Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forgin...Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forging is difficult to control. Many simulations and analysis of precision forging process were taken by previous researchers. But no concrete method is proposed to evaluate and optimize the forming quality of half axel gears. The primary purpose of this work is improving the forming quality of half axel gears by analyzing and optimizing the affected factors of forming quality. The enclosed-die warm forging process of half axle gears was developed, and a new type of die-set used on double action hydraulic press was brought forward. The main influential factors of precision forming quality were analyzed after the forming process had been simulated by using finite element method(FEM). These factors include die structure, web thickness and web position. A method used to evaluate the forming quality was established, which investigated the maximal forming load, the metal filling rate and the material damage factor. The FEM simulations of half axle gears precision forging were evaluated by this method. The results show that the best forming quality can be achieved when the punches were added with bosses, the web located at the middle plant of the gear, and the web thickness was 30 percent of the inner hole diameter. Verification experiments taking the above optimized parameters were performed on a 7.8 MN double action hydraulic press. The trial products were formed well. And their geometric precision meets the demand. The verification result shows that the optimization of the influential factors, according to the simulations and the evaluation method, can improve the forming quality. The new structure of precision forging die-set and the new evaluation method guarantee a high forming quality ofhalfaxel gears.展开更多
Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade wi...Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade with a tenon as an object, the influence of process parameters on the temperature distribution in precision forging process was investigated using 3D coupled thermo-mechanical FEM (finite element method) code developed by the authors. The results obtained illustrate that: (1) the gradient of temperature distribution increases with increasing the deformation degree; (2) with increasing the initial temperature of the billet, the zones of high temperature become larger, and the gradient of temperature distribution hardly has any increase; (3) friction factors have little effect on the distribution of temperature field; (4) with increasing upper die velocity, temperature of the billet increases while the temperature gradient in billet decreases. The results are helpful to the design and optimization of the process parameters in precision forging process of Ti-alloy blade.展开更多
Forging spur gears are widely used in the driving system of mining machinery and equipment due to their higher strength and dimensional accuracy.For the purpose of precisely calculating the volume of cylindrical spur ...Forging spur gears are widely used in the driving system of mining machinery and equipment due to their higher strength and dimensional accuracy.For the purpose of precisely calculating the volume of cylindrical spur gear billet in cold precision forging,a new theoretical method named average circle method was put forward.With this method,a series of gear billet volumes were calculated.Comparing with the accurate three-dimensional modeling method,the accuracy of average circle method by theoretical calculation was estimated and the maximum relative error of average circle method was less than 1.5%,which was in good agreement with the experimental results.Relative errors of the calculated and the experimental for obtaining the gear billet volumes with reference circle method are larger than those of the average circle method.It shows that average circle method possesses a higher calculation accuracy than reference circle method(traditional method),which should be worth popularizing widely in calculation of spur gear billet volume.展开更多
Blade precision forging is a high temperature and large plastic deformation process. Interaction of deformation andheat conduction results in producing large temperature unevenness inside the billet. The unevenness ha...Blade precision forging is a high temperature and large plastic deformation process. Interaction of deformation andheat conduction results in producing large temperature unevenness inside the billet. The unevenness has a greateffect on the mechanical property and microstructure of the forged blade. However, internal quality of the blade isdecided by its microstructure, it is necessary to conduct a research on the microstructure of the blade forging process.Taking a blade with a tenon as an object, its precision forging process is simulated and analyzed using a 3D coupledthermo-mechanical FEM code. And based on the prediction model of Ti-6Al-4V presented by the predecessor, astudy of the evolution of grain size in the forging process is made. The distribution characteristics of grain size intypical sections are obtained under various deformation degrees. This study may provide a base for designing theblade forging process and working out its parameters.展开更多
The finite element analysis (FEA) software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face struc...The finite element analysis (FEA) software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom corner of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom corner. When non-uniform interference is adopted the first principal stress at the corner on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the corner stress concentration. The first principal stress at the corner of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.展开更多
To investigate the effects of billet geometry on the cold precision forging process of a helical gear,six different billet geometries were designed utilizing the relief-hole principle.And the influences of the billet ...To investigate the effects of billet geometry on the cold precision forging process of a helical gear,six different billet geometries were designed utilizing the relief-hole principle.And the influences of the billet geometry on the forming load and the deformation uniformity were analyzed by three-dimensional(3D)finite element method(FEM)under the commercial software DEFORM 3D.The billet geometry was optimized to meet lower forming load and better deformation uniformity requirement.Deformation mechanism was studied through the distribution of flow velocity field and effective strain field.The forging experiments of the helical gear were successfully performed using lead material as a model material under the same process conditions used in the FE simulations.The results show that the forming load decreases as the diameter of relief-hole d0 increases,but the effect of d0 on the deformation uniformity is very complicated.The forming load is lower and the deformation is more uniform when d0 is 10mm.展开更多
