High pressure is one of the fundamental thermodynamic parameters, which can induce the structural changes in soft matter systems. By combining the spatial resolution of small-angle X-ray scattering (SAXS), this technique can be employed to explore the dynamics of protein folding and the mechanisms of nucleic acid structural stability. Moreover, it has promising and broad applications in the field of life sciences. Currently, the specialized equipment for high-pressure solution scattering is still lacking in China. For this purpose, a high-pressure in-situ sample device and a manual pressurization system for specialized solution X-ray scattering have been developed at BL19U2 beamline at SSRF, which can complete the hydrostatic pressure measurements from 0.1 to 250 MPa. More important, the apparatus can keep the X-ray window in the same place throughout the experiment, which can help to subtract the accurate background scattering and achieve the measurements with high signal-to-noise ratio. This will provide a valuable research platform for wide range of areas, including food science, pharmacology, and structural biology.

Polymers are one of the most widely used materials in modern society. The interest of applying polymers under extreme conditions (high pressure and high temperature) is ever increasing. However, our knowledge of the equation of state (EOS) and phase transition of polymers at high pressures and high temperatures is extremely limited, which prevents their applications in broad fields. Because of their mixed phases and their hierarchical structures, investigation on the structures and properties of polymers at extreme conditions is a big challenge to date. In this short review, we summarize the recently published studies on the EOS and phase transition of polymers at extreme conditions. We point out the challenges faced and the limitations of the experimental techniques used, which is expected to be useful for the investigations of the EOS and phase transition of polymers in the future.

Utilizing first-principles calculations based on density functional theory, this study investigates the geometric, electronic, and mechanical properties of NaCl, KCl, and KBr crystals in phase Ⅰ and phase Ⅱ structures under varying pressures. The relationships between these properties and the phase transition points are explored. Additionally, the Gibbs free energy method was employed to judge the phase transition points of NaCl, KCl, and KBr crystals. The results show that in the phase Ⅰ structure of NaCl, the band gap value increases with pressure from 0 to 30 GPa. However, in the range of 30−50 GPa, the band gap value decreases, indicating that 30 GPa is the phase transition point for NaCl phase Ⅰ. This suggests that pressure-induced changes in electronic structure can be indicative of metal halide phase transition points to some extent. However, pressure-induced alterations in crystal structure, phonon spectrum, and mechanical stability cannot reliably indicate alkali metal halide phase transition points. Furthermore, the phase transition points for NaCl, KCl and KBr calculated by Gibbs free energy method are 22.26, 3.47 and 3.11 GPa, respectively.

Uncertainty cannot be eliminated in the indirect calibration of the detonation pressure, and the predictability and credibility of the model can be enhanced through uncertainty quantification of the detonation pressure. However, the indirect calibration function of the detonation pressure exhibits complex nonlinearity coupled with multiple inputs, making the study of uncertainty propagation of detonation pressure prone to issues such as the “curse of dimensionality”. Active subspace is proven to be an effective tool for handling uncertainty quantification of the detonation pressure model. The specific steps are as follows: to begin with, the covariance matrix is derived based on gradient of the system response quantity (SRQ). Then an active variable is deduced through the Monte Carlo method, which is the direction whose perturbations produce the greatest change in SRQ. A single derived active subspace is used as the input uncertainty instead of the six parameters. The “curse of dimensionality” can be relieved in this case. Finally, a fourth-order polynomial response surface model is established based on a one-dimensional active variable. The results show that the effects of input uncertainty on SRQ are successfully characterized using the means of the active subspace technique. The test data fall within the confidence interval of the predicted values from the surrogate model, and the predictive capability of the detonation pressure model is validated. The study also reveals that there is a significant degree of dispersion in detonation pressure, which is consistent with the viewpoint of Prof. Chengwei Sun. Furthermore, a new detonation pressure model is constructed in this paper. This model is a composite operation between an affine transformation and a polynomial function. It retains the characteristic of a concise form, sufficient smoothness, strong robustness, and fast computation. The input of the model is a random variable rather than a fixed value, and the polynomial coefficients remain unchangeable when it confronts the variability of input uncertainty. The research is an extension and development of previous scholars. Moreover, the research methodology is systematic, which can be applied to detonation pressure prediction for other types of explosives.

The glass laminated composite armor exhibits good light transmission and impact resistance, making it widely used in military and civil protection fields. However, due to the susceptibility of glass to failure and breakage, the experiments and numerical simulations were carried out to investigate the impact damage mechanism of the target plate under high-speed impact of the steel ball projectile. Results show that under the action of breaking cone of first glass layer and stress wave propagation, the volume of breaking cone in the second layer of glass and the overall damage area are significantly larger than those in the first layer. During high-speed impact, many radial and circumferential cracks form in the glass layer. The circumferential cracks, resulting from Rayleigh waves, can prevent the propagation of secondary cracks caused by the radial crack propagation. The glass layer can be divided into the powder region, small fragment region, large fragment region and radial crack region according to different damage degrees. Along the thickness direction, the combined action of stress wave propagation, bending deformation of the target plate and volume expansion of the broken glass result in vertical and oblique cracks along the breaking cone in the glass layer. The PU bonding layer between the glass layer can deflect vertical cracks and hinder the propagation of the cracks along the thickness direction. At the interfaces between the glass/PU/PC layers, shear wave action arises due to the differences in dielectric wave impedance, leading to localized stratification within the adhesive layer. The deformation of PC layer gathers broken glass particles, forming a local high-stress area and complets the continuous obstruction of the projectile. Finally, the deformation of the PU adhesive layer is primarily induced by the shear stress caused from the breaking cone of the glass layer.

