Discrete dislocation dynamics (DDD) simulation method, as an ideal tool for bridging the gap in space and time scales between atomistic and continuum models, has made great progress in the past few decades. One prominent example is the coupling between DDD and finite element method (FEM), which leads to the capability of DDD to investigate the problems with complicated boundary conditions and multi-physics coupling effect. This work firstly reviewed the development of DDD method, and the coupling algorithm between DDD and FEM. Then, the advances and application of these methods in disclosing the microscopic mechanisms and developing the continuum models are reviewed under the extreme environment of high strain rate, high temperature, and irradiation.

For shock deformation behavior of materials under high temperature, high pressure and high strain-rate loading conditions, dynamic crystal plasticity models can directly reflect the anisotropy of plastic slip and its dependence of temperature, pressure and microstructure in crystals. In consequence, dynamic crystal plasticity models are widely used in simulations of material impact dynamic response, microstructure evolution and dynamic damage. Theoretical models of dynamic crystal plasticity under high pressure shock loading conditions were reviewed in this paper, mainly including: deformation kinetics, hyperelastic constitutive models incorporating equations of state, and crystal plasticity constitutive models. This paper also covers plastic deformation mechanisms, including dislocation slip, phase transition and twinning; as well as dynamic damage, including spalling and adiabatic shear band.

For achieving the hypervelocity launching of about 10 km/s, an implosion-driven launcher with the caliber of 8 mm diameter was analyzed using the AUTODYN 2D software. The projectile launching velocities under typical operation condition were obtained. Based on numerical simulation results, several tests of the implosion-driven launcher with the caliber of 8 mm diameter were carried out. The driven gas of helium with the pressure of 5 MPa was filled in the compressed pipe. The experimental results show that the 0.55 g aluminum and 0.37 g magnesium projectiles could be launched to the velocity of 7.95 km/s and 10.28 km/s, respectively, and the relative deviations between the numerical and experimental results are 15.3% and 3.7%, respectively. Consequently, the designed implosion-driven launcher can realize the launching of the projectiles to 10 km/s or even higher which could provide a new ground-test method for investigating the impact features of orbital debris and corresponding shield technologies.

Sound velocity is an intrinsic property of material, which is equal to the spread velocity of weak perturbation. Measurements of sound velocity are very important for the research of equation of state, phase transition and component of matter at extreme conditions. A continuous side-release method which can work to terapascal pressure was newly developed. In this paper, we described details of high precision targets fabrication of this method, including requirements, methodology and detection. Also, key factors which lead to fatal issues are analyzed for better signals and reliability. Experimental results on SGIII prototype laser facility are shown to validate the technology of targets fabrication.

The influences of air gap and metal interlayer on the shock initiation of the $\varnothing $50 mm stepped explosive B have been investigated by means of the sapphire flyer planar impact experiment and photonic doppler velocimetry (PDV) technique. In the experiment, a lithium fluoride (LiF) window was stuck to the rear interface of explosive sample to allow the rear interface velocity between the metal and the sample explosive be measured by PDV technique. Both the transmission shock pressure and the incident shock pressure can be obtained by the impedance-match method. The experiment results have shown that the air gap divided the impact compression process into quasi-isentropic compression and impact compression, respectively, and at the same time, the amplitude of the shock pressure was declined. Specifically, the shock wave attenuation range caused by 5 mm thick metal was achieved. When the explosive A was used as the booster, and with a 0.3 mm thick air gap and 5 mm thick metal experimental setup, the reaction of sample explosive B started in a range from 7 mm to 10 mm.

In order to study the growth law of the impact initiation reaction of high energy insensitive PBX-3explosive based on tri-amino-tri-nitro-benzene (TATB), containing a small amount of Oktokin (HMX), a one-dimensional plane impact test was carried out by the artillery-driven sapphire flyer method and the aluminum-based embedded multiple electromagnetic particle velocity gauge technique. The Hugoniot relationship of the unreacted PBX-3 explosive was obtained by measuring the velocity of the explosive on the surface and different depths inside. The x-t of the explosive to the detonation time versus distance was established by the data measured by the shock wave tracer, and the Pop-plot reflecting the explosive initiation performance of the explosive was obtained. Six speed-to-detonation speed curves with an incident pressure of 12.964 GPa were trimmed to the same zero point. The time and width of the chemical reaction zone were obtained by reading the separation point of the six curves (the C-J point at the end of the reaction zone).

