Magnesium alloy,the lightest structural metal substance currently known,has garnered a great deal of interest in recent times.Magnesium alloys not only offer high specific strength,high specific stiffness,and low dens...Magnesium alloy,the lightest structural metal substance currently known,has garnered a great deal of interest in recent times.Magnesium alloys not only offer high specific strength,high specific stiffness,and low density,but they also have outstanding anti-electromagnetic interference properties,shock absorption,are easy to recycle,and are biocompatible.It has a wide range of uses,including automotive,aerospace,military,and biological.Magnesium alloy’s compact hexagonal structure creates few slip systems at room temperature,leading to low plasticity and limited applicability.Deep drawing of magnesium alloys is a major procedure in the aerospace and automotive sectors due to the high strength-to-weight ratio.This paper presents all the aspects of deep drawing of magnesium alloys,covering the innovative methods of deep drawing,factors influencing the performance of deep drawing,simulation and modeling,optimization of deep drawing,and the microstructural changes during deep drawing and its impact on mechanical properties.Finally,the challenges and scope for future research are explored.展开更多
In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural feature...In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural features.Then the influence of annealing temperature on the formability of stainless steel-copper composites and the quality of micro composite cups manufactured by micro deep drawing(MDD)were investigated,and the underlying mechanism was analyzed.Three finite element(FE)models,including basic FE model,Voronoi FE model and surface morphological FE model,were developed to analyze the forming performance of stainless steel-copper composites during MDD.The results show that the stainless steel-copper composites annealed at 900℃possess the best plasticity owing to the homogeneous and refined microstructure in both stainless steel and copper matrixes,and the micro composite cup with specimen annealed at 900℃exhibits a uniform wall thickness as well as high surface quality with the fewest wrinkles.The results obtained from the surface morphological FE model considering material inhomogeneity and surface morphology of the composites are the closest to the experimental results compared to the basic and Voronoi FE model.During MDD process,the drawing forces decrease with increasing annealing temperature as a consequence of the strength reduction.展开更多
In this work,the{10–12}tensile twins are introduced to improve the drawability of the AZ31 Mg alloy sheet.Concretely,the drawing depth is increased by 32%compared with the as-received sheet at 200℃.This is because{1...In this work,the{10–12}tensile twins are introduced to improve the drawability of the AZ31 Mg alloy sheet.Concretely,the drawing depth is increased by 32%compared with the as-received sheet at 200℃.This is because{10–12}tensile twins promote the occurrences of many deformation mechanisms during warm deep drawing,such as slips,detwinning,dynamic recrystallization(DRX)behaviors,etc.Further,based on the different stress states during deep drawing,these mechanisms and their competition relationships,as well as texture evolutions,are systematically studied.Combined with critical resolved shear stress(CRSS)and microstructure evolution,the global Schmid factor(GSF)obtained by quantizing stress states by stress tensor(σ)can accurately predict the activation trend of deformation mechanisms.It is found that the stress states have a reverse influence on the activation trend of the{10–12}twinning and detwinning.The change of stress states affects the competitive relationships between detwinning and DRX,and then affects the process and degree of DRX.The{10–12}tensile twins and large plane strain promote the activation of prismatic slips,and the larger plane strain also deflected the{10–12}twinning lattice.The{10–12}tensile twins and their induced deformation mechanisms can prominently weaken the basal texture and improve the drawability.展开更多
The development of microstructure and texture during cold deep drawing of commercially pure titanium（CP-Ti） was investigated.Three parts,stretching region,drawing region and flange region,were sequentially formed in...The development of microstructure and texture during cold deep drawing of commercially pure titanium（CP-Ti） was investigated.Three parts,stretching region,drawing region and flange region,were sequentially formed in the deep drawing process of the hemispheric surface part,with reference to deformation modes and strain regimes.Results show that the plastic strain is accommodated by dislocation slip and deformation twinning in the whole deep drawing process.The texture of the CP-Ti sheet and its drawn part consists of rolling texture component and recrystallization texture component.The intensity and type of the initial texture varied during the drawing process are related to the production of deformation twinning and dislocation slip.Twinning weakens the initial texture by randomizing the orientations of crystals,especially for the recrystallization texture.The recrystallization texture in the drawing region disappears due to the significant forming of twinning.Furthermore,over drawing would result in the predominance of dislocation slip and the texture is strengthened.展开更多