To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die ...To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.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
A new cold precision forging technique is proposed to form a spur gear from a hollow billet, that is blocking the divided flow region and then final forging by the relief hole. 3D FEM simulation of the whole process o...A new cold precision forging technique is proposed to form a spur gear from a hollow billet, that is blocking the divided flow region and then final forging by the relief hole. 3D FEM simulation of the whole process of a pure aluminium spur gear is performed using DEFORM 3D TM . The load stroke curve, effective stress distribution, effective strain distribution, velocity distribution, and so on, are achieved. These results are compared with those achieved using the conventional closed die forging in the same conditions. The results show that this new technique has many advantages over the conventional one. The deformation load is reduced by near 30% and the filling ability of the tooth profile is also improved. Precision forging experiments of spur gears with the new process were performed using material Pb. The experimental results show a good agreement with the numerical results.展开更多
In order to obtain the desired final shape, the blade precision forging requires a reasonable preformed billet which can be obtained from a given final shape by using backward tracing scheme based on FEM. The key tech...In order to obtain the desired final shape, the blade precision forging requires a reasonable preformed billet which can be obtained from a given final shape by using backward tracing scheme based on FEM. The key technologies of backward tracing scheme based on 3D rigid-viscoplastic FEM were explored, and some valid algorithms or methods were proposed. A velocity field was generated by combining the direct iterative method with Newton-Raphson iterative method, and then the initial velocity field of backward tracing simulation was achieved by reversing the direction of the velocity field. A new method, namely the tracking-fitting-revising method, was proposed and can be used to determinate the criterion of separating a node from die in the backward tracing simulation. The ceasing criterion of the backward tracing simulation is that all the boundary nodes are detached from dies. Based on the above key technologies, the 3D backward tracing simulation system for the blade precision forging was developed, and its feasibility and reliability were verified by forward loading simulation.展开更多
Fundamental investigations on precision forging technology of magnesium alloys were studied.As-cast billet prestraining and a new concept of hollow billet were proposed in order to reduce the maximum forming load.A sc...Fundamental investigations on precision forging technology of magnesium alloys were studied.As-cast billet prestraining and a new concept of hollow billet were proposed in order to reduce the maximum forming load.A schcme of isothermal forming and the use of combined female dies were adopted,which can improve the die filling capacity and ensure the manufacture of high quality forgings.By means of the developed technique,AZ80 alloy wheel and AZ31 alloy bracket were produced successfully at suitable process parameters and applied in the automotive industries.The results show that the hot compression of AZ80 magnesium alloy has the peak flow stresses of pre-strained alloy with finer grain,which are lower by 20%than those of as-cast alloy under the same deformation conditions.The forming load is related to contact area and average positive stress on interface during forging process.展开更多
The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance f...The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance for making decision on the optimal choice of process parameters and mould structure. Trial forging was used to verify the effectiveness of FEM simulation results.展开更多
The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The uneve...The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade with a tenon into consideration, a 3D mechanical model in precision forging is built up. The distribution laws of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.展开更多
基金supported by Chongqing Municipal Science and Technology Committee of China (Grant No. 2005AA3012-4)
文摘Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forging is difficult to control. Many simulations and analysis of precision forging process were taken by previous researchers. But no concrete method is proposed to evaluate and optimize the forming quality of half axel gears. The primary purpose of this work is improving the forming quality of half axel gears by analyzing and optimizing the affected factors of forming quality. The enclosed-die warm forging process of half axle gears was developed, and a new type of die-set used on double action hydraulic press was brought forward. The main influential factors of precision forming quality were analyzed after the forming process had been simulated by using finite element method(FEM). These factors include die structure, web thickness and web position. A method used to evaluate the forming quality was established, which investigated the maximal forming load, the metal filling rate and the material damage factor. The FEM simulations of half axle gears precision forging were evaluated by this method. The results show that the best forming quality can be achieved when the punches were added with bosses, the web located at the middle plant of the gear, and the web thickness was 30 percent of the inner hole diameter. Verification experiments taking the above optimized parameters were performed on a 7.8 MN double action hydraulic press. The trial products were formed well. And their geometric precision meets the demand. The verification result shows that the optimization of the influential factors, according to the simulations and the evaluation method, can improve the forming quality. The new structure of precision forging die-set and the new evaluation method guarantee a high forming quality ofhalfaxel gears.
