A critical assessment is made herein on the accuracy of the Johnson-Cook (JC) constitutive model by comparing the model predictions with the test data for 2024-T351 aluminum alloy, 6061-T6 aluminum alloy, OFHC copper, 4340 steel, Ti-6Al-4V alloys and Q235 mild steel. These materials are selected because their test data are more complete in terms of true stress-true strain relationships, strain rate effects, temperature effects and failure. To further assess its accuracy numerical results for the ballistic perforation of plates made of 2024-T351 aluminum alloy using the JC constitutive model are also presented and compared with corresponding test data. It transpires that the JC constitutive model is applicable to Mises materials at quasi-static to intermediate strain rates and low to moderate temperature. It also transpires that for non-Mises materials the agreement between the model predictions and the test results are poor in terms of shear stress-shear strain curve and fracture strain. Furthermore, the accuracy of the JC model decreases with increasing strain rate, temperature and, above all, it fails to produce consistent results at high strain rates when the experimentally obtained dynamic increase factors (DIF) are employed in the calculations implying the form of the model’s equation (namely, quasi-static stress-strain curve multiplied by DIF) may be inadequate at least for the scenarios where high strain rates are involved.

The bridge is an essential part in the transportation system, and its damage effect under the strong impact load is always a hot issue in the world. Currently, the explosive explosion is one of the most effective bridge damage methods. Therefore, the research on the explosive shock wave propagation law in the bridge structure plays an important role in the process of anti-explosion design and explosion accident rescue. In this paper, a local imitation structure of the bridge was constructed, and the experiment of the explosive blasting in the bridge was performed. Then, the self-developed software EXPLOSION-3D was adopted to simulate the propagation process of explosive shock wave inner the imitation bridge structure. The numerical simulation results were compared with the experimental results to verify the effectiveness of the numerical algorithm. Further, the propagation laws were analyzed according to pressure-time history curves at different positions. Besides, the explosion damage effects of the bridge structure at different locations and equivalent explosives were also evaluated. Based on the numerical simulation results, the damage degree towards to the human body and vehicle which reside in the imitation bridge structure were obtained. Finally, some safety preventive suggestions were given in the view of simulation after compared and analyzed the numerical results in the different conditions.

Super hard materials have wide applications in industry, such as cutting tools, abrasive materials, wear resistant coatings. As one of the 5d transition metals double nitrogen compound, ReN₂ contains both covalent bond, ionic bond and metallic bonding. In view of its many excellent physical properties, such as high hardness, high melting point and corrosion resistance, ReN₂ earns much research interests. This article has calculated the structural properties of C2/m-ReN₂ under zero temperature and zero pressure using the plane wave pseudo-potential method of density functional theory, and has studied the mechanical structure stability and elastic properties of C2/m-ReN₂ under high pressure for the first time. The relations of the elastic constants, various modulus of elasticity, Debye temperature and the sound speed of C2/m-ReN₂ with the pressure have obtained. In addition to the individual elastic constants, these quantities increase with the increase in pressure. In addition, we have also predicted the toughness and brittleness of C2/m-ReN₂, and have estimated the Vickers hardness of C2/m-ReN₂.

High pressure Raman scattering spectrometry which based on the diamond anvil cell technology plays an important role in the high pressure scientific research. The fluorescence of diamond anvil affects on the signal-to-noise ratio of Raman spectral for the sample in cell. The defect centers of 202 gem-grade diamonds have been confirmed by the photoluminescence spectra. The concentration of N3, H3 and NV⁰ defect centers controls the intensity of the zero-phonon line and the fluorescence emission spectrum, and it is positively correlated to the fluorescence intensity. While, the ratio of background intensity on the two sides of the diamond’s second-order Raman peak (about 2664 cm^–1) has a negative correlation with the fluorescence intensity, thus it could be used to estimate the fluorescence intensity of diamond. In addition, the inhomogeneous of the concentration of defect centers is common in diamond, and it will provide more comprehensive information by multipoint analysis. The results will provide effective theoretical and practical basis for the selection of diamond anvil in high pressure Raman spectra measurement.

