In the large-volume press (LVP), the pressure calibration for the sample chamber is generally carried out by using phase transitions of specific materials with resistance changes. But there are no suitable materials for pressure calibration in the range of 22.5−34.5 GPa. As we know, the mineral 50 mol%MgSiO₃-50 mol%Al₂O₃ (En₅₀Cor₅₀) systems in deep earth undergo structural transition to perovskite phase under high pressure and high temperature (HPHT) conditions. Moreover, the content of Al₂O₃ dissolved in perovskite MgSiO₃ increases gradually with raised pressure above 27 GPa. Therefore, En₅₀Cor₅₀ was selected as the pressure calibration material for further calibrating 28 GPa in the LVP in this study, and this is an indirect pressure calibration method. First, the low-pressure calibration curve (6.0−22.5 GPa) of system oil pressure versus chamber pressure was obtained by using the phase transitions of different pressure calibration materials. Then, based on the low-pressure calibration curve and previous research results En₅₀Cor₅₀, the estimated system oil pressure corresponding to the 28 GPa of chamber pressure is 65 MPa. At the estimated oil pressure, the En₅₀Cor₅₀ samples were heated to 2000 K and maintained for 3−7 h. The results of X-ray diffraction, Raman, and electron probe measurements indicate that bridgmanite has been successfully synthesized, and the dissolved Al₂O₃ molar fraction is greater than 13.7%. According to the previous research results, the corresponding sample chamber pressure is about 29 GPa. This method successfully calibrated the sample chamber pressure around 28 GPa in the LVP, which fill in the blanks for calibrating this pressure range.

Based on the LS-DYNA three-dimensional numerical modeling method and the modified Kong-Fang concrete material model, the numerical investigation on damage and failure of ultra-high performance concrete (UHPC) targets subjected to dislocation multi-attacks was carried considering the two-dimensional normal distribution of strike points. The numerical model and material models along with the corresponding parameters were firstly validated by comparing the numerical simulation results of the UHPC targets subjected to projectile penetration followed by explosion to the corresponding test data. Then numerical simulation of the damage and failure in UHPC targets under the multi-attacks by a typical warhead were conducted with 10 groups different circular error probable (CEP) to discuss the effects of the CEP and strike times on the damage and penetration depth. The numerical results demonstrate that the damage evolution caused by the subsequent projectile penetration and explosion continues to develop along the damage area caused by the first projectile penetration. The penetration depth gradually increases as the number of strike increases. The penetration depth calculated with explosion is larger than that calculated without explosion when the CEP is same during multi-attacks. When CEP is equal to 3 m and 1 m, the relative penetration depth is about 1.2 and 1.7, respectively. In other words, the relative penetration depth increased with decreasing of the CEP. The research conclusion shows that the design method of shielding layer thickness in the existing protective design code is dangerous subjected to multi-attacks.

Exploring the influence of size effect on the physical properties of materials under high pressure is helpful for the development of new materials with novel or improved properties. The static compression behaviors of polycrystalline tungsten powder with average grain sizes of 30 and 65 nm under high pressure were studied by using diamond anvil cell (DAC) combined with synchrotron radiation X-ray diffraction respectively. By analyzing the peak position and the half-height width of the X-ray diffraction spectrum at each pressure, the unit cell volume, grain size, and microscopic strain of nano-tungsten metal under high pressure were obtained. By fitting the third Birch-Murnaghan equation, the bulk moduli of 30 and 65 nm tungsten are obtained to be 257(7) GPa and 343(8) GPa, respectively. Combined with the results of previous studies, it is found that when the gain size decreases from micron to 10 nm, the yield strength of tungsten at 10 nm increases by 3.5 times compared with that of microcrystal samples; the bulk modulus shows a tendency of increasing firstly and then decreasing, and the bulk elastic modulus of tungsten at 30 nm decreases by 25% compared with that of tungsten at 65 nm.

In recent years, the development of rapid loading techniques (such as dynamic diamond anvil cell, dDAC) and time-resolved detection technologies based on diamond anvil presses has opened up new research directions in high-pressure science. This involves exploring the evolution of material structures and physical properties under pressure (or over time) in high-pressure non-equilibrium physical processes that lie between static high-pressure and shock-wave experiments in terms of time scale and loading rate. By reviewing and summarizing the rapid loading and time-resolved probe techniques that have emerged in recent years, this paper attempts to think about and generalize high-pressure science issues and technical challenges on the microsecond to second time scale. It starts from aspects such as structure phase transition dynamics that depend on loading rate, phase transition pathways, the formation of metastable phases, microstructures, and mechanoluminescence, aiming to provide some inspiration and reference for researchers in this field.

As highly efficient absorbing and dissipating materials, porous materials were widely used in the study of detonation wave attenuation. In order to further explore the mechanism of explosion suppression by porous materials, the effects of typical flexible (sponge) and rigid (wire mesh) porous materials on the detonation cellular structure for hydrogen and oxygen mixture were investigated systematically. The effects of thickness and porosity of sponge and wire mesh on the structure and size of detonation cell were discussed in detail. The cellular pattern of detonation wave was recorded by using smoke plate technology, and the cell size was calculated. The pressure sensors were used to record the arrival time of the detonation wave, and the average propagation velocity of detonation wave was obtained. The results show that the detonation cellular structure closely depends on the thickness and porosity of sponge and wire mesh, and three phases of the propagation can be observed in the tube, including detonation failure, acceleration and re-initiation. In addition, size of the detonation cell is also closely related to the thickness and porosity of sponge and wire mesh. Increasing the thickness of porous materials and decreasing the porosity both can increase the size of the detonation cell. By comparing the effects of sponge and wire mesh on the detonation cellular structure, it can be found that at the same initial condition, the rigid porous material has a stronger inhibition effect on detonation. But the difference will be gradually decreased with the increase of the thickness of the porous materials. Finally, the limit of the detonation propagation is analyzed quantitatively by introducing the dimensionless parameter D_H/λ. For flexible and rigid porous materials, the detonation limit can be nearly quantified as D_H/λ≈3.0 and D_H/λ≈3.1.

