共查询到18条相似文献,搜索用时 343 毫秒
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为了减轻导弹发射系统的质量和降低导弹发射的成本,研究了一种柔性气囊弹射系统,实现了对导弹做功。通过理论分析,试验验证和数值计算相结合的方法,对柔性气囊弹射系统的工作机理和弹射性能进行了研究。结果表明:通过粒子法计算柔性气囊展开过程的结果与试验测量结果吻合较好,误差不超过1.04%,验证了粒子法计算柔性气囊展开的准确性;柔性气囊弹射系统的弹射性能与弹射工质的种类、温度、柔性气囊的作用距离和作用面积等因素有关。在对弹射工质和柔性气囊结构参数的研究中发现:弹射工质的摩尔质量越小,温度越高,柔性气囊弹射系统的弹射性能就越好;当作用面积相同时,柔性气囊的长径比越大,柔性气囊弹射系统的弹射性能就越好;当作用距离相同时,柔性气囊的长径比越小,柔性气囊弹射系统的弹射性能就越好,导弹获得的动能就越大。 相似文献
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为了解决弹射座椅研究中风洞试验不足和气动参数缺乏的问题,尝试了采用计算流体力学(CFD)
方法,利用CFD计算软件Fluent求解N-S方程,对弹射座椅的外流场进行数值计算,求得了弹射座椅不同姿态
下的气动参数值,并将部分气动参数与风洞试验的测量值进行了对比,结果发现,计算结果与试验值的变化趋
势完全相同,大多数计算值与试验值的误差都在10%以内,能够满足工程计算的需要,可以作为试验值的补充
和替代。通过CFD方法在弹射座椅气动参数计算中的应用,可以看到CFD方法在弹射座椅的研究中有着广阔的
应用前景。 相似文献
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《中国新技术新产品》2016,(13)
本文以火箭弹射座椅及飞机座舱舱盖为研究对象,建立座椅侧板有限元模型和舱盖模型,模拟椅盆侧板的穿盖过程,评估侧板的动态冲击性能。这种方法可降低研发过程中的试验经费,缩短试验周期,具有很重要的工程意义。 相似文献
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《工程数学学报》2021,38(2)
格子Boltzmann方法作为一种较成熟的数值模拟方法被广泛应用到了各个领域,尤其在解决多孔介质问题时有其独特的优越性,但当流动问题过于复杂时计算效率较低.因此本文将惯量松弛因子引入到格子Boltzmann方法中,对二维、三维顶盖驱动方腔流动进行了数值模拟.模拟分别从计算效率、计算精度、以及计算稳定性等方面将使用不同惯量松弛因子所得的结果与基准解进行比较,并进行讨论和分析.结果显示当惯量松弛因子取0.03到0.05之间时能使模拟结果在保持较高精度的同时提高计算效率,而且随着惯量松弛因子的增大计算效率提高得也越快,在工程材料与能源环境领域将有着重要应用. 相似文献
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针对大惯量专用转台运行过程中存在的系统响应时间长、易产生振荡以及末端位置定位误差较大的问题,提出了一种基于全闭环+模糊自适应PID (proportion integral differential,比例积分微分)的精度控制方法。在大惯量专用转台执行机构处加入多圈绝对式编码器,以实现控制系统的全闭环;利用模糊自适应PID控制实现不同负载下高精度控制系统的快速调节。为更加深入研究大惯量对专用转台控制系统的影响,对转台进行了系统建模;同时在MATLAB仿真环境中分别建立了基于模糊自适应PID控制和普通PID控制的转台控制系统仿真模型,并搭建了转台测试平台进行验证实验。对比不同控制方式下系统控制性能的仿真结果可知:普通PID控制系统响应时间长,系统跟随误差大;而使用模糊自适应PID控制可使系统的响应速度提高75%,跟随误差降低降低70%。由实验结果可知专用转台定位精度为[-0.2°,0.2°],满足了设计精度要求。仿真和实验结果表明利用模糊自适应PID控制可有效提高系统的响应速度,全闭环控制可使系统的定位精度得到有效提高。研究结果为转台控制系统的设计提供了有效的参考数据,促进了大惯量转台的高精度化发展。 相似文献
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Current golf carts and LSV's (Low Speed Vehicles) produce a significant number of passenger ejections during sharp turns. These LSV's do not typically possess seatbelts, but do provide outboard bench seat hip restraints that also serve as handholds. However, many current restraint designs appear incapable of preventing passenger ejections due to their low height and inefficient handhold position. Alternative handhold and hip restraint designs may improve passenger safety. Accordingly, this paper examines minimum size requirements for hip restraints to prevent passenger ejection during sharp turns and evaluates the effectiveness of a handhold mounted at the center of the bench seat. In this study, a simulation of a turning cart supplies the dynamic input to a biomechanical model of an adult male seated in a golf cart. Various restraint combinations are considered, both with and without the central handhold, to determine the likelihood of passenger ejection. It is shown that only the largest restraint geometries prevent passenger ejection. Adequate hip restraints should be much larger than current designs and a central handhold should be provided. In this way, golf cart and LSV manufacturers could reduce passenger ejections and improve fleet safety by incorporating recommendations provided herein. 相似文献
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目的研究铁路货物装载加固座架的强度估算方法。方法进行了卷钢座架的静态和冲击动强度试验,测量了静态和冲击过程中座架危险截面的应力。同时,依据《铁路货物装载加固规则》的有关规定,计算了卷钢座架所受的作用力,利用有限元方法计算了在此力作用下座架的强度,对比了卷钢座架静态和冲击试验测量的应力和理论计算的应力。结果试验值与理论计算值的误差约为10%,理论计算的应力值具有较高的精度。结论在缺乏试验条件的场合下,可以用理论的方法来估算座架的强度。 相似文献
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MTMD减震结构体系的频域分析 总被引:6,自引:0,他引:6
将主结构简化为串联多自由度模型,通过对主结构稳态响应的频域传递函数的模值来分析MTMD控制效果。主结构稳态响应的频域传递函数分别采用以下三种方法求取:1)推导结构系统振动方程,将其从时域转化为频域,推导频域传递函数;2)将MTMD系统对主结构的反力与地震荷载共同作为主结构的荷载输入,根据MTMD的反力为各阶模态耦合对结构进行控制的方法求取频域传递函数;3)根据MTMD的反力为各阶模态非耦合对结构进行控制的方法求取频域传递函数。利用以上方法分析MTMD系统对主结构的单模态和多模态进行控制的控制效果。根据非耦合控制作用的频域传递函数提出惯性质量参与量。给出一算例,并且给出时程分析的结果加以比较验证。 相似文献
