The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic s...The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic strain,contact pressure,and area.The interface promotes lubrication and support when wall angles were≤40°,a 0.5 mm-thin sheet was used,and a 10 mm-large tool radius was employed.This mainly results in micro-plowing and plastic extrusion flow,leading to lower friction coefficient.However,when wall angles exceed 40°,significant plastic strain roughening occurs,leading to inadequate lubrication on the newly formed surface.Increased sheet thickness and decreased tool radius elevate contact pressure.These actions trigger micro-cutting and adhesion,potentially leading to localized scuffing and dimple tears,and higher friction coefficient.The friction mechanisms remain unaffected by the part’s plane curve features.As the forming process progresses,abrasive wear intensifies,and surface morphology evolves unfavorably for lubrication and friction reduction.展开更多
The forming quality of metal bipolar plate(BPP)flow channels in proton exchange membrane fuel cells(PEMFCs)is a key factor affecting battery performance.A flow channel with straight sidewalls and a low thinning rate c...The forming quality of metal bipolar plate(BPP)flow channels in proton exchange membrane fuel cells(PEMFCs)is a key factor affecting battery performance.A flow channel with straight sidewalls and a low thinning rate can enhance battery output.Roll forming,as a new technology for BPP production,offers advantages such as a low thinning rate and high efficiency.However,existing roll curve design methods struggle to accommodate both low thinning rates and straight sidewall angles simultaneously.This study aims to develop flow channels with right-angled sidewalls,which provide benefits such as a low thinning rate,reduced residual stress,and high accuracy.A roller tooth profile was designed to achieve a flow channel with right-angled sidewalls and minimal thinning.Simulations and experiments were conducted to validate the feasibility of this novel design method for the roll forming process.The study investigated the effects of roller tooth parameters on sidewall angle,thinning rate,and residual stress.A multifactor evaluation method was developed to optimize the tip fillet radius and the tooth profile backlash of the roller.The results indicated that the tip fillet radius and the tooth profile backlash were negatively correlated with the sidewall angle.As the tip fillet radius and tooth profile backlash increased,the thinning rate and residual stress decreased.With a tip fillet radius of 0.25 mm and a tooth profile backlash of 0.19 mm,the flow channel achieved an approximately right-angled sidewall,a maximum thinning rate of 7.7%,a 29.6%reduction in maximum residual stress,and maximum and average residual stress imbalance values of 7.1%and 3.2%,respectively.This study proposes a new design method for a right-angled sidewall runner roller gear profile,facilitating the roll forming of metal BPPs with right-angled sidewalls and minimal thinning.This method provides theoretical support for the large-scale application of roll forming in the manufacture of PEMFC BPPs.展开更多
The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co...The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.展开更多
A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on...A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on the three-dimensional morphology of TiB2 particles.Different preparation routes result in different reaction forms,which accounts for the morphology variation of TiB2 particles.When the Al-Ti-B master alloy is prepared using ＂halide salt＂ route,TiB2 particles exhibit hexagonal platelet morphology and are independent with each other.In addition,the reaction temperature almost does not have influence on the morphology of TiB2 particles.However,TiB2 particles exhibit different morphologies at different reaction temperatures when the master alloys are prepared with Al-3B and Ti sponge.When the master alloy is prepared at 850 ℃,a kind of TiB2 particle agglomeration forms with a size larger than 5 μm.The TiB2 particles change to layered stacking morphology even dendritic morphology with the reaction temperature reaching up to 1200 ℃.展开更多
The casting-forging combined technique and the closed die forging without flash-less are both new developed material working methods. The former can not only decrease forming operations of forgings, but also increase ...The casting-forging combined technique and the closed die forging without flash-less are both new developed material working methods. The former can not only decrease forming operations of forgings, but also increase the material utilization ratio. Therefore, it is applied to produce more complex forgings. The latter is required for forging precise parts without burrs. The alternator pole is a complex forging, which was usually produced by hot forging, upsetting-extrusion or upsetting-extrusion and bending processes. During these processes, not only the forming force is higher, but the material of burrs accounts for 30 percent or so of total required material. And burrs are difficult to remove in the sequential machining process. In accordance with defects exiting in current manufacturing of alternator poles by upsetting-extruding process, such as more material demand, higher forming force and difficulty of next machining, a casting-forging precision process