Mg-xSi （x=0, 1.5, 3.3） alloys were fabricated and subjected to cyclic closed-die forging （CCDF）, a new severe plastic deformation process, at 450 ℃ for 1, 3, and 5 passes. With applying CCDF, tensile strength, el...Mg-xSi （x=0, 1.5, 3.3） alloys were fabricated and subjected to cyclic closed-die forging （CCDF）, a new severe plastic deformation process, at 450 ℃ for 1, 3, and 5 passes. With applying CCDF, tensile strength, elongation and hardness increase, while coarse Mg2Si particles break into smaller pieces and exhibit more uniform distribution. Mg-1.5%Si alloy exhibits a combination of improved strength and elongation after 5 passes of CCDF processing. The tensile strength is about 142 MPa and elongation is about 8%. The improvement in mechanical properties was further characterized by dry sliding wear testing. The results show that wear resistance improves with silicon content and CCDF process passes, particularly the first pass. The wear resistance increases by about 38% for Mg-3.3%Si after 5 passes of CCDF compared with pure Mg. The improvement of wear is related to microstructure refinement and homogenization based on the Archard equation and friction effect.展开更多
The closed-died cold forging technology of the bevel gears used in Jada car was investigated. With the analysis of the strain field and velocity field of the plastic deformation and the endured forces of the dies, the...The closed-died cold forging technology of the bevel gears used in Jada car was investigated. With the analysis of the strain field and velocity field of the plastic deformation and the endured forces of the dies, the filling rules for the metal were analyzed by the elastic-plastic finite element method （FEM）. The results show that there is a great difference among closed-die cold forging, extrusion and forging, as far as the metal flowing is concerned. The outer addendum cannot be filled completely in the closed-die cold forging of the bevel gears, and the round angle will be formed. But it does not influence the application of the bevel gears. At the beginning, the rigid area is formed in the cavity of the lower die. And then it will move upwards to supply the metal for the gear filling. For the closed-die cold forging of the bevel gears, the force acting on the upper die and the lower die is significantly different.展开更多
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
Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The hom...Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.展开更多
To understand the forming behaviour of aluminum alloys, the upsetting test of aluminum alloys at evaluated temperature is conducted. Because in warm forging the flow stress decreases with increasing straining, which i...To understand the forming behaviour of aluminum alloys, the upsetting test of aluminum alloys at evaluated temperature is conducted. Because in warm forging the flow stress decreases with increasing straining, which is so-called work softening, no appropriate material formulation is available. For the evaluation of flow stress of aluminum alloys in warm forging processes, in this paper, a formula is derived by analyzing the stress data measured at various temperatures. It is demonstrated that the formula fits the flow stress obtained from experiment.展开更多
To understand the forming behaviour of magnesium alloys, the upsetting test of Mg alloys at evaluated temperature was conducted. It is found that Mg alloys are brittle at temperatures below 200 ℃. When temperature is...To understand the forming behaviour of magnesium alloys, the upsetting test of Mg alloys at evaluated temperature was conducted. It is found that Mg alloys are brittle at temperatures below 200 ℃. When temperature is higher than 400 ℃, Mg alloy is not suitable for forging because of heavy oxidation. Mg alloy shows an excellent workability at temperatures from 250 to 400 ℃. Because in warm forging the flow stress decreases with increasing strain, which is so called work softening, no appropriate material formulation is available for Mg alloys. For the evaluation of flow stress of Mg alloys in warm forging processes, a formula is derived by analyzing the stress data measured at various temperatures in upsetting test. It is demonstrated that the formula fits the flow stress obtained from experiment.展开更多
A multistage warm/hot forming is simulated for the cross grove outer race ofconstant velocity joint, using a thermo-mechanical coupled rigid viscoplastic finite element method,and specially some problem for process de...A multistage warm/hot forming is simulated for the cross grove outer race ofconstant velocity joint, using a thermo-mechanical coupled rigid viscoplastic finite element method,and specially some problem for process development and die design are analyzed. A forming testshows that computed results have good agreement with experimental results. Above obtained resultscan be applied to development of multistage warm/hot forming process and die design for outer race.展开更多
