Shock transformation and shock-induced chemical reaction in materials can lead to their obvious changes of physical and chemical properties. In this paper, the powder mixtures of nitrogen-rich of C₂N₄H₄ and P25 TiO₂ or metatitanic acid were shocked by the impact of flyer plates driven by explosive detonation, and the recovered samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and UV-Vis spectra and evaluated by the photocatalytic degradation of methylene blue and Rhodamine B. The results indicate that the doping level of nitrogen-doped TiO₂ reaches 8.88% (atom fraction) using the P25 TiO₂ as raw materials which exhibits obvious absorption in visible region. Its energy gap decreases to 1.75 eV together with the formation of srilankite high-pressure phase. The doping level is 3%-4% (atom fraction) corresponding to the small variation of the energy gap using the metatitanic acid as raw materials. The specific surface area of the sample increases dramatically due to the unique shock dehydration-expansion mechanism. The nitrogen-doped TiO₂ have better adsorption capability and photocatalytic activity under visible irradiation for the degradation of methylene blue and Rhodamine B, among which treated at higher impact velocity shows the higher photocatalytic activity.

A set of temperature-controlling system adapted to high temperature split Hopkinson pressure bar (SHPB) experiments is developed and presented. Using this high temperature SHPB system comprised of a temperature-controlling system and a general Ø100 mm SHPB apparatus, the dynamic mechanical properties of concrete are investigated at 20, 200, 400, 600, 800 and 1 000 ℃, respectively. The experimental results show that the temperature-controlling system composed of a box preheating furnace and a tube real-time heating device is convenient to operate and can improve efficiency greatly, and the sample assembly method is simple and feasible; the temperature variance of sample and the local temperature rising of pressure bar due to heat conduction can be ignored, and the experimental technique is reliable. Temperature effects on dynamic mechanical properties of concrete at high temperature are obvious. With temperature increasing, the average strain rate and dynamic peak strain increase gradually, and the dynamic stress-strain curves exhibit plastic properties; moreover, the dynamic compressive strength rises at first and then falls.

In order to investigate the shape and evolution process of water column caused by a near surface explosion in deep water situation, underwater explosion experiments with 1 kg of RDX charge at different detonation depths are carried out using a high-speed camera. The evolution characteristics and parameters of water columns including the height, width and prominent time are obtained and compared with those published by Cole, Hole and Swisdak et al. The results show that vertical ejection is the main shape of water column, and a few additional radial ejections occur when the bubble reaches the free surface at its expanding phase. The maximum height of water column fluctuates with the explosion depth, while the width of water column decreases linearly. Empirical formula of water column height by Swisdak is not suitable to near surface underwater explosion in deep water situation.

A hydraulic pressure testing machine and a 100 mm-diameter split Hopkinson pressure bar (SHPB) apparatus are used to investigate the quasi-static and dynamic mechanical properties of ceramic fiber reinforced concrete (CRFRC), which are compared to those of carbon fiber reinforced concrete (CFRC) at the same volume fractions of 0.1%, 0.2% and 0.3%. The strengthening mechanism of ceramic fiber is analyzed. The experimental results show that the ceramic fiber improves the quasi-static mechanical property of plain concrete effectively. When the volume fraction is 0.3%, the compressive strength, splitting tensile strength and flexural strength enhance by 15.0%, 8.5% and 12.7% respectively. The dynamic compressive strength and specific energy absorption of CRFRC are strain rate-dependent under impact load, and the effect can be expressed by linear approximations. The strength and toughness of CRFRC come to the best at the volume fraction of 0.2%. The strength and energy absorption properties of CRFRC are superior to those of CFRC as a whole.

According to the previous simulation results of two-dimensional fluid-structure interaction, the model of impulsive load generated by a single explosive rod and shaped by the buffer is built. Then the loads generated by multiple explosive rods are superposed and applied on the surface of the cylindrical shell, and a two-dimensional decoupled simulation is performed. The results basically agree with those of the fluid-structure interaction simulation. Based on that, a three-dimensional decoupled simulation of the Ø265 mm×380 mm cylindrical shell loaded by 19 explosive rods is accomplished. Meanwhile, the corresponding test is performed. There shows a good agreement between the three-dimensional numerical and tested strain histories at typical locations. These results prove the effectiveness of decoupled numerical simulation and provide a foundation for improving the modeling and computational efficiency in performing a large number of numerical simulations.