of alternator poles was developed and investigated in this paper. In the process, the pole was formed by two operations. One is the pre-forming operation by casting. The other is the final forming operation by the closed precision forging process. This can not only shorten processes, decrease material and power demand, but also increase precision of forgings. First, the casting blocker was designed considering the casting process and the forging ratio and the mode of deformation. Then the die structure for closed precision forging was designed, and the closing device for forging dies with spring assemblies in order to provide the necessary closing force was also designed. Finally the forming processes was investigated by test and numerical simulation method to optimum process parameters and die structure design parameters. The result can provide basis for applying the process to manufacture poles in practice.展开更多
Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic...Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.展开更多
A new concept referred to the non-synchronous deformation effect of particle in sheet metal forming is proposed. The results of finite element analysis show that the flow resistance of sheet metal can be effectively r...A new concept referred to the non-synchronous deformation effect of particle in sheet metal forming is proposed. The results of finite element analysis show that the flow resistance of sheet metal can be effectively reduced and thus the forming property can be greatly improved if the moving and deformation state of the neighboring elements with equal perpendicular distance to the entrance contour of die is non-synchronous. Experiment tests are presented and the results agree well with FEA simulation. In addition, the mechanism of the non-synchronous effect is analyzed in detail.展开更多
Ductile damage often occurs during metal forming processes due to the large thermo-elasto （visco） plastic flow Iocalisation. This paper presents a numerical methodology, which aims to virtually improve any metal for...Ductile damage often occurs during metal forming processes due to the large thermo-elasto （visco） plastic flow Iocalisation. This paper presents a numerical methodology, which aims to virtually improve any metal forming processes. The methodology is based on elastoplastic constitutive equations accounting for nonlinear mixed isotropic and kinematic hardening strongly coupled with isotropic ductile damage. An adaptive remeshing scheme based on geometrical and physical error estimates including a kill element procedure is used. Some numerical results are presented to show the capability of the model to predict the damage initiation and growth during the metal forming processes.展开更多
In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre...In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre-forming by conventional forming,followed by incremental sheet forming.The main objective is analyzing strain evolution.The pre-forming induced in the conventional forming stage will determine the strain paths,directly influencing the strains produced by the incremental process.To conduct the study,in the conventional processes,strains were imposed in three different ways with distinct true strains.At the incremental stage,the pyramid strategy was adopted with different wall slopes.From the experiments,the true strains and the final geometries were analyzed.Numerical simulation was also employed for the sake of comparison and correlation with the measured data.It could be observed that single-stretch pre-strain was directly proportional to the maximum incremental strains achieved,whereas samples subjected to biaxial pre-strain influenced the formability according to the degree of pre-strain applied.Pre-strain driven by the prior deep-drawing operation did not result,in this particular geometry,in increased formability.展开更多
The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis ...The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late timesfin the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.展开更多
The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coo...The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coordination number of Al^(3+) and Fe^(3+) in cement clinker burned by different method with x^- ray fluorescence analysis and Moss- bauer spectroscopy. The results show that the clin- ker melt under rapid burning may come into exis- tence at lower temperature and It's viscosity is lower. So the forming processes of clinker may be different at rapid burning from ordinary burning. They are probably an important factor to promote the formation of clinker burned at lower temperature with rapid burning method.展开更多
[Objectives]To optimize the forming process of Yi medicine Tongfeng Granules.[Methods]The forming process of Yi medicine Tongfeng Granules was optimized,with paste density,ethanol volume fraction,and type and proporti...[Objectives]To optimize the forming process of Yi medicine Tongfeng Granules.[Methods]The forming process of Yi medicine Tongfeng Granules was optimized,with paste density,ethanol volume fraction,and type and proportion of excipient as influencing factors,and granule formability,solubility,moisture absorption,and angle of repose as evaluation indicators.Critical relative humidity(CRH)was investigated to select optimal storage conditions.[Results]Maltodextrin was selected as the excipient,and the best process parameters was the ratio of drug to excipient at 1∶2(g/g),under which the forming rate,solubility,moisture absorption rate,and angle of repose were 81.38%,98.90%,8.81%,and 27.5°,respectively.The critical relative humidity was 72%.[Conclusions]The forming process adopted is reasonable and feasible,and can provide a reference for large-scale production of Yi medicine Tongfeng Granules.展开更多