A series of high-quality Ib diamonds was successfully synthesized by {100} seed crystals with different shapes in NiMnCo-C system, using the temperature gradient method at pressure of 5.5 GPa and temperature of 1260–1300 ℃. The morphology of the crystal was characterized by optical microscopy and electron microscopy. It is found that cutting the {100} surface of synthetic seed crystal into different shapes will only change the aspect ratio of the crystal, and the crystal will not deviate from the normal morphology of {100} crystal due to the change of the shape of seed crystal. The quality of crystal synthesis is affected by the aspect ratio of the seed. When the ratio of length to width of seed crystal is small, the quality of crystal synthesis can be guaranteed and high quality crystal can be synthesized. However, there are many defects in the lower surface of synthetic crystal when the ratio of seed length to width is too large. This study reveals the relationship between seed shape and synthetic crystal morphology, which is conducive to a deeper understanding of crystal growth process and epitaxial growth mechanism. This study will be useful for future synthesis of diamond with different morphologies. At the same time, this research will help to expand the scope of seed crystal selection, reduce the difficulty of seed crystal selection, improve the utilization rate of industrial grade diamond, and provide technical support for the seed crystal selection of synthetic large single crystal diamond.

Fe₃C (cementite) is a widely used material with excellent mechanical and magnetic properties; therefore the preparation method of Fe₃C has been widely concerned. In this paper, dense and high-purity bulk Fe₃C samples were prepared based on the solid-phase reaction of iron and carbon under high temperature and high pressure, and the influence of raw material type, particle size, sintering temperature, pressure, and holding time are investigated for the sintered samples. It shows that the densest samples were produced under the sintering pressure and temperature of 4 GPa and 1000 ̊C when the Fe and graphite particles were 9 $ {\text{μ}}{\rm{m}}$ and 1.3 $ {\text{μ}}{\rm{m}}$ respectively.

During the manufacturing process of a filament wound pressure vessel, we embed the strain gauges between the metal tank and glass fiber reinforced epoxy composite layer to obtain the capability of in-situ monitoring . Experiments with a full-scale composite pressure vessel during hydraulic fatigue cycling and pressurization are performed. The maximum and minimum pressures in the fatigue test are set as 25 and 2 MPa, and the maximum cycle number is set as 5700 cycles, respectively. The pressurization speed is set as 2 MPa/s from 0 MPa to busting pressure. The strain of the pressure vessel in the two loading tests is monitored by the embedded strain gauge. The relationship between the stain and the loading conditions of the pressure vessel was thus built. Results show that, by embedding the strain gauges during the processing, it is possible to monitor the health status of the vessel under hydraulic fatigue cycling and pressurization load without hurting the sensors by the external load.

Based on the discrete element algorithm (DEM), a numerical split Hopkinson pressure bar (SHPB) platform is established by the mean of particle flow code software (PFC^2D), and the feasibility of the system has been verified. The failure mode and the dynamic compressive strength of an inorganic glass specimen at different strain rates are investigated. The numerical simulation shows that the inorganic glass exhibits typical brittle characteristics during dynamic compression, and its compressive strength is significantly affected by the strain rate. The Young’s modulus, however, is strain rate insensitive. The failure mode of the specimen is affected by the boundary friction as well as the Poisson ratio. In the case of frictional contact, the initial micro-cracks within the specimen are distributed in a triangular zone due to the combined effect of longitudinal pressure and frictional force. With the increase of the longitudinal stress, the transverse tensile stress creates the longitudinal cracks, resulting in the axial splitting. The failure mode in the case of frictionless contact differs from the frictional case, in which no triangular crack zone exists. Moreover, the value of Poisson ratio affects the failure mode as it results in the transverse tensile stress during dynamic loading. Numerical simulations of dynamic Brazilian compression are also conducted to support future experimental works. It shows that Brazilian disk starts failure at the center in the moderate strain rate and the macroscopic splitting tensile strength is strain rate dependent.

