In order to investigate the parameters of shock wave in air blast, the ground reflected overpressures of TNT, HL0（RDX 95%+Wax 5%）and HL15（RDX 80%+Wax 5%+Al 15%） at different locations were tested. Test resultes show that the peak overpressures of HL15 are maximal at 3 m, 4 m and 5 m from the center of explosion compared with TNT and HL0. The peak overpressures of three explosives get closer to each other at 7 m, 9 m and 12 m from the center of explosion with the increase in distance. Power exponential formulas are used to fit the relationship between peak overpressure and scaled distance. The fitting results show that the magnitude order of peak overpressures is HL0≥HL15>TNT for R≤ 2.6 m; the magnitude order of peak overpressures is HL15> HL0 >TNT for 2.6 m

In order to improve the survival ability of armored vehicles in the war, the protecting technology has been attached importance and developed completely by the world military powers. The paper presented the research state and protecting level of modern armor, and enumerated protecting furnishment of advanced armored vehicles, and summarized the research state and level of key protecting technologyarmor material. After introducing situation of armor protecting technology, taking the research content of U.S. and U.K., the development trend to the modern armor technologysynthesis protection system were analyzed.

The inside load characteristics of broadside cabin of defensive structure subjected to underwater contact explosion is researched. The interaction between underwater explosion bubble and broadside empty cabin at the time when is three fold of the first pulsation period of underwater explosion bubble and the inside load characteristics of broadside empty cabin are numerically analyzed by using LS_DYNA software. The model experiment is performed to validate the creditability of simulation results and analysis. The research shows that the blast gas flows into or out the broadside empty cabin from the plate crevasss along with bubble expansion or contraction, and the broadside plate is sunken or upheaved at the same time. The broadside empty cabin is separated by plate petals into two regions, and the load in the front of plate petals is different from that in the back of plate petals. If the largest plate damage is evaluated by using finite element method, the calculation time could be just 5% of the first pulsation period of underwater explosion bubble.Key

The experimental research on drop hammer impacting of gun-propellant was made to obtain an effective analysis method for the elastic modulus of typical gun-propellant under impact loading. The stress and strain curves of gun-propellant during drop hammer impact test were obtained through high-speed photography and digital image correlation method. On this basis, the linear-elastic, nonlinear-elastic and viscoelastic analysis methods are used to get the change laws of elastic modulus of DAGR125-21/19 with impact energy and velocity at normal and low temperatures. The results show that the elastic modulus of gun-propellant changes slightly at normal and low temperatures with the increase in the impact velocity. Furthermore, the magnitude of elastic modulus from viscoelastic analysis is least, the results from linear elastic analysis are close to those from nonlinear elastic analysis, and the elastic modulus of gun-propellant at low temperature is much greater than that at normal temperature. The elastic modulus of SF-3 double-base gun-propellant was studied. It is found that the elastic modulus of SF-3 double-base gun-propellant is equivalent to that of DAGR125-21/19 at normal temperature, but the elastic modulus of the former is much bigger than that of the latter at low temperature. The reliable and accurate elastic modulus of gun-propellant can be derived by using viscoelastic analysis based on digital image correlation method.

In order to study the difference between detonation processes of HMX-based and TATB-based plastic bonded explosives and know more about the detonation growth characteristics of insensitive high energy explosives, an one-dimensional Lagrangian experimental test system is built based on manganin piezoresistive pressure gauge measurement technique, in which the aluminum flyers are used for planar impact loading. The impact initiation experiments are performed for PBXC03 (mainly HMX) and PBXC10 (mainly TATB) explosives. The pressure histories at different Lagrangian locations and the time-distance curve of shock front are obtained through experiment. The results show that the detonation growth progress of PBXC10 explosives distinctly distinguishes from that of PBXC03 explosives. This indicates that the physical mechanism of the shock initiation and detonation growth of HMX-based plastic bonded explosives is different from that ofTATB-based plastic bonded explosives. The experimental data can be used to calibrate the reaction rate equation of insensitive high energy explosives.