By employing the two-stage light gas gun and flyer impact technology, the impact recovery experiments of nibium-silicon powder mixtures with different initial porosity at high impact intensity were achieved. The recycled products were characterized to investigate the effect of porosity on the impact chemical reaction of nibium-silicon powder at high impact strength. The results showed that the sample with low porosity (10%) was hardly reacted; When the porosity is 20%, the nibium-silicon powder experienced a partial chemical reaction to form a NbSi₂ compound; As the porosity was increased to 35%, a complete reaction has occurred to generate a Nb₅Si₃ intermetallic compound under the same impact strength (the flyer velocity about 2.35 km/s). Such results have shown that the complete reaction in the powder reactant of high-porosity powder mixture is mainly due to the high temperature generated by the pore collapse.

In order to study the continuous collapse behavior of reinforced concrete frame under impact load, the finite element model of reinforced concrete frame is established by ANSYS/LS-DYNA. The impact mass is 1 000 kg and the impact velocity is 4 m/s. The effectiveness of the numerical simulation is guaranteed by the verification of the of reinforced concrete members impact experiment and the frame collapse process. The analysis draws following conclusions: in the process of structure collapse of the mid column impacted, there is a mechanism of “arch effect” to “suspension effect”, the top of the middle column first goes up and then down, and the top of the side column first goes out and then inward; under the same impact load, the smaller the column axial force, the stronger column impact resistance and the column impact resistance is affected by different eccentric pressure. The impact resistance of reinforced concrete columns can be enhanced by infill column stirrups which can delay or even avoid the reinforced concrete frame structures continuous collapse.

In order to study the low velocity impact response of the core-layer structure, this paper simulates the damage process of sandwich structure, that carbon fiber (T700)/epoxy composite laminates are used as the top and bottom panel, the foam aluminum is used as core layer, under impact loading of drop hammer. The composite laminates were modeled with three-dimensional solid elements, and the failure criteria of three-dimensional Hashin were introduced to simulate the damage of composite materials by the user subroutine VUMAT in the finite element software ABAQUS. The bonding layer failure between the layers was simulated with criterion of the secondary stress and cohesive unit. The aluminum foam core layer was modeled by a 3D Voronoi mesoscopic model. By analyzing the damage initiation, damage propagation and final failure modes of composite sandwich structures under low speed impact, the progressive failure mechanism of composite materials was clarified. The contact force and displacement through the hammer head, internal energy of sandwich panel, rear panel to study the stress distribution and maximum displacement energy absorption and impact resistance of sandwich structure. The optimal design of the coupling relation between the relative density and thickness of five different core layers under the condition of a certain quality control have been obtained, which provides designed guidance for satisfying the requirements of practical engineering.

Concrete is a heterogeneous that is composed of coarse aggregate and cement mortar. The dynamic damage process of concrete was numerically simulated by the action mechanism of ultrasonic in concrete crushing in this paper. The random placement procedure of 3D concrete aggregate was prepared by APDL and introduced into ABAQUS, and the plastic damage constitutive relationship of each phase material was applied to study concrete damage law for dynamic loading. The numerical simulation results show that with the increase of ultrasonic dynamic load, the concrete with 40% coarse aggregate can always withstand the maximum stress load. As the amplitude of ultrasonic stress wave increases, the damage value of concrete under dynamic load increases gradually, and the damage resistance is optimal when the volume fraction is 40%. When the maximum particle size of the coarse aggregate gradually increases, or the minimum particle size of the coarse aggregate increases, the concrete grading is unreasonable, resulting in unstable performance and more vulnerable to damage.

