对38Cr Mo Al液压柱塞进行低温离子渗氮,研究不形成白亮层的工艺条件。采用金相显微镜、X射线衍射仪、显微硬度计、摩擦磨损试验机对处理后的38Cr Mo Al钢显微组织、截面硬度、渗层脆性、耐磨性进行了分析。研究结果表明,相比于510℃常...对38Cr Mo Al液压柱塞进行低温离子渗氮,研究不形成白亮层的工艺条件。采用金相显微镜、X射线衍射仪、显微硬度计、摩擦磨损试验机对处理后的38Cr Mo Al钢显微组织、截面硬度、渗层脆性、耐磨性进行了分析。研究结果表明,相比于510℃常规离子渗氮工艺,38Cr Mo Al钢经450℃低温离子渗氮工艺处理后无白亮层产生,X射线衍射分析表明表层无γ'-Fe4N相生成。同时,38Cr Mo Al钢经450℃低温离子渗氮工艺处理后,不仅截面硬度满足使用要求,而且渗层脆性显著降低,压痕周围均无裂纹产生。耐磨性研究表明,在较大载荷下,450℃低温离子渗氮后耐磨性比510℃常规离子渗氮好。展开更多
The flow field in the flat plate boundary layer induced by the pulsed plasma actuator was simulated by solving the Navier-Stokes equations with a phenomenological DBD plasma model. The effects of actuation strength,wa...The flow field in the flat plate boundary layer induced by the pulsed plasma actuator was simulated by solving the Navier-Stokes equations with a phenomenological DBD plasma model. The effects of actuation strength,wave form and frequency on the flow structures induced by the unsteady pulsed plasma actuator were investigated. The results indicated that a series of vortex pairs were formed in the boundary layer,and decayed in downstream convection following the exponential law. The strength of vortex pair was dominated by the effective plasma actuation strength,and the vortex streamwise spacing depended on the actuation frequency. If the duty cycle is not so large that interaction of adjacent vortex pairs can be negligible,then the actuation wave form has little influence on the vortex pair induced by the unsteady plasma actuator.展开更多
We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyze...We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.展开更多
文摘对38Cr Mo Al液压柱塞进行低温离子渗氮,研究不形成白亮层的工艺条件。采用金相显微镜、X射线衍射仪、显微硬度计、摩擦磨损试验机对处理后的38Cr Mo Al钢显微组织、截面硬度、渗层脆性、耐磨性进行了分析。研究结果表明,相比于510℃常规离子渗氮工艺,38Cr Mo Al钢经450℃低温离子渗氮工艺处理后无白亮层产生,X射线衍射分析表明表层无γ'-Fe4N相生成。同时,38Cr Mo Al钢经450℃低温离子渗氮工艺处理后,不仅截面硬度满足使用要求,而且渗层脆性显著降低,压痕周围均无裂纹产生。耐磨性研究表明,在较大载荷下,450℃低温离子渗氮后耐磨性比510℃常规离子渗氮好。
基金supported by the National Natural Science Foundation of China(Grant No.10872021)the Fundamental Research Funds for the Central Universities(Grant No.YWF-10-01-A05)
文摘The flow field in the flat plate boundary layer induced by the pulsed plasma actuator was simulated by solving the Navier-Stokes equations with a phenomenological DBD plasma model. The effects of actuation strength,wave form and frequency on the flow structures induced by the unsteady pulsed plasma actuator were investigated. The results indicated that a series of vortex pairs were formed in the boundary layer,and decayed in downstream convection following the exponential law. The strength of vortex pair was dominated by the effective plasma actuation strength,and the vortex streamwise spacing depended on the actuation frequency. If the duty cycle is not so large that interaction of adjacent vortex pairs can be negligible,then the actuation wave form has little influence on the vortex pair induced by the unsteady plasma actuator.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804031, 41074114, 40921063)the Specialized Research Fund for State Key Laboratories
文摘We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.
