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1.
《中国航空学报》2020,33(2):391-406
A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior. It results in contact damage until systems fail, which may cause significant economic losses and catastrophic consequences. The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment. This has been a hot topic in the area of mechanical reliability. The main work in this paper can be concluded as follows. Firstly, the main industries in which the “sliding/impact behavior” takes place have been introduced. Then, existing studies on the wear mechanism and degree analysis are presented, which includes surface morphology analysis, wear debris analysis, and wear degree measurement. Meanwhile, existing problems in theoretical modeling and experiments in current research are summarized, so as to point out a bright direction for future research on wear prediction. They include interface contact modeling, mathematic coupling mechanism modeling, wear equation establishment, and wear life characterization, which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior. 相似文献
2.
用数值方法模拟双锥,圆柱,椭球、圆锥和倒圆锥五类等质量异形铝粒子五种高宽比共25种粒子对半无限铝靶的超高速撞击侵蚀,撞击速度为4km/s,给出了坑深、坑径、坑形参数和坑体积随粒子形状及高宽比的变化曲线。结果与非圆球异形粒子超高速撞击侵蚀计算有重要参考价值。 相似文献
3.
Emergence of a Habitable Planet 总被引:2,自引:0,他引:2
Kevin Zahnle Nick Arndt Charles Cockell Alex Halliday Euan Nisbet Franck Selsis Norman H. Sleep 《Space Science Reviews》2007,129(1-3):35-78
We address the first several hundred million years of Earth’s history. The Moon-forming impact left Earth enveloped in a hot
silicate atmosphere that cooled and condensed over ∼1,000 yrs. As it cooled the Earth degassed its volatiles into the atmosphere.
It took another ∼2 Myrs for the magma ocean to freeze at the surface. The cooling rate was determined by atmospheric thermal
blanketing. Tidal heating by the new Moon was a major energy source to the magma ocean. After the mantle solidified geothermal
heat became climatologically insignificant, which allowed the steam atmosphere to condense, and left behind a ∼100 bar, ∼500 K
CO2 atmosphere. Thereafter cooling was governed by how quickly CO2 was removed from the atmosphere. If subduction were efficient this could have taken as little as 10 million years. In this
case the faint young Sun suggests that a lifeless Earth should have been cold and its oceans white with ice. But if carbonate
subduction were inefficient the CO2 would have mostly stayed in the atmosphere, which would have kept the surface near ∼500 K for many tens of millions of years.
Hydrous minerals are harder to subduct than carbonates and there is a good chance that the Hadean mantle was dry. Hadean heat
flow was locally high enough to ensure that any ice cover would have been thin (<5 m) in places. Moreover hundreds or thousands
of asteroid impacts would have been big enough to melt the ice triggering brief impact summers. We suggest that plate tectonics
as it works now was inadequate to handle typical Hadean heat flows of 0.2–0.5 W/m2. In its place we hypothesize a convecting mantle capped by a ∼100 km deep basaltic mush that was relatively permeable to
heat flow. Recycling and distillation of hydrous basalts produced granitic rocks very early, which is consistent with preserved
>4 Ga detrital zircons. If carbonates in oceanic crust subducted as quickly as they formed, Earth could have been habitable
as early as 10–20 Myrs after the Moon-forming impact. 相似文献
4.
5.
When a micro-debris or a micrometeoroid impacts a spacecraft surface, a large number of secondary particles, called ejecta, are produced. These particles can contribute to a modification of the debris environment: either locally by the occurrence of secondary impacts on the components of complex and large space structures, or at great distance by the formation of a population of small orbital debris. This paper describes firstly, the ejecta overall production, and secondly, the lifetime and the orbital evolution of the particles. Finally the repartition of ejecta in LEO is computed. Some results describing the population as a function of size and altitude are presented. 相似文献
6.
7.
The strain–stress state of the solid propellant rocket engines (SPREs) is simulated under impact. The effect of orientation of elastic and strength properties of orthotropic organoplastic shell material on the strain–stress state of the solid propellant is investigated. Normal and oblique impact of single steel cylinder projectiles, both simultaneous and at different times of multiple, converging steel spheric particles with SPRE are investigated in this study. The investigation is conducted numerically. The numerical modeling was carried out in a three-dimensional formulation by the method of finite elements for the continuous approach of the mechanics of a deformable solid. The destruction of the anisotropic material is described by the tensor-polynomial criterion of the fourth degree, which takes into account the influence of hydrostatic pressure. 相似文献
8.
文章介绍了用约翰逊空间中心超高速碰撞试验设备(HIT-F)上的BUMPER计算程序,对航天飞机观察窗表面在低地球轨道(LEO)环境受到超高速碰撞时的损害进行预测,并与实际损害情况进行了比较。 相似文献
9.
液体推进剂泄漏应急处理 总被引:4,自引:0,他引:4
提出液体推进剂泄漏事故的应急处理措施,包括人员疏散、隔离区划分、受伤和中毒人员救治,抢救人员个人安全防护以及其他控制险情的方法。 相似文献
10.
叙述了用声-超声进行复合材料危害性缺陷无损评价的研究,认为,声-超声信号在试样厚度上产生纵不皮共振,使得频谱能量集中在某些频率点附近,而声波又以切波的形式由发射换能器传向接收换能器,可用声-超声谱峰的位置来无损评价纤维缠绕增强型复合材料的层间结合质量。实验结果表明这一参量对纤维增强型合材料中的分层或紧贴型分层比较灵敏。 相似文献