Abstract:To obtain the change of thermal stress in the slow cook-off test of explosive charge, a set of thermal stress testing device was designed.The change curves of the thermal stress with temperature of octogen(HMX) based aluminized explosive charge under the closed confinement condition were obtained.Through adjusting the volume ratio of inert coating layer and charge, and changing the rising rate of thermal stress in the slow cook-off process, the critical response temperature of cook-off bomb and the intensity of response under three working conditions were researched.The difference of change rate of thermal stress, the whose process can be divided into six stages.Its influencing factors is thermal expansion, porosity decrease, HMX crystal transformation, slow decomposition of HMX, partial small molecule gas leakage, and accelerated decomposition of HMX in the order.When the temperature rises to 208 ℃, the thermal stress reaches 9.2 MPa and the charge is ignited immediately.Increasing the silicone rubber coating layer with greater thermal expansion on the charge surface of cook-off bomb, can make the growth rate of the thermal stress of charge accelerate and the critical ignition temperature of charge reduce, but the drastic degree of the response of charge does not change.

Abstract:To study the damage efficiency of axial-expanding directional warhead, AUTODYN software was systematically used to analyze the influence of the expansion angle and the initiation position on the fragment performance of axial-expanding directional warhead. The influence law of the axial expansion angle and the initiation position of warhead on the formation of fragment mass distribution, flying dispersion velocity and flying dispersion angle was obtained. Results show that the velocity of the forward explosively formed projectile (EFP) decreases with the increase of the axial expansion angle, while increasing the length-diameter ratio of EFP, taking the wing-diameter ratio of about 4.2, increasing the axial expansion angle of the warhead can improve the percentage of effective fragment mass, and the maximum flying dispersion velocity of the fragment appears at about 33.33% from the initiation end. The percentage of effective fragment of warhead at the outer side of the charge is up to 67.57%. Selecting the axial expansion angle of the warhead as about 60°, and the initiation point located at the outer side of the charge, can realize the effective damage function of directional and convergent strike of axial-expanding directional warhead.

Abstract:To furtherly improve the penetration capability of explosively formed penetrator(EFP), a type of cone-arc liner which can form long rod-shaped compacted EFP was proposed based on the arc section design of large cone angle liner structure. The difference in collapse process for cone-arc liner and the traditional large cone angle liner as well as arc-cone liner was analyzed. The influences and regulars of cone-arc liner structure parameters (curvature radius, cone angle and wall thickness) on the formation parameters of penetrator, such as EFP velocity, length-diameter ratio and compactness, were calculated and obtained by LS-DYNA simulation software. The range of each parameters of optimum EFP are gained: the curvature radius is 1.1-1.3 times of charge diameter, the cone angle is 155°-160°, and the wall thickness is 0.04-0.046 times of charge diameter. And a kind of cone-arc liner structure that can form EFP with length-diameter ratio as 2 and compactness as 0.88 was designed and obtained.

Abstract:To enhance the damage effectiveness of anti-light armor target ammunition, a kind of variational-wall-thickness arc-cone liner with low-density loading material was proposed. The influence law of each cone angle on explosively formed projectiles (EFP) forming and the penetration effect of EFP on target plate were analyzed by finite element software LS-DYNA. The curve of EFP forming parameters with each cone angle was obtained by fitting. Results show that when the inner cone angle α₁ of liner takes 166°-170.2°, the inner cone angle α₂ of filler takes 160°-166°, the outer cone angle α₃ of filler takes 140°-152°, the outer cone angle α₄ of liner takes 132°-140°, the EFP forming speed is fast and forming effect is good. The α₃ has the greatest influence on the forming speed, length and radial dimension of EFP, and the α₁ has the greatest influence on the center thickness of EFP. Based on the research results, the structure of the liner was optimized. The optimized liner can form an EFP with distinct penetrator with enhanced lateral efficiency(PELE) effect, which expands the hole when penetrating the target plate and forms some high-speed fragments in the target interior to cause secondary damage after penetrating the target plate.

