The capability of the torsion extrusion （TE） process as a severe plastic deformation （SPD） method was compared with the conventional forward extrusion （FE） process. The TE and FE processes were successfully perf...The capability of the torsion extrusion （TE） process as a severe plastic deformation （SPD） method was compared with the conventional forward extrusion （FE） process. The TE and FE processes were successfully performed on AA1050 alloy samples at room temperature. To simulate the above mentioned processes, finite element analysis was carried out using the commercial elasto-plastic finite element analysis ABAQUS/Explicit Simulation. It is shown that load requirement for the TE process is lower than that for the FE process. The equivalent plastic strain calculated by the FEA proved that higher values of strain are imposed to the sample in the TE process. The strain distribution for the TE sample at the final stage of extrusion shows smoother strain gradient in comparison with the one produced by the FE process.展开更多
The motion track of belt spindle is important for the radial error of belt spindle. An analytical modeling method for the motion track of belt spindle under the combined effects of bending moment-torque-thermal deform...The motion track of belt spindle is important for the radial error of belt spindle. An analytical modeling method for the motion track of belt spindle under the combined effects of bending moment-torque-thermal deformation is proposed in this paper. Three running phases of belt spindle have been analyzed and modeled: the start-up phase with leaping change due to the change in force and bending moment, the accelerating phase with axis deflection, and the constant speed phase with axis regression because of the combined effects of bending moment-torque-thermal deformation. The simulation and test were completed on the belt spindle of SKVM850 machine tool, which illustrates the variation law of the radial error of belt spindle during the whole running phases.展开更多
Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twi...Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus （BP）. We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.展开更多
Electrostatic torsional micromirrors are widely applied in the fields·of micro-optical switches,optical attenuators,optical scanners,and optical displays.In previous lectures,most of the micromirrors were twisted...Electrostatic torsional micromirrors are widely applied in the fields·of micro-optical switches,optical attenuators,optical scanners,and optical displays.In previous lectures,most of the micromirrors were twisted along the urtiaxial or biaxial direction,which limited the range of light reflection.In this·paper,a quasicrystal torsional micromirror that can be deflected in any direction is designed and the dynamic model of the electrostatically driven micromirror is established.The static and dynamic phenomena and pull-in characteristics are analyzed through the numerical solution of the strain gradient theory.The results of three kinds of mirror deflection directions are compared and analyzed.The results show the significant differences in the torsion models with different deflection axis directions.When the deflection angle along the oblique axis reaches 45°,the instability voltage is the smallest.The pull-in instability voltage increases with the increment ofphonon-phason coupling elastic modulus and phason elastic modulus.The perrriittivity of quasicrystal,the strain gradient parameter,and the air damping influence the torsion of the micromirror dynaniic system.A larger pull-in instability voltage generates with the decrease of surface distributed forces.展开更多
基金been conducted using research grants of Islamic Azad University,Shiraz Branch
文摘The capability of the torsion extrusion （TE） process as a severe plastic deformation （SPD） method was compared with the conventional forward extrusion （FE） process. The TE and FE processes were successfully performed on AA1050 alloy samples at room temperature. To simulate the above mentioned processes, finite element analysis was carried out using the commercial elasto-plastic finite element analysis ABAQUS/Explicit Simulation. It is shown that load requirement for the TE process is lower than that for the FE process. The equivalent plastic strain calculated by the FEA proved that higher values of strain are imposed to the sample in the TE process. The strain distribution for the TE sample at the final stage of extrusion shows smoother strain gradient in comparison with the one produced by the FE process.
基金Supported by the State S&T Projects for Upmarket NC Machine and Fundamental Manufacturing Equipments of China(No.2012ZX04012-031)
文摘The motion track of belt spindle is important for the radial error of belt spindle. An analytical modeling method for the motion track of belt spindle under the combined effects of bending moment-torque-thermal deformation is proposed in this paper. Three running phases of belt spindle have been analyzed and modeled: the start-up phase with leaping change due to the change in force and bending moment, the accelerating phase with axis deflection, and the constant speed phase with axis regression because of the combined effects of bending moment-torque-thermal deformation. The simulation and test were completed on the belt spindle of SKVM850 machine tool, which illustrates the variation law of the radial error of belt spindle during the whole running phases.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11274380, 11004244 and 91433103)the National Basic Research Program of China (Grant No. 2012CB932704)
文摘Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus （BP）. We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11572191,51701117,and 51779139).
文摘Electrostatic torsional micromirrors are widely applied in the fields·of micro-optical switches,optical attenuators,optical scanners,and optical displays.In previous lectures,most of the micromirrors were twisted along the urtiaxial or biaxial direction,which limited the range of light reflection.In this·paper,a quasicrystal torsional micromirror that can be deflected in any direction is designed and the dynamic model of the electrostatically driven micromirror is established.The static and dynamic phenomena and pull-in characteristics are analyzed through the numerical solution of the strain gradient theory.The results of three kinds of mirror deflection directions are compared and analyzed.The results show the significant differences in the torsion models with different deflection axis directions.When the deflection angle along the oblique axis reaches 45°,the instability voltage is the smallest.The pull-in instability voltage increases with the increment ofphonon-phason coupling elastic modulus and phason elastic modulus.The perrriittivity of quasicrystal,the strain gradient parameter,and the air damping influence the torsion of the micromirror dynaniic system.A larger pull-in instability voltage generates with the decrease of surface distributed forces.