The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mai...The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.展开更多
As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas e...As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas es. A key component of an integrated environment is the use of computational eng ineering to assist and support solutions for complex design. Computer methods fo r structural, flow and thermal analysis are well developed and have been used in design for many years. Many software packages are now available which provi de an advanced capability. However, they are not designed for modelling of powde r forming processes. This paper describes the powder compaction software (PCS_SU T), which is designed for pre- and post-processing for computational simulatio n of the process compaction of powder. In the PCS_SUT software, the adaptive analysis of transient metal powder forming process is simulated by the finite element method based on deformation theories . The error estimates and adaptive remeshing schemes are applied for updated co -ordinate analysis. A generalized Newmark scheme is used for the time domain di scretization and the final nonlinear equations are solved by a Newton-Raphson p rocedure. An incremental elasto-plastic material model is used to simulate the compaction process. To describe the constitutive model of nonlinear behaviour of powder materials, a combination of Mohr-Coulomb and elliptical yield cap model is applied. This model reflects the yielding, frictional and densification char acteristics of powder along with strain and geometrical hardening which occurs d uring the compaction process. A hardening rule is used to define the dependence of the yield surface on the degree of plastic straining. A plasticity theory for friction is employed in the treatment of the powder-tooling interface. The inv olvement of two different materials, which have contact and relative movement in relation to each other, must be considered. A special formulation for friction modelling is coupled with a material formulation. The interface behaviour betwee n the die and the powder is modelled by using an interface element mesh. In the present paper, we have demonstrated pre- and post-processor finite elem ent software, written in Visual Basic, to generate the graphical model and visua lly display the computed results. The software consist of three main part: · Pre-processor: It is used to create the model, generate an app ropriate finite element grid, apply the appropriate boundary conditions, and vie w the total model. The geometric model can be used to associate the mesh with th e physical attributes such as element properties, material properties, or loads and boundary conditions. · Analysis: It can deal with two-dimensional and axi-symmetric applications for linear and non-linear behaviour of material in static and dyna mic analyses. Both triangular and quadrilateral elements are available in the e lement library, including 3-noded, 6-noded and 7-noded (T6B1) triangles and 4 -noded, 8-noded and 9-noded quadrilaterals. The direct implicit algorithm bas ed on the generalized Newmark scheme is used for the time integration and an aut omatic time step control facility is provided. For non-linear iteration, choice s among fully or modified Newton-Raphson method and quasi-Newton method, using the initial stiffness method, Davidon inverse method or BFGS inverse method, ar e possible. · Post-processor: It provides visualization of the computed resu lts, when the finite element model and analysis have been completed. Post-proce ssing is vital to allow the appropriate interpretation of the completed results of the finite element analysis. It provides the visual means to interpret the va st amounts of computed results generated. Finally, the powder behaviour during the compaction of a multi-level component is numerically simulated by the PCS_SUT software, as shown in Fig.1. The predict ive compaction forces at different displacements are computed and compared with the available experimental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
Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This r...Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This review mainly summarized the research reports on short process forming techniques for brazing and soldering materials.Firstly,the traditional process and its shortcomings were presented.Secondly,the latest research of short process forming technologies,such as continuous casting technique,atomization powder technique,solder ball forming technique,and rapid solidification technique,was summarized,and the traditional forming performance of several brazing and soldering materials was introduced.Finally,the current restrictions and research trends of short process forming technique for brazing and solder materials were put forward,providing theoretical guidance and reference for related research and technique development in brazing and soldering field.展开更多
