For hot rolling of titanium alloy large rings,evolution laws of stress and strain fields in rings with various sizes were explored and compared based on a reliable coupled thermo-mechanical three-dimensional （3D） fi...For hot rolling of titanium alloy large rings,evolution laws of stress and strain fields in rings with various sizes were explored and compared based on a reliable coupled thermo-mechanical three-dimensional （3D） finite element （FE） model.The results show that for forming processes of different rings,as γ^-（the equivalent distribution ratio of feed amount per revolution of a process） decreases,the final peak Mises stress may transfer from the biting point at the driver roll side to that at the idle roll side,and the final peak equivalent plastic strain may transfer from the outside surface to the inside surface;as L^- （the equivalent deformation zone length of a process） increases,the final peak Mises stress may appear in the middle layer.The final positions of peak Mises stress and equivalent plastic strain are the combined effects of the above two aspects.In the deformation zone of a deformed ring,the surface layers are in the 3D compressive stress state,while the middle layer is in the 1D compressive and 2D tensile stress state or 2D compressive and 1D tensile stress state;the whole ring is in the 1D compressive and 2D tensile strain state.展开更多
目的为提升大变形技术的加工效率和质量,消除变形热带来的影响,提出一种基于传统切削的深冷挤压切削(Cryogenic Temperature Extrusion Machining,CT-EM)工艺,并通过数值模拟与实验验证了该方法的可靠性。方法利用DEFORM软件中的点追踪...目的为提升大变形技术的加工效率和质量,消除变形热带来的影响,提出一种基于传统切削的深冷挤压切削(Cryogenic Temperature Extrusion Machining,CT-EM)工艺,并通过数值模拟与实验验证了该方法的可靠性。方法利用DEFORM软件中的点追踪与流动网格法对不同切削压缩比(1.4、1.6、1.8)条件下的等效应变、应变率及切屑成形过程进行了有限元模拟,开展了切削实验,并对切屑的形貌及微观组织进行了分析。结果挤压切削分为初始切入、切屑成形以及稳定成形3个阶段,第二变形区的网格畸变最严重;等效应变随着压缩比的增大而增大,其值在1.2~1.6之间,与计算值较吻合;等效应变率产生于第一变形区宽度为200~250μm的区域,且CT-EM具有更高的等效应变率;CT-EM制备的切屑带材表面粗糙度低、裂纹少、成形能力更优,切屑内的微观组织被强烈细化(<200 nm),达到了超细晶结构,且产生了大量的位错缠结区。结论深冷处理可提升7系铝合金切削加工时的成形能力,晶粒细化是较大的等效应变与应变率共同作用的结果,模拟数据对实验结果有较好的支撑。展开更多
To obtain final parts with the desired dimensional accuracy and repeatability via electrochemical machining(ECM), the machining process must enter an ECM balanced state. However,for the ECM processing of blisk, a key ...To obtain final parts with the desired dimensional accuracy and repeatability via electrochemical machining(ECM), the machining process must enter an ECM balanced state. However,for the ECM processing of blisk, a key component of aerospace engines, the surface of the blade blank often has an uneven allowance distribution due to the narrow passage of the cascade. It is difficult to remedy this issue in subsequent processing steps, which is necessary to ensure the dimensional accuracy and repeatability of the final blade profile. To solve this problem, electrolytic machining must be preceded by electrolytic shaping, which requires cathode tools with large leveling ratios to quickly homogenize the blank surface of the blade. In this study, to obtain a cathode tool with an extremely high leveling ratio, a design method based on the variation in the electrode gap in the non-equilibrium electrolytic state is proposed, and a dissolution model based on the nonequilibrium state is established. In this design method, the allowance on the blank to be machined is first divided into many discrete allowances with the normal direction. The initial machining clearance, feed rate, and total machining time are then calculated using classical ECM equilibrium state theory based on the maximum allowance. Meanwhile, the point coordinates of the cathode tool at maximum allowance can be determined. The non-equilibrium model can then be used to calculate the relative coordinate positions corresponding to the remaining discrete allowances. Finally, the entire cathode tool profile is designed. Simulations, fundamental experiments, and blisk unit workpiece experiments were carried out to validate the design approach. In the simulated processing of the plane workpiece, the leveling ratio of the cathode tool designed by the proposed method(0.77)was 83% higher than that of the cathode tool designed using the traditional method. The simulation results were confirmed by processing experiments. In the machining of blisk unit workpieces with complex curved surfaces, the leveling ratios of the convex and concave parts of the blade machined using the proposed cathode tool respectively reached 0.75 and 0.54, which are 75% and 38% higher than those obtained using the traditional method. This new cathode design method and machining technology can significantly improve the surface allowance distribution of blank before electrolytic finishing. It is helpful for finishing machine to enter electrolytic equilibrium state. Finally, the final blade profile accuracy can be guaranteed and repeated errors can be reduced.展开更多
基金Project(51005258) supported by the National Natural Science Foundation of China
文摘For hot rolling of titanium alloy large rings,evolution laws of stress and strain fields in rings with various sizes were explored and compared based on a reliable coupled thermo-mechanical three-dimensional （3D） finite element （FE） model.The results show that for forming processes of different rings,as γ^-（the equivalent distribution ratio of feed amount per revolution of a process） decreases,the final peak Mises stress may transfer from the biting point at the driver roll side to that at the idle roll side,and the final peak equivalent plastic strain may transfer from the outside surface to the inside surface;as L^- （the equivalent deformation zone length of a process） increases,the final peak Mises stress may appear in the middle layer.The final positions of peak Mises stress and equivalent plastic strain are the combined effects of the above two aspects.In the deformation zone of a deformed ring,the surface layers are in the 3D compressive stress state,while the middle layer is in the 1D compressive and 2D tensile stress state or 2D compressive and 1D tensile stress state;the whole ring is in the 1D compressive and 2D tensile strain state.