Based on the recent researches of the author and his collaborators on penetration acceleration test, the paper summarizes and reviews the researches both in China and abroad on high g acceleration field test during projectile penetration into hard target with high velocity for over the last decade，especially the on-board test application in acceleration test. The paper also summarizes correlative technology on penetration acceleration test, including the anti-high shock capability and calibration of accelerometer, and the anti-proshock ability of battery. At last, based on the existing research works and potential national defense demands, the development trends and problems worth of consideration in the field are demonstrated.

The structure of water chamber is modified for high strength underwater shock loading in laboratory on the basis of the non-explosive underwater shock wave loading device. The loading characteristics of the non-explosive high strength underwater equivalent shock wave are studied using the combined experimental and numerical methods. The dependences of shock wave strength and decay constant on the flyer plate and piston mass are investigated, and the expression of shock wave strength is established. The underwater shock loading experiments for 0.5 mm thick aluminium alloy target plate are carried out by using the modified device. The experimental results indicate that the improved device could effectively simulate high strength underwater shockloading.

Bottom protection，which is of great significance for improving the survivability of military vehicles and providing effective protection for crew，has become one of the research hotspots of the military vehicles. The research on bottom protection technique of military vehicles, the analysis of protection capability and optimization of structure based on numerical simulation, the evaluation of bottom protection capability, the bottom protection strategies and their applications, the technical measures and protection capability of typical vehicles are reviewed. The technical measures which include V-shape bottom hull, tabulate bottom floor made of new type material, interior structure of vehicle and crew restraintsystems are expatiated. The application and researchstatus of numerical simulation technology which is used to analyze the protection capability of military vehicle and optimize the bottom structure of vehicle are discussed. The research status of the effects of explosion shock on vehicle and its crew and the test evaluation of the bottom protection abilities of vehicle are analyzed. Simple local protection, locally added protection kits, special protection body with protection kits, and integrated protection solution are summed up. The bottom protection measures and capability of typical vehicles are analyzed. In addition，the future research direction andpriorities of bottom protection , and how to develop the protection capability of military vehicles are suggested.

In order to study the fracture mechanism of explosively-formed projectile （EFP） in axial direction, the forming and fracturing processes of OFHC EFP with typical charge structure are simulated by using LS-DYNA software, in which Johnson-Cook failure model and adaptive algorithm are introduced. Hemispherical liners with different extrinsic curvatures are simulated, and the simulated results of fracture are validated through experiment. The stress wave theory is used to analyze the fracture mechanism of long rod EFP, and confirm the critical velocity gradient. The results show that the fracture phenomenon of EFP can be well simulated by using LS-DYNA software based on Johnson-Cook failure model and adaptive algorithm. For certain EFP charge structure with hemispherical liner, a critical liner curvature which makes the long rod EFP fracture in forming process exists. The critical value of 60~83 m/s calculated from stress wave theory agrees well with the critical velocity gradient(76 m/s) of EFP fracture. The theoretical analysis method can be used to confirm the critical velocity gradient of long rod EFP fracture. Key

In order to cope with armored target with double explosive reactive armor, it is necessary to study the field of explosive reactive armor systematically. Based on the research on the flying plate motion law of the double explosive reactive armor, a theoretical model of applied field about double explosive re- active armor has been developed. Using the model, reaction time of double-layer explosive reactive ar- mor爷s applied field has been studied under the conditions of different arranged angles and wedge angles. The flash X-ray test is accomplished to verify the theoretical results. The results show that the arranged angle and wedge angle have a larger influence on explosion field, in the certain range, making reaction time of applied field improved about 1. 75 times. The calculation results have a good fit to the experiment results.

Damage criterion of torpedo shell subjected to underwater explosion is researched. A damage criterion is proposed according to the general form of the characteristic parameters of underwater explosive shock wave. A damage criterion method which is based on “0-1”probability distribution function is proposed. For 1∶2 ring stiffened cylinder scale model of heavy torpedo, the undersea explosion experiments of torpedoes with different charge masses are done. The quantitative criterion of heavy torpedo shell damage is obtained through similarity transformation of scale model. The peak overpressure and specific impulse threshold values of each damage level are analyzed based on this criterion. The results show that the threshold of peak overpressure decreases with the increase in charge mass under the same damage grade, and the threshold of specific impulse increase; and the smaller the charge is, the greater the change amplitudes of the two threshold values are.

