Abstract:As the arch structure is one of the common structural forms of underground engineering， the majority of current research focuses on the numerical simulation. The numerical results of structural damage characteristics and response lack corresponding experimental verification， which cannot sufficiently guide the blast resistance design of underground engineering. In order to study the failure mode and blasting resistant performance of underground arch structures with reinforced concrete under explosive load， 5 independent experiments under top explosion had been carried out with different blasting distances and charges. Results show that the damage degree of the arch structure gradually increases with the increase of charge under the same blasting distance. The characteristics of failure mode developed from the concrete cracks at the back surface of blast to the concrete spalling and deformation of steel bars. At last， the concrete collapsed significantly at the center of the vault and the steel bars were severely bent and deformed. The damage of the arch structure under top explosion is not only related to the scaled distance， but also affected by the blasting distance. Under the same scaled distance，the damage degree of arch structure increases significantly with the increase of blasting distance. By analyzing the relationships between the displacement response and the charge mass， the displacement response and the blasting distance， a method is initially proposed for dividing the damage grade based on the deflection-span ratio， which provides experimental support for the structural failure evaluation and analysis in the future.

Abstract:To improve the penetration depth in the target subjected to the jet of reactive materials liner， a shaped charge with Al/Ni-Cu double-layered reactive liners based on the K-charge structure was proposed. The outer and inner liner of the double-layered reactive liner are made of oxygen-free copper and Al/lNi reactive material， respectively. Experimetal study of jet formation， static armor-piercing into steel ingots and the penetration power to typical concrete targets were carried out seperately by using X-ray cinematography. Results show that the double-layered reactive liners with K-charge can form a continuous jet after detonation with obvious pit areas in steel and concrete targets. However， the jet has no obvious reaming effect on penetrating the target. A combined damage effect of kinetic energy and chemical reaction can be achieved by the Al/Ni-Cu double-layered reactive liners. Compared with the Cu-Cu double-layered， less jet accumulated in the target penetrated by the new double-layered reactive linears. Meanwhile， the penetration depth and volume of the steel targets were increased by 20.1% and 23.0%， respectively， while the penetration depth and volume of the concrete targets were increased by 17.2% and 45.6%， respectively.

Abstract:To achieve an effective evaluation of the damage power of all-energetic penetration warhead， a test system for damage power assessment was established based on the 125mm artillery， accompany by a description in multiple physical fields from various aspects such as penetration， reaming， high temperature， high pressure， and arson ignition by arson. Results show that a 16 kg warhead can penetrate a 5-layered steel target at a speed of 952 m·s^-1 to form strong fire which lasts for about 120 ms， with a maximum diffusion range of over 6 m×10 m and a maximum temperature of about 2100 ℃. Compared with the inert warhead， the gains of temperature and overpressure at 1.2 m are about 1270 ℃ and 0.16-0.5MPa， respectively， and the cumulative gain of the broken hole area of 5-layered steel target reaches beyond 300%. Moreover， the warhead has a good arson ignition effect on the fuel tank.

Abstract:To predict the resistance to penetration of the ultrahigh molecular weight polyethylene laminate（UHMWPEL） accurately， a three-dimensional finite element simulating method of composite structures laminate based on the ABAQUS/Explicit solver platform was developed. A user-defined subroutine VUMAT was proposed to define material behavior by dividing the laminate into two parts with orthotropic lamina and cohesive interface. The lamina and cohesive interface utilized the Hashin criterion and the quadratic stress criterion as the damage initiation criterion separately， while both of them adopted the bilinear constitutive model and the damage evolution method derived from fracture toughness. The residual velocities and damage states of UHMWPEL with thickness of 10 mm and 20 mm penetrated by wedge-shaped steel fragment simulation projectile（FSP） with different initial impact velocities were simulated. The results show that， compared with the existing experiments， the prediction errors of ballistic limits of 10 mm and 20 mm UHMWPEL are 0.6% and 11.3%， respectively， and those of all residual velocities of FSP are less than 14.2%. During the damage and failure process of UHMWPEL， punching failure and local bulging occur in the first stage， followed by large-scale bulging， large-area delamination and fiber tensile failure. This two-stage characterization is similar to that observed in existing experiments， which verifies the reliability of the proposed simulating method.

Abstract:In order to improve the ballistic stability of penetrating projectile obliquely penetrating multi-layer concrete target， the structure design of head grooved projectile and pointed oval projectile is proposed. Numerical simulation was carried out based on LS-DYNA software， and two projectiles penetrating 10-layer concrete target were tested. Research shows that in the process of penetrating single-layer concrete thin target， the attitude deflection angle of projectile increases with the increase of initial attack angle， and the attitude deflection of grooved projectile is relatively small compared with that of sharp oval projectile. Compared with the test results of penetrating 10-layer concrete target， grooved projectiles can significantly reduce the deflection attitude of projectiles relative to Ogive-nosed projectiles， which has good ballistic stability and provides reference for the design of projectile with ballistic stability of penetrating multiple targets.