The effect of friction coefficient on the deep drawing of aluminum alloy AA6111 at elevated temperatures was analyzed based on the three conditions using the finite element analysis and the experimental approach.Resul...The effect of friction coefficient on the deep drawing of aluminum alloy AA6111 at elevated temperatures was analyzed based on the three conditions using the finite element analysis and the experimental approach.Results indicate that the friction coefficient and lubrication position significantly influence the minimum thickness,the thickness deviation and the failure mode of the formed parts.During the hot forming process,the failure modes are draw mode,stretch mode and equi-biaxial stretch mode induced by different lubrication conditions.In terms of formability,the optimal value of friction coefficient determined in this work is 0.15.At the same time,the good agreement is performed between the experimental and simulated results.Fracture often occurs at the center of cup bottom or near the cup corner in a ductile mode or ductile-brittle mixed mode,respectively.展开更多
Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in co...Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.展开更多
In this paper, the forming features of tapered rectangular box during hydrodynamic deep drawing are studied by means of FEM.The effect rules of square blank corner corner amount on body wrinkling are recognized and co...In this paper, the forming features of tapered rectangular box during hydrodynamic deep drawing are studied by means of FEM.The effect rules of square blank corner corner amount on body wrinkling are recognized and corresponding methods are discussed. At last, the results of FEM are verified by experi- ment.展开更多
In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead ...In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead force is one of the most important pa- rameters in sheet metal forming process control. This paper derives the model of loop drawbead restraining force (DBRF) using plastic forming theory, and gives the min imum blankholding force. Experiments are carried out to verify the proposed DBRF model. The good agreement between the calculated values and experiments data justi- fies the proposed loop drawbead restraining force model.展开更多
The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other...The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other plastic process. The common test methods in laboratories are analyzed. It shows that though all those test methods can test the friction coefficient, the probe test method is most suitable for the research of friction and lubrication and the process in deep drawing, for this method is identical with the actual work condition either from the test principle or deformation status of the blank. Last the successful application in the deep drawing simulator newly developed the the probe method are intro- duced in detail.展开更多
In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To in...In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To investigate the effects of loading paths on the HDD with independent radial hydraulic pressure, the forming process of 5A06 aluminum alloy cylindrical cup with a hemispherical bottom was studied by numerical simulation. By employing the dynamic explicit analytical software ETA/Dynaform based on LS-DYNA3D, the effects of loading paths on the sheet-thickness distribution and surface quality were analyzed. The corresponding relations of the radial hydraulic pressure loading paths and the part＇s strain status on the forming limit diagram （FLD） were also discussed. The results indicated that a sound match between liquid chamber pressure and independent radial hydraulic pressure could restrain the serious thinning at the hemisphere bottom and that through adjusting radial hydraulic pressure could reduce the radial tensile strain and change the strain paths. Therefore, the drawing limit of the aluminum cylindrical cup with a hemispherical bottom could be increased significantly.展开更多
Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance...Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.展开更多
Basing on warm mechanical property of SUS304 stainless steel and hydro-mechanical deep drawing process, warm hydro-mechanical deep drawing process is proposed and discussed with experiments in this paper. The experime...Basing on warm mechanical property of SUS304 stainless steel and hydro-mechanical deep drawing process, warm hydro-mechanical deep drawing process is proposed and discussed with experiments in this paper. The experiments are performed at four different temperatures. The results show that the formability of stainless steel is improved under the condition of warm temperature. Warm hydro-mechanical deep drawing raises limiting drawing ratio of SUS304 effectively, and limiting drawing ratio 3.3 is obtained, which is beyond 2.0 with conventional deep drawing. The temperature of 90℃ is beneficial to the forming of SUS304 stainless steel, the strain-induced martensite is controlled effectively, and the thickness distribution is more uniform.展开更多