The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by...The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.展开更多
A cable dome has no stiffness or load carrying capacity unless it has been prestressed.Analyses of cable domes are based on successful prestressing designs,making force finding analysis very important.A new force find...A cable dome has no stiffness or load carrying capacity unless it has been prestressed.Analyses of cable domes are based on successful prestressing designs,making force finding analysis very important.A new force finding method named the imbal-ance force iterative method is proposed,which can overcome some limitations of the integrity feasible prestressing method.For instance,even if groups are assigned by mistake,the pretension distribution that satisfies the known geometry form can also be found.This method possess good stability and calculation efficiency,and a case study indicates that it is applicable to the force finding of large and complicated cable domes.On the other hand,form finding analysis of cable domes is also a key engineering problem.However,rigid displacement occurs in this process,which makes the analysis more complex.In this pa-per,the dynamic relaxation method was selected,and the problem of rigid displacement was therefore effectively solved.The method includes two steps:first,the stretching cables are released,and secondly,an axial force is imposed on the two ends of each released cable.This method is convenient in its calculation and clear in its conception.A case study indicates that the method is suitable for the simulation of the construction process of various cable domes and cable-strut tension structures.Moreover,a form finding experiment was conducted on a model of a cable dome with a diameter of 4.8 m by tensing diagonal cables.The behavior of the model in the form finding process was investigated.The experimental results indicate that the ini-tial lengths of members and prestress loss are key issues in cable domes design.The results also prove that the methods of form finding and force finding proposed in this paper are reliable and effective.展开更多
A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphso...A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphson counterpart, the present scheme features an iterative solution procedure on entire time and space domain. Validity and feasibility of foe present scheme are further justiced by the numerical investigation herewith presented.展开更多
Selective laser melting(SLM)has been widely used in the fields of aviation,aerospace and die manufacturing due to its ability to produce metal components with arbitrarily complex shapes.However,the instability of SLM ...Selective laser melting(SLM)has been widely used in the fields of aviation,aerospace and die manufacturing due to its ability to produce metal components with arbitrarily complex shapes.However,the instability of SLM process often leads to quality fluctuation of the formed component,which hinders the further development and application of SLM.In situ quality control during SLM process is an effective solution to the quality fluctuation of formed components.However,the basic premise of feedback control during SLM process is the rapid and accurate diagnosis of the quality.Therefore,an in situ monitoring method of SLM process,which provides quality diagnosis information for feedback control,became one of the research hotspots in this field in recent years.In this paper,the research progress of in situ monitoring during SLM process based on images is reviewed.Firstly,the significance of in situ monitoring during SLM process is analyzed.Then,the image information source of SLM process,the image acquisition systems for different detection objects(the molten pool region,the scanned layer and the powder spread layer)and the methods of the image information analysis,detection and recognition are reviewed and analyzed.Through review and analysis,it is found that the existing image analysis and detection methods during SLM process are mainly based on traditional image processing methods combined with traditional machine learning models.Finally,the main development direction of in situ monitoring during SLM process is proposed by combining with the frontier technology of image-based computer vision.展开更多
基金the support of the Key Research and Development Program of Shaanxi Province,China(No.2021GXLH-Z-049)。
文摘The influence of geometric configuration on the friction characteristics during incremental sheet forming of AA5052 was analyzed by integrating surface morphology and its characteristic parameters,along with plastic strain,contact pressure,and area.The interface promotes lubrication and support when wall angles were≤40°,a 0.5 mm-thin sheet was used,and a 10 mm-large tool radius was employed.This mainly results in micro-plowing and plastic extrusion flow,leading to lower friction coefficient.However,when wall angles exceed 40°,significant plastic strain roughening occurs,leading to inadequate lubrication on the newly formed surface.Increased sheet thickness and decreased tool radius elevate contact pressure.These actions trigger micro-cutting and adhesion,potentially leading to localized scuffing and dimple tears,and higher friction coefficient.The friction mechanisms remain unaffected by the part’s plane curve features.As the forming process progresses,abrasive wear intensifies,and surface morphology evolves unfavorably for lubrication and friction reduction.