Abstract:To study the initiation process under jet impact and obtain the critical initiation threshold of explosives with different thicknesses， experiments of jet formation with Φ40 mm shaped charge were performed and captured by the high-speed video. The 43-mm thick TNT explosives were covered by 50SiMnVB cover plates with different thicknesses in experiments. The critical initiation threshold， the response under different stimulus intensities and the expansion velocity of reaction products were obtained. The numerical simulation of finite-thickness explosive under jet impact was carried out by using numerical simulation software. The propagation process of bow wave in explosive under jet impact and the relationship between critical initiation threshold and the thickness of finite-thickness explosive were analysed. The simulation results were compared and verified by the experimental data. The results show that the critical initiation threshold of TNT with a thickness of 43 mm is 37 mm³·μs^-2， and the expansion rate of reaction products varies by at least one order of magnitude between different responses. When the jet impacts on a finite-thickness explosive， a certain distance is required for a bow shock wave evolving into a detonation wave. The higher the tip velocity of the residual jet is， the shorter the distance is required for the evolution of bow shock wave to detonation wave. Therefore， the decrease of explosive thickness will lead to the increase of critical initiation threshold of finite-thickness explosive， and the logarithm of critical initiation threshold is approximately linear with the logarithm of explosive thickness.

Abstract:To study the stability of a cast polymer-bonded explosive （PBX） during penetration， projectiles with the PBX-1 charge was launched by a 155mm gun to penetrate concrete targets. The penetration depths at different velocities were obtained， and the critical penetration velocity for maintaining the charge stability was about 490 m·s^-1. Based on the viscoelastic statistical crack （Visco-SCRAM） model， the experiments for testing penetration stability were modelled by a fluid-solid coupling method with large deformation. Thermal-mechanical responses of the charge during penetration were obtained and reasons for the unexpected ignition of the charge were analyzed. The numerical results and experimental data are in a good agreement. The results show that no obvious deformation or damage is observed for the projectile shell， while the cast PBX charge undergoes large deformation and part of charge seeps out from the end gap. During the penetration process， the charge collides with the bottom of charge chamber at high speed and forms a local high-pressure zone. The maximum pressure exceeds 500 MPa when the charge tail is impacted. The tail of the charge is deformed and damaged severely， which may lead to a highly localized temperature and even ignition.

Abstract:To study the jet formation and penetration characteristics of the shaped charge with elliptical cross-section， and the influence of the ratio of long axis to short axis at a fixed short axis， DOP （Depth of Penetration） tests at stand-off 80 mm were carried out for shaped charges with elliptical cross-section. The short axis diameter of elliptical cross-section is 56 mm and the ratio of long axis to short axis are 1， 1.5 and 2， respectively. By using ANSYS/LS-DYNA software to construct related finite element models， the jet formation and penetration process are simulated numerically. The results showed that except for the jet head， the rest of jet was cohesionless at the late stage of stretching. The non-condensed part of jet consists of two fluids with lateral velocity symmetrically distributed over the section of long axis. The non-condensation of jet will significantly reduce the penetration ability of the shaped charge with elliptical cross-section. For the shaped charge with a short axis diameter of 56 mm， the penetration depth decreased by 68.3% from 150 mm to 47.5 mm when the ratio of long axis to short axis changed from 1 to 1.5， while no significant change of penetration ability occurred while the ratio of long axis to short axis changed from 1.5 to 2.

Abstract:To investigate the shock initiation characteristics of the insensitive aluminized melt-cast explosives， a one-dimensional Lagrangian test system was established with the manganin piezoresistive pressure gauges and the loading technique of chemical explosion. The shock initiation process of an aluminized DNAN-based melt-cast explosive was measured， and the growth histories of pressure were obtained under different loading pressures. By virtue of the mesoscopic model of reaction rate of the aluminized melt-cast Duan-Zhang-Kim （DZK） ， the parameters of the aluminized explosive were determined and then the shock initiation process was simulated numerically. It is found that the higher the loading pressure is， the faster the detonation grows inside the aluminized explosive. In the shock initiation of the aluminized melt-cast explosive， the reaction degree and reaction rate are low near the leading wave front. However， the reaction rate of explosive after wave increases continuously and reaches the peak value in a while with the ignition reaction and the accumulation of chemical reaction Furthermore， compared with the growth history of particle velocity， those of pressure involve more detail of the growth of reaction rate， which are more suitable to be used in validating the reaction rate models and determining the parameters of reaction flow models.

Abstract:With the deepening and development of the concept of long-range operations， long-range strike of missile has become an indispensable part of modern warfare. Therefore， the damage assessment of target hit by missile warhead has been the focus of damage research in recent years. Research of damage assessment in the process of missile warhead striking the target are summarized from four aspects： damage assessment model of target， main subjects in damage process， damage of classified targets， and methods of damage assessment， respectively. Problems such as non-standard judgment of damage degree， unclear relationship of damage mapping and inaccurate solution of damage probability in current stage are pointed out. According to the insufficiency of current study， some suggestions are proposed for the research in the future， which can provide reference for the investigations in the related fields.

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