Zr Ti Al V合金具有较低的密度和优异的力学性能,使其有可能代替传统材料作为空间活动构件的新型材料使用。该文通过分离式霍普金森压杆、二级轻气炮和激光驱动飞片等实验技术,系统研究了Zr Ti Al V合金的准静态和动态力学性能,冲击压...Zr Ti Al V合金具有较低的密度和优异的力学性能,使其有可能代替传统材料作为空间活动构件的新型材料使用。该文通过分离式霍普金森压杆、二级轻气炮和激光驱动飞片等实验技术,系统研究了Zr Ti Al V合金的准静态和动态力学性能,冲击压缩性能和微小碎片高速撞击特性。研究发现,该合金具有较高的强度和较好的塑性,屈服强度随应变速率的提高而增加,变形过程中有塑性应变现象。通过热处理可以改善Zr Ti Al V合金的力学性能。高温退火后合金完全由β相组成,在准静态和动态条件下均具有较好的塑性;退火后再回火可在β相中析出细小的α相,从而提高合金的强度,但经回火处理后合金在较高应变速率下塑性较差。经9Me V质子辐照后,Zr Ti Al V合金的动态压缩强度随质子累积注量的增加而下降,经累积注量1×1013/cm2质子辐照后,合金的动态压缩强度随应变速率的增加而减小,而原始锻造态的合金动态压缩强度随应变速率的增加而增加,合金的塑性较差,且辐照前后的变化不大。通过冲击压缩实验,得到了Zr Ti Al V合金的冲击波速度和波后粒子速度的关系,获得了该合金的Grüneisen参数和P-V-T物态方程。获得了微小碎片对Zr Ti Al V合金单次和累积撞击损伤规律,分析了损伤机理。展开更多
Debris flows caused by heavy rainfall in mountain areas near expressways lead to severe social and economic losses and sometimes result in casualties.Therefore, the development of a real-time system for debris-flow ha...Debris flows caused by heavy rainfall in mountain areas near expressways lead to severe social and economic losses and sometimes result in casualties.Therefore, the development of a real-time system for debris-flow hazard assessment is necessary to provide preliminary information for rapid decision making about evacuations or restoration measures, as well as to prevent secondary disasters caused by debris flows. Recently,various map-based approaches have been proposed using multi-attribute criteria and assessment methods for debrisflow susceptibilities. For the macrozonation of debris-flow hazard at a national scale, a simplified method such as the Korea Expressway Corporation(KEC) debris-flow hazard assessment method can be applied for systematic analysis based on geographic information systems(GIS) and monitoring networks. In this study, a GIS-based framework of real-time debris-flow hazard assessment for expressway sections is proposed based on the KEC debris-flow hazard assessment method. First, the KEC-based method was standardized in a systematic fashion using Arc GIS,enabling the objective and quantitative acquisition of various attribute datasets. The quantification of rainfall criteria also was considered. A safety management system for debris-flow hazard was developed based on the GIS platform. Finally, the method was applied and verified on three expressway sections in Korea. The grading standard for each individual influencing attribute was subsequently modified to more accurately assess the debris-flow hazards.展开更多
Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not en...Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not entirely clear. Currently, impact-generated plasma is thought to be the primary cause of electrical spacecraft anomalies, while the effects of impact-generated mechanical damage have rarely been researched. This paper presents new evidence showing that impact-generated mechanical damage strongly influences electrostatic discharge. Hypervelocity impact experiments were conducted in a plasma drag particle accelerator, using particles with diameters of 200–500 ?m and velocities of 2–7 km/s. The impact-generated mechanical damage on a specimen surface was measured by a stereoscopic microscope and 3D Profilometer and it indicated that microscopic irregularities around the impact crater could be responsible for local electric field enhancement. Furthermore, the influence of impact-generated mechanical damage on electrostatic discharge was simulated in an inverted potential gradient situation. The experimental results show that the electrostatic discharge voltage threshold was significantly reduced after the specimen was impacted by particles.展开更多
文摘Zr Ti Al V合金具有较低的密度和优异的力学性能,使其有可能代替传统材料作为空间活动构件的新型材料使用。该文通过分离式霍普金森压杆、二级轻气炮和激光驱动飞片等实验技术,系统研究了Zr Ti Al V合金的准静态和动态力学性能,冲击压缩性能和微小碎片高速撞击特性。研究发现,该合金具有较高的强度和较好的塑性,屈服强度随应变速率的提高而增加,变形过程中有塑性应变现象。通过热处理可以改善Zr Ti Al V合金的力学性能。高温退火后合金完全由β相组成,在准静态和动态条件下均具有较好的塑性;退火后再回火可在β相中析出细小的α相,从而提高合金的强度,但经回火处理后合金在较高应变速率下塑性较差。经9Me V质子辐照后,Zr Ti Al V合金的动态压缩强度随质子累积注量的增加而下降,经累积注量1×1013/cm2质子辐照后,合金的动态压缩强度随应变速率的增加而减小,而原始锻造态的合金动态压缩强度随应变速率的增加而增加,合金的塑性较差,且辐照前后的变化不大。通过冲击压缩实验,得到了Zr Ti Al V合金的冲击波速度和波后粒子速度的关系,获得了该合金的Grüneisen参数和P-V-T物态方程。获得了微小碎片对Zr Ti Al V合金单次和累积撞击损伤规律,分析了损伤机理。
基金supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources (KIGAM)the National Research Foundation of Korea (NRF) Grant (No. 2015R1A5A7037372) funded by the Korean Government (MSIP)the Korea Expressway Corporation for its leadership and support
文摘Debris flows caused by heavy rainfall in mountain areas near expressways lead to severe social and economic losses and sometimes result in casualties.Therefore, the development of a real-time system for debris-flow hazard assessment is necessary to provide preliminary information for rapid decision making about evacuations or restoration measures, as well as to prevent secondary disasters caused by debris flows. Recently,various map-based approaches have been proposed using multi-attribute criteria and assessment methods for debrisflow susceptibilities. For the macrozonation of debris-flow hazard at a national scale, a simplified method such as the Korea Expressway Corporation(KEC) debris-flow hazard assessment method can be applied for systematic analysis based on geographic information systems(GIS) and monitoring networks. In this study, a GIS-based framework of real-time debris-flow hazard assessment for expressway sections is proposed based on the KEC debris-flow hazard assessment method. First, the KEC-based method was standardized in a systematic fashion using Arc GIS,enabling the objective and quantitative acquisition of various attribute datasets. The quantification of rainfall criteria also was considered. A safety management system for debris-flow hazard was developed based on the GIS platform. Finally, the method was applied and verified on three expressway sections in Korea. The grading standard for each individual influencing attribute was subsequently modified to more accurately assess the debris-flow hazards.
文摘Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not entirely clear. Currently, impact-generated plasma is thought to be the primary cause of electrical spacecraft anomalies, while the effects of impact-generated mechanical damage have rarely been researched. This paper presents new evidence showing that impact-generated mechanical damage strongly influences electrostatic discharge. Hypervelocity impact experiments were conducted in a plasma drag particle accelerator, using particles with diameters of 200–500 ?m and velocities of 2–7 km/s. The impact-generated mechanical damage on a specimen surface was measured by a stereoscopic microscope and 3D Profilometer and it indicated that microscopic irregularities around the impact crater could be responsible for local electric field enhancement. Furthermore, the influence of impact-generated mechanical damage on electrostatic discharge was simulated in an inverted potential gradient situation. The experimental results show that the electrostatic discharge voltage threshold was significantly reduced after the specimen was impacted by particles.
