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71.
高压弹射装置内弹道二维模型及发射腔内流场特性分析 总被引:4,自引:1,他引:4
高压弹射装置中火药先燃烧积聚成高压气体,后瞬间打开,弹射弹丸攻击目标。为了掌握这一过程中发射腔内流场的复杂变化,建立了高压弹射装置内弹道二维气相模型,采用Runger-Kutta算法和MacCormark差分格式耦合方法进行数值模拟,并将计算所得的压力曲线与试验结果进行对比,验证了数值计算的可靠性。进一步根据计算得到发射腔内气体压力、速度等参量的分布情况,分析发射腔内的流场特性。结果表明,弹射关键阶段在弹丸启动的较短时间内,高压气体大小和分布是影响弹丸弹射效果的直接因素。 相似文献
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74.
介绍了喷气织机用异形筘的发展现状,从主要原材料、制造装备、创新能力3方面分析了我国在异形筘制造技术上与国外先进水平的差距;指出,我国异形筘应在筘齿齿形,玻璃纤维织物专用筘,提高耐磨损及抗蚀性能,研发智能化全自动编筘机、筘梁注胶机及检测用工装与量具,如筘齿垂直度、倾侧度测量器等方面多下功夫。 相似文献
75.
Julie Brown Derek Wainohu Basuki Suratno Lynne E. Bilston 《Accident; analysis and prevention》2010,42(1):112-121
Accessory child safety harnesses are available in some countries as alternative restraints for young children or as an accessory restraint used with booster seats. Their use, in Australia at least, is becoming more common. There have been concerns that the risk of misuse of these restraints outweighs any potential benefit this system might have over a retractable lap-shoulder belt system used with a booster seat. However to date there is no evidence to confirm or deny this. This study used laboratory simulated frontal crash tests to examine the performance of accessory child safety harness systems compared to the lap-shoulder belt when used alone and when used with two common designs of Australian booster seat. The performance of the child safety harness system when misused was also investigated. The results demonstrate that the correctly used child safety harness system performed no better than the lap-shoulder system, and in fact allows for a greater risk of submarining. Furthermore, one common form of child safety harness misuse, where the harness is over-tightened causing the lap belt to be positioned high over the abdomen, allowed extremely undesirable dummy motion. This involved gross submarining and direct contact between the harness system and the dummy's neck. These findings suggest that the risks associated with accessory child safety harness systems most likely outweigh any potential benefits, in frontal impacts at least. 相似文献
76.
采用有限元软件ANSYS Workbench对某特装车汽车座椅进行建模、划分网格及模态分析,计算了座椅的固有频率和振型,同时对计算结果进行了分析,为汽车座椅设计提供了理论依据,具有借鉴和参考作用。 相似文献
77.
建立了门座式起重机门座的空间力学模型,分析了由于荷载作用位置的非对称性造成门腿变形的非均匀性从而引起的门座顶平面及塔身的倾斜,并给出了此倾角的计算方法及计算公式。这将为门座式起重机的合理、精确设计,提供有益的参考。 相似文献
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The current automobile seat comfort development process, which is executed in a trial and error fashion, is expensive and outdated. The prevailing thought is that process improvements are contingent upon the implementation of empirical/prediction models. In this context, seat-interface pressure measures, anthropometric characteristics, demographic information, and perceptions of seat appearance were related to an overall comfort index (which was a single score derived from a previously published 10-item survey with demonstrated levels of reliability and validity) using two distinct modeling approaches-stepwise, linear regression and artificial neural network. The purpose of this paper was to compare and contrast the resulting models. While both models could be used to adequately predict subjective perceptions of comfort, the neural network was deemed superior because it produced higher r2 values (0.832 vs. 0.713) and lower average error values (1.192 vs. 1.779). 相似文献
80.
The possibility of obtaining highlydense compacts by single pressing and sintering and the use of heatresistant solid lubricants (graphite, talc) instead of conventional lubricant was studied. It was shown that the addition of graphite is most effective to obtain highly-dense powder metallurgy materials since it substantially facilitates ejection of the part from the die and improves the mechanical properties. 相似文献