基金The authors express their appreciation for the financial support of the Aeronautical Science Foundation of China (No. 02H53061) the National Natural Science Foundation of China for Distinguished Young Scholar (No. 50225518) the Innovation Foundation of Ph.D. Dissertation in NPU of China (No. CX200405).
文摘Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade with a tenon as an object, the influence of process parameters on the temperature distribution in precision forging process was investigated using 3D coupled thermo-mechanical FEM (finite element method) code developed by the authors. The results obtained illustrate that: (1) the gradient of temperature distribution increases with increasing the deformation degree; (2) with increasing the initial temperature of the billet, the zones of high temperature become larger, and the gradient of temperature distribution hardly has any increase; (3) friction factors have little effect on the distribution of temperature field; (4) with increasing upper die velocity, temperature of the billet increases while the temperature gradient in billet decreases. The results are helpful to the design and optimization of the process parameters in precision forging process of Ti-alloy blade.
文摘Forging spur gears are widely used in the driving system of mining machinery and equipment due to their higher strength and dimensional accuracy.For the purpose of precisely calculating the volume of cylindrical spur gear billet in cold precision forging,a new theoretical method named average circle method was put forward.With this method,a series of gear billet volumes were calculated.Comparing with the accurate three-dimensional modeling method,the accuracy of average circle method by theoretical calculation was estimated and the maximum relative error of average circle method was less than 1.5%,which was in good agreement with the experimental results.Relative errors of the calculated and the experimental for obtaining the gear billet volumes with reference circle method are larger than those of the average circle method.It shows that average circle method possesses a higher calculation accuracy than reference circle method(traditional method),which should be worth popularizing widely in calculation of spur gear billet volume.
基金This work was supported by the National Natural Science Foundation of China for Distinguished Young Scholar (No.50225518), the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE,P.R.C.,the Aeronautical Science Foundation of China (No.02H53061)and the Natural Science Foundation of shaan'xi Province (NO,2001CS0401).
文摘Blade precision forging is a high temperature and large plastic deformation process. Interaction of deformation andheat conduction results in producing large temperature unevenness inside the billet. The unevenness has a greateffect on the mechanical property and microstructure of the forged blade. However, internal quality of the blade isdecided by its microstructure, it is necessary to conduct a research on the microstructure of the blade forging process.Taking a blade with a tenon as an object, its precision forging process is simulated and analyzed using a 3D coupledthermo-mechanical FEM code. And based on the prediction model of Ti-6Al-4V presented by the predecessor, astudy of the evolution of grain size in the forging process is made. The distribution characteristics of grain size intypical sections are obtained under various deformation degrees. This study may provide a base for designing theblade forging process and working out its parameters.
基金Project(2006BAF04B06) supported by the National Key Technology R & D Program of ChinaProject(2005AA101B19) supported by the Key Technology R & D Program of Hubei Province, China
文摘The finite element analysis (FEA) software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom corner of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom corner. When non-uniform interference is adopted the first principal stress at the corner on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the corner stress concentration. The first principal stress at the corner of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.
