Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad appli...Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad application prospect in industrial manufactur-ing.Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field.In this review,metals were classified according to their crystal structures.The effects of ultrasonic vibration on the microstructure of face-centered cubic,body-centered cubic,and hexagonal close-packed metals during plastic forming and the mech-anism underlying ultrasonic vibration forming were reviewed.The main challenges and future research direction of the ultrasonic vibra-tion plastic forming of metals were also discussed.展开更多
Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affe...Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects: testing, characterizing, modeling and optimization/controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.展开更多
A combined method of selective laser sintering (SLS) and cold isostatic pressing (CIP) was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost...A combined method of selective laser sintering (SLS) and cold isostatic pressing (CIP) was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K展开更多
Metal flowing has been numerically simulated for synchronizer hub at different forming conditions. The influences of billet shape, frictional factor,deformation degree and radius of rounded corner on form- ing for be...Metal flowing has been numerically simulated for synchronizer hub at different forming conditions. The influences of billet shape, frictional factor,deformation degree and radius of rounded corner on form- ing for been studied and the processing parameters have been optimized. On the basis, a new technol- ogy of refilling multiplicity forming has been put forward and workpiece that meets the requirement of synchronizer hub has been manufactured.展开更多
The bulk metal forming processes were simulated by using a one-step finite element(FE)approach based on deformation theory of plasticity,which enables rapid prediction of final workpiece configurations and stress/stra...The bulk metal forming processes were simulated by using a one-step finite element(FE)approach based on deformation theory of plasticity,which enables rapid prediction of final workpiece configurations and stress/strain distributions.This approach was implemented to minimize the approximated plastic potential energy derived from the total plastic work and the equivalent external work in static equilibrium,for incompressibly rigid-plastic materials,by FE calculation based on the extremum work principle.The one-step forward simulations of compression and rolling processes were presented as examples,and the results were compared with those obtained by classical incremental FE simulation to verify the feasibility and validity of the proposed method.展开更多
This paper presents an experimental research on extrude-bulge forming of tee tubes with plastic medium,an universal device especially designed for this forming process and some parameters having effects on the forming...This paper presents an experimental research on extrude-bulge forming of tee tubes with plastic medium,an universal device especially designed for this forming process and some parameters having effects on the forming process.Comparison of results of the theoretical analysis with experimental results shows a very good agreement between them.展开更多
MEM(model element method) is proposed to resolve the present difficulties and problems in CAE about plastic forming of material.There are four advantages when MEM is integrated with FEM(finite element method) and UBM(...MEM(model element method) is proposed to resolve the present difficulties and problems in CAE about plastic forming of material.There are four advantages when MEM is integrated with FEM(finite element method) and UBM(upper boundary element method).First,it can make full use of their own advantages and overcome their own disadvantages;second,it can analyse material plastic fluid expediently;third,it can optimize design;finally,it can improve technological content and application effect of CAE software.Based on introducing the principle of MEM briefly,features and applications of MEM are pointed out.In conclusion,a new analysis method for plastic forming comes forth.展开更多
The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In o...The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.展开更多
A creating technology of the part forming was discussed and finite volume method(FVM)was used to simulate the forming process of the non-symmetrical axostyle spring core-bar.The results show that the no-even radial fl...A creating technology of the part forming was discussed and finite volume method(FVM)was used to simulate the forming process of the non-symmetrical axostyle spring core-bar.The results show that the no-even radial flange on the top part of the eccentric peachy surface can remarkably block the metal flow and the eccentric peachy can be filled contentedly.Increasing the radius of punch near the inner pocket,the head bulge also can be filled contentedly.The temperature distribution in the part and the forming force,which helps to decide the forming temperature and to select the equipment,was also analyzed.The comparison between the simulation and the experiment result shows that they are accordant.展开更多
The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control...The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.展开更多