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Cunill M Gras ME Planes M Oliveras C Sullman MJ 《Accident; analysis and prevention》2004,36(3):439-445
Seat belt use on Spain's highways is more than 80%, while on the urban roads this figure is around 50%. As there was little information available to explain the difference in seat belt use rates, the main aim of this study was to investigate why there is a lower rate of seat belt use on urban roads. A number of perceptions, beliefs and expectancies about seat belt use were examined to identify variables that discriminated between seat belt users and non-users on urban roads. The subjects were 398 undergraduate students (aged 17-47) studying at the University of Girona, Spain. On the urban roads reported discomfort from using the seat belt was higher, while perceptions of risk (for non-users), safety perceptions (for those using a seat belt), beliefs about the seriousness of a crash or the effectiveness of the seat belt were all lower than on the highway. Perceptions of safety, discomfort, and social influence predicted seat belt use on urban roads. Concern about being fined for not using a seat belt did not predict seat belt use. The results of this research suggest that in order to increase seat belt use on urban roads, the issue of discomfort must be addressed. In addition, prevention campaigns should include information about the effectiveness of the seat belt in preventing/reducing injuries or deaths on urban roads. The results also highlight the importance of social influence for determining seat belt use/non-use and the potential role social influence could play in increasing seat belt usage. 相似文献
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根据测量的25个人体形体指标,用Barter回归方程以及人体模型的定义计算得到人体环节的质量、几何尺寸和质量惯性矩等环节惯性参数。用Hanavan人体模型采用变换矩阵获得运动中人体环节相对惯性参考系的环节惯性参数,同时根据合力矩定理和平行轴定理计算运动中人体质心和主转动惯性等惯性参数,为研究人体运动提供可靠的定量分析依据。研究方法很好地体现了人体惯性参数的个体特征和任意姿态特征,其计算结果与国内报道用CT法和三线摆的研究结果相符。 相似文献
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The percent of occupant fatalities preventable by eliminating ejection is calculated using Fatal Accident Reporting System (FARS) data for 1975 through 1986. The calculation requires estimates of two quantities. First, the fraction of all fatally injured occupants who were ejected; this is obtained directly from the FARS data. Second, the probability that an ejected occupant was killed compared to the probability that the occupant would have been killed in a similar crash in the absence of ejection; this quantity is estimated using the double pair comparison method, and its dependence on occupant age and sex and on car mass and model year is examined. High precision estimates of the reduction in fatalities that would result from eliminating ejection as functions of these same variables are thereby obtained. These estimates depend on assuming that whatever method is used to prevent ejection would cause the formerly ejected occupant to acquire the same fatality risk as a nonejected occupant in a similar crash; the study does not address how to prevent ejection. It is concluded that ejection elimination would decrease fatalities to unrestrained car occupants by 18 +/- 1%. The fatality reductions are independent of car seating position (19%, 19%, 17%, 16%, 19%, and 18% for drivers, middle front, right front, left rear, middle rear, and right rear passengers, respectively); they decrease with driver age, from 25% at age 18 years to 7% at 70 years; they decrease with increasing mass, but remained relatively independent of car model year since the early 1970s, being somewhat higher for earlier model years. 相似文献