The shock initiation experiments on the PBXC03 explosives in two different formulations, namely, the medium and the coarse one, are performed to obtained in-situ manganin piezoresistive pres- sure gauge data at various shock pressure. The loading technique of explosive plane-wave lens and the at- tenuation technique produced by both air-gap and Al-gap are used in the one-dimensional Lagrangian ex- perimental system. The Numerical simulation on the shock initiation of the two kinds of PBXC03 explo- sives are performed by using the two-dimensional hydrodynamics software DYNA2D. The computational propagation trajectory and pressure growth process of the shock front agree well with the experimental da- ta, and the computational run-distance-to-detonation points show good agreement with previously pub- lished Pop-plot data, which confirms that the mesoscopic reaction rate model used in this paper is reason- able.

To investigate the underwater explosion performance of RDX-based aluminized explosive, the underwater explosion experiments for RDX-based aluminized explosives with different charge masses and aluminum contents were carried out in outdoor pools. The process of generation, expansion and contraction of underwater explosion bubbles was observed through the high-speed camera placed in water, and the pressure history of shock wave was measured by a pressure sensor. Under the experimental conditions, the secondary reaction process of powdered aluminum for RDX-based aluminized explosive during underwater explosion was captured by the high-speed camera firstly, which indicates that secondary reaction process of powdered aluminum is in the order of milliseconds. According to the experimental data, the pressure in flow field and the bubble pulsation were analyzed. The experimental results indicate that the secondary reaction of powdered aluminium occurs in both the initial stage of bubble expansion and the end of bubble contraction. The secondary reaction of powdered aluminium significantly increases the pulsation ability of bubble. The secondary reaction of powdered aluminium has little effect on the peak value of shock wave and great influence on the peak value of bubble pulsation. The secondary reaction of powdered aluminium obviously affects the energy structure distribution of underwater explosion. Key

The secondary damage effect of tempered glass subjected to blast shock waves was researched through experiments, and the statistics of mass distribution of glass fragments were done in the experiments. The mass distribution of fragments is analyzed and researched according to the statistical results. A dimensionless function of the relationship between the fragment mass and the splashing distance is derived based on the dimensional analysis. According to the dimensionless function and the experimental statistical data, a semiempirical prediction formula to calculate the fragment mass distribution is obtained by employing the least square fit. The characteristics of the formula are analyzed, and its reasonableness and effectiveness are verified. The research result shows that the mass distribution laws of glass fragments are consistent for thetempered glasses with the same thickness in the same damage mode. Key

Strain and strain rate are two important factors that affect the mechanical behavior of materials, and the split Hopkinson pressure bar (SHPB) technique is one of the effective ways to realize different strain and strain rate loading conditions. To study the plastic deformation and fracture behavior of TC18 titanium alloy under dynamic loading (ranging from 300 to 3 000 s^-1), a series of dynamic compression tests on TC18 titanium alloy have been performed by means of SHPB technique at room temperature. The different strain and strain rate loading conditions are realized by changing the length and velocity of the striker. Macro true stress-true strain curves are obtained under different strain rate loading, so are the true stress-true strain curves under the same strain rate with different strain loading conditions. The effects of strain hardening and strain rate hardening on the dynamic mechanical properties of TC18 titanium alloy are discussed. Results indicate that the collapse of specimen occurs along a plane inclined at an angle of about 45° to the compression axis, namely, shear failure is the main failure mechanism for TC18 titanium alloy under compression loading at room temperature, and it is dependent on strain and strain rate;the higher the strain rate is, the larger the flow stress (or yield stress) of TC18 titanium alloy is, therefore, the material shows clearly evident strain rate hardening effect; and the analyses of microstructure and fracture morphology show that adiabatic shear bands are the precursor to the crack formation and fracture.Key

