analyzed.Forming limit and TTZ movement for TRB square box during the drawing process were respectively discussed,when transition zones of TRB were located at different positions and blanks were of different sizes.The results indicate that lubrication condition exerts greater influence on TRB forming limit in comparison with TTZ movement,and the smaller blank size and TTZ being located at the blank center or slightly offset to the thinner side are preferable for acquiring greater forming limit and smaller TTZ movement.
基金supported by the International Cooperation Projects between China and Singapore under Grant No.2009DFA12640
文摘The Brillouin gain properties in a double-clad As2Se3 photonic crystal fiber（PCF）are simulated based on the finite-element method（FEM）.The results indicate that the Brillouin gain spectrum（BGS）of our proposed chalcogenide PCF exhibits a multipeaked behavior and has a high Brillouin gain coefficient.We also find that a larger size of inner cladding air holes will lead to a more pronounced second peak in the BGS.On the other hand,the size of the outer cladding has nearly no effect on the BGS behavior.Through these results,one can tailor the Stimulated Brillouin scattering effect in PCFs for a wide range of applications.
文摘The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simulation methods have been used to compare and analyze the springback characteristics of equal thickness blanks and tailor rolled blanks in U-channel forming.From the results,the overall springback angles of tailor rolled blanks at thin and thick sides are respectively 106.79° and 99.705°,which are both lower than those of the corresponding equal thickness blanks.Due to the existence of the thickness transition zone,the stress distribution in thin and thick sides of blanks is changed.The location of dangerous region in thin side of tailor rolled blanks is closer to the end of side,and the thick side moved to the middle of straight wall,which are different with the equal thickness blanks.Afterwards,the released quantitles of tangential stress and strain per unit section of blank are adopted to calculate relative springback angles and give novel evaluation criteria for qualitatively analyzing the amount of springback angles.By comparing the results,it shows that the tangential strain method is more suitable for the actual situation.
文摘BACKGROUND Hallux valgus(HV)is a common foot deformity that manifests with increasing age,especially in women.The associated foot pain causes impaired gait and decreases quality of life.Moderate and severe HV is a deformity that is charac-terized by the involvement of lesser rays and requires complex surgical treatment.In this study,we attempted to develop a procedure for this condition.AIM To analyse the treatment results of patients who underwent simultaneous surgical correction of all parts of a static forefoot deformity.METHODS We conducted a prospective clinical trial between 2016 and 2021 in which 30 feet with moderate or severe HV associated with Tailor’s bunion and metatarsalgia were surgically treated via a new method involving surgical correction of all associated problems.This method included a modified Lapidus procedure,M2M3 tarsometatarsal arthrodesis,intermetatarsal fusion of the M4 and M5 bases,and the use of an original external fixation apparatus to enhance correction power.Preoperative,postoperative,and final follow-up radiographic data and American Orthopaedic Foot and Ankle Society(AOFAS)scores were compared,and P values<0.05 were considered to indicate statistical significance.RESULTS The study included 28 females(93.3%)and 2 males feet(6.7%),20(66.7%)of whom had a moderate degree of HV and 10(33.3%)of whom had severe deformity.M2 and M3 metatarsalgia was observed in 21 feet,and 9 feet experienced pain only at M2.The mean follow-up duration was 11 months.All patients had good correction of the HV angle[preoperative median,36.5 degrees,interquartile range(IQR):30-45;postoperative median,10 degrees,IQR:8.8-10;follow-up median,11.5 degrees,IQR:10-14;P<0.01].At follow-up,metatarsalgia was resolved in most patients(30 vs 5).There was a clinically negligible decrease in the corrected angles at the final follow-up,and the overall AOFAS score was significantly better(median,65 points,IQR:53.8-70;vs 80 points,IQR:75-85;P<0.01).CONCLUSION The developed method showed good sustainability of correction
基金the Natural Science Foundation of Fujian Province(2021J01299)school-enterprise cooperation project supported by Shandong Hongao Automotive Lightweight Technology Co.,Ltd.