文摘目的为提升大变形技术的加工效率和质量,消除变形热带来的影响,提出一种基于传统切削的深冷挤压切削(Cryogenic Temperature Extrusion Machining,CT-EM)工艺,并通过数值模拟与实验验证了该方法的可靠性。方法利用DEFORM软件中的点追踪与流动网格法对不同切削压缩比(1.4、1.6、1.8)条件下的等效应变、应变率及切屑成形过程进行了有限元模拟,开展了切削实验,并对切屑的形貌及微观组织进行了分析。结果挤压切削分为初始切入、切屑成形以及稳定成形3个阶段,第二变形区的网格畸变最严重;等效应变随着压缩比的增大而增大,其值在1.2~1.6之间,与计算值较吻合;等效应变率产生于第一变形区宽度为200~250μm的区域,且CT-EM具有更高的等效应变率;CT-EM制备的切屑带材表面粗糙度低、裂纹少、成形能力更优,切屑内的微观组织被强烈细化(<200 nm),达到了超细晶结构,且产生了大量的位错缠结区。结论深冷处理可提升7系铝合金切削加工时的成形能力,晶粒细化是较大的等效应变与应变率共同作用的结果,模拟数据对实验结果有较好的支撑。
基金sponsored by the Industrial Technology Development Program (Grant No. JCKY2021605B026, and National Natural Science Foundation of China (Grant No. 92160301))。
文摘To obtain final parts with the desired dimensional accuracy and repeatability via electrochemical machining(ECM), the machining process must enter an ECM balanced state. However,for the ECM processing of blisk, a key component of aerospace engines, the surface of the blade blank often has an uneven allowance distribution due to the narrow passage of the cascade. It is difficult to remedy this issue in subsequent processing steps, which is necessary to ensure the dimensional accuracy and repeatability of the final blade profile. To solve this problem, electrolytic machining must be preceded by electrolytic shaping, which requires cathode tools with large leveling ratios to quickly homogenize the blank surface of the blade. In this study, to obtain a cathode tool with an extremely high leveling ratio, a design method based on the variation in the electrode gap in the non-equilibrium electrolytic state is proposed, and a dissolution model based on the nonequilibrium state is established. In this design method, the allowance on the blank to be machined is first divided into many discrete allowances with the normal direction. The initial machining clearance, feed rate, and total machining time are then calculated using classical ECM equilibrium state theory based on the maximum allowance. Meanwhile, the point coordinates of the cathode tool at maximum allowance can be determined. The non-equilibrium model can then be used to calculate the relative coordinate positions corresponding to the remaining discrete allowances. Finally, the entire cathode tool profile is designed. Simulations, fundamental experiments, and blisk unit workpiece experiments were carried out to validate the design approach. In the simulated processing of the plane workpiece, the leveling ratio of the cathode tool designed by the proposed method(0.77)was 83% higher than that of the cathode tool designed using the traditional method. The simulation results were confirmed by processing experiments. In the machining of blisk unit workpieces with complex curved surfaces, the leveling ratios of the convex and concave parts of the blade machined using the proposed cathode tool respectively reached 0.75 and 0.54, which are 75% and 38% higher than those obtained using the traditional method. This new cathode design method and machining technology can significantly improve the surface allowance distribution of blank before electrolytic finishing. It is helpful for finishing machine to enter electrolytic equilibrium state. Finally, the final blade profile accuracy can be guaranteed and repeated errors can be reduced.