The test systems for impact pressure of polyvinylidene fluoride (PVDF) and electrical output characteristics of piezoelectric ceramics were built to study the influence of impact pressure on the electrical output characteristics of PZT-5H piezoelectric ceramics. The one-stage light gas gun is used as a loading means, and the experiments of which the cylindrical aluminum alloy projectiles vertically impact an composite target plate (steel sheet-piezoelectric ceramic-plexiglass) at the speeds of 195 m/s, 487 m/s, 532 m/sand 613 m/s are conducted. The projectile impact on target is analyzed by using ANSYS/LS-DYNA. The time histories of shock pressure of PZT-5H at the different speeds are analyzed. A simplified model of stress wave propagation is established based on the experimental system, and the pressure peak of PZT-5H in the composite structure is calculated by the proposed model. The change rules of PZT-5H piezoelectric ceramics under different peak pressure are analyzed from the time histories of shock pressure, output voltage of piezoelectric ceramics, and charging voltage of energy-storing capacitance. The research results show that the calculated impact pressure peaks are consistent with the simulated and experimental results; the output voltage peak of PZT-5H piezoelectric ceramics rises with the increase in impact pressure peak in the range of pressure peak of 200-700 MPa; the conversion efficiencies of kinetic and electric energies are low when PZT-5H piezoelectric ceramics is impacted by high-speed projectile. As the ratio of energy storage capacity to piezoelectric ceramic capacitance is 5.9∶1, the energy conversion rate of piezoelectric ceramics is 1.1% compared to the primary kinetic energy of projectile.Key

The working condition of barrel forcing cone is worse during the firing process of small arms. To study the influence of the forcing cone angles on the stress of barrel forcing cone, the three-dimensional finite element models of barrel and projectile at different forcing cone angles are established, in which the structures of barrel and projectile, and nonlinear constitutive relations are considered. The effects of different forcing cone angles on the projectile engraving process are analyzed. The data of engraving resistance is obtained under the condition of different forcing cone angles. A response surface model of engraving resistance is established. The formula and the variation rules of projectile engraving resistance along with the forcing cone angle and engraving displacement are calculated based on the above data by using Hermite polynomial. A dynamic model of projectile engraving process is established in consideration ofthe engraving resistance. The engraving pressure during the projectile engraving process is solved by programming. The forcing cone angles among 0.11° and 1.13°, which satisfy the requirement of muzzle velocity of the projectile, are obtained, and then the best forcing cone angle of 0.56°, which could reduce the barrel stress to ensure the highest velocity and meet the design range of forcing cone angles in case of satisfying the interior ballistic behaviors, is got.

A series experiments that the explosively-formed projectiles (EFPs) penetrate 10-40 mm-thick mild carbon steel (45# steel) were designed to investigate the effect of behind armor debris(BAD) after EFP penetrating into steel target. The morphology and scattering characteristics of BAD are observed by pulsed X-ray photography, and the number and damage ability of BAD are obtained by measuring the perforation on witness target. It can be seen from the pulsed X-ray photographs that the shape of BAD presented as fragments is of partial ellipse with the scattering angle of about 50°. The perforation on witness plate shows that BAD could penetrate 10mm-thick aluminum plate, the perforation distribution is relatively random, and the diameter of hole on witness plate approximately conform to normal distribution. The scattering angle varies little with the increase in the target thickness, while the number of BAD increases first and then decreases, namely there is a target thickness that maximizes the number of BAD. It can also be seen from recovered fragments that EFP and steel target debris together constitute the BAD.Key

In order to decrease the volume and manufacturing cost of exploding foil initiator system, an exploding foil initiator (EFI) with high voltage planar switch is designed. The exploding foil and high voltage planar switch are prepared on the observational side and the reverse side of ceramic substrate, respectively. That substrate and other parts are assembled into an exploding foil initiator, and the electrical explosion performance of the exploding foil initiator is studied. The results indicates that the exploding foil initiator with high voltage planar switch had similar initiating performance as the traditional exploding foil initiator which uses a spark gap switch. The high voltage planar switch could meet the initiating requirement of exploding foil initiator instead of spark gap switch.

