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61.
《防务技术》2020,16(1):217-224
Experiments on shaped charge penetration into high and ultrahigh strength steel-fiber reactive powder concrete (RPC) targets were performed in this paper. Results show that the variation of penetration depth and crater diameter with concrete strength is different from that of shaped charge penetration into normal strength concrete (NSC). The crater diameter of RPC is smaller than that of NSC penetrated by the shaped charge. The jet particles are strongly disturbed and hardly reach the crater bottom because they pass through the narrow channel formed by jet penetration into the RPC. The effects of radial drift velocity and gap effects of jet particles for a shaped charge penetration into RPC target are discussed. Moreover, a theoretical model is presented to describe the penetration of shaped charge into RPC target. As the concrete strength increases, the penetration resistance increases and the entrance crater diameter decreases. Given the drift velocity and narrow crater channel, the low-velocity jet particles can hardly reach the crater bottom to increase the penetration depth. Moreover, the narrow channel has a stronger interference to the jet particles with increasing concrete strength; hence, the gap effects must be considered. The drift velocity and gap effects, which are the same as penetration resistance, also have significant effects during the process of shaped charge penetration into ultrahigh-strength concrete. The crater profiles are calculated through a theoretical model, and the results are in good agreement with the experiments. 相似文献
62.
《防务技术》2019,15(3):264-271
To simulate explosion fragments, it is necessary to predict many variables such as fragment velocity, size distribution and projection angle. For active protection systems these predictions need to be made very quickly, before the weapon hits the target. Fast predictions also need to be made in real time simulations when the impact of many different computer models need to be assessed. The research presented in this paper focuses on creating a fast and accurate estimate of one of these variables - the initial fragment velocity. The Gurney equation was the first equation to calculate initial fragment velocity. This equation, sometimes with modifications, is still used today where finite element analysis or complex mathematical approaches are considered too computationally expensive. This paper enhances and improves Breech’s two-dimensional Gurney equation using available empirical data and the principals of conservation of momentum and energy. The results are computationally quick, providing improved accuracy for estimating initial fragment velocity. This will allow the developed model to be available for real-time simulation and fast computation, with improved accuracy when compared to existing approaches. 相似文献
63.
《防务技术》2019,15(2):179-185
In this article, parametric study of single confined fragment launch device was carried out. The configuration proposed was further studied to derive the empirical relationship for effect of fragment size, charge size, confinement thickness on fragment velocity. The simulations were carried out using ANSYS-AUTODYNE explicit solver. Fragment velocities were estimated as a function of different parametric combinations of explosive quantities, charge length to diameter ratio, fragment height to diameter ratio, confinement thickness, fragment material and fragment mass. The data was further converted to charge to metal ratio under fragment and confinement. It was observed that, increase in confinement thickness, charge quantity and decrease in fragment height increases the fragment velocity. It is also noted that, charge to metal mass ratio under fragment significantly affects the fragment velocity. At the end, an empirical relationship for fragment velocity interms of all these parameters was established. Using these relations, two velocities 1831.92 m/s and 2523.9 m/s required for NATO STANAG 4496 IM test were estimated. The design parameters for these velocities are presented. Also, the results estimated using the empirical relationship has been compared with published experimental data. Error in the predicted velocities is within the acceptable range. The empirical relationship proposed will be useful for finalization of design of the fragment launch device. 相似文献
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对某大型降落伞系统的拉直过程进行多阶段、多有限段和多自由度的动力学建模。通过仿真研究了牵顶伞和剥离带等改进措施对主伞拉直后伞衣抽打现象影响,重点分析比较了带与不带牵顶伞时伞衣位形、抽打速度、偏离距离等参数的变化,分析结果可为大型降落伞的工程设计、改进和使用提供理论支持。 相似文献
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该文以体院排球普修课男生为对象,通过高速摄影方法,对"空气阻力对正面上手发球水平方向飞行距离的影响"这一问题进行了实验研究.初步揭示了当击球高度,击球角度和击球初速度等条件一定的情况下同,正面上手发球在水平方向飞行的理论距离与实际距离的差值规律. 相似文献