In the present work,austenitic stainless steel(ASS)304 foils with a thickness of 50μm were first annealed at temperatures ranging from 700 to 1100℃for 1 h to obtain different microstructural characteristics.Then the...In the present work,austenitic stainless steel(ASS)304 foils with a thickness of 50μm were first annealed at temperatures ranging from 700 to 1100℃for 1 h to obtain different microstructural characteristics.Then the effects of microstructural characteristics on the formability of ASS 304 foils and the quality of drawn cups using micro deep drawing(MDD)were studied,and the mechanism involved was discussed.The results show that the as-received ASS 304 foil has a poor formability and cannot be used to form a cup using MDD.Serious wrinkling problem occurs on the drawn cup,and the height profile distribution on the mouth and the symmetry of the drawn cup is quite non-uniform when the annealing temperature is 700℃.At annealing temperatures of 900 and 950℃,the drawn cups are both characterized with very few wrinkles,and the distribution of height profile,symmetry and mouth thickness are uniform on the mouths of the drawn cups.The wrinkling becomes increasingly significant with a further increase of annealing temperature from 950 to 1100℃.The optimal annealing temperatures obtained in this study are 900 and 950℃for reducing the generation of wrinkling,and therefore improving the quality of drawn cups.With non-optimized microstructure,the distribution of the compressive stress in the circumferential direction of the drawn foils becomes inhomogeneous,which is thought to be the cause of the occurrence of localized deformation till wrinkling during MDD.展开更多
Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature,in order to reveal the effect of high freque...Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature,in order to reveal the effect of high frequency vibration on deformation behavior of AZ31 during the process.From the drawn results and the observation of the microstructure within the large deformation area,high frequency vibration has a great influence on the formability,the forming load and the failure mode of AZ31 sheet during the deep drawing process;the influence is a comprehensive result of so-called "volume effect" and "surface effect",and relies on the vibrating amplitude.Total forming load decreased significantly as soon as the vibration superimposed.According to the tensile test results of AZ31 bars under ultrasonic vibration,the formability of AZ31 sheet increases firstly with the increase of stimulating energy,then decreases and finally becomes brittle.Under the combined influence of "surface effect" and the "softening" in the "volume effect" near the relative low amplitude of 25%A in the experiment(A is the maximum amplitude),the formability of AZ31 reaches the largest value,and the samples possess the same distribution trend of cracks as those added with lubricating oil.With the increase of excitation energy,the "volume effect" gradually becomes apparent,and finally the "hardening" of the "volume effect" occupies a dominant position.展开更多
Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,pr...Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,process window diagrams（PWDs） for Al1050-O,pure copper and DIN 1623 St14 steel are obtained for HDDRP process.The PWD is determined to provide a quick assessment of part producibility for sheet hydroforming process.Finite element method is used for this purpose considering the process parameters including pressure path,and the blank material and its thickness.Numerical results are validated by experiments.It is shown that the sheets with less initial thickness and higher strength show better formability and uniformity of thickness distribution on final product.The results demonstrate that the obtained PWD can predict appropriate forming area and probability of rupture or wrinkling occurrence under different pressure loading paths.展开更多
Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, ...Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.展开更多
At present,iron and steel enterprises mainly use“after spot test ward”to control final product quality.However,it is impossible to realize on-line quality predetermining for all products by this traditional approach...At present,iron and steel enterprises mainly use“after spot test ward”to control final product quality.However,it is impossible to realize on-line quality predetermining for all products by this traditional approach,hence claims and returns often occur,resulting in major eco-nomic losses of enterprises.In order to realize the on-line quality predetermining for steel products during manufacturing process,the predic-tion models of mechanical properties based on deep learning have been proposed in this work.First,the mechanical properties of deep drawing steels were predicted by using LSTM(long short team memory),GRU(gated recurrent unit)network,and GPR(Gaussian process regression)model,and prediction accuracy and learning efficiency for different models were also discussed.Then,on-line re-learning methods for transfer learning models and model parameters were proposed.The experimental results show that not only the prediction accuracy of optimized trans-fer learning models has been improved,but also predetermining time was shortened to meet real time requirements of on-line property prede-termining.The industrial production data of interstitial-free(IF)steel was used to demonstrate that R2 value of GRU model in training stage reaches more than 0.99,and R2 value in testing stage is more than 0.96.展开更多
Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and...Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.展开更多
Austenitic stainless steel 304 was deep drawn with different blank diameters under warm conditions using 20 t hydraulic press. A number of deep drawing experiments both at room temperature and at 150 ℃ were conducted...Austenitic stainless steel 304 was deep drawn with different blank diameters under warm conditions using 20 t hydraulic press. A number of deep drawing experiments both at room temperature and at 150 ℃ were conducted to study the metallography. Also, tensile test experiments were conducted on a universal testing machine up to 700 ℃ and the broken specimens were used to study the fractography of the material using scanning electron microscopy in various regions. The microstructure changes were observed at limiting draw ratio （LDR） when the cup is drawn at different temperatures. In austenitic stainless steel, martensite formation takes place that is not only affected by temperature, hut also influenced by the rate at which the material is deformed. In austenitic stainless steel 304, dynamic strain regime appears above 300 ℃ and it decreases the formability of material due to brittle fracture as studied in its fractography. From the metallographic studies, the maximum LDR of the material is observed at 150 ℃ before dynamic strain regime. It is also observed that at 150 ℃, grains are coarse in the drawn cups at LDR.展开更多
To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element s...To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element simulations based on continuous damage mechanics were used to study the failure behavior during a cylindrical deep drawing of metal sheets with nickel coating. It is shown that taking the effect of blank holder force into account, these two failure modes can be predicted. The simulation results are well consistent with that obtained from experiments.展开更多
文摘Magnesium alloy,the lightest structural metal substance currently known,has garnered a great deal of interest in recent times.Magnesium alloys not only offer high specific strength,high specific stiffness,and low density,but they also have outstanding anti-electromagnetic interference properties,shock absorption,are easy to recycle,and are biocompatible.It has a wide range of uses,including automotive,aerospace,military,and biological.Magnesium alloy’s compact hexagonal structure creates few slip systems at room temperature,leading to low plasticity and limited applicability.Deep drawing of magnesium alloys is a major procedure in the aerospace and automotive sectors due to the high strength-to-weight ratio.This paper presents all the aspects of deep drawing of magnesium alloys,covering the innovative methods of deep drawing,factors influencing the performance of deep drawing,simulation and modeling,optimization of deep drawing,and the microstructural changes during deep drawing and its impact on mechanical properties.Finally,the challenges and scope for future research are explored.
基金Projects(51975398,52105392)supported by the National Natural Science Foundation of ChinaProject(YDZJSX2021A006)supported by the Central Government Guided Local Science and Technology Development Fund Project,China+1 种基金Project(20210035)supported by the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province,ChinaProject(2020-037)supported by the Fund Program for the Research Project Supported by Shanxi Scholarship Council,China。
文摘In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural features.Then the influence of annealing temperature on the formability of stainless steel-copper composites and the quality of micro composite cups manufactured by micro deep drawing(MDD)were investigated,and the underlying mechanism was analyzed.Three finite element(FE)models,including basic FE model,Voronoi FE model and surface morphological FE model,were developed to analyze the forming performance of stainless steel-copper composites during MDD.The results show that the stainless steel-copper composites annealed at 900℃possess the best plasticity owing to the homogeneous and refined microstructure in both stainless steel and copper matrixes,and the micro composite cup with specimen annealed at 900℃exhibits a uniform wall thickness as well as high surface quality with the fewest wrinkles.The results obtained from the surface morphological FE model considering material inhomogeneity and surface morphology of the composites are the closest to the experimental results compared to the basic and Voronoi FE model.During MDD process,the drawing forces decrease with increasing annealing temperature as a consequence of the strength reduction.
基金supported by the National Natural Science Foundations of China[No.52374395,52474419]Natural Science Foundation of Chongqing[CSTB2024NSCQMSX0267]+6 种基金the Natural Science Foundation of Shanxi province[No.20210302123135,20210302123163]the China Postdoctoral Science Foundation[No.2022M710541]the Research Project Supported by Shanxi Scholarship Council of China[No.2022-038]Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi Province[202104021301022,202204021301009]the Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant[no.075-15-2022-1133]he National Research Foundation(NRF)grant funded by the Ministry of Science and ICT[2015R1A2A1A01006795]Korea through the Research Institute of Advanced Materials.