Abstract:To achieve efficient damage of the ammunition, a directional and focusing multiple explosively formed penetrator (EFP) warhead was designed. The structure and operational principle of the warhead, and the relation between deployment angle and number density of EFP on the target were described. In addition, to obtain the optimal structural parameters of the warhead, the multi-objective optimization model of warhead parameters was established with the velocity and total number of EFP as the objective function, and the Pareto optimal solution was obtained by NSGA-Ⅱ genetic algorithm. Based on the optimized parameters of the warhead, the EFP formation process of the single charge structure under the optimized structure was numerically simulated, and the change of the focusing ability of warhead with the deployment angle of directional segment at different target distance (10, 15 m and 20 m) was analyzed. Results show that the initial velocity of EFP under the optimized structure reaches to 2283.4 m·s^-1. When the EFP is stable, the calculation from formula shows that it can penetrate 35.94 mm thick 45 steel target. At the target distance of 15 m, the optimal deployment angle of the directional segment is 91.15°, and the EFP number density is 169 per square meter.

Abstract:To improve the damage power.of anti-armor and anti-personnel composite warhead, the effect of charge-shell weight ratio on the armor-penetrating and killing power of warhead was researched. The formation and killing radius of fragments were calculated by theoritical analysis mehtod when the charge-shell mass ratio of warhead increased from 0.71 to 2.00. A non-linear finite element software, LS-DYNA, was used to compare and analyze the depth of armor penetration by molding jet when the charge-shell mass ratio of warhead was 0.80, 1.00, 1.20, 1.40 and 1.60, and the relationship of the charge-shell mass ratio vs. the killing radius of fragments and the depth of armor penetration by molding jet was obtained. Results show that the killing radius increases from 9.1 m to 10.2 m with the increase of charge-shell mass ratio from 0.71 to 1.86. The killing radius doesn′t increase anymore when the charge-shell mass ratio increases to 2.00. The average weight of fragments decreases with the increase of charge-shell mass ratio.The depth of armor penetration decreases first and then increases with the increase of charge-shell mass ratio from 0.80 to 1.60, and the maximum perforation deep is 143.30 mm.

Abstract:To enhance the damage probability of munitions at various encounter distances, a faceted prismatic warhead composed of flat faces and convex faces is numerically studied in this work, and the dispersion patterns and lethality parameters of fragment beams from different faces are analyzed. The results reveal that this warhead structure could produce two types of fragment beams. One is the fragment beam with high speed and small scattering angle, and the other shows low speed and wide coverage. These fragment beams are suitable for attacking targets at different missing distances. The asymmetrical initiations could enhance the fragment velocity of flat face by 21.68%, reduce the dispersion angle of 3.38° and improve the lethality of fragment opposite to detonating point without changing the property of producing two kinds of fragment beams. The lateral two line initiations could change the fragment dispersion angle of the flat face of 4.94° without reducing the velocity of the fragment, which is higher than other initiations. Under large warhead-target missing distance, this change could alter the aiming direction and improve the damage probability.

Abstract:Different types of equipments are installed in the warship cabins according to their functions. However, present research of cabin internal blast damage mainly focuses on the effects of damage elements on vacant cabin, and the effects of the equipments installed in the cabin are seldomly considered. By using the finite element software LS-DYNA, three types of rib-reinforced cabin models, including the one installed with no equipment, the one with one equipment, and the one with two equipments, were built. The analysis of the damage of cabin structure and equipments caused by the internal blast of warhead charge and the comparative analysis of the influence of equipments on the damage effect were conducted. The comparative analysis results show that, because of the obstruction of the equipments, different arrangements of equipments affect the internal flow field distribution of shock waves in a cabin and convergence of shock waves in corners, reduce the maximum overpressure value and change its location, which finally lead to the change of the cabin structure′s damage process .

Abstract:In order to accurately describe the shape of behind-armor debris cloud from vertical penetration of a finite-thickness target plate by an explosively formed projectile（EFP），the dimensional analysis and the theory of orthogonal design were used as bases in this work. The effect of EFP molding parameters and the material parameters of projectile and target plate on the shape of behind-armor debris cloud were studied using SPH algorithm in AUTODYN software. A mathematical description model of the debris cloud shape behind armor from vertical penetration by an EFP was established. The shape parameter of major semi-axis of behind-armor debris cloud from a vertical EFP penetration was calculated using that model and compared with the simulated and related experimental results. It is proved that the error between the calculated major semi-axis result of debris cloud by that model and the related experimental result is controlled within 3%，and the shape of behind-armor debris cloud formed by an vertical EFP penetration can be described accurately with this model.