A numerical analysis of mechanical behavior of aluminum alloy sheet under cyclic plastic deformation was investigated.Forming limit at fracture was derived from Cockcroft-Latham ductile damage criterion.The strain pat...A numerical analysis of mechanical behavior of aluminum alloy sheet under cyclic plastic deformation was investigated.Forming limit at fracture was derived from Cockcroft-Latham ductile damage criterion.The strain path of bending center of incremental roller hemming could be accepted as a kind of plane strain bending deformation process.Incremental rope roller hemming could be used to alleviate ductile fracture behavior by changing the stress state of the hemming-effected area.SEM observation on the fracture surface indicates that cyclic plastic deformation affects ductile fracture mechanism.展开更多
Advanced high-strength steels have been widely used to improve the crashworthiness and lightweight of vehicles.Different from the popular cold stamping,hot forming of boron-alloyed manganese steels,such as 22MnB5,coul...Advanced high-strength steels have been widely used to improve the crashworthiness and lightweight of vehicles.Different from the popular cold stamping,hot forming of boron-alloyed manganese steels,such as 22MnB5,could produce ultra-high-strength steel parts without springback and with accurate control of dimensions.Moreover,hot-formed medium-Mn steels could have many advantages,including better mechanical properties and lower production cost,over hot-formed 22MnB5.This paper reviews the hot forming process in the automotive industry,hot-formed steel grades,and medium-Mn steel grades and their application in hot forming in depth.In particular,the adaptabilities of medium-Mn steels and the presently popular 22MnB5 into hot forming were compared thoroughly.Future research should focus on the technological issues encountered in hot forming of medium-Mn steels to promote their commercialization.展开更多
Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or...Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or minimum plastic work path), the concept of an optimum forming path is proposed in this paper. The forming path can be described by the initial configuration, objective configuration and a series of intermediate configurations. According to the deformation theory and constitutive equation in ideal path forming, a finite element method to calculate the initial configuration is set up. The functional to determinate intermediate configurations is introduced and the numerical method to solve the configuration is presented. Based on the method presented in the paper, multi-step multi-point forming tests for sheet metal are designed. The test results demonstrate that when the sheet is deformed along an approximate optimum forming path, the maximum deformation curvature for the sphere objective shape and saddle objective shape are 11%∼40% and 15%∼50% greater than those of a sheet deformed along a common path respectively.展开更多
The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mo...The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co(Cu)Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry(XRD), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC) were used to investigate the glassy alloys structure and their glass forming ability(GFA). In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy(SEM) were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr(56) Co(22) Cu6 Al(16) alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr(56) Co(22) Cu)6 Al(16) BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.展开更多
It is necessary to use the integrated stainless steel pipe having two fitting bodies without welds while train travelling at high speed. In order to form this type of integrated stainless steel pipe, the method of pre...It is necessary to use the integrated stainless steel pipe having two fitting bodies without welds while train travelling at high speed. In order to form this type of integrated stainless steel pipe, the method of preforming combined finish forming process is developed. The preforming process is characterized by flaring combined upsetting for left fitting body which is like a flange, and is characterized by tube axial compressive process under die constraint for right fitting body which is like a double-wall pipe. The finite element simulations of the processes are carried out by software package DEFORM, and the results indicate that: 1) left or right fitting body can be formed by a two-step forming process without folding and under-filling defects; 2) by using two-step forming, strain and stress in left fitting body are larger than those in right fitting body, and deformation in right fitting body is more homogenous than the deformation in left fitting body; 3) two or more preforming steps may be needed for left fitting body considering the distributions of strain and stress.展开更多