The meso-scale characteristics of granular metal materials play an important role in macroscopic mechanical behavior. The dynamic compression behavior of metal powders still needs further researches. In this paper, the copper powders persisting rich experimental results were selected as the research objects. Based on the multi-particle finite element method, a two-dimensional numerical analysis model of granular metal materials was established, and the mechanical behavior of copper powders under impact compression was studied. The numerical results show that the granular metal materials exhibit a highly localized deformation band under high velocity impact, and the deformation bands propagate from the impact end to the support end like a shock wave. By using the velocity field calculation method, the position of the plastic impact wave front was calculated, and the Hugoniot relationship between the particle velocity and the shock wave velocity of copper powders with different porosities (0.25–0.60) was obtained. The numerical results agree well with the experimental results at high impact velocities (200–300 m/s). The shock wave model using the dynamic locking strain as the only parameter was developed. It is found that the Hugoniot relationship and the stress behind the shock wave front of the copper powders under high velocity impact are well characterized.

In order to achieve full fragmentation of the rock and effectively use the explosive energy, the impact of different hole spacing on the rock (hornfels) blast crack extension was studied via ANSYS/LS-DYNA software package using fluid-structure interaction (ALE) algorithm. The results showed that with the increase of the distance between the two holes, the crack growth around the single gun hole becomes more sufficient, the comminution area around the gun hole increases, the generated branch small crack gradually decreases, the main crack increases, and the crack growth rate is about 0.42 times that of the longitudinal wave velocity of the rock. In the area between the two holes affected by the explosion stress wave of the adjacent holes, the main crack growth and expansion are more obvious, and with the increase of hole spacing, the position of the main crack interconnection is closer to the direction of connecting the center of the two holes. Engineering practice suggested that the results of numerical simulation has positive effect on blasting engineering, the results of numerical simulation can be used to guide the design of blasting scheme and can provide important reference value for the blasting engineering.

It is necessary to evaluate the fatigue life of coiled tube (CT) under the coupled load of internal pressure, bending load and torsion. First, the failure mechanism of low cycle fatigue of CT under coupling loading is analyzed. Based on Brown-Miller fatigue life model, a numerical calculation model of CT fatigue life is established. The low cycle fatigue life of CT under the coupling load of internal pressure and bending load is calculated. And also the low cycle fatigue life of CT under the load of internal pressure, bending load and torsion is calculated. The calculation results show that the maximum plastic strain and fatigue sensitive areas of CT appear on the axial tensile surface and compression surface, which is consistent with the failure of CT on oil field. The critical torque value and internal pressure of CT are obtained by calculation for CT safety service.

Shadowgraphs of shockwave expansion could be directly obtained by time-resolved shadowgraph imaging system when femtosecond ablating metal surface. The shock wave expansion on Cu and Fe surface obeys spherical propagation compared with that on Al target. Due to the influence of material ejection, the shockwave expansion on Al surface changes from spherical propagation to cylindrical propagation.

Low-velocity impact tests were performed for the [45₄/–45₄]_4T carbon fiber reinforced plastics (CFRP) laminates for exploring the low-velocity impact behaviors. The effects of impact angle of strip impactor and impactor diameter of hemispherical impactor on the impact responses of laminates are studied. Besides, the damage characteristics are evaluated by dent depth and delamination damage area simultaneously. The experimental results show that larger maximum center displacement and more energy dissipation can be caused when the impact direction of the strip impactor is parallel to the fibers in the surface plies and the impactor diameter is smaller. The dent depth and delamination damage area are also larger at the two situations above. In addition, the dent depth is positive correlated with the delamination damage area under single factor variables of impact angle and impactor diameter. There has significant fiber break around the impact area under the impact of 10 mm hemispherical impactor, but no obvious fiber break appears around the impact area for 14 mm and 16 mm impactors.

