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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.
沈蕾 《郑州航空工业管理学院学报(管理科学版)》2006,24(3):79-85
对混合式机器学习系统(HML)进行了全面系统的介绍,并将其运用于服装消费商店偏好决策行为的研究中。采用上海统计局家庭调查网络,对300户家庭进行抽样分析后发现,服装消费商店偏好的主要影响因素是地区、季节、丈夫和妻子的学历、职业以及子女性别。在此基础上,将HML分析所得的结论与传统的研究方法和结果进行了系统比较:从方法上来看,因为属性变量包含间断变量和连续变量两种,因此传统统计分析要运用两种不同的检测方法对影响因素的相关性作出判断,结果需要经过统计学分析,才能得到结论;而HML分析结果比较直观和简单,便于理解。 相似文献
3.
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
4.
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
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.
滚珠丝杠螺距误差补偿法提高数控机床定位精度的研究 总被引:2,自引:0,他引:2
在详细论述、对比了实现数控机床滚珠丝杠螺距误差补偿的硬件、软件方法的原理基础上,对滚珠丝杠螺距误差软件补偿法可有效提高数控机床的定位精度进行了试验验证。 相似文献
7.
8.
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
9.
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
10.
四足步行机运动机构及步态参数对行走稳定性影响分析 总被引:3,自引:0,他引:3
本文研究了四足步行机的行走稳定性问题,建立了考虑运动机构包括腿机构及其传动系统影响的稳定性模型;分析了各步态参数对稳定性的影响,并以研制的四足步行样机为例进行了计算机仿真。 相似文献