With the continuous expansion of the application range of microelectromechanical systems,microdevice forming technology has achieved remarkable results.However,it is challenging to develop new microforming processes t...With the continuous expansion of the application range of microelectromechanical systems,microdevice forming technology has achieved remarkable results.However,it is challenging to develop new microforming processes that are low cost,environmentally friendly,and highly flexible;the high-energy shock wave in a cavitation bubble's collapse process is used as the loading force.Herein,a new process for the microbulging of the water-jet cavitation is proposed.A series of experiments involving the water-jet cavitation shock microbulging process for TA2 titanium foil is performed on an experimental system.The microforming feasibility of the water-jet cavitation is investigated by characterizing the shape of the formed part.Subsequently,the effects of the main parameters of the water-jet cavitation on the bulging profile,forming depth,surface roughness,and bulging thickness distribution of TA2 titanium foil are revealed.The results show that the plastic deformation increases nonlinearly with the incident pressure.When the incident pressure is 20 MPa,the maximum deformation exceeds 240 pm,and the thickness thinning ratio changes within 10%.The microbulging feasibility of water-jet cavitation is verified by this phenomenon.展开更多
The lightweight of high-end equipment relies on high mechanical properties magnesium(Mg) alloy structural components, because it is the best way to improve equipment service performance and reduce energy consumption. ...The lightweight of high-end equipment relies on high mechanical properties magnesium(Mg) alloy structural components, because it is the best way to improve equipment service performance and reduce energy consumption. This article summarizes the current progress and characteristics of large-scale high-performance Mg alloy components by analyzing the strengthening-toughening mechanisms, characteristics of plastic forming, and the preparation of large high mechanical properties forging blanks. Due to the lack of breakthroughs in the key technologies for forming large-scale Mg alloy components, their uniformity of mechanical properties and consistency are poor, the forming accuracy of components is low, and the production cost is high, which limit their engineering application and restrict the lightweight level of high-end equipment. In view of the above problems, the forming trends and research directions of large-scale and high mechanical properties Mg alloy components are proposed in this paper. It can provide help for the breakthrough of the key technology of large-scale Mg alloy components with high mechanical properties and expand the application of Mg alloy in high-end products.展开更多
An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the int...An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the integrally stiffened aircraft panels. Based on the in-depth analysis of the mechanics of the bending and springback of the detailed model and the equivalent model of the integral panels,the plastic equivalent model of the virtual material with special initial yield stress and hardening coefficients was constructed. FEM results indicate that the objective of getting the similar contour with the same press bend forming path is achieved with the error less than 6%,and the efficiency of FEM simulation is improved by more than 80%. The plastic equivalent model is valuable and essential for the further research on the press bend forming process of large scale complicated integral panels.展开更多
The current study performed a finite element analysis of the strain localization behavior of a voided ductile material using a non-local plasticity formulation in which the yield strength depends on both an equivalent...The current study performed a finite element analysis of the strain localization behavior of a voided ductile material using a non-local plasticity formulation in which the yield strength depends on both an equivalent plastic strain measurement (hardening parameter) and Laplacian equivalent. The introduction of gradient terms to the yield function was found to play an important role in simulating the strain localization behavior of the voided ductile material. The effect of the mesh size and characteristic length on the strain localization were also investigated. An FEM simulation based on the proposed non-local plasticity revealed that the load-strain curves of the voided ductile material subjected to plane strain tension converged to one curve, regardless of the mesh size. In addition, the results using non-local plasticity also exhibited that the dependence of the deformation behavior of the material on the mesh size was much less sensitive than that with classical local plasticity and could be successfully eliminated through the introduction of a large value for the characteristic length.展开更多
An approximate macroscopic yield criterion for anisotropic porous sheet metals is adopted in a failure prediction methodology that can be used to investigate the failure of sheet metals under forming operations. This...An approximate macroscopic yield criterion for anisotropic porous sheet metals is adopted in a failure prediction methodology that can be used to investigate the failure of sheet metals under forming operations. This failure prediction methodology is developed based on the Marciniak-Kuczynski approach by assuming a slightly higher void volume fraction inside randomly oriented imperfecte analysis. Here, a nonproportional deformation history including relative rotation of principal stretch directions is identified in a selected critical element of an aluminum sheet from a FEM fender forming simulation. Based on the failure prediction methodology, the failure of the critical sheet element is investigated under the non-proportional deformation history. The results show that thiven non-proportional deformation history.展开更多
基金supported by the National Key R&D Program of China(No.2022YFE0121300)the Introduction Plan for High end Foreign Experts,China(No.G2023105001L)the Young Foreign Talent Program,China(No.QN2023105001L).