This paper discussed the strain rate effect of glass fiber/epoxy resin composite (GFRP)-reinforced Q235 circular steel tube under low-velocity impact load. Firstly, the responses (axial load and displacement) of GFRP-reinforced steel tube under quasi-static and low-velocity impact load were obtained through axial compression tests and low-velocity impact tests respectively, which provided gist for the subsequent simulation. Secondly, a VUMAT subroutine considered initial failure modes, damage evolution and strain rate effect of GFRP was introduced; then the axial compression and low-velocity impact processes were simulated. Finally, the results under 4 situations (ignoring strain rate effect, considering the strain rate effect of steel tube, considering the strain rate effect of GFRP and considering the strain rate effect of both steel tube and GFRP) was compared using simulation.

A new damage assessment method of aircraft targets under blast wave was studied based on the strength of aircraft structures. The failure criterion of typical aircraft targets was determined according to the strength design criterion of aircraft structure. Further, the critical blast wave overpressure causing the aircraft failure was obtained by the finite element analysis. It shows that the simulation results were consistent with the previous experimental results and the method was proved to be reasonable. Based on the method, the structural response under dynamic loading was further investigated. A series of blast wave overpressures and corresponding durations causing the aircraft failure were studied by the numerical simulations. Consequently, the overpressure-impulse damage criterion of typical aircraft target under blast wave was established. The results were considered to be a more reasonable method for assessing the aircraft overall damage effects under blast wave loading.

Numerical simulations are conducted for perforation of conical projectile impacting on thin steel target with various yaw angles to investigate the influence of yaw angle. The finite element models of conical projectile impacting on thin steel target with yaw angle varying from 2° to 10° are established with the non-linear finite element code ANSYS/LS-DYNA. After the reliability of numerical simulations is verified, numerical simulations of conical projectile impacting on thin steel target with different yaw angles and initial velocities are carried out. A four-step model to analyze the process of projectile’s deflection is addressed by comparing the process of target’s failure and projectile’s deflection. At last, we discuss the projectile’s trajectory angel deflection and angular velocity through the validated numerical analysis. The results show that the failure of asymmetric petalling occurs when a thin plate is impacted by conical-nosed projectile with yaw angle. With the increase of the yaw angle and the decrease of initial velocity, the deflection of the trajectory will be more obvious; the deflection change of projectile relates to the initial velocity; the deflection angle shows a trend of increasing first and subsequently decreasing when the initial impact velocity is relatively high (greater than about 1.4 times the ballistic limit). When the projectile moves out of target, the angular velocity rises with the increase of the yaw angle, but it increases reversely and then reduces with the increase of initial velocity.

Without changing the mass characteristics and other cabin features of a prototype, the damage area of aviation bomb can be increased by more than 20% via designing a new structure of internal fragments assembly in the head lid and effectively loading this head lid by compartment cabin. These two measures make effective use of head lid. The damage caused by aviation bomb to the ground targets near the expected fall point and blast point is also enhanced.

In order to study the load of underwater explosion near the surface of the harbor basin and the damage effect on the wharf, we designed a typical wharf structure and built a harbor basin environment. Then through a series of numerical analysis which was accomplished based on finite element program LS-DYNA, the explosion phenomenon, loading characteristics, structural dynamic response and energy absorption characteristics were studied in details, the influence rules and action mechanism of the boundary, scaled collapse distance and other parameters were analyzed. The results show that: the explosion bubble pulsation is mainly affected by wharf structure boundary and free surface, the bottom and the movement of fluid in the limited space also have some impacts. The shock wave load is symmetrically distributed in the vertical direction with the scaled explosion depth as the center, and the bubble pulsation load is mainly distributed below the scaled explosion depth. The structural deformation and damage are mainly formed on the propagation of shock wave, and the secondary damage effect of bubble pulsation and jet is weak. Concrete and caisson fill absorb most of the explosive energy.