文摘In this work,the{10–12}tensile twins are introduced to improve the drawability of the AZ31 Mg alloy sheet.Concretely,the drawing depth is increased by 32%compared with the as-received sheet at 200℃.This is because{10–12}tensile twins promote the occurrences of many deformation mechanisms during warm deep drawing,such as slips,detwinning,dynamic recrystallization(DRX)behaviors,etc.Further,based on the different stress states during deep drawing,these mechanisms and their competition relationships,as well as texture evolutions,are systematically studied.Combined with critical resolved shear stress(CRSS)and microstructure evolution,the global Schmid factor(GSF)obtained by quantizing stress states by stress tensor(σ)can accurately predict the activation trend of deformation mechanisms.It is found that the stress states have a reverse influence on the activation trend of the{10–12}twinning and detwinning.The change of stress states affects the competitive relationships between detwinning and DRX,and then affects the process and degree of DRX.The{10–12}tensile twins and large plane strain promote the activation of prismatic slips,and the larger plane strain also deflected the{10–12}twinning lattice.The{10–12}tensile twins and their induced deformation mechanisms can prominently weaken the basal texture and improve the drawability.
基金Project(SKLSP200906) supported by the Fund of State Key Laboratory of Solidification Processing in NWPUProject(B08040) supported by Program of Introducing Talents of Discipline in the Project of Advanced Materials and Their Forming Technology
文摘The development of microstructure and texture during cold deep drawing of commercially pure titanium（CP-Ti） was investigated.Three parts,stretching region,drawing region and flange region,were sequentially formed in the deep drawing process of the hemispheric surface part,with reference to deformation modes and strain regimes.Results show that the plastic strain is accommodated by dislocation slip and deformation twinning in the whole deep drawing process.The texture of the CP-Ti sheet and its drawn part consists of rolling texture component and recrystallization texture component.The intensity and type of the initial texture varied during the drawing process are related to the production of deformation twinning and dislocation slip.Twinning weakens the initial texture by randomizing the orientations of crystals,especially for the recrystallization texture.The recrystallization texture in the drawing region disappears due to the significant forming of twinning.Furthermore,over drawing would result in the predominance of dislocation slip and the texture is strengthened.
基金Project(2009ZX04014-074)supported by the National Science and Technology Major Project of ChinaProject(P2014-15)supported by the State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology,ChinaProject(20120006110017)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The effect of friction coefficient on the deep drawing of aluminum alloy AA6111 at elevated temperatures was analyzed based on the three conditions using the finite element analysis and the experimental approach.Results indicate that the friction coefficient and lubrication position significantly influence the minimum thickness,the thickness deviation and the failure mode of the formed parts.During the hot forming process,the failure modes are draw mode,stretch mode and equi-biaxial stretch mode induced by different lubrication conditions.In terms of formability,the optimal value of friction coefficient determined in this work is 0.15.At the same time,the good agreement is performed between the experimental and simulated results.Fracture often occurs at the center of cup bottom or near the cup corner in a ductile mode or ductile-brittle mixed mode,respectively.
基金supported by Chengdu Aircraft Industrial Corporation
文摘Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.
文摘In this paper, the forming features of tapered rectangular box during hydrodynamic deep drawing are studied by means of FEM.The effect rules of square blank corner corner amount on body wrinkling are recognized and corresponding methods are discussed. At last, the results of FEM are verified by experi- ment.
文摘In sheet metal forming, drawbeads are often used to control uneven material flow which may cause defects such as wrinkles, fracture, surface distortion and springback. Appropriate setting and adjusting the drawbead force is one of the most important pa- rameters in sheet metal forming process control. This paper derives the model of loop drawbead restraining force (DBRF) using plastic forming theory, and gives the min imum blankholding force. Experiments are carried out to verify the proposed DBRF model. The good agreement between the calculated values and experiments data justi- fies the proposed loop drawbead restraining force model.