文摘Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad application prospect in industrial manufactur-ing.Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field.In this review,metals were classified according to their crystal structures.The effects of ultrasonic vibration on the microstructure of face-centered cubic,body-centered cubic,and hexagonal close-packed metals during plastic forming and the mech-anism underlying ultrasonic vibration forming were reviewed.The main challenges and future research direction of the ultrasonic vibra-tion plastic forming of metals were also discussed.
基金Projects(50905144,51275415)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by the Program for New Century Excellent Talents in University,China
文摘Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects: testing, characterizing, modeling and optimization/controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.
基金Project(2007AA03Z115) supported by the High-Tech Research and Development Program of China
文摘A combined method of selective laser sintering (SLS) and cold isostatic pressing (CIP) was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K
文摘Metal flowing has been numerically simulated for synchronizer hub at different forming conditions. The influences of billet shape, frictional factor,deformation degree and radius of rounded corner on form- ing for been studied and the processing parameters have been optimized. On the basis, a new technol- ogy of refilling multiplicity forming has been put forward and workpiece that meets the requirement of synchronizer hub has been manufactured.
基金Project(50575143)supported by the National Natural Science Foundation of ChinaProject(20040248005)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The bulk metal forming processes were simulated by using a one-step finite element(FE)approach based on deformation theory of plasticity,which enables rapid prediction of final workpiece configurations and stress/strain distributions.This approach was implemented to minimize the approximated plastic potential energy derived from the total plastic work and the equivalent external work in static equilibrium,for incompressibly rigid-plastic materials,by FE calculation based on the extremum work principle.The one-step forward simulations of compression and rolling processes were presented as examples,and the results were compared with those obtained by classical incremental FE simulation to verify the feasibility and validity of the proposed method.
文摘This paper presents an experimental research on extrude-bulge forming of tee tubes with plastic medium,an universal device especially designed for this forming process and some parameters having effects on the forming process.Comparison of results of the theoretical analysis with experimental results shows a very good agreement between them.
文摘MEM(model element method) is proposed to resolve the present difficulties and problems in CAE about plastic forming of material.There are four advantages when MEM is integrated with FEM(finite element method) and UBM(upper boundary element method).First,it can make full use of their own advantages and overcome their own disadvantages;second,it can analyse material plastic fluid expediently;third,it can optimize design;finally,it can improve technological content and application effect of CAE software.Based on introducing the principle of MEM briefly,features and applications of MEM are pointed out.In conclusion,a new analysis method for plastic forming comes forth.
基金Supported by National Natural Science Foundation of China(Grant No.51335009)Major National Science and Technology Project of China(Grant No.2011ZX04001-011)
文摘The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.
基金Project of Science and Technology Foundation of Shanghai Committee,China(No.04NB14)
文摘A creating technology of the part forming was discussed and finite volume method(FVM)was used to simulate the forming process of the non-symmetrical axostyle spring core-bar.The results show that the no-even radial flange on the top part of the eccentric peachy surface can remarkably block the metal flow and the eccentric peachy can be filled contentedly.Increasing the radius of punch near the inner pocket,the head bulge also can be filled contentedly.The temperature distribution in the part and the forming force,which helps to decide the forming temperature and to select the equipment,was also analyzed.The comparison between the simulation and the experiment result shows that they are accordant.
文摘The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.
基金Project(2010CB731703) supported by the National Basic Research Program of China Project(0804) supported by the Shanghai Automotive Industry Corporation Foundation,ChinaProject(MSV-2010-03) supported by State Key Laboratory of Mechanical System and Vibration,Shanghai Jiao Tong University,China
文摘A numerical analysis of mechanical behavior of aluminum alloy sheet under cyclic plastic deformation was investigated.Forming limit at fracture was derived from Cockcroft-Latham ductile damage criterion.The strain path of bending center of incremental roller hemming could be accepted as a kind of plane strain bending deformation process.Incremental rope roller hemming could be used to alleviate ductile fracture behavior by changing the stress state of the hemming-effected area.SEM observation on the fracture surface indicates that cyclic plastic deformation affects ductile fracture mechanism.