In order to investigate the ballistic performance of boron carbide ceramics, we carried out experiments of a ${\varnothing}$12.7 mm steel ball penetrating the boron carbide ceramic and composite target, and a 12.7 mm long-rod projectile penetrating the boron carbide ceramic composite target constrained by the ultrahigh molecular weight polyethylene (UHMWPE) fibers. In the experiments, the failure mode of boron carbide ceramics was discussed, and the influence of the constraint mode of ballistic performance on boron carbide ceramics was studied. The results show that under the constraint of titanium alloy/UHMWPE backing plate, the interaction time between projectile and ceramic is longer, which could create finer ceramic powder and decrease the size of fragments. Hence, as the carbide ceramics absorb more energy, it could achieve better ballistic performance. As the result of the combination of the projectile and the ceramic cone, the titanium alloy back plate was damaged, forming the petal shape. And the UHMWPE laminate is accompanied by a large-scale interlayer delamination, forming an " X”-shaped bulging phenomenon. The fiber-constrained ceramics enable the boron carbide ceramic plate to remain intact when the bullet penetrates, enhance the abrasive effect on the projectile, improve the elastic resistance, and have a certain resistance against multiple impacts. Besides, the anti-penetration mechanism of boron carbide ceramic composite armor has also been analyzed, and we hope this paper can help with the optimization design of composite armor in the future.

Material constants played a significant role in the numerical prediction of warhead impacting metal targets, in order to obtain a set of valuable material constants fitting methods, JC strength model and JC failure model constants were acquired by different fitting method based on material mechanical properties and failure experiments. Simulation results were compared with experiment outcome in which different nose warhead penetrated different thickness metal plates, and it indicated: (1) simulation results could be distinct using JC strength model and JC failure mode constants from different fitting methods for the same material mechanical property tests; (2) JC strength model constants fitting by stress-strain curves using high reference strain rate were suitable for the numerical predicting warhead penetrating metal plates; (3) JC failure model constants fitting by initial stress triaxiality or average stress triaxiality had few influence on calculation results. This research could provide assistance for the material constants fitting method in numerical simulation.

To verify impact safety and implosion power of a composed charge, the drop hammer tests and implosion power experiments were conducted. The results show that critical height of the single thermo-baric explosive is 2.2 m under loading of 400 kg hammer, while the composed charge did not ignite under height from 2.2 m to 2.7 m, which means that the composed charge holds a better impact safety property. Peak overpressure of the composed charge was 61.9% of the single thermo-baric explosive, the impulse of the composed charge was 99.4% of the single thermo-baric explosive, and the peak quasi-static pressure of the composed charge was 94.5% of the single thermo-baric explosive. Considering energy release characteristics within a limited space, it is more suitable to use peak quasi-static pressure as an evaluation standard. The test results show that implosing energy release characteristics of the composed charge is almost the same as the single thermo-baric explosive.

In order to explore the influence of ambient temperature on the explosion properties of aluminium/ether/nitromethane gas-fluid-solid multiphase mixtures, we use a 20 L spherical explosion tank to experimentally obtain the effect of temperature on the mixture explosion over pressure, the maximum explosion pressure rise rate and the lower explosive limit. The results show that: under the experimental condition, the explosive characteristic parameters of ether decrease with the increase of temperature. The explosion characteristic parameters of aluminum powder are less affected by the changing temperature. The explosion pressure of gas-liquid-solid polyphase mixture decreases slightly with the increase of temperature, and the maximum explosion pressure rises first and then decreases. There is an optimum concentration ratio for the optimum explosion power. The lower explosive limit of gas-liquid-solid polyphase mixture decreases with the increase of temperature, and the lower limit of mixture tends to be stable after gasification of most volatile substances.