基金Supported by Major Special Projects of Public Bidding in Shanxi Province of China(Grant No.20201101020)Central Guidance on Local Science and Technology Development Fund Project of China(Grant No.YDZJSX2022A053)Open Fund Subjectof National Key Laboratory of Material Forming and Mold Technology of China(Grant No.P2024-002)。
文摘The forming quality of metal bipolar plate(BPP)flow channels in proton exchange membrane fuel cells(PEMFCs)is a key factor affecting battery performance.A flow channel with straight sidewalls and a low thinning rate can enhance battery output.Roll forming,as a new technology for BPP production,offers advantages such as a low thinning rate and high efficiency.However,existing roll curve design methods struggle to accommodate both low thinning rates and straight sidewall angles simultaneously.This study aims to develop flow channels with right-angled sidewalls,which provide benefits such as a low thinning rate,reduced residual stress,and high accuracy.A roller tooth profile was designed to achieve a flow channel with right-angled sidewalls and minimal thinning.Simulations and experiments were conducted to validate the feasibility of this novel design method for the roll forming process.The study investigated the effects of roller tooth parameters on sidewall angle,thinning rate,and residual stress.A multifactor evaluation method was developed to optimize the tip fillet radius and the tooth profile backlash of the roller.The results indicated that the tip fillet radius and the tooth profile backlash were negatively correlated with the sidewall angle.As the tip fillet radius and tooth profile backlash increased,the thinning rate and residual stress decreased.With a tip fillet radius of 0.25 mm and a tooth profile backlash of 0.19 mm,the flow channel achieved an approximately right-angled sidewall,a maximum thinning rate of 7.7%,a 29.6%reduction in maximum residual stress,and maximum and average residual stress imbalance values of 7.1%and 3.2%,respectively.This study proposes a new design method for a right-angled sidewall runner roller gear profile,facilitating the roll forming of metal BPPs with right-angled sidewalls and minimal thinning.This method provides theoretical support for the large-scale application of roll forming in the manufacture of PEMFC BPPs.
基金the National Natural Science Foundation of China(52275378).
文摘The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.
基金Project(50625101) supported by the National Science Fund for Distinguished Young Scholars of ChinaProject supported by Graduate Independent Innovation Foundation of Shandong University(GIIFSDU),ChinaProject(51071097) supported by the National Natural Science Foundation of China
文摘A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on the three-dimensional morphology of TiB2 particles.Different preparation routes result in different reaction forms,which accounts for the morphology variation of TiB2 particles.When the Al-Ti-B master alloy is prepared using ＂halide salt＂ route,TiB2 particles exhibit hexagonal platelet morphology and are independent with each other.In addition,the reaction temperature almost does not have influence on the morphology of TiB2 particles.However,TiB2 particles exhibit different morphologies at different reaction temperatures when the master alloys are prepared with Al-3B and Ti sponge.When the master alloy is prepared at 850 ℃,a kind of TiB2 particle agglomeration forms with a size larger than 5 μm.The TiB2 particles change to layered stacking morphology even dendritic morphology with the reaction temperature reaching up to 1200 ℃.