基金The authors acknowledge the financial supports from the National Natural Science Foundation of China(Nos.51861135302 and 51831002)Fundamental Research Funds for the Central Universities,China(No.FRF-TP-18-002C2).
文摘Advanced high-strength steels have been widely used to improve the crashworthiness and lightweight of vehicles.Different from the popular cold stamping,hot forming of boron-alloyed manganese steels,such as 22MnB5,could produce ultra-high-strength steel parts without springback and with accurate control of dimensions.Moreover,hot-formed medium-Mn steels could have many advantages,including better mechanical properties and lower production cost,over hot-formed 22MnB5.This paper reviews the hot forming process in the automotive industry,hot-formed steel grades,and medium-Mn steel grades and their application in hot forming in depth.In particular,the adaptabilities of medium-Mn steels and the presently popular 22MnB5 into hot forming were compared thoroughly.Future research should focus on the technological issues encountered in hot forming of medium-Mn steels to promote their commercialization.
文摘Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or minimum plastic work path), the concept of an optimum forming path is proposed in this paper. The forming path can be described by the initial configuration, objective configuration and a series of intermediate configurations. According to the deformation theory and constitutive equation in ideal path forming, a finite element method to calculate the initial configuration is set up. The functional to determinate intermediate configurations is introduced and the numerical method to solve the configuration is presented. Based on the method presented in the paper, multi-step multi-point forming tests for sheet metal are designed. The test results demonstrate that when the sheet is deformed along an approximate optimum forming path, the maximum deformation curvature for the sphere objective shape and saddle objective shape are 11%∼40% and 15%∼50% greater than those of a sheet deformed along a common path respectively.
基金Iran University of Science and Technology for the financial support
文摘The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co(Cu)Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry(XRD), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC) were used to investigate the glassy alloys structure and their glass forming ability(GFA). In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy(SEM) were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr(56) Co(22) Cu6 Al(16) alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr(56) Co(22) Cu)6 Al(16) BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.
基金Project(51305334)supported by the National Natural Science Foundation of ChinaProject(51335009)supported by the National Natural Science Foundation of China for Key Program+1 种基金Project(CXY1442(4))supported by the Science and Technology Planning Project of Xi’an,ChinaProject supported by Shaanxi Province Postdoctoral Science Research Program of China
文摘It is necessary to use the integrated stainless steel pipe having two fitting bodies without welds while train travelling at high speed. In order to form this type of integrated stainless steel pipe, the method of preforming combined finish forming process is developed. The preforming process is characterized by flaring combined upsetting for left fitting body which is like a flange, and is characterized by tube axial compressive process under die constraint for right fitting body which is like a double-wall pipe. The finite element simulations of the processes are carried out by software package DEFORM, and the results indicate that: 1) left or right fitting body can be formed by a two-step forming process without folding and under-filling defects; 2) by using two-step forming, strain and stress in left fitting body are larger than those in right fitting body, and deformation in right fitting body is more homogenous than the deformation in left fitting body; 3) two or more preforming steps may be needed for left fitting body considering the distributions of strain and stress.
基金Supported by Nati onal Natural Science Foundation of China(Grant Nos.51575245,51679112)Jiangsu Province Key Research and Development Program of China(Grant No.BE2016161),Jiangsu Province"Six Tale nts Peak"Project of China(Grant No.XNYQC-002).