To investigate the influence of carbon fiber reinforced polymer (CFRP) strip with different number on the creep mechanical properties of coal samples under axial compression, a coupled numerical simulation using PFC^3D and FLAC^3D software was conducted, and a hybrid contact model combining the Burger’s model and the Linearpbond model was established. The reliability of the numerical model was validated based on laboratory uniaxial compressive creep tests of unconstrained coal and coal samples constrained with 6 strips of CFRP sheet. The mechanical properties and energy evolution of coal samples constrained with 2 to 7 strips of CFRP sheet under uniaxial compression were studied by numerical simulations. The results show that as the number of strips increases, the initial axial strain of the coal sample tends to increase overall, with a significant increase in axial strain during the accelerated creep stage, and the maximum internal contact force in the hybrid contact model tends to increase overall. The ratio of the contact quantity of Burger’s model to that of Linearpbond model is about 1∶9, and this ratio in the numerical simulation model could reflect the creep mechanical properties of coal samples. Increasing the number of CFRP strips restricts radial deformation, increases the number of shear micro-cracks, causes more severe shear damage within the coal sample, and the failure mode of the coal sample changes from tensile failure to shear failure. As the number of strips increases, the total energy, elastic energy, and dissipated energy all increase, and the change in elastic energy is similar to the change in total energy before the coal sample experiencing creep instability.

To investigate the dispersion characteristics of spherical tungsten fragments driven by a cylindrical charge, dispersion tests were conducted on a warhead with spherical prefabricated fragments. Considering the limitation of traditional comb targets, which can only measure the maximum velocity instead of the velocity distribution of the fragment group, a novel crossed-comb target was designed and fabricated. This velocity measurement device successfully recorded the pulse signals generated by multiple fragments penetrating the target and the impact positions. Numerical simulations were conducted using LS-DYNA to calculate the dispersion characteristics of spherical fragments driven by cylindrical charges. The results indicate that the numerical simulation results agree well with the test data. The designed crossed-comb shaped target can accurately measure the scattering velocities of multiple fragments. Increasing the length-to-diameter ratio can mitigate the effect of rarefaction waves at both ends of the charge on the fragment velocities; however, this mitigating effect diminishes as the length-to-diameter ratio continues to increase.

As a common ignition element, the ignition characteristic in limited space of a bridgewire electric ignition element (EIE) is the internal embodiment of its precision and reliability as an explosion-transfer sequence. The limited space environment of bridgewire electric fusehead ignition is simulated by preparing test samples and the test system of the ignition parameter is designed to test the time structure of the ignition process, the gas pressure, ignition light intensity and other parameters in limited space; using the high-speed camera to test the dynamic ignition process of the EIE, a physical model of ignition in the limited space of EIE is established. The research shows that with the increase of the ignition voltage, the phase transition time of the bridgewire is shortened, the duration of the plasma stage increases, and then tends to stabilize. The ignition time of the electric fusehead fluctuates at about 5.6 ms, and the ignition pressure time and the ignition light intensity time are maintained in the 3.0–5.0 ms range. After the ignition voltage reaches 20 V, the ignition characteristic parameters tend to be stable, and it can reliably output uniform ignition energy for igniting the next sequence of charging. In the limited space of the air chamber, the dynamic process of EIE can be divided into four stages: bridgewire heating up and heating fusehead agent, fusehead agent ignition, heat flow diffusion and shock wave reflection.

Using visual simulation technology to investigate the damage mechanism and target response of projectile penetration into concrete is an important research topic in the field of explosive impact. Concrete, as a common building material, has complex and varied damage behavior when subjected to explosive impact or high-speed projectile penetration. Herein, a visual simulation method is introduced, which is based on the combination of theoretical research and visualization technology. An optimized model of penetration calculation is established based on the theory of cavity expansion, which can predict the characteristics of the penetration depth of concrete penetrated by the projectile. Using a visualization physics engine, the trajectory of the projectile, the aperture of the open pit, the damage of the target slab, and the debris splash are carefully characterized and simulated, which enhances to the realism and reliability of the scene. The developed visual simulation system can not only observe the process of projectile penetration into concrete from multiple perspectives, but also efficiently and accurately analyze and predict the damage behavior and dynamic response of projectile penetration into concrete targets. It has important application prospects in the design and safety assessment of construction projects, providing a novel perspectives for understanding and exploring the mechanism of concrete penetration.