Using statistical physical model, the equation of state of UH₃ crystal and its chemical decomposition products were constructed in this paper. The phase diagram of UH₃ at high temperature and high pressure was obtained by Gibbs free energy comparison, and the shock compression properties of UH₃ with different initial densities were investigated. The results show that the chemical decomposition of UH₃ crystals occurs at about 74.0 GPa under isothermal compression. Increasing the temperature promotes the chemical decomposition, but the influence of pressure on the chemical decomposition of UH₃ is non-monotonic. Solid UH₃ decomposes at 35–50 GPa under shock compression, and the chemical decomposition process is accompanied by obvious volume collapse, therefore, the Hugoniot of UH₃ decomposition products lies below the isotherm, which is an abnormal phenomenon in comparison with ordinary metals or compounds. Moreover, the decomposition pressure of UH₃ decreases with the increase of initial porosity. When the initial porosity is about 1.5, the decomposition products of UH₃ are more difficult to compress than UH₃ in crystal phase, thus showing a phenomenon similar to the abnormal expansion of large porosity materials under shock compression. These results enrich our understanding of dynamical compression behavior of UH₃, and can serve as theoretical basis for further research on physical and chemical properties of actinide metal hydrides at high temperature and high pressure.

In this study, molecular dynamics method was used to simulate the deformation and spallation behavior of [100] single crystal aluminum under the action of equivalent ramp waves and square waves. Accordingly, the correlation between loading waveform and spallation behavior was analyzed. The results showed that the synergistic effect of the pulse shape transition and the thermodynamic path affected the material spallation. The nucleation of non-uniform holes dominated by defects was not the decisive factor affecting the spallation strength of materials. The difference of spallation characteristics of materials under different loading waveforms was mainly determined by the difference of temperature rise under different thermodynamic paths, which led to uniform spallation at maximum velocity of 3.00 km/s, but the spall strength of ramp wave group was 56.6% higher than that of square wave group. Due to the gradual compression and slight temperature softening effect, the ramp wave loading made the material presented milder damage than the impact loading, which became more significant with the increase of loading speed.

The 3D printing manufacturing process and mechanical behaviors of “carbon fiber-graphene” (CF-G) reinforced thermoplastic polyurethane (TPU) composites were investigated. The CF-G reinforced TPU composite filaments were prepared by the screw extrusion process, then the G+CF/TPU composites were manufactured by the fused deposition modeling (FDM) technology and microwave post-treatment process. It shows that the CF-G heterostructure can synergistically enhance the mechanical properties of TPU composites. Especially, by adopting the novel microwave post-treatment process, the G+CF/TPU specimens exhibited the further improved tensile strength and toughness, which may be attributed to the promoted interface bonding between the reinforcing phase and matrix, and the reduced internal defects between points, layers, and channels induced by the synergistic effect between the CF-G heterostructure and microwave. This study has positive significance for exploring the mechanical reinforcement and post-treatment processes of 3D printed materials.

To effectively predict slope stability and prevent slope instability occurrence, a hybrid model WOA-RF, combining whale optimization algorithm (WOA) and random forest (RF) was proposed. Based on the collected slope cases, the classification and generalization performance of the model was evaluated according to the classification performance indicators given by the confusion matrix and the area under the receiver operating characteristic curve. Additionally, WOA was used to optimize four widely used machine learning models, and the optimized machine learning models were compared with WOA-RF. The results demonstrate that WOA is effective in optimizing hyperparameters and improving model performance. The optimal WOA-RF model achieves an accuracy of 0.99 on training set and of 0.94 on test set. After optimization, the accuracy, the precision, the recall, and the hamonic mean of the precision and recall are increased by 11.9%, 19.0%, 4.8%, and 11.9%, respectively. Comparative analysis reveals that the WOA-RF model is superior to the others in all indicators. Furthermore, the feature importance ranking was determined. Analysis of the feature importance indicates that unit weight is the most sensitive feature affecting slope stability. The established WOA-RF model is proved effective in predicting slope stability and facilitating the development of appropriate protective measures based on the predicted results.

Polymers are widely used in various fields of national defense and national economy. They are inevitably exposed to extreme conditions of high temperature and high pressure during applying. Thus, it is necessary to study their physical properties and “phase transition” under impact loading. Because of their characteristic molecular chain structure, polymers show different properties from most materials such as metals. The intercept extrapolated from Hugoniot curve at low pressure is obviously higher than their body sound velocity at atmospheric pressure. The wave profile at low pressure presents a structure with an arc shape. At 20–30 GPa, the Hugoniot line turns obviously, indicating that the material has undergone a “phase transition” under impact loading. The “phase transition” is explained as chemical decomposition or lattice structure transformation, and the kinetics of “phase transition” is studied. In addition, the modeling method of equation of state based on chemical decomposition is briefly introduced. Finally, the prospect is put forward according to the doubtful points in the study of physical properties and “phase transition” of polymers under impact loading.