Materials with the same elastic modulus E and representative stress and strain （σr,εr） present similar indentation-loading curves, whatever the value of strain hardening exponent n. Based on this definition, a goo...Materials with the same elastic modulus E and representative stress and strain （σr,εr） present similar indentation-loading curves, whatever the value of strain hardening exponent n. Based on this definition, a good approach was proposed to extract the plastic properties or constitutive equations of metals from nanoindentation test combining finite element simulation. Firstly, without consideration of strain hardening, the representative stress was determined by varying assumed representative stress over a wide range until a good agreement was reached between the computed and experimental loading curves. Similarly, the corresponding representative strain was determined with different hypothetical values of strain hardening exponent in the range of 0-0.6. Through modulating assumed strain hardening exponent values to make the computed unloading curve coincide with that of the experiment, the real strain hardening exponent was acquired. Once the strain hardening exponent was determined, the initial yield stress ay of metals could be obtained by the power law constitution. The validity of the proposed methodology was verified by three real metals： AISI 304 steel, Fe andA1 alloy.展开更多
In order to improve the machinability but not to impair other properties of the prehardened mold steel for plastic, the composition was designed by application of Thermo-Calc software package to regulate the type of n...In order to improve the machinability but not to impair other properties of the prehardened mold steel for plastic, the composition was designed by application of Thermo-Calc software package to regulate the type of non-metallic inclusion formed in the steel. The regulated non-metallic inclusion type was also observed by SEM and EDX. Then the machinability assessment of the steel with designed composition under different conditions was studied by the measurement of tool wear amount and cutting force. The results show that the composition of free cutting elements adding to mold steel for plastic can be optimized to obtain proper type of non-metallic inclusion in the aid of Thermo-Calc, compared with the large volume fraction of soft inclusion which is needed for promoting ductile fracture at low cutting speeds, the proper type of inclusion at high cutting speeds is glassy oxide inclusion. All those can be obtained in the present work.展开更多
The paper investigates theoretically the optimization of the doped ablator layers for the plastic ignition capsule. The high-resolved one-dimensional implosion simulations show that the inner pure CFI layer of the Si-...The paper investigates theoretically the optimization of the doped ablator layers for the plastic ignition capsule. The high-resolved one-dimensional implosion simulations show that the inner pure CFI layer of the Si-doped design is excessively preheated by the hard x-ray, leading to the unstable ablator-fuel interface compared to the Ge-doped capsule. This is because that the Si K-shell absorption edge （1.8 keV） is higher than the Ge L-edge （1.3 keV）, and Si dopant makes more hard x-ray penetrate through the doped ablator layers to preheat the inner pure CH layer. So an optimization of the doped ablator layers （called ＂Si/Ge capsule＂） is performed： an Si-doped CH layer is placed next to the outer pure CH layer to keep the high implosion velocity; next to the Si-doped layer is a thin Ge-doped layer, in order to absorb the hard x-ray and protect the inner undoped CH-layer from excessively preheating. The simulations show that the Si/Ge capsule can effectively improve hydrodynamic stability at the ablator-fuel interface while keeping the high implosion velocity.展开更多
基金Project （51171125） supported by the National Natural Science Foundation of China Project （20110321051 ） supported by the Science and Technology Key Project of Shanxi Province, China
文摘Materials with the same elastic modulus E and representative stress and strain （σr,εr） present similar indentation-loading curves, whatever the value of strain hardening exponent n. Based on this definition, a good approach was proposed to extract the plastic properties or constitutive equations of metals from nanoindentation test combining finite element simulation. Firstly, without consideration of strain hardening, the representative stress was determined by varying assumed representative stress over a wide range until a good agreement was reached between the computed and experimental loading curves. Similarly, the corresponding representative strain was determined with different hypothetical values of strain hardening exponent in the range of 0-0.6. Through modulating assumed strain hardening exponent values to make the computed unloading curve coincide with that of the experiment, the real strain hardening exponent was acquired. Once the strain hardening exponent was determined, the initial yield stress ay of metals could be obtained by the power law constitution. The validity of the proposed methodology was verified by three real metals： AISI 304 steel, Fe andA1 alloy.
基金Project(015211010) supported by the Key Project of Science and Technology Commission of Shanghai Local Govern ment China
文摘In order to improve the machinability but not to impair other properties of the prehardened mold steel for plastic, the composition was designed by application of Thermo-Calc software package to regulate the type of non-metallic inclusion formed in the steel. The regulated non-metallic inclusion type was also observed by SEM and EDX. Then the machinability assessment of the steel with designed composition under different conditions was studied by the measurement of tool wear amount and cutting force. The results show that the composition of free cutting elements adding to mold steel for plastic can be optimized to obtain proper type of non-metallic inclusion in the aid of Thermo-Calc, compared with the large volume fraction of soft inclusion which is needed for promoting ductile fracture at low cutting speeds, the proper type of inclusion at high cutting speeds is glassy oxide inclusion. All those can be obtained in the present work.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11105013,11205017,and 11371065the National High-Tech R&D Program(863 Program) through Grant No.2012AA01A303
文摘The paper investigates theoretically the optimization of the doped ablator layers for the plastic ignition capsule. The high-resolved one-dimensional implosion simulations show that the inner pure CFI layer of the Si-doped design is excessively preheated by the hard x-ray, leading to the unstable ablator-fuel interface compared to the Ge-doped capsule. This is because that the Si K-shell absorption edge （1.8 keV） is higher than the Ge L-edge （1.3 keV）, and Si dopant makes more hard x-ray penetrate through the doped ablator layers to preheat the inner pure CH layer. So an optimization of the doped ablator layers （called ＂Si/Ge capsule＂） is performed： an Si-doped CH layer is placed next to the outer pure CH layer to keep the high implosion velocity; next to the Si-doped layer is a thin Ge-doped layer, in order to absorb the hard x-ray and protect the inner undoped CH-layer from excessively preheating. The simulations show that the Si/Ge capsule can effectively improve hydrodynamic stability at the ablator-fuel interface while keeping the high implosion velocity.