文摘The casting-forging combined technique and the closed die forging without flash-less are both new developed material working methods. The former can not only decrease forming operations of forgings, but also increase the material utilization ratio. Therefore, it is applied to produce more complex forgings. The latter is required for forging precise parts without burrs. The alternator pole is a complex forging, which was usually produced by hot forging, upsetting-extrusion or upsetting-extrusion and bending processes. During these processes, not only the forming force is higher, but the material of burrs accounts for 30 percent or so of total required material. And burrs are difficult to remove in the sequential machining process. In accordance with defects exiting in current manufacturing of alternator poles by upsetting-extruding process, such as more material demand, higher forming force and difficulty of next machining, a casting-forging precision process of alternator poles was developed and investigated in this paper. In the process, the pole was formed by two operations. One is the pre-forming operation by casting. The other is the final forming operation by the closed precision forging process. This can not only shorten processes, decrease material and power demand, but also increase precision of forgings. First, the casting blocker was designed considering the casting process and the forging ratio and the mode of deformation. Then the die structure for closed precision forging was designed, and the closing device for forging dies with spring assemblies in order to provide the necessary closing force was also designed. Finally the forming processes was investigated by test and numerical simulation method to optimum process parameters and die structure design parameters. The result can provide basis for applying the process to manufacture poles in practice.
基金This work was supported by the Brain Korea 2lProject and the Grallt of Post-Doc Program, KyungpookNational University (1999).
文摘Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.
文摘A new concept referred to the non-synchronous deformation effect of particle in sheet metal forming is proposed. The results of finite element analysis show that the flow resistance of sheet metal can be effectively reduced and thus the forming property can be greatly improved if the moving and deformation state of the neighboring elements with equal perpendicular distance to the entrance contour of die is non-synchronous. Experiment tests are presented and the results agree well with FEA simulation. In addition, the mechanism of the non-synchronous effect is analyzed in detail.
文摘Ductile damage often occurs during metal forming processes due to the large thermo-elasto （visco） plastic flow Iocalisation. This paper presents a numerical methodology, which aims to virtually improve any metal forming processes. The methodology is based on elastoplastic constitutive equations accounting for nonlinear mixed isotropic and kinematic hardening strongly coupled with isotropic ductile damage. An adaptive remeshing scheme based on geometrical and physical error estimates including a kill element procedure is used. Some numerical results are presented to show the capability of the model to predict the damage initiation and growth during the metal forming processes.
基金Fabio Lora gratefully acknowledge LdTM/UFRGS,SENAI CIMATEC and IBF/RWTH-Aachen for their support during the development of this workas well as CAPES for financial support in the form of a scholarship+3 种基金Daniel Fritzen acknowledges CNPq 234851/2014-7(Doutorado Sanduíche no Exterior)-SWERicardo J.Alves de Sousa acknowledges grants UID/EMS/00481/2019-FCT and CENTRO-01-0145-FEDER-022083-Centro2020European Regional Development Fund(ERDF)This research was support by CNPq/DAAD 2010-Doutorado no Exterior-GDE Grant Number 290096/2010-3 in the form of a scholarship.
文摘In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre-forming by conventional forming,followed by incremental sheet forming.The main objective is analyzing strain evolution.The pre-forming induced in the conventional forming stage will determine the strain paths,directly influencing the strains produced by the incremental process.To conduct the study,in the conventional processes,strains were imposed in three different ways with distinct true strains.At the incremental stage,the pyramid strategy was adopted with different wall slopes.From the experiments,the true strains and the final geometries were analyzed.Numerical simulation was also employed for the sake of comparison and correlation with the measured data.It could be observed that single-stretch pre-strain was directly proportional to the maximum incremental strains achieved,whereas samples subjected to biaxial pre-strain influenced the formability according to the degree of pre-strain applied.Pre-strain driven by the prior deep-drawing operation did not result,in this particular geometry,in increased formability.
基金This research was supported by the Chinese Foundation for Development of Geological Science and Technology (Project 49273162)the National Natural Science Foundation of China(Project 49273162)
文摘The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late timesfin the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.
文摘The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coordination number of Al^(3+) and Fe^(3+) in cement clinker burned by different method with x^- ray fluorescence analysis and Moss- bauer spectroscopy. The results show that the clin- ker melt under rapid burning may come into exis- tence at lower temperature and It's viscosity is lower. So the forming processes of clinker may be different at rapid burning from ordinary burning. They are probably an important factor to promote the formation of clinker burned at lower temperature with rapid burning method.