Gas explosion often occurs in the course of closing fired coal mine. The explosion limit and maximum explosion pressure under temperatures ranging from 25 ℃ to 200 ℃ and CO volume fractions of 1%−10% are studied by using a special 20 L explosive device. The results show that upper and lower explosion limits all decrease with increasing CO volume fraction, the range of explosion limit is widened in the presence of only CO. The upper gas explosive limit increases while its lower limit decreases as temperature increases. At ambient pressure, the upper gas explosive limit increases quadratically with initial temperature while the lower limit increases logarithmically with initial temperature. Increasing CO volume fraction results in increase in both the upper pressure limit and the lower pressure limit. Coupling CO gas with high temperature, the gas explosive upper limit increases and the lower limit decreases thus higher risk is expected in such condition. Explosive limits, especially the upper limit are more sensitive to coupling factors than to single factor.

The project of loop pipeline in Pingtan test area is used as the engineering background. To compare the anti-explosion performance of " foam aluminum” and " steel plate-foamed aluminum-steel plate” anti-explosion structure under gas explosion, a 3D pipe gallery and soil structure is studied and analyzed by ANSYS/LS-DYNA. The results show that: the structure closest to the explosion gas on the internal wall is broken down at first followed by the damaging of the joint structure of interior and exterior wall in the gas cabin. The stress in the aluminum foam sandwich structure attenuates most quickly. Measuring point peak stress can be reduced as much as 67.35% by aluminum foam sandwich structure compared with no explosion-proof structure. Measuring point peak stress is reduced by 43.99% by aluminum foam structure. The kinetic energy peak value of gallery without anti-explosion is 0.11 kJ. The kinetic energy peak value of gallery with aluminum foam sandwich is 0.021 kJ. By comparison to the gallery without any explosion-proof structure, the kinetic energy is reduced by 80.9%. A comprehensive suggestion is that, laying aluminum foam and aluminum foam core material can reduce the damage of the corridor structure, and the aluminum foam sandwich structure behaves the best.

To control the risk of disaster that may be caused by ice-coated power line, a novel de-icing method by applying linear shaped explosive blast has been proposed in the past decade. To investigate the mechanism and the key technology, blast tests on short ice-coated power line are performed as well as corresponding LS-DYNA simulations. The effects of blast parameters on de-icing efficiency are also discussed. Results show that, ice on the blast side immediately crush while through-wall cracks appear in the other side ice which then fractures or falls from the line. The blast energy rapidly attenuates from the weakly constrained side of ice when the detonation cord is placed outside of the ice. As a consequence, in order to de-ice with high efficiency, the gap between conductor and detonation cord should be optimized according to estimation ice coating thickness to ensure that the detonation cord is located within the ice coating.

Transmission line is the important equipment to transport electrical energy through power grid. Mountain fires are frequent events in recent years, which severely damages the safe operation of the high voltage transmission lines. Therefore, it is very important to study the mechanical characteristics of transmission lines after mountain fire. Based on the simulation test of transmission lines in the mountain fire, we studied the effects of the annealing temperature on the fatigue of overhead transmission lines. The fatigue failure of the transmission lines in aeolian vibration was reflected in the continuous axial fatigue tensile state. First, we conducted an experiment by the thermostatic tube X resistance furnaces to stimulate different transmission lines (JL/G1A-400/35, JL/G1A-300/25, JL/G1A-240/30, JL/G1A-300/40) burned in the mountain fire at different temperatures. Then, we carried out a fatigue tensile test on the single transmission line, and found that the frequency of fatigue tensile failure was correlated with temperature. Furthermore, we compared the data between new transmission lines and those burned in an actual mountain fire. Finally, we proposed reference for the protection of transmission lines in a mountain fire and prevention against being burned. The results showed that the fatigue limit of wires was reduced with the rise of the temperature. When the temperature was between 250 ℃ and 300 ℃, the tensile cycle times deceases sharply; when the temperature is above 300 ℃, it tended to be stable.