Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mecha...Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mechanical model,radial forging process of a hollow stepped gear shaft for automobile was simulated.The optimal combination of three process parameters including initial temperature,rotation rate and radial reduction was also selected using orthogonal design method.To examine the strain inhomogeneity of the forging workpiece,the strain inhomogeneity factor was introduced.The results reveal that the maximum effective strain and the minimum effective strain appeared in the outermost and innermost zones of different cross sections for the hollow stepped gear shaft,respectively.Optimal forging parameters are determined as a combination of initial temperature of 780°C,rotation rate of 21°/stroke and radial reduction of 3 mm.展开更多
Many high-quality forging productions require the large-sized hydraulic press machine（HPM） to have a desirable dynamic response. Since the forging process is complex under the low velocity, its response is difficult...Many high-quality forging productions require the large-sized hydraulic press machine（HPM） to have a desirable dynamic response. Since the forging process is complex under the low velocity, its response is difficult to estimate. And this often causes the desirable low-velocity forging condition difficult to obtain. So far little work has been found to estimate the dynamic response of the forging process under low velocity. In this paper, an approximate-model based estimation method is proposed to estimate the dynamic response of the forging process under low velocity. First, an approximate model is developed to represent the forging process of this complex HPM around the low-velocity working point. Under guaranteeing the modeling performance, the model may greatly ease the complexity of the subsequent estimation of the dynamic response because it has a good linear structure. On this basis, the dynamic response is estimated and the conditions for stability, vibration, and creep are derived according to the solution of the velocity. All these analytical results are further verified by both simulations and experiment. In the simulation verification for modeling, the original movement model and the derived approximate model always have the same dynamic responses with very small approximate error. The simulations and experiment finally demonstrate and test the effectiveness of the derived conditions for stability, vibration, and creep, and these conditions will benefit both the prediction of the dynamic response of the forging process and the design of the controller for the high-quality forging. The proposed method is an effective solution to achieve the desirable low-velocity forging condition.展开更多
Large complex 7A85 aluminum wing-body joint was forged employing isothermal forging process and its mechanical properties were studied.The tensile strength after forging is up to 587.5 MPa in longitudinal direction,15...Large complex 7A85 aluminum wing-body joint was forged employing isothermal forging process and its mechanical properties were studied.The tensile strength after forging is up to 587.5 MPa in longitudinal direction,15% higher than that using free forging.Moreover,the tensile strength of the forging is almost the same in three directions.Isothermal forging also performs well on overall fracture toughness,with a maximum value of 39.8 MPa·m1/2,and that of short transverse direction all reaches 36 MPa·m1/2 and above,with a maximum relative error of only 3.6%.The results indicate that the isothermal forging leads to better performance as well as higher uniformity in mechanical properties.展开更多
In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated...In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated in detail using Gleeble-1500 thermal mechanical simulator, universal testing machine and optical microscope （OM）. The compression deformation experimental data of commercially pure titanium （CP-Ti） were mapped to be a T vs lg diagram in which data fall into three distinct regions, i.e., three-stage work hardening, two-stage work hardening and flow softening, which can be separated by border lines at 17.5 and 15.4 for lg Z, where Z represents the Zener-Hollomon parameter. The deformation twin is found to have higher Z-value corresponding to the work hardening region. The differences in microstructures and mechanical properties for two kinds of billets indicate that forged billet consists of deformation twins and some twin intersections, and many twins cross the grain boundaries. However, nearly no twins can be seen in the microstructure of billet formed by rolling under optical microscope （OM）, but there are equiaxed and platelike grains. Tensile tests and Vickers hardness test indicate that yield strength, tensile strength and microhardness of the samples after forging are higher than those after rolling.展开更多
Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated t...Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.展开更多
A process parameter optimization method for mold wear during die forging process is proposed and a mold life prediction method based on polynomial fitting is presented,by combining the variance analysis method in the ...A process parameter optimization method for mold wear during die forging process is proposed and a mold life prediction method based on polynomial fitting is presented,by combining the variance analysis method in the orthogonal test with the finite element simulation test in the forging process.The process parameters with the greatest influence on the mold wear during the die forging process and the optimal solution of the process parameters to minimize the wear depth of the mold are derived.The hot die forging process is taken as an example,and a mold wear correction model for hot forging processes is derived based on the Archard wear model.Finite element simulation analysis of die wear process in hot die forging based on deform software is performed to study the relationship between the wear depth of the mold working surface and the die forging process parameters during hot forging process.The optimized process parameters suitable for hot forging are derived by orthogonal experimental design and analysis of variance.The average wear amount of the mold during the die forging process is derived by calculating the wear depth of a plurality of key nodes on the mold surface.Mold life for the entire production process is predicted based on average mold wear depth and polynomial fitting.展开更多
Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro...Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro-double gear with central shaft.In the paper,a novel hy-brid-forming process with two kinds of piercing method have been proposed to manufacture the micro-double gear using micro forming technology.The tests of hybrid forming process were carried out with two steps and the micro-double gear was successfully manufactured with good surface quality.The results also show that the hybrid micro-forming process with central piercing method can improve the defects of inclining shaft generated by double-ended piercing method.The quality evaluation of micro-double gear was conducted with surface roughness,micro-hardness and impact tests.The results show that the micro-double gear with good mechanical properties can meet the requirements of application for milli-machines.展开更多
Microstructures and tensile properties of a newβhigh-strength titanium alloy Ti-5321(Ti-5 Al-3 Mo-3 V-2 Zr-2 Cr-1 Nb-1 Fe)were investigated in this study.Four microstructures,including equiaxed microstructure(EM),bim...Microstructures and tensile properties of a newβhigh-strength titanium alloy Ti-5321(Ti-5 Al-3 Mo-3 V-2 Zr-2 Cr-1 Nb-1 Fe)were investigated in this study.Four microstructures,including equiaxed microstructure(EM),bimodal microstructure(BM),basket-weave microstructure(WM)and lamellar microstructure(LM),were tailored by changing the forging process,and the influences of different microstructures on tensile properties were also analyzed.The results indicated that Ti-5321 exhibits a better combination of strength and ductility,compared to Ti-5553,Ti-1023,BT22 and Ti15-3.The ultimate tensile strength,total elongation and reduction in area could be achieved in a range of 1200-1300 MPa,10%-15%and40%-60%,respectively.The influences of variant selection on the tensile properties in Ti-5321 alloy were also analyzed.Afterβforging and solution treatment,αphase maintained strictly Burgers orientation relation with adjacentβphase.Morphological features of the fractography in BM and LM were also explored to further explain the tensile properties and the fracture mode of Ti-5321 alloy.展开更多
基金Projects(51774054,51974050)supported by the National Natural Science Foundation of China。
文摘Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mechanical model,radial forging process of a hollow stepped gear shaft for automobile was simulated.The optimal combination of three process parameters including initial temperature,rotation rate and radial reduction was also selected using orthogonal design method.To examine the strain inhomogeneity of the forging workpiece,the strain inhomogeneity factor was introduced.The results reveal that the maximum effective strain and the minimum effective strain appeared in the outermost and innermost zones of different cross sections for the hollow stepped gear shaft,respectively.Optimal forging parameters are determined as a combination of initial temperature of 780°C,rotation rate of 21°/stroke and radial reduction of 3 mm.
基金Supported by National Basic Research Program of China(973 Program,Grant No.2011CB706802)National Natural Science Foundation of China(Grant No.51205420)+1 种基金Program for New Century Excellent Talents in University of China(Grant No.NCET-13-0593)Hunan Provincial Natural Science Foundation of China(Grant No.14JJ3011)
文摘Many high-quality forging productions require the large-sized hydraulic press machine（HPM） to have a desirable dynamic response. Since the forging process is complex under the low velocity, its response is difficult to estimate. And this often causes the desirable low-velocity forging condition difficult to obtain. So far little work has been found to estimate the dynamic response of the forging process under low velocity. In this paper, an approximate-model based estimation method is proposed to estimate the dynamic response of the forging process under low velocity. First, an approximate model is developed to represent the forging process of this complex HPM around the low-velocity working point. Under guaranteeing the modeling performance, the model may greatly ease the complexity of the subsequent estimation of the dynamic response because it has a good linear structure. On this basis, the dynamic response is estimated and the conditions for stability, vibration, and creep are derived according to the solution of the velocity. All these analytical results are further verified by both simulations and experiment. In the simulation verification for modeling, the original movement model and the derived approximate model always have the same dynamic responses with very small approximate error. The simulations and experiment finally demonstrate and test the effectiveness of the derived conditions for stability, vibration, and creep, and these conditions will benefit both the prediction of the dynamic response of the forging process and the design of the controller for the high-quality forging. The proposed method is an effective solution to achieve the desirable low-velocity forging condition.