基金National Key R&D Program(2018YFC1708005)Sichuan Provincial Key R&D Project(2021YFS0043)Fundamental Research Funds for the Central Universities(2020NGD01).
文摘[Objectives]To optimize the forming process of Yi medicine Tongfeng Granules.[Methods]The forming process of Yi medicine Tongfeng Granules was optimized,with paste density,ethanol volume fraction,and type and proportion of excipient as influencing factors,and granule formability,solubility,moisture absorption,and angle of repose as evaluation indicators.Critical relative humidity(CRH)was investigated to select optimal storage conditions.[Results]Maltodextrin was selected as the excipient,and the best process parameters was the ratio of drug to excipient at 1∶2(g/g),under which the forming rate,solubility,moisture absorption rate,and angle of repose were 81.38%,98.90%,8.81%,and 27.5°,respectively.The critical relative humidity was 72%.[Conclusions]The forming process adopted is reasonable and feasible,and can provide a reference for large-scale production of Yi medicine Tongfeng Granules.
基金The authors would like to thank NSFC for support toenable the performing of this research (No. 59775055).
文摘The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.
文摘As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas es. A key component of an integrated environment is the use of computational eng ineering to assist and support solutions for complex design. Computer methods fo r structural, flow and thermal analysis are well developed and have been used in design for many years. Many software packages are now available which provi de an advanced capability. However, they are not designed for modelling of powde r forming processes. This paper describes the powder compaction software (PCS_SU T), which is designed for pre- and post-processing for computational simulatio n of the process compaction of powder. In the PCS_SUT software, the adaptive analysis of transient metal powder forming process is simulated by the finite element method based on deformation theories . The error estimates and adaptive remeshing schemes are applied for updated co -ordinate analysis. A generalized Newmark scheme is used for the time domain di scretization and the final nonlinear equations are solved by a Newton-Raphson p rocedure. An incremental elasto-plastic material model is used to simulate the compaction process. To describe the constitutive model of nonlinear behaviour of powder materials, a combination of Mohr-Coulomb and elliptical yield cap model is applied. This model reflects the yielding, frictional and densification char acteristics of powder along with strain and geometrical hardening which occurs d uring the compaction process. A hardening rule is used to define the dependence of the yield surface on the degree of plastic straining. A plasticity theory for friction is employed in the treatment of the powder-tooling interface. The inv olvement of two different materials, which have contact and relative movement in relation to each other, must be considered. A special formulation for friction modelling is coupled with a material formulation. The interface behaviour betwee n the die and the powder is modelled by using an interface element mesh. In the present paper, we have demonstrated pre- and post-processor finite elem ent software, written in Visual Basic, to generate the graphical model and visua lly display the computed results. The software consist of three main part: · Pre-processor: It is used to create the model, generate an app ropriate finite element grid, apply the appropriate boundary conditions, and vie w the total model. The geometric model can be used to associate the mesh with th e physical attributes such as element properties, material properties, or loads and boundary conditions. · Analysis: It can deal with two-dimensional and axi-symmetric applications for linear and non-linear behaviour of material in static and dyna mic analyses. Both triangular and quadrilateral elements are available in the e lement library, including 3-noded, 6-noded and 7-noded (T6B1) triangles and 4 -noded, 8-noded and 9-noded quadrilaterals. The direct implicit algorithm bas ed on the generalized Newmark scheme is used for the time integration and an aut omatic time step control facility is provided. For non-linear iteration, choice s among fully or modified Newton-Raphson method and quasi-Newton method, using the initial stiffness method, Davidon inverse method or BFGS inverse method, ar e possible. · Post-processor: It provides visualization of the computed resu lts, when the finite element model and analysis have been completed. Post-proce ssing is vital to allow the appropriate interpretation of the completed results of the finite element analysis. It provides the visual means to interpret the va st amounts of computed results generated. Finally, the powder behaviour during the compaction of a multi-level component is numerically simulated by the PCS_SUT software, as shown in Fig.1. The predict ive compaction forces at different displacements are computed and compared with the available experimental
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National Key Research and Development Program(2021YFB3401101)。
文摘Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This review mainly summarized the research reports on short process forming techniques for brazing and soldering materials.Firstly,the traditional process and its shortcomings were presented.Secondly,the latest research of short process forming technologies,such as continuous casting technique,atomization powder technique,solder ball forming technique,and rapid solidification technique,was summarized,and the traditional forming performance of several brazing and soldering materials was introduced.Finally,the current restrictions and research trends of short process forming technique for brazing and solder materials were put forward,providing theoretical guidance and reference for related research and technique development in brazing and soldering field.