The dynamic responses of projectile-borne electronic devices which are protected by encapsulating materialunder impact loading are studied through numerical simulation. A LS-DYNA user defined material subroutine is established according to the ZWT nonlinear viscoelastic model which is used for simulating the dynamic response of the encapsulating material in the projectile. The simulations of projectile penetration were performed by adjusting the controllable parameters of ZWT model, such as nonlinear elasticity modulus, low strain rate Maxwell elastic constant, high strain rate Maxwell elastic constant, high strain rate Maxwell relaxation time and material density. Thus the dynamic responses of projectile-borne electronic devices could be obtained from the numerical results. The research results show that the shock absorption and protection effects of the encapsulating materials are better when the values of nonlinear elasticity modulus, low strain rate Maxwell elastic constant, high strain rate Maxwell relaxation time and material density are decreased. Key

The core task of tank overall design is to get the best overall performance, minimum size and minimum weight without increasing the technical difficulty of parts. Relationship among the three main performances and the general dimensions of main battle tank (MBT) is analyzed by decomposing the specifications of firepower, mobility and protection. An optimization model is established for MBT's firepower, mobility and protection performance based on physical dimension. Restraining the height of tank is the key to coordinate the firepower, mobility and protection performance of tank. Approaches to restrain the height, width and length of tank are proposed.Key

The load of missile erection system is time-varying and an excessiveload exists. When the closed or open loop control method is used, the control accuracy is low, and a large hydraulic impact is easily generated in starting-braking process. An independent metering technology is proposed to control the erection process. The inlet and outlet of hydraulic cylinder are controlled by two independently adjustable throttle valves, respectively. The inlet throttle valve is used to control the flow of inlet, and the outlet throttle valve is used to control the pressure of outlet. The flow and pressure controllers are designed based on computational flow feedback and pressure closed loop, respectively. Flow and pressure compound control strategy was achieved. Experiment of the control strategy was accomplished. Through comparison with displacement closed loop, it is shown that the flow and pressure compound control method is used to reduce the hydraulic impact and improve the control precision of erection system. Key

An experimental method is developed to simulate the plutonium aerosol source term in the circumstance of high-explosive detonation with ordinary surrogate metals on an aerosol test facility consisting of a confinement vessel and a non-viable aerosol sizing sampler. Five kinds of metals, including silver (Ag), tungsten (W), tin (Sn), cerium (Ce) and vanadium (V), are detonated in confinement vessel. Aerosol samples with aerodynamic diameter of smaller than 10 μm are collected. The cumulative mass and size distribution of each metal aerosolized in experiment are investigated and compared to the plutonium aerosol source term obtained from operation roller coaster-double tracks experiment of USA. The results show that the silver aerosol can simulate the plutonium aerosol source term in the laboratory environment, of which the cumulative mass distribution is in good agreement with that of plutonium, while the aerosol source terms of other four metals are quite different from that of plutonium. Two samples of the silver aerosol in confinement vessel are collected at different time after detonation, which are compared based on energy spectrum analysis and scanning electron microscope characterization. A solid sample on the bottom of confinement vessel is also collected, and the scanning electron microscope method is used to analyze the size distribution of the sediments. The results show that the AD of silver aerosol obtained just after detonation is in the range from 1.1 μm to 2.1 μm, while the aerosol size is larger for the late sample, suggesting that settlement and combination of the silver aerosol take place with time in confinement vessel.

Shielding effectiveness of electromagnetic shielded enclosure would be decreased by blast shocks. An electromagnetic shielded enclosure with the shock isolator with own patented technology is designed and constructed. The field blasting and shielding performance tests are conducted to study the effect of blast shock on the the shielding effectiveness of electromagnetic shielded enclosure with integral shock isolation. The results show that the vibration acceleration of electromagnetic shielded enclosure with integral shock isolation is only 18 m/s² although the input vibration acceleration peak is up to 115 m/s² under the blast shocks of 160 kg cumulative charge. This means that the integral shock isolation effectively reduces the impact of blast shock on electromagnetic shielded enclosure. The electromagnetic shielded enclosure meets the requirement of GradeⅠ.

The deformation and damage patterns of clamped sandwich plates with aluminum foam core subjected to blast loading are investigated experimentally. The deflections of the center point on the rear face sheet of sandwich plates under five blast loadings are obtained. The deformation and damage patterns of the front face sheet, aluminum foam core and rear face sheet subjected to different blast loadings are given also. Two types of the fracture mechanism of the foam cores, which are shear fracture and tensile fracture, are analyzed. The research results show that the foam core subjected to intensive dynamic loading is deformed in a “progressive” compressive mode, and the maximum deflection of the rear face sheet quadratically increases with the blast impulse approximately.