基金Project(2010CB731701) supported by the National Basic Research Program of ChinaProject(2012ZX04010-081) supported by National Science and Technology Major Program of China
文摘Large complex 7A85 aluminum wing-body joint was forged employing isothermal forging process and its mechanical properties were studied.The tensile strength after forging is up to 587.5 MPa in longitudinal direction,15% higher than that using free forging.Moreover,the tensile strength of the forging is almost the same in three directions.Isothermal forging also performs well on overall fracture toughness,with a maximum value of 39.8 MPa·m1/2,and that of short transverse direction all reaches 36 MPa·m1/2 and above,with a maximum relative error of only 3.6%.The results indicate that the isothermal forging leads to better performance as well as higher uniformity in mechanical properties.
文摘In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated in detail using Gleeble-1500 thermal mechanical simulator, universal testing machine and optical microscope （OM）. The compression deformation experimental data of commercially pure titanium （CP-Ti） were mapped to be a T vs lg diagram in which data fall into three distinct regions, i.e., three-stage work hardening, two-stage work hardening and flow softening, which can be separated by border lines at 17.5 and 15.4 for lg Z, where Z represents the Zener-Hollomon parameter. The deformation twin is found to have higher Z-value corresponding to the work hardening region. The differences in microstructures and mechanical properties for two kinds of billets indicate that forged billet consists of deformation twins and some twin intersections, and many twins cross the grain boundaries. However, nearly no twins can be seen in the microstructure of billet formed by rolling under optical microscope （OM）, but there are equiaxed and platelike grains. Tensile tests and Vickers hardness test indicate that yield strength, tensile strength and microhardness of the samples after forging are higher than those after rolling.
基金the National Science and Technology Major Project of China(No.2012ZX04012-011-02)the National Basic Research Program(973)of China(No.2011CB012903)
文摘Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.
基金This work was supported in part by the National Natural Science Foundation of China(No.51575008).
文摘A process parameter optimization method for mold wear during die forging process is proposed and a mold life prediction method based on polynomial fitting is presented,by combining the variance analysis method in the orthogonal test with the finite element simulation test in the forging process.The process parameters with the greatest influence on the mold wear during the die forging process and the optimal solution of the process parameters to minimize the wear depth of the mold are derived.The hot die forging process is taken as an example,and a mold wear correction model for hot forging processes is derived based on the Archard wear model.Finite element simulation analysis of die wear process in hot die forging based on deform software is performed to study the relationship between the wear depth of the mold working surface and the die forging process parameters during hot forging process.The optimized process parameters suitable for hot forging are derived by orthogonal experimental design and analysis of variance.The average wear amount of the mold during the die forging process is derived by calculating the wear depth of a plurality of key nodes on the mold surface.Mold life for the entire production process is predicted based on average mold wear depth and polynomial fitting.
基金Funded by the Technology Research and Development Program of China (2006AA04Z331)Young Scholars of Heilongjiang Province (JC-05-11 and JC-06-07)
文摘Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro-double gear with central shaft.In the paper,a novel hy-brid-forming process with two kinds of piercing method have been proposed to manufacture the micro-double gear using micro forming technology.The tests of hybrid forming process were carried out with two steps and the micro-double gear was successfully manufactured with good surface quality.The results also show that the hybrid micro-forming process with central piercing method can improve the defects of inclining shaft generated by double-ended piercing method.The quality evaluation of micro-double gear was conducted with surface roughness,micro-hardness and impact tests.The results show that the micro-double gear with good mechanical properties can meet the requirements of application for milli-machines.
基金financially supported by the International Science and Technology Cooperation Program of China(No.2015DFA51430)the National Natural Science Foundation of China(No.51471136)。
文摘Microstructures and tensile properties of a newβhigh-strength titanium alloy Ti-5321(Ti-5 Al-3 Mo-3 V-2 Zr-2 Cr-1 Nb-1 Fe)were investigated in this study.Four microstructures,including equiaxed microstructure(EM),bimodal microstructure(BM),basket-weave microstructure(WM)and lamellar microstructure(LM),were tailored by changing the forging process,and the influences of different microstructures on tensile properties were also analyzed.The results indicated that Ti-5321 exhibits a better combination of strength and ductility,compared to Ti-5553,Ti-1023,BT22 and Ti15-3.The ultimate tensile strength,total elongation and reduction in area could be achieved in a range of 1200-1300 MPa,10%-15%and40%-60%,respectively.The influences of variant selection on the tensile properties in Ti-5321 alloy were also analyzed.Afterβforging and solution treatment,αphase maintained strictly Burgers orientation relation with adjacentβphase.Morphological features of the fractography in BM and LM were also explored to further explain the tensile properties and the fracture mode of Ti-5321 alloy.