The influence of blasting seismic effect on buried pipes has been an important research hotspot in the field of engineering blasting. Taking two kinds of buried X70 steel pipes with Y-type welds (groove with 2 mm weld reinforcement and groove without weld reinforcement) as examples, the dynamic behaviors of buried X70 steel pipes near the weld zone under blast loads were studied numerically by the finite element software ANSYS/LS-DYNA. The blast loads are formed by detonating 4.473 kg TNT with different blast heights (60.0, 85.0 and 110.0 cm). The results show that when the blast height is 60.0 cm, the pipe with weld reinforcement is greatly affected by stress concentration and that it yields earlier than the pipe without weld reinforcement. When the blast heights are 60.0 cm and 85.0 cm, the ability of the pipe with weld reinforcement to resist deformation is significantly weaker than that of the pipe without weld reinforcement. The interaction between soil and pipe supports the explosion-back surface of the X70 pipe, which can effectively reduce the displacement of the explosion-back surface of the X70 pipe. Under the same conditions, the vibration resistance performance of the X70 pipe with weld reinforcement is weaker than that of pipe without weld reinforcement. Moreover, compared with the weld form, blast height plays an important role in the maximum vibration velocity of the X70 pipe near weld zone.

Steel fiber reinforced concrete (SFRC) is widely used in protective structures due to its excellent ductility, toughness and energy absorption capacity. K&C model is a common constitutive model for studying the response of normal concrete components under impact and blast loads, but it cannot accurately characterize the dynamic response of SFRC. In order to improve prediction of K&C model for the dynamic response of SFRC plate under impact and blast load, this work improves K&C model: a new failure strength surface parameter model was established based on a large number of triaxial compression experimental data, a new damage evolution model was established by trial-and-error method, and the damage parameters of tensile and compressive were calibrated. A new compression dynamic increase factor (CDIF) model was established based on a large number of uniaxial compression experimental data of SFRC under high strain rate. The dynamic response of SFRC plate is simulated by explicit dynamic analysis software LS-DYNA. The effectiveness and reliability of the above improvements have been verified by simulation results.

In this paper, the influence of the gun-bullet coupling gap on the internal ballistic characteristics during the full underwater launch of the gun have been studied. The internal ballistic process of setting 0.1 mm gap and no gap is simulated by AUTODYN finite element simulation software. And the internal ballistic process of underwater gun with underwater clearance is simulated using 21, 25 and 30 g propellant. The projectile velocity, pressure inside the barrel and the distribution of components, pressure and velocity of over-gap gas jets during the internal ballistic process are obtained from the simulation, and the simulation results is verified by experiment. The simulation and experimental results show that the proper gun coupling gap can effectively improve the underwater gun launch performance. When the gun-bullet coupling gap is set as 0.1 mm, the gas curtain are all obtained from the propellant with three different masses. Meanwhile, the pressure decreased obviously during the internal ballistic process, and the projectile speed at muzzle is improved significantly, which is beneficial to the production of stable supercavitation warp projectile. The resistance of the projectile moving underwater reduces greatly and the travel of the projectile increases underwater.

To investigate the blast-resistant performance of metallic sandwich structures subjected to intensive underwater impulsive loading, the lab-scaled underwater explosive simulator is employed to conduct water-based impulsive loading on metallic honeycomb sandwich structures. Based on the completed experimental study, this paper conducts a numerical investigation on the dynamic response and blast resistance of the metallic honeycomb sandwich structures subjected to intensive underwater impulsive loading. The results show that the comparison among the numerical simulation, experiments, and analytical solutions shows a good agreement in terms of dynamic response and transverse deflections. For the different honeycomb sandwich with identical thickness, the dynamic responses, failure modes, and blast-resistant performances of sandwich panels are shown different characteristics due to the energy absorption and loading transferring caused by the relative core densities. The impulsive resistance in terms of dynamic deformation, transverse deflection, reaction force, transmitted impulse and plastic energy dissipation is evaluated in relation to the load intensity and the relative core density. Quantitative structure-load-performance relation is carried out to facilitate the advanced study on the structures and provides guidance for structural design.