In order to investigate the distribution law of pressure on the liner surface and the effect of initiation point parameter on the pressure distribution, the interaction of detonation waves with each other and with the liner is simulated by LS-DYNA software. The simulation results coincide well with the experimental data. The results of the study indicate that detonation waves collide with each other on the symmetry plane of the initiation points, and the pressure of collision position increases, which make the pressure distribution of liner uneven. While the distance between initiation points is bigger, the pressure of tip liner increases quickly, but the pressure of edge region of liner decreases gradually. When the distance is 50 mm, the pressure drops suddenly, namely the distance has a maximum value. The pressure of liner increases with the number of initiation point, but the increase rate reduces gradually, and the pressure distribution laws on the liner surface with different initiation numbers are similar. The conclusions can supply a theoretical basis for choosing appropriate initiation point parameters of the explosively formed projectile with star shaped tail.

The Richtmyer-Meshkov instability occurring on a heavy gas (SF₆) bubble surrounded by N₂ is numerically investigated in the present work. The interface evolution, shock focusing and jet development are emphasized. Numerical schlieren images and distributions of pressure, density and vorticity are exhibited for an incident shock wave of Mach number 1.23. The jet velocity, circulation and baroclinic torque versus time as well as peak values of pressure and density in the flow field are quantitatively analyzed. The results indicate that SF₆ gas bubble accelerated by a planar shock wave has a strong cumulative energy effect so that it produces nearly ideal shock focusing and point source explosion phenomenon near the downstream pole within the bubble interface, which directly results in a secondary wave pattern and a slender jet moving in the streamwise direction. Compared with the secondary wave pattern, the incident shock wave brings on more intense baroclinic torque and vorticity.

In order to investigate the influence of crystallographic properties of materials on the formation mechanism of surface craters, high current pulsed electron beam (HCPEB) was used to irradiate a 304 austenitic stainless steel with and without shot peening treatment. The morphologies of surface crater induced by HCPEB were characterized in detail. The experimental results indicate that a large number of volcano-like craters are inevitably formed on the surface sample after HCPEB irradiation. The number density and dimension of craters decrease with the increase in electron beam energy. It is found that inclusions on the surface layer easily become the new nucleation sites of craters; however, they are gradually removed during the period of eruption in the formation of the crater, and showing a surface purification effect. Additionally, it is established that the number density of craters on shot peening samples is significantly increased than untreated ones. The number densities of craters on the samples with and without shot peening treatment follow the similar law. The present results indicate that the crystallographic properties of materials have a great importance to the formation of surface craters, and the structure defects, such as grain boundaries and dislocations are the preferred sites of the nucleation of craters.

A series of impact experiments are conducted to investigate the ballistic performances of stuffed Whipple shields with Kevlar fiber clothes using a two-stage light gas gun facilities. Based on the impact limit curve of Nextel/Kevlar stuffed Whipple shields, the protective performances of Kevlar stuffed Whipple shields, the damage morphology and mechanism of stuffed material and bulkhead are obtained and compared. The main results show as following: the stuffed Whipple shields with Kevlar fiber clothes have excellent protection performance at the low impact velocity; the double-layer packing structure can improve the protective performance. Kevlar fibers sufficiently absorb energy by plastic deformation and fracture when the impact velocity is low. In addition, high temperature melting and carbonization phenomenon appear in the hypervelocity region, which help break up and melt the projectiles that minimize the damage to cabin wall. This exploratory method provides us a useful way to make the ballistic performances of stuffed Whipple shields more perfect in space debris protection field.

To acquire the interference status of typical logic chips in spacecraft caused by plasma generated from a hypervelocity impact, the triple Langmuir probe system established by selfishness is used for diagnostics of plasma characteristic parameters created by 2024-T4 aluminum projectile hypervelocity impact on 2024-T4 aluminum target, with the impact velocity and incidence angle of 6.10 km/s and 30°, respectively. The plasma electron density is measured at a given position with a given azimuth, and the interference estimation is performed for logic chip by data acquisition system. The experimental results show that the logic chips in spacecraft will be seriously influenced by plasma generated at hypervelocity impact.