A combined warhead with annular jet and central explosively formed projectile (EFP), which can produce large holes on reinforced concrete wall, is designed to solve the problem of perforating large hole on the wall. To solve the problems of twisting and deflection in forming process of annular jet, the annular liner with variable wall thickness is proposed. The variable wall thickness of annular liner is realized by two eccentric circles, and the changing gradient of wall thickness is determined by eccentricity. The forming processes of annular liner with four different wall thickness gradients were analyzed through numerical simulation, and the numerical simulation of the annular jet and the central EFP combined warhead penetrating into concrete wall was carried out. The annular jet with better density also has a certain angle of expansion. The perforation capability of the combined warhead to the concrete wall was verified through test. The test results show that the combined warhead can produce a through hole with a diameter of more than 2.5 times larger than the diameter of charge caliber on the concrete wall.

Bullet-proof effects of composite materials and the protective capability of armored vests BPV- I、Ⅱ were investigated. Materials constituting the BPV- I、Ⅱ armored vests include ： aluminium alloy plates processed through quenching and ageing , high intensity polyamide fabric and trauma packs having special structures. The results showed that armored vest BPV- I can effectively prevent the penetration of 7. 62mm pistol bullets (Model 54，Made in China) fired at a distance of 3. 41m or more and that armored vest BPV- Ⅱ can be used to protect from shell fragments traversing at 422. 1m/s ?426. 8m/s in V50. Animal experiments proved that armored vests BPV- I、Ⅱ can avoid or remarkably attenuate non-penetrating trauma (NPT ) which has appeared puzzling for so many years because of the special design of the trauma pack.

The principle of a new antidetonation device is based on explosive dispersion. If fire and ex?plosion happen, water can be dispersed explosively to form water cloud to cover the whole firing zone, which can prevent the flame and shock wave from propagating. By comparison with tranditional spray?ing system, it has many advantages, such as rapid water cloud formation and larger water cloud vol?ume .The formed process of dispersed explosively water cloud was emphatically analyzed. Based on the computer fluia dynamics commercial software FLUENT, the processes of water cloud explosive disper?sion and the formation of water cloud were simulated numerically using Euler/Euler mode (two phase fluid model) in two-phase fluid dynamic theory. The profile of liquid droplet vector and the developing process of water cloud concentration with time and space were given by using two antidetonation de?vices, which provide a theory guidance for improving the antidetonation effect of the system.

Mathematical model for the formulation design of powdery ammonium nitrate (AN) explosives was studied. The theoretical explosion heat, specific volume and toxic gas volume of AN explosive without TNT, AN explosive containing TNT and fuel oil, as well as AN explosive containing aluminum powder and TNT at different oxygen balance values have been calculated respectively. The following results are con?firmed, viz. that when the oxygen balance value of powdery AN explosive is decreased, the theoretical ex?plosion heat is reduced, the specific volume increases, and toxic gas volume also increases. In this paper, a method for formulation design was proposed, in which maximum theoretical explosion heat was obtained at an assumed oxygen balance condition. A way for the predictable calculation of the theoretical explosion heat, specific volume and volume of toxic gas AN explosive was suggested. These are useful for the deter?mination of AN explosives formulation.

A novel pressure-conducted velocity probe was developed to continuously measure the propagation traces of detonation wave and near-field shock wave in a single underwater explosion test. An underwater explosion measuring system with the new probe for spherical charge was designed. The repeated experiments of 120 mm-diameter spherical RDX chargewere performed, and the time-history curves of several sets of detonation-shock waves were measured in the experiments. The detonation velocities of RDX explosive under test were obtained by fitting the detonation and shock wave data, respectively, and the detonation pressure, adiabatic exponent, and attenuation rule of underwater shock wave were calculated from the time-history curves of detonation-shock waves, which were compared with the calculated results of Kamlet semi-empirical formula and the numerically simulated results. The results show that the relative errors of the measured and calculated detonation velocity, detonation pressure and adiabatic exponent are not more than 3%, 5% and 2%, respectively. The simulated peak pressure and propagation velocity of near-field shock wave are basically in agreement with the experiments, of which maximum errors are less than 10%. Key