该文对前8届国际塑性加工会议(International Conference on Technology of Plasticity)论文集中锻造方面的文献进行了综述,分析了24年来锻造工艺的发展历程。总结了热锻、温锻和冷锻的技术优缺点和近年来的技术突破。从中可以较充分地...该文对前8届国际塑性加工会议(International Conference on Technology of Plasticity)论文集中锻造方面的文献进行了综述,分析了24年来锻造工艺的发展历程。总结了热锻、温锻和冷锻的技术优缺点和近年来的技术突破。从中可以较充分地了解该技术的一些新的发展动向。展开更多
基金Projects(50674067,51074106)supported by the National Natural Science Foundation of ChinaProject(2011BAE22B01-5)supported by the National Key Technologies R&D Program during the 12th Five-Year Plan Period,ChinaProject(09JC1408200)supported by the Science and Technology Commission of Shanghai Municipality,China
文摘Mg-xSi （x=0, 1.5, 3.3） alloys were fabricated and subjected to cyclic closed-die forging （CCDF）, a new severe plastic deformation process, at 450 ℃ for 1, 3, and 5 passes. With applying CCDF, tensile strength, elongation and hardness increase, while coarse Mg2Si particles break into smaller pieces and exhibit more uniform distribution. Mg-1.5%Si alloy exhibits a combination of improved strength and elongation after 5 passes of CCDF processing. The tensile strength is about 142 MPa and elongation is about 8%. The improvement in mechanical properties was further characterized by dry sliding wear testing. The results show that wear resistance improves with silicon content and CCDF process passes, particularly the first pass. The wear resistance increases by about 38% for Mg-3.3%Si after 5 passes of CCDF compared with pure Mg. The improvement of wear is related to microstructure refinement and homogenization based on the Archard equation and friction effect.
文摘The closed-died cold forging technology of the bevel gears used in Jada car was investigated. With the analysis of the strain field and velocity field of the plastic deformation and the endured forces of the dies, the filling rules for the metal were analyzed by the elastic-plastic finite element method （FEM）. The results show that there is a great difference among closed-die cold forging, extrusion and forging, as far as the metal flowing is concerned. The outer addendum cannot be filled completely in the closed-die cold forging of the bevel gears, and the round angle will be formed. But it does not influence the application of the bevel gears. At the beginning, the rigid area is formed in the cavity of the lower die. And then it will move upwards to supply the metal for the gear filling. For the closed-die cold forging of the bevel gears, the force acting on the upper die and the lower die is significantly different.
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Project(51105287)supported by the National Natural Science Foundation of ChinaProject(2013M531750)supported by China Postdoctoral Science Foundation
文摘Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.
文摘To understand the forming behaviour of aluminum alloys, the upsetting test of aluminum alloys at evaluated temperature is conducted. Because in warm forging the flow stress decreases with increasing straining, which is so-called work softening, no appropriate material formulation is available. For the evaluation of flow stress of aluminum alloys in warm forging processes, in this paper, a formula is derived by analyzing the stress data measured at various temperatures. It is demonstrated that the formula fits the flow stress obtained from experiment.
文摘To understand the forming behaviour of magnesium alloys, the upsetting test of Mg alloys at evaluated temperature was conducted. It is found that Mg alloys are brittle at temperatures below 200 ℃. When temperature is higher than 400 ℃, Mg alloy is not suitable for forging because of heavy oxidation. Mg alloy shows an excellent workability at temperatures from 250 to 400 ℃. Because in warm forging the flow stress decreases with increasing strain, which is so called work softening, no appropriate material formulation is available for Mg alloys. For the evaluation of flow stress of Mg alloys in warm forging processes, a formula is derived by analyzing the stress data measured at various temperatures in upsetting test. It is demonstrated that the formula fits the flow stress obtained from experiment.
文摘A multistage warm/hot forming is simulated for the cross grove outer race ofconstant velocity joint, using a thermo-mechanical coupled rigid viscoplastic finite element method,and specially some problem for process development and die design are analyzed. A forming testshows that computed results have good agreement with experimental results. Above obtained resultscan be applied to development of multistage warm/hot forming process and die design for outer race.
文摘该文对前8届国际塑性加工会议(International Conference on Technology of Plasticity)论文集中锻造方面的文献进行了综述,分析了24年来锻造工艺的发展历程。总结了热锻、温锻和冷锻的技术优缺点和近年来的技术突破。从中可以较充分地了解该技术的一些新的发展动向。
