The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic sim...The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic simulation research of the new type reversing valve is conducted. The effects of the system parameters on the working performance are researched systematically and deeply. The regular understanding on the motion of the reversing valve is obtained, which provides theoretical basis for the innovation and manufacturing of a new generation of hydraulic breaker reversing valve.展开更多
There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging,i.e.larger forming loads,lower material utilization,larger subsequent machining allo...There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging,i.e.larger forming loads,lower material utilization,larger subsequent machining allowance and nonuniform microstructure.For this reason,based on the orthogonal test,the semisolid diecasting process of a certain type of four-way valve was simulated with FLOW-3D.The simulation results show that the optimized process parameters are:the pouring temperature of 897.25 ?C,the shot velocity of 2.0 m/s and the preheated die temperature of 260 C.The simulation results demonstrate that the cavity can be filled smoothly and completely,the surface defects are small,the temperature field and the pressure field are uniform,and the casting quality is satisfactory.The effectiveness and availability of applying this technology are well verified by the numerical simulation.展开更多
The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnet...The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio （MR） and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.展开更多
文摘The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic simulation research of the new type reversing valve is conducted. The effects of the system parameters on the working performance are researched systematically and deeply. The regular understanding on the motion of the reversing valve is obtained, which provides theoretical basis for the innovation and manufacturing of a new generation of hydraulic breaker reversing valve.
基金Project(50375117) supported by the National Natural Science Foundation of China
文摘There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging,i.e.larger forming loads,lower material utilization,larger subsequent machining allowance and nonuniform microstructure.For this reason,based on the orthogonal test,the semisolid diecasting process of a certain type of four-way valve was simulated with FLOW-3D.The simulation results show that the optimized process parameters are:the pouring temperature of 897.25 ?C,the shot velocity of 2.0 m/s and the preheated die temperature of 260 C.The simulation results demonstrate that the cavity can be filled smoothly and completely,the surface defects are small,the temperature field and the pressure field are uniform,and the casting quality is satisfactory.The effectiveness and availability of applying this technology are well verified by the numerical simulation.
基金financially supported by the National Natural Science Foundation of China (Nos. 61025021and 60936002)the National Key Project of Scienceand Technology of China (Nos. 2009ZX02023-001-3 and 2011ZX02403-002)the Independent Scientific Research of Tsinghua University (No. 2010THZ0)
文摘The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio （MR） and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.