The impact testing, quasi-static and dynamic compressions and finite element simulation were performed to investigate the impact-resistant properties and rate-dependence mechanism of an impact-hardening polymer composite (PBDMS-silica). PBDMS-silica shows liquid-to-solid transition under impact loading, and such impact-resistant behavior is volume fraction-dependentand rate-dependent. This is confirmed by over 10⁴ times increase in compressive and shear strength in the range from quasi-static to dynamic loading. Finite element method (FEM) shows a compression-shear-coupled stress state in PBDMS-silica during impact loading, and the shear stress plays an increasingly important role in impact resistance. Jamming transition is captured during the deformation of the impact-hardening polymer by high-speed imaging with digital image correlation (DIC) technique. Combined with the mechanical responses, the conclusions are made that jamming transition induced by dynamic compression is the source of impact-resistant behavior, and the dynamic shear during impact determines how such behavior is rate-dependent. This provides a solution for the improvement of impact resistance by strengthening the dynamic shear response of the material. Key

A new asymmetrical initiation multiple explosively formed penetrator（MEFP） warhead is designed to improve the damage efficiency of MEFP warhead. Two principle prototypes with central initiation and eccentric initiation were made for static detonation experiment. The forming and dispersing processes of MEFP with hemispherical liners under different ways of initiation are analyzed through numerical simulation. The numerically simulated results illustrate that the length-diameter ratio of EFP is larger, and the EFP is more dense in two-point eccentric initiation mode. The static detonation experimental results of MEFP warheads in two different initiation modes are compared. The comparative results show that the ecentric initiation can is used to improve the velocity, density distribution and penetration power of EFP. The two-point eccentric initiation can effectively improve the comprehensive damage effectiveness of MEFP warhead. Key

In order to investigate the damage criteria of reinforced concrete (RC) beams under blast loading, the experimental study of two different dimensions of RC beams under different blast distances and charge masses is carried out. Two common RC beams designed for tall buildings and frame structures are taken as the research objects. The damage mode and characteristics of RC beams are got through 11 independent blast experiments. The results show that, when RC beams are subjected to close-in blast loading, the damage level increases with the increase in explosive mass at the same blast distance, the damage mode of RC beams changes from a few fall-off of concrete on the two sides of upper side and a few ruptures on the rear face to the compressed flexural damage of reverse triangle cone-shaped concrete on the upper side and triangle cone-shaped crack and a fall-off of concrete on the rear face, and finally the triangle cone-shaped damage areas on both upper side and rear face are perforated to result in a crushed and punched damage of concrete in the middle area. The damage area increases with the increase in explosive mass. Under close-in blast loading (blast distance= 0.5 m for example), the damage criteria of the RC beams used in the experiment are: the beam suffers from minor damage for scaled burst distance Z>0.4 m/kg^1/3; it suffers from moderate damage for scaled burst distance 0.3 m/kg^1/3<0.4 m="" g1/3; it suffers from high damage for scaled burst distance 0.28 m/kg^1/3<0.3 m="" g1/3; it suffers from serious damage for scaled burst distance Z<0.28 m/kg^1/3. It is also found that the damage of RC beam not only depends on the scaled burst distance under close-in blast loading, but also depends on the burst distance. At the same scaled burst distance, the more the burst distance is, the damage of RC beam is more serious. The results can be useful for engineering application and damage assessments.

A novel multi-coil magnetorheological (MR) absorber, which has the capability of being applied with input currents individually, is proposed for the impact mitigation of a gun. The dynamic response characteristics of the proposed MR absorber working in three different modes, namely, uniform loading, combined control and open-loop cascade, are discussed according to ideal profile of recoil resis- tanceat 45-degree angle. Impact experimental results show that, in the non-controllable region, a gas compression stage exists in single-stroke damping process, resulting in a significant hysteresis between the damping force and recoil speed; in the controllable region, given a total 2 A input current, the maximum Coulomb damping force generated by the mode of combined control of more than two working coils behaves better than that generated by equivalent loading; and the mode of open-loop cascade control can effectively reduce the peak force and delay its occurrence moment for approaching the ideal buffer effect. However, this requires additional effective stroke for the recoil buffer. It can be seen through analysis that the MR absorber can be used to achieve flexible and variable damping output based on the temporal and spatial two-dimensional current loading sequence, which shows a certain controllability in the application of gun recoil systems with large firing angles. Key

