Small cylindrical object navigating near free-surface is subject to wave disturbance. Wave disturbance can dramatically influence the depth control of the near-surface navigating object. A self-regulating fuzzy depth control method is proposed to keep the small cylindrical object navigate at the expected depth under free-surface disturbance. The near-surface dynamic model of the cylindrical object is presented and the fuzzy depth control method is modeled. The results obtained by a series of hardware-in-loop simulations demonstrate that the self-tuning fuzzy depth control method is valid to keep the small cylindrical object navigate steadily in the expected depth under free-surface disturbances.
For the short-range defensive weapons, extracting the acoustic characteristic of attacking aircraft at low altitude is an effective way to detect and recognize the target. The signal characteristics of radiated noise of the typical vehicle propulsion system are analyzed, and thus the signal models for propulsion system noise and for passive acoustic early-warning system are given. Finally, the analysis result of the measured aircraft noise validates the feasibility of the signal model.
The impact explosive temperature of reactive material is not only an important indicator to measure the ability of explosive reaction, but also a required parameter to carry out thermo-chemical calculation. So there is important practical significance to study the impact explosive temperature effect of reactive material. Based on one-dimensional shock wave, thermodynamics and physical chemistry theory, mathematical analysis model of impact explosive temperature vs. mass ratio of the reactive material is established. By MATLAB programming, the curve of impact explosive temperature vs. the mass ratio of PTFE/Al reactive material is received, which can be used to analyze variations. Fitting function equations is obtained by MATLAB CFTOOL. At last, the contrast of original calculation curve with fitting curve validates the appropriateness of the fitting function equations. From the view of impact explosive temperature effect, we suggest that the established model and research method can be applied to the dynamic properties research of other reactive material.
Polyurethane foam has the properties of energy absorption and mitigating the impact, it has been used in internal protection head cap of cylindrical objects as cushion material, its theory and simulation has been widely discussed by the domestic and foreign scholars, but little experimental research is involved. In this paper, a dynamic loading water-entry impact experiment was designed for polyurethane foam plastics with different densities. In addition, ANSYS/LS-DYNA finite element analysis software was used to simulate water-entry process of cushion materials with different densities. The experimental and simulation results show that the 0.18 g/cm3 polyurethane material can effectively protect the cylindrical head, reduce the stress and have a good cushion effect on it.
Partial penetration means partial body of projectile is in target, the other out of target. Analysis model of slender nose projectile partial penetrates steel target is proposed base on cavity expansion theory (plate thickness is smaller than projectile nose length), and the variation relation of penetration depth with initial velocity is concluded when projectile partially penetrates steel target. Penetration tests are carried out on hard projectile penetrates steel target, and the predicted results of penetration depth have good agreement with experimental results.
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