文摘The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other plastic process. The common test methods in laboratories are analyzed. It shows that though all those test methods can test the friction coefficient, the probe test method is most suitable for the research of friction and lubrication and the process in deep drawing, for this method is identical with the actual work condition either from the test principle or deformation status of the blank. Last the successful application in the deep drawing simulator newly developed the the probe method are intro- duced in detail.
文摘In order to meet the forming demands for low plasticity materials and large height-diameter ratio parts, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure is proposed. To investigate the effects of loading paths on the HDD with independent radial hydraulic pressure, the forming process of 5A06 aluminum alloy cylindrical cup with a hemispherical bottom was studied by numerical simulation. By employing the dynamic explicit analytical software ETA/Dynaform based on LS-DYNA3D, the effects of loading paths on the sheet-thickness distribution and surface quality were analyzed. The corresponding relations of the radial hydraulic pressure loading paths and the part＇s strain status on the forming limit diagram （FLD） were also discussed. The results indicated that a sound match between liquid chamber pressure and independent radial hydraulic pressure could restrain the serious thinning at the hemisphere bottom and that through adjusting radial hydraulic pressure could reduce the radial tensile strain and change the strain paths. Therefore, the drawing limit of the aluminum cylindrical cup with a hemispherical bottom could be increased significantly.
文摘Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.
文摘Basing on warm mechanical property of SUS304 stainless steel and hydro-mechanical deep drawing process, warm hydro-mechanical deep drawing process is proposed and discussed with experiments in this paper. The experiments are performed at four different temperatures. The results show that the formability of stainless steel is improved under the condition of warm temperature. Warm hydro-mechanical deep drawing raises limiting drawing ratio of SUS304 effectively, and limiting drawing ratio 3.3 is obtained, which is beyond 2.0 with conventional deep drawing. The temperature of 90℃ is beneficial to the forming of SUS304 stainless steel, the strain-induced martensite is controlled effectively, and the thickness distribution is more uniform.
基金Supported by National Natural Science Foundation of China(Grant Nos.51975398,51974196)Research Project Supported by Shanxi Scholarship Council of China(Grant No.2020-037).
文摘In the present work,austenitic stainless steel(ASS)304 foils with a thickness of 50μm were first annealed at temperatures ranging from 700 to 1100℃for 1 h to obtain different microstructural characteristics.Then the effects of microstructural characteristics on the formability of ASS 304 foils and the quality of drawn cups using micro deep drawing(MDD)were studied,and the mechanism involved was discussed.The results show that the as-received ASS 304 foil has a poor formability and cannot be used to form a cup using MDD.Serious wrinkling problem occurs on the drawn cup,and the height profile distribution on the mouth and the symmetry of the drawn cup is quite non-uniform when the annealing temperature is 700℃.At annealing temperatures of 900 and 950℃,the drawn cups are both characterized with very few wrinkles,and the distribution of height profile,symmetry and mouth thickness are uniform on the mouths of the drawn cups.The wrinkling becomes increasingly significant with a further increase of annealing temperature from 950 to 1100℃.The optimal annealing temperatures obtained in this study are 900 and 950℃for reducing the generation of wrinkling,and therefore improving the quality of drawn cups.With non-optimized microstructure,the distribution of the compressive stress in the circumferential direction of the drawn foils becomes inhomogeneous,which is thought to be the cause of the occurrence of localized deformation till wrinkling during MDD.
基金the Fundamental Research Funds for the Central Universities (No.CDJZR10110029)
文摘Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature,in order to reveal the effect of high frequency vibration on deformation behavior of AZ31 during the process.From the drawn results and the observation of the microstructure within the large deformation area,high frequency vibration has a great influence on the formability,the forming load and the failure mode of AZ31 sheet during the deep drawing process;the influence is a comprehensive result of so-called "volume effect" and "surface effect",and relies on the vibrating amplitude.Total forming load decreased significantly as soon as the vibration superimposed.According to the tensile test results of AZ31 bars under ultrasonic vibration,the formability of AZ31 sheet increases firstly with the increase of stimulating energy,then decreases and finally becomes brittle.Under the combined influence of "surface effect" and the "softening" in the "volume effect" near the relative low amplitude of 25%A in the experiment(A is the maximum amplitude),the formability of AZ31 reaches the largest value,and the samples possess the same distribution trend of cracks as those added with lubricating oil.With the increase of excitation energy,the "volume effect" gradually becomes apparent,and finally the "hardening" of the "volume effect" occupies a dominant position.