To investigate the explosion seismic and vibration isolation in underground protective engineering, a method for an artificial synthesis of blast-induced ground motion by matching the target response spectra is presented. The calculation and processes of the matching target spectrum method are described. In the process of generating non-stationary acceleration time histories in the near or far field, two types of wave functions of blast ground acceleration are adopted to deduce the envelope functions. A procedure for construction of blast-induced ground motion design response spectra is introduced, and a modified function of the design response spectrum is proposed. As an illustration, an induced ground acceleration time history for a shallowly buried engineering is artificially synthesized using the matching-target-spectrum method. The example shows that, after iterative calculation, the adjusted response spectrum can be close to the target response spectrum within the given fitting accuracy, the synthetic blast-induced ground motion time history meets the spectrum design requirements and can reflect the spectral characteristics and non-stationary characteristics of blast-induced ground motion.

In order to analyze the mitigating effect of water mist on the explosive shock wave inside a cabin,a series of TNT explosion experiments in the center of a cabin were carried out, from which the wall pressure and quasi-static pressure inside the cabin in different cases with and without water mist were measured. Results show that water mist truly has an evident effect on attenuating the overpressure peak of blast wave and the quasi-static pressure. In the experiment of 27.5g TNT exploding in cabin, the attenuation rate of initial shock wave overpressure is 26.47%, the attenuation rate of secondary reflected wave pressure is is about 27.27%, and the attenuation rate of quasi-static pressure is about 31.82%. For the same water mist density, the mitigating effect of water mist on the blast wave decreases with the increase in TNT charge. Key

A simulated equivalent target of passenger compartment of the typical armored personnel carrier is built to investigate the damage effect of shock wave on the advanced armor target. The tests of shock wave in closed cabin were carried out in the conditions of SC static penetration and the static explosion of detonator in cabin. The results indicate that the shaped charge jet can produce a certain damage effect when penetrating the armored cabin; and the test waveforms differ greatly due tocabin vibration, test position, wall reflection and installation methods of sensors when the bulkhead is penetrated by shaped charge jet. Compared with the static explosion of bare charge in cabin, the shock waves produced by shaped charge explosion and jet penetration are more complex, therefore the effective waveform is beneficial to obtain by using the test method of removing the simulated cabin bottom. Key

In order to solve the problem of high expense in the underwater explosion of directional warhead, the similarity is researched by dimensional analysis. The aim is to research the relationship of explosion pressure between original and small scale models. The result of dimensional analysis is verified by the simulation of AUTODYN. As a result, if the mass of TNT in the small scale model is β³ times of that in original model, the peak pressure in original model is as same as that in the small scale at β times distance. It indicates that the small scale model can replace the original model if the similarity rule is used. This research provide the theoretical basis for underwater explosion experiment which uses the small scale model. It has engineering significance to some extent.

An ignition and growth reaction rate equation with 10 parameters is implanted into LS-DYNA software to precisely describe the shock initiation of explosives and simplify the calibration of reaction rate equation. The reaction rate equation is used to simulate the shock initiation of a DNAN-based melt-cast explosive. The parameters of the reaction rate equation are calibrated by comparing the pressure-time curves in experiment and simulation, and the advantages of the reaction rate equation are analyzed. The results indicate that the reaction rate equation can be easily calibrated due to a few number of parameters. The difference between the simulated and experimental arrival times of shock wave does not exceed 0.2 μs,and thus the reaction rate equation can be used to precisely describe the shock initiation of explosives. The algorithm for implanting the reaction rate equation in LS-DYNA software is efficient because the iterations for every grid does not exceed 3 times.Key

The influence of particle size and gradation of RDX particles on the shock sensitivity of a polymer bonded explosive RDX/F2641 (95 /5) with different dencities was experimentally investigated by small scale gap tests, In this study, the particle size of RDX is changed from Iμm to 150 μm, densities of the compos?ite formulation are 80% , 90% and 95 % TMD. Generally, shock sensitivity decreases with the increase of mean particle size of RDX, but the tendency of influence in different dencities are different. The results mainly represent the effect of particle size of explosive on the hot spot ignition under test conditions.