文摘The mechanical mismatch effect frequently occurs in the dissimilar materials welded joints, thus leading to plastic gradient at the interface between the weld and heat-affected zone(HAZ). In this work, the boron steel and Q235 steel were selected for laser tailor welding,which obtained boron/Q235 steel tailor-welded blanks(TWBs). The method of welding with synchronous thermal field(WSTF) was utilized to eliminate the mismatch effects in TWBs. The WSTF was employed to adjust cooling rates of welded joints, thereby intervening in the solidification behaviors and phase transition of the molten pool. Boron/Q235 steel was welded by laser under conventional and WSTF(300-600 ℃) conditions, respectively. The results show that the microstructure of weld and HAZ(boron) was adequately transitioned to ferrites and pearlites instead of abundant martensite by WSTF. Meanwhile, the discrepancy of microhardness and yield strength between various regions of welded joints was greatly reduced, and the overall plasticity of welded joints was enhanced by WSTF. It is indicated that WSTF can effectively contribute to reducing plastic gradient and achieving mechanical congruity in welded joints by restraining the generation of hardbrittle phase, which could significantly improve the formability of TWBs in subsequent hot stamping.
基金Sponsored by Natural Science Foundation of CQ CSTC of China(cstc2012jj A70001)
文摘The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle of volume invariance. Based on this assumption, the formula for time step of vertical motion of rolls was proposed and the time-displacement curve of the verti- cal motion of rolls was established. In the preliminary simulation, the time-displacement curve was used as an initial method to control the vertical motion of rolls. Based on the simulation result, the formula for vertical velocity of roll in variable gauge rolling was derived from the common rolling principle. According to the formula, reasonable vertical velocity of rolls in the subsequent simulation was determined. It can accurately control the motion of rolls along the vertical direction. The desired thickness and out- line profile of transition zone were acquired and the formula proved effective by the simulation. Further analysis shows that the di fference of thickness in the thick zone and the thin zone of TRB, length of the transition zone of TRB, radius of work rolls and rota- tion speed of rolls have a significant effect on the vertical velocity of rolls.
基金Item Sponsored by National Natural Science Foundation of China ( 10932003 , 50974039 , 50872126 )National Basic Research Program of China ( 2010CB832700 )Fundamental Research Funds for Central Universities of China ( 893324 , DUT11ZD202 )
文摘In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation and stamping experiments.Fundamental theories of springback were analyzed.The stamping and springback processes of annealed 1.2 / 2.0mm TRB , 1.2mm and 2.0mm plates for U-channel were simulated , and the simulation results were compared with the experiments.The results indicate that the springback of TRB falls in between those of the 1.2mm and 2.0mm plates.It is desirable for the TRB U-channel to have die clearance of 1.1times maximum blank thickness and friction coefficient of about 0.12 , and longer thickness transition zone is preferable.The simulation data demonstrate reasonably good agreement with the experiments.
基金Item Sponsored by National Science and Technology Support Program of China(2011BAF15B02)Natural Science Foundation of Hebei Province of China(E2012203108)+2 种基金Science and Technology Research Program of the Colleges and Universities in Hebei of China(ZD2014034)Independent Research Project of Yanshan University of China(14LGA003)Open Project of National Engineering Research Center for Equipment and Technology of Cold Rolling Strip of China(NECSR-201206)
文摘Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the local carrying capacity of the stamping parts, but also determines the maximum value and variation characteristics of rolling force. How to get the best transitional zone＇s shape is a key problem for production of tailor rolled blank. A double power function is put forward using for transitional curve, which is continuous and smooth at all connection points inde- pendent of its parameters, so the sudden change of mechanical parameters during rolling and forming process can be avoided. At the same time, the velocity formula and restriction for arbitrary transitional curve are derived to preset vertical velocity of the roller and judge whether the curve can be rolled successfully or not. Then, the finite element method （FEM） is used to verify the precision of velocity formula and study the mechanical characteristics of different curves. Finally, a method to obtain the optimal curve equation is put forward and verified.
基金Supported by National Natural Science Foundation of China(Grant No.51375346)Doctoral Fund of Ministry of Education of China(Grant No.20110072110056)
文摘In practical engineering, finite element（FE） modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded（FSW） blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone（HAZ）, thermal-mechanically affected zone（TMAZ） and weld nugget（WN）. Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation（DIC） techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.