文摘Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,process window diagrams（PWDs） for Al1050-O,pure copper and DIN 1623 St14 steel are obtained for HDDRP process.The PWD is determined to provide a quick assessment of part producibility for sheet hydroforming process.Finite element method is used for this purpose considering the process parameters including pressure path,and the blank material and its thickness.Numerical results are validated by experiments.It is shown that the sheets with less initial thickness and higher strength show better formability and uniformity of thickness distribution on final product.The results demonstrate that the obtained PWD can predict appropriate forming area and probability of rupture or wrinkling occurrence under different pressure loading paths.
文摘Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.
基金financially supported by the National Natural Science Foundation of China (No. 52175284)the State Key Lab of Advanced Metals and Materials in University of Science and Technology Beijing (No. 2021ZD08)
文摘At present,iron and steel enterprises mainly use“after spot test ward”to control final product quality.However,it is impossible to realize on-line quality predetermining for all products by this traditional approach,hence claims and returns often occur,resulting in major eco-nomic losses of enterprises.In order to realize the on-line quality predetermining for steel products during manufacturing process,the predic-tion models of mechanical properties based on deep learning have been proposed in this work.First,the mechanical properties of deep drawing steels were predicted by using LSTM(long short team memory),GRU(gated recurrent unit)network,and GPR(Gaussian process regression)model,and prediction accuracy and learning efficiency for different models were also discussed.Then,on-line re-learning methods for transfer learning models and model parameters were proposed.The experimental results show that not only the prediction accuracy of optimized trans-fer learning models has been improved,but also predetermining time was shortened to meet real time requirements of on-line property prede-termining.The industrial production data of interstitial-free(IF)steel was used to demonstrate that R2 value of GRU model in training stage reaches more than 0.99,and R2 value in testing stage is more than 0.96.
文摘Blank holder force (BHF) is an important measure to control the sheet metal forming. BHF is identified quickly using artificial neural network (ANN) on the basis of its analytical description. And critical rupture and wrinkle BHF curves are given. A close-loop control system is established to finish the forming process.
基金Sponsored by Department of Science and Technology Government of India(SR/S3/MERC/0129/2012)
文摘Austenitic stainless steel 304 was deep drawn with different blank diameters under warm conditions using 20 t hydraulic press. A number of deep drawing experiments both at room temperature and at 150 ℃ were conducted to study the metallography. Also, tensile test experiments were conducted on a universal testing machine up to 700 ℃ and the broken specimens were used to study the fractography of the material using scanning electron microscopy in various regions. The microstructure changes were observed at limiting draw ratio （LDR） when the cup is drawn at different temperatures. In austenitic stainless steel, martensite formation takes place that is not only affected by temperature, hut also influenced by the rate at which the material is deformed. In austenitic stainless steel 304, dynamic strain regime appears above 300 ℃ and it decreases the formability of material due to brittle fracture as studied in its fractography. From the metallographic studies, the maximum LDR of the material is observed at 150 ℃ before dynamic strain regime. It is also observed that at 150 ℃, grains are coarse in the drawn cups at LDR.
基金supported by the National Natural Science Foundation of China(Nos.51172192 and 11102176)Hunan Provincial Natural Science Foundation of China(No.09JJ3003)+1 种基金the Natural Science Foundation of Hunan Province for Innovation Group,China(No.09JJ7004)the Key Special Program for Science and Technology of Hunan Province,China(No.2009FJ1002)
文摘To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element simulations based on continuous damage mechanics were used to study the failure behavior during a cylindrical deep drawing of metal sheets with nickel coating. It is shown that taking the effect of blank holder force into account, these two failure modes can be predicted. The simulation results are well consistent with that obtained from experiments.