文摘With the continuous expansion of the application range of microelectromechanical systems,microdevice forming technology has achieved remarkable results.However,it is challenging to develop new microforming processes that are low cost,environmentally friendly,and highly flexible;the high-energy shock wave in a cavitation bubble's collapse process is used as the loading force.Herein,a new process for the microbulging of the water-jet cavitation is proposed.A series of experiments involving the water-jet cavitation shock microbulging process for TA2 titanium foil is performed on an experimental system.The microforming feasibility of the water-jet cavitation is investigated by characterizing the shape of the formed part.Subsequently,the effects of the main parameters of the water-jet cavitation on the bulging profile,forming depth,surface roughness,and bulging thickness distribution of TA2 titanium foil are revealed.The results show that the plastic deformation increases nonlinearly with the incident pressure.When the incident pressure is 20 MPa,the maximum deformation exceeds 240 pm,and the thickness thinning ratio changes within 10%.The microbulging feasibility of water-jet cavitation is verified by this phenomenon.
基金The financial support from Joint Funds of the National Natural Science Foundation of China (No.U20A20230)the Natural Science Foundation of China (No.52075501)+1 种基金Young Elite Scientists Sponsorship Program by CAST (2022QNRC001)the Key R&D program of Shanxi Province (No.2020XXX015)。
文摘The lightweight of high-end equipment relies on high mechanical properties magnesium(Mg) alloy structural components, because it is the best way to improve equipment service performance and reduce energy consumption. This article summarizes the current progress and characteristics of large-scale high-performance Mg alloy components by analyzing the strengthening-toughening mechanisms, characteristics of plastic forming, and the preparation of large high mechanical properties forging blanks. Due to the lack of breakthroughs in the key technologies for forming large-scale Mg alloy components, their uniformity of mechanical properties and consistency are poor, the forming accuracy of components is low, and the production cost is high, which limit their engineering application and restrict the lightweight level of high-end equipment. In view of the above problems, the forming trends and research directions of large-scale and high mechanical properties Mg alloy components are proposed in this paper. It can provide help for the breakthrough of the key technology of large-scale Mg alloy components with high mechanical properties and expand the application of Mg alloy in high-end products.
基金Project(50675010) supported by the National Natural Science Foundation of China
文摘An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the integrally stiffened aircraft panels. Based on the in-depth analysis of the mechanics of the bending and springback of the detailed model and the equivalent model of the integral panels,the plastic equivalent model of the virtual material with special initial yield stress and hardening coefficients was constructed. FEM results indicate that the objective of getting the similar contour with the same press bend forming path is achieved with the error less than 6%,and the efficiency of FEM simulation is improved by more than 80%. The plastic equivalent model is valuable and essential for the further research on the press bend forming process of large scale complicated integral panels.
文摘The current study performed a finite element analysis of the strain localization behavior of a voided ductile material using a non-local plasticity formulation in which the yield strength depends on both an equivalent plastic strain measurement (hardening parameter) and Laplacian equivalent. The introduction of gradient terms to the yield function was found to play an important role in simulating the strain localization behavior of the voided ductile material. The effect of the mesh size and characteristic length on the strain localization were also investigated. An FEM simulation based on the proposed non-local plasticity revealed that the load-strain curves of the voided ductile material subjected to plane strain tension converged to one curve, regardless of the mesh size. In addition, the results using non-local plasticity also exhibited that the dependence of the deformation behavior of the material on the mesh size was much less sensitive than that with classical local plasticity and could be successfully eliminated through the introduction of a large value for the characteristic length.
文摘An approximate macroscopic yield criterion for anisotropic porous sheet metals is adopted in a failure prediction methodology that can be used to investigate the failure of sheet metals under forming operations. This failure prediction methodology is developed based on the Marciniak-Kuczynski approach by assuming a slightly higher void volume fraction inside randomly oriented imperfecte analysis. Here, a nonproportional deformation history including relative rotation of principal stretch directions is identified in a selected critical element of an aluminum sheet from a FEM fender forming simulation. Based on the failure prediction methodology, the failure of the critical sheet element is investigated under the non-proportional deformation history. The results show that thiven non-proportional deformation history.