基金the support of the National Natural Science Foundation of China(Nos.51605388,51675433)111 Project(B08040)+2 种基金the Research Fund of the State Key Laboratory of Solidification Processing(NWPU)in China(Grant No.131-QP-2015)the Fundamental Research Funds for the Central Universitiesthe Open Research Fund of State Key Laboratory of Materials Processing and Die&Mold Technology at Huazhong University of Science and Technology
文摘The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element（FE） simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology（RSM）.The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components.
文摘A cable dome has no stiffness or load carrying capacity unless it has been prestressed.Analyses of cable domes are based on successful prestressing designs,making force finding analysis very important.A new force finding method named the imbal-ance force iterative method is proposed,which can overcome some limitations of the integrity feasible prestressing method.For instance,even if groups are assigned by mistake,the pretension distribution that satisfies the known geometry form can also be found.This method possess good stability and calculation efficiency,and a case study indicates that it is applicable to the force finding of large and complicated cable domes.On the other hand,form finding analysis of cable domes is also a key engineering problem.However,rigid displacement occurs in this process,which makes the analysis more complex.In this pa-per,the dynamic relaxation method was selected,and the problem of rigid displacement was therefore effectively solved.The method includes two steps:first,the stretching cables are released,and secondly,an axial force is imposed on the two ends of each released cable.This method is convenient in its calculation and clear in its conception.A case study indicates that the method is suitable for the simulation of the construction process of various cable domes and cable-strut tension structures.Moreover,a form finding experiment was conducted on a model of a cable dome with a diameter of 4.8 m by tensing diagonal cables.The behavior of the model in the form finding process was investigated.The experimental results indicate that the ini-tial lengths of members and prestress loss are key issues in cable domes design.The results also prove that the methods of form finding and force finding proposed in this paper are reliable and effective.
文摘A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphson counterpart, the present scheme features an iterative solution procedure on entire time and space domain. Validity and feasibility of foe present scheme are further justiced by the numerical investigation herewith presented.
基金financially supported by the KGW Program(Grant No.2019XXX.XX4007Tm)the National Natural Science Foundation of China(Grant Nos.51905188,52090042 and 51775205)。
文摘Selective laser melting(SLM)has been widely used in the fields of aviation,aerospace and die manufacturing due to its ability to produce metal components with arbitrarily complex shapes.However,the instability of SLM process often leads to quality fluctuation of the formed component,which hinders the further development and application of SLM.In situ quality control during SLM process is an effective solution to the quality fluctuation of formed components.However,the basic premise of feedback control during SLM process is the rapid and accurate diagnosis of the quality.Therefore,an in situ monitoring method of SLM process,which provides quality diagnosis information for feedback control,became one of the research hotspots in this field in recent years.In this paper,the research progress of in situ monitoring during SLM process based on images is reviewed.Firstly,the significance of in situ monitoring during SLM process is analyzed.Then,the image information source of SLM process,the image acquisition systems for different detection objects(the molten pool region,the scanned layer and the powder spread layer)and the methods of the image information analysis,detection and recognition are reviewed and analyzed.Through review and analysis,it is found that the existing image analysis and detection methods during SLM process are mainly based on traditional image processing methods combined with traditional machine learning models.Finally,the main development direction of in situ monitoring during SLM process is proposed by combining with the frontier technology of image-based computer vision.
