The microstructures and properties of AgCuO composites were researched after severe plastic deformation. The results showed that CuO particles secondly were dispersed along with increasing of true strain. The purpose of microstructure homogenization was achieved. The value of density, tensile strength and resistivity was increasing along. The value of hardness was reduced. The value of the elongation was increasing before true strain 8.0 and decreasing after true strain 8.0 in AgCuO composites.
The mechanical properties and microstructures of three different VN, Nb, V-Nb microalloyed rebars were investigated by using tensile testing machine, impact machine, metallographic microscopy, scaning electron microcopy, transmission electron microscopy and X-ray diffraction apparatus. The results showed that the microstructure of V-Nb microalloyed specimen is consisted of ferrite, pearlite and a small amount of fine bainite (6.7wt%), and obvious effect of grain refinement was obtained with more than 10 size grade of ferrite grain, showing optimal comprehensive properties. SEM micrograph of tensile fracture surface for V-Nb microalloyed 500MPa high-strength rebar is dimple and ductile, ductile-brittle transformation temperature is lower than-30°C, which has good plasticity-toughness and impact toughness at low temperature. The results of precipitates have shown that a large number of small and dispersive V(CN) and Nb (CN) precipitates with size of 5~30nm are formed, good effect of precipitation strengthening was achieved in 500MPa high-strength rebars produced by different microalloying and controlled cooling technology.
Using metallographic test, physicochemical phase analysis, X-ray diffraction and transmission electron microscope, the microstructure of seismic rebars with yield strength of 500MPa, which were fabricated by vanadium and nitrogen microalloying and controlled rolling and controlled cooling, were investigated. The results of metallographic test show that the microstructure in centre and interlayer of tested rebar samples are made up of ferrite, pearlite and a small amount of bainite, but tempered sorbite with thickness of 0.9mm on the edge of the rebars. Physicochemical phase analysis indicates that vanadium in the rebars had precipitated by VN mainly, and the precipitation rates of V and N are 60% and 70%, respectively. The result of strengthening mechanisms analysis shows that fine grain strengthening and transformation strengthening are the dominated contributions to strength and strengthening increments of them are 184.4 MPa and 111.6 MPa, respectively.
In permanent magnet spherical motor control system, in order to obtain control current of the stator winding, it is required to solve the generalized inverse of the torque matrix of high dimension, which increases the computational burden of the control system. To solve this problem, the torque-sharing strategy of double-pole structure of PMSM was discussed. The target torque was decomposed into the rotation torque and the tilting torque through comparing the torque component of different stator windings. The set of control winding is divided. Further, according to the torque characteristics of a collection of internal stator winding and rotor position, an energizing strategy of the windings was developed, and the rotation and tilt torque control matrix were obtained, and two dimensional reduction matrixes reduced the computational burden. On this basis, the dynamics model and electrical model of PMSM were established, and the control system consisted of position loop and current loop. Control torque was obtained by the calculation of the torque method, and control current was obtained by torque-sharing strategy. Simulation results show that the system is able to achieve independent control of rotation and tilt and track the desired trajectory.
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