The aim of this work is to investigate the mechanical properties and microstructures of friction-stir welded(FSWed) St52 structural steel joints. In this study, St52 steel plates with a thickness of 4 mm were butt-wel...The aim of this work is to investigate the mechanical properties and microstructures of friction-stir welded(FSWed) St52 structural steel joints. In this study, St52 steel plates with a thickness of 4 mm were butt-welded by friction-stir welding(FSW) using a tungsten carbide tool having a conical pin. The microstructure of the welded zone consists of equiaxed fine ferrite, grain boundary ferrite, Widmanstatten ferrite, and aggregates of ferrite + cementite. The microhardness measurements showed that the hardness of the welded zone was significantly higher than that of the base metal. The FSWed St52 joint exhibited a significant strength overmatching in the weld region and a strength performance similar to or slightly higher than that of the base plate.展开更多
A siliconizing process to manufacture 6.5% Si steel sheet has been developed. Electric components, such as transformers and reactors are made easily from 6.5% Si steel sheet. However, improved workability is desirable...A siliconizing process to manufacture 6.5% Si steel sheet has been developed. Electric components, such as transformers and reactors are made easily from 6.5% Si steel sheet. However, improved workability is desirable to increase the applications. Therefore the improvement of workability of 6.5% Si steel sheet was investigated, and the results were obtained as follows: (a) workability of 6.5% Si steel sheet is deteriorated by grain boundary oxidization, (b) grain boundary oxidization can be restrained by the addition of C. Workability and magnetic properties of 6.5% Si steel sheet with C addition are discussed. Furthermore, it was found that the workability of high Si steel sheet was improved remarkably by varying the Si content gradient along the thickness without deterioration of high frequency magnetic properties. This newly developed magnetic gradient high Si steel sheet is also discussed.展开更多
A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is cou...A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of hysteresis.The NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with NiTi-ST.The generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of NOFRFs.Finally,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy absorption.The results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural frequency.Moreover,the NES with NiTi-ST can be directly used in practical engineering applications.展开更多
The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz....The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There existed an optimum Si content of the material depending on the tooth flux density. Both reduction of material thickness and stress-relief annealing of the stator core improved the motor efficiency. The influence of Si content on the efficiency was small at lower PWM frequencies, while at higher frequencies the motor efficiency increased with increasing Si content. The Cu loss WC increased and the Fe loss Wi counteractiveiy decreasedwith increasing Si content at lower frequencies; while at higher frequencies Wi had dominant effect on the efficiency. Newly developed materials RMA, having lower Fe losses after stress-relief annealing and higher flux densities with lower Si contents, showed motor efficiencies superior to conventional J1S grade materials with comparable Fe losses.展开更多
In the work, we studied the effect of the plasma of a runaway electron preionized （REP） diffuse discharge （DD） on the composition, structure, and properties of ST3PS steel surface layers. Voltage pulses with an in...In the work, we studied the effect of the plasma of a runaway electron preionized （REP） diffuse discharge （DD） on the composition, structure, and properties of ST3PS steel surface layers. Voltage pulses with an incident wave amplitude of up to 30 kV, FWHM of around 4 ns, and rise time of around 2.5 ns were applied to the gap in an inhomogeneous electric field. The ST3PS steel specimens exposed to this type of discharge revealed changes in their defect subsystem, suggesting that the runaway electron preionized diffuse discharge provides surface hardening of the steel.展开更多
文摘The aim of this work is to investigate the mechanical properties and microstructures of friction-stir welded(FSWed) St52 structural steel joints. In this study, St52 steel plates with a thickness of 4 mm were butt-welded by friction-stir welding(FSW) using a tungsten carbide tool having a conical pin. The microstructure of the welded zone consists of equiaxed fine ferrite, grain boundary ferrite, Widmanstatten ferrite, and aggregates of ferrite + cementite. The microhardness measurements showed that the hardness of the welded zone was significantly higher than that of the base metal. The FSWed St52 joint exhibited a significant strength overmatching in the weld region and a strength performance similar to or slightly higher than that of the base plate.
文摘A siliconizing process to manufacture 6.5% Si steel sheet has been developed. Electric components, such as transformers and reactors are made easily from 6.5% Si steel sheet. However, improved workability is desirable to increase the applications. Therefore the improvement of workability of 6.5% Si steel sheet was investigated, and the results were obtained as follows: (a) workability of 6.5% Si steel sheet is deteriorated by grain boundary oxidization, (b) grain boundary oxidization can be restrained by the addition of C. Workability and magnetic properties of 6.5% Si steel sheet with C addition are discussed. Furthermore, it was found that the workability of high Si steel sheet was improved remarkably by varying the Si content gradient along the thickness without deterioration of high frequency magnetic properties. This newly developed magnetic gradient high Si steel sheet is also discussed.
基金Project supported by the National Natural Science Foundation of China(No.11772205)the Scientific Research Fund of Liaoning Provincial Education Department(No.L201703)+1 种基金the Liaoning Revitalization Talent Program(No.XLYC1807172)the Training Project of Liaoning Higher Education Institutions in Domestic and Overseas(No.2018LNGXGJWPY-YB008)
文摘A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of hysteresis.The NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with NiTi-ST.The generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of NOFRFs.Finally,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy absorption.The results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural frequency.Moreover,the NES with NiTi-ST can be directly used in practical engineering applications.
文摘The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There existed an optimum Si content of the material depending on the tooth flux density. Both reduction of material thickness and stress-relief annealing of the stator core improved the motor efficiency. The influence of Si content on the efficiency was small at lower PWM frequencies, while at higher frequencies the motor efficiency increased with increasing Si content. The Cu loss WC increased and the Fe loss Wi counteractiveiy decreasedwith increasing Si content at lower frequencies; while at higher frequencies Wi had dominant effect on the efficiency. Newly developed materials RMA, having lower Fe losses after stress-relief annealing and higher flux densities with lower Si contents, showed motor efficiencies superior to conventional J1S grade materials with comparable Fe losses.
文摘In the work, we studied the effect of the plasma of a runaway electron preionized （REP） diffuse discharge （DD） on the composition, structure, and properties of ST3PS steel surface layers. Voltage pulses with an incident wave amplitude of up to 30 kV, FWHM of around 4 ns, and rise time of around 2.5 ns were applied to the gap in an inhomogeneous electric field. The ST3PS steel specimens exposed to this type of discharge revealed changes in their defect subsystem, suggesting that the runaway electron preionized diffuse discharge provides surface hardening of the steel.