基金Project(51105287)supported by the National Natural Science Foundation of China
文摘To investigate the effects of billet geometry on the cold precision forging process of a helical gear,six different billet geometries were designed utilizing the relief-hole principle.And the influences of the billet geometry on the forming load and the deformation uniformity were analyzed by three-dimensional(3D)finite element method(FEM)under the commercial software DEFORM 3D.The billet geometry was optimized to meet lower forming load and better deformation uniformity requirement.Deformation mechanism was studied through the distribution of flow velocity field and effective strain field.The forging experiments of the helical gear were successfully performed using lead material as a model material under the same process conditions used in the FE simulations.The results show that the forming load decreases as the diameter of relief-hole d0 increases,but the effect of d0 on the deformation uniformity is very complicated.The forming load is lower and the deformation is more uniform when d0 is 10mm.
基金Project(51375042)supported by the National Natural Science Foundation of ChinaProject supported by Beijing Laboratory of Modern Transport Metal Materials and Processing Technology,China
文摘To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.
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.
文摘A new cold precision forging technique is proposed to form a spur gear from a hollow billet, that is blocking the divided flow region and then final forging by the relief hole. 3D FEM simulation of the whole process of a pure aluminium spur gear is performed using DEFORM 3D TM . The load stroke curve, effective stress distribution, effective strain distribution, velocity distribution, and so on, are achieved. These results are compared with those achieved using the conventional closed die forging in the same conditions. The results show that this new technique has many advantages over the conventional one. The deformation load is reduced by near 30% and the filling ability of the tooth profile is also improved. Precision forging experiments of spur gears with the new process were performed using material Pb. The experimental results show a good agreement with the numerical results.
基金Project(50225518) supported by the National Science Foundation of China for Distinguished Young Scholars Project(02H53061) supported by the Aeronautical Science Foundation of China Project(05-1) supported by the Foundation of State Key Laboratory of Plastic Forming Simulation and Mould Technology
文摘In order to obtain the desired final shape, the blade precision forging requires a reasonable preformed billet which can be obtained from a given final shape by using backward tracing scheme based on FEM. The key technologies of backward tracing scheme based on 3D rigid-viscoplastic FEM were explored, and some valid algorithms or methods were proposed. A velocity field was generated by combining the direct iterative method with Newton-Raphson iterative method, and then the initial velocity field of backward tracing simulation was achieved by reversing the direction of the velocity field. A new method, namely the tracking-fitting-revising method, was proposed and can be used to determinate the criterion of separating a node from die in the backward tracing simulation. The ceasing criterion of the backward tracing simulation is that all the boundary nodes are detached from dies. Based on the above key technologies, the 3D backward tracing simulation system for the blade precision forging was developed, and its feasibility and reliability were verified by forward loading simulation.
基金Project(50575213)supported by the National Natural Science Foundation of China
文摘Fundamental investigations on precision forging technology of magnesium alloys were studied.As-cast billet prestraining and a new concept of hollow billet were proposed in order to reduce the maximum forming load.A schcme of isothermal forming and the use of combined female dies were adopted,which can improve the die filling capacity and ensure the manufacture of high quality forgings.By means of the developed technique,AZ80 alloy wheel and AZ31 alloy bracket were produced successfully at suitable process parameters and applied in the automotive industries.The results show that the hot compression of AZ80 magnesium alloy has the peak flow stresses of pre-strained alloy with finer grain,which are lower by 20%than those of as-cast alloy under the same deformation conditions.The forming load is related to contact area and average positive stress on interface during forging process.
文摘The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance for making decision on the optimal choice of process parameters and mould structure. Trial forging was used to verify the effectiveness of FEM simulation results.
基金supported by the Aeronautical Science Foundation of China(No.02H53061)the National Science Found of China for Distinguished Young Scholar(No.50225518)the Shaan'xi Provincial Natural Science Foundation of China(No.2001CS0401)
文摘The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade with a tenon into consideration, a 3D mechanical model in precision forging is built